I've been doing research on static pressure to understand it better, and this is the best video I've seen on the subject. Highly recommended to HVAC people.
33 year HVAC guy, who started in Air Balance for 3 years. Your videos rock, and you're an effective communicator. I've attended many classes with brilliant instructors who couldn't instruct. That's not you.
As a retired service and training manager for a major brand and an instructor of manual J & D, I ground your video to be excellent, correct, and very well explained. Great job! Airflow and air duct testing is so important as many system failures are traceable back to a faulty duct system. A “ tip” if I may. When drilling into a furnace or air handler beware that there’s insulation ( in many cases) that’s only glued on and any excess pressure from the drill may loosen the insulation causing an eventual failure of adhesion allowing the insulation to start flopping around with some ending up on the evaporator coil. Another way, on furnaces, would be to remove the high limit and go in there. You’ll be between heat exchanger cells right above the blower and get a accurate reading too. This way you will not damage the insulation. Just of course be aware that one leg on the limit is hot with 24 volts, so as not to blow the fuse on the board. Real bummer 😖 This video has very valuable information guys, please use it.
Thanks Wayne! And yes, limit switch hole is better than nothing, but the reading obtained there will be higher than actual. If they can pass ESP with that spot, great, but in my experience installers need every 0.1” wc they can get to be at .54” and round down.
I've been searching for a good static pressure explanation video all over TH-cam and none of them are as thorough and precise as yours has been! Thanks for taking the time to explain this procedure step by step.
My instructor gave us topics to research before discussing it, and static pressure is one of them. This cleared up a WHOLE LOT for me! Great explanation! Thank you!
Well done SIMPLE video. We use this in our training (for a few years now) when we are onboarding new team members. Thanks for the content, keep it coming brother.
I paid thousands of dollars to go to college for HVACR in order to become an HVACR Technician, and my instructor didn't teach us any of this. We either learned (almost) everything from an online educational program (Cengage Learning) or our book. Our teacher often took days off in order to go fishing. I'm pissed; I learned more from this guy about static pressure (and other sections of HVACR from other people here on TH-cam) than I have from my 'teacher'. 🤬🤬🤬 Thank you, Corbett. I actually just watched this video about five times back-to-back. After all, repetition is the basis of all teaching. 😏
@@HomePerformance I agree. I think the teachers' philosophy at school is, "We're just giving you enough to get you started. If you really want it bad enough, you'll go get it." And that alone cost $10,000. Next time, I'll just rely on Google and TH-cam, and treat myself to another brand new bike.
This is invaluable… I want to incorporate this because very few tradesman take this into consideration in the field, and comfort problems are the hardest things for me to solve. I can fix anything that’s broken but when it comes to humidity issues and the refrigerant levels look good… oh boy I start scratching my head
Awesome! By far the most clear explanation of static pressure I've seen! It's been a while for me and I need to do it next week, so I appreciate the refresher! A few notes: 1. That is a quiet AHU, I couldn't hear it in the video! 2. Don't forget the low limit for TESP, 0.08" WC. I've been finding 0.12" is the bottom on some systems - the second floor doesn't cool for squat below that. 3. The positive/negative thing still messes with me. (I'm a little slow sometimes...) Perhaps talk about the difference or spread between the two? The spread -.38 and +.21 is .59. Like I said, I'm a bit slow sometimes... Thanks again for the refresher, I get to freak out once again while I drill holes in a perfectly good furnace next week!
+Energy Smart Home Performance glad to help my friend. Easiest way to calc the spread is just drop the neg sign at the get-go and add the two together.
Great presentation. This helped me get more involved in air flow testing a few years ago. Hence to name, static pressure nerd. I would be interested to see the pressure drops in the return drop!
First: thank you for the descriptive and informative video.it was very helpful. I have been doing hvac for 30 years and believe it or not I never considered evaluating static pressures. UNTIL one day I did a change out and removed a zoned damper system including the bypass per customers request and was unable to get my subcooling or super heat correct. It was a nightmare. I called the manufacturer technician support and discovered just how important static pressure truly is. It's not enough just to replace a system without verifying that the ductwork was seized correctly. Now I ALWAYS check static pressures on every job including surveys for new accounts. Be safe everyone
Thanks for your clear, concise explanations! I am a residential remodeling contractor. I am having trouble explaining some of these concepts to a client, who thinks that simply closing off vents to half the house in the winter will save energy, that the furnace burns less fuel/gas when vents are closed, and that static pressure can/will damage the furnace components. They have a single stage unit, no AC. Do you have a video that might explain these concepts? My analogy of "getting 10 pounds of sugar in a 5 pound bag" is not getting the point across 🙂 Thank you!
You might try this one first, Scott- it’s shorter and simpler: Static Pressure Testing for Home HVAC: What, Why, and How in 2 Minutes th-cam.com/video/Ks55DcS1ZgQ/w-d-xo.html
Very clear demonstration, thanks for posting. I've just determined that my furnace (which was installed by previous owner in 2012) is staved for return air. I found that the heat limit switch was tripping every time the system was kicked into 2nd stage heat. When I remove the panel before the blower the limit switch doesn't trip -- I posit that this allows enough airflow to keep the furnace in operating temperature range. I think the installers never fully tested their installation and now I have to figure out how to solve this inadequate return issue for them. My furnace installation does not have any of the ports you called out as needed in order to make TESP measurements.
Greetings Just wanted to let you know that I appreciate the video’s you make. I’m sure you get push back from businesses that, in reality, should be thanking you for the information you provide but instead “they” just want things how “they” want them and not to be checked or questioned. Please don’t get discouraged. Just keep on keeping on. Know that you have thousands of guys that appreciate knowing how things are supposed to be. Hope you and your family are well. Grace and Peace Slick
I know isn't it crazy how slow the growth is working for someone compared when going out on your own. Thats why I'm out here learning a few things, my employer refrained from me to keep me from fully independent lol well here I come! 😂
You got it right! The .59 TESP should and does total your other 4 SP readings. SA duct -.07, Coil - .14, Filter -.19, RA duct -.19 = .59 TESP. As you mentioned, the other readings clearly show where the problem of too high TESP is. Thanks
Well explained and after watching several times and mapping my system which is different than most, I finally understand the pressures and meanings. Thanks.
To clarify, all A/C is just refrigerant and airflows. The refrigerant PERFORMANCE is affected by airflow, but the pressures in the lines and the ducts don't talk directly to each other.
We always did static pressure, temperature rise and gas pressure tests on all of our start ups, then recorded the readings and put them in a customer file. If you don’t do this you are not determining if the furnace is running properly and under design conditions
We do it on every start up, every single maintenance just to ensure the system is operating properly and nothing has changed within the system. I love it
Great video. Thankfully it confirms they way I test static. That is typically ow I test TESP. One slight difference I usually pullout the high limit switch to get the post-blower pre-coil number.
Thanks, Nate! The high limit switch is not ideal- you get a higher than actual TESP. You will pick up some of the pressure induced by the top half of the heat exchanger- which they do not want you to include in the TESP.
If you study anything from ACCA, you will know now in 2022 with the Air handlers, furnaces and package units, the static pressures can exceed 0.5 without causing any issues. Is it ideal to be 0.5 or below, sure I suppose so. But I have seen systems run just fine at 0.9-1.1 without an issue. Variable speed ECM blowers were practically designed for that. But a properly built system with the right amount of return air, a large filtration system 4-6" filters with good air flow, a good variable speed system properly matched with the ducting design and system functions with be most likely below 0.5 but can safely run much higher. For the homes that are completely finished, and ducting cannot be upgraded, the HVAC system can still be spec'ed properly that could be running 0.5-0.9 without a single hiccup. There are just too many variables to say 0.5 is the maximum these days, but this is a 6-7-year-old video and the 80%-98% units have come a long-ways. This is an outdated video but still has some validity for older systems. Like, don't put in a Filtrete 1900 1" in a single stage 20-year-old 80% system, sure you will have problems. But anything with an ECM blower will run fine but I still don't recommend that ridiculous filter. But also, stop putting on those no MERV rated filters that you can see through that cannot even stop flour. Depending, a MERV 8 is a good average for older systems. If you want to pay a $1 a filter and change it monthly with very little filtration, so be it. It is your stuff, but a MERV 5-6 would be fine for that use. Anyone can add a 5" filtration box to their system and have reduced static pressure and better filtration, no matter what year it was built. Just make sure you have good return air, good intake air and generally you will have a pretty healthy system, if serviced yearly and cleaned properly on your coil, condenser and blower. Maintenance is just like a car, after all, they do cost as much to replace! But these days, you can get some amazing systems for a decent price. I sell my clients the best system possible at the best price. Find a small HVAC company that has good reviews, and you will get better service than some big-name company who advertises on TV or mailers. You get to pay for all their advertising, fancy vans/trucks etc. Make sure they do a full manual J, S and D and get 4-5 quotes and ask neighbors and friends on social media for referrals to friends and family. I promise, if you follow some of these rules, you will have success and be happy. Have a great day!!
@@wojtek-33 Do you mean your furnace or AHU is in the attic? You can buy Honeywell, AprilAire, Trion Bear and many other filter boxes. Or are you talking about return air ducts. You can buy filters that have a lip and the filter extends up into the cavity. One brand is Flow Right. And you get get filters at Filterbuy in the custom sizes. So many options available but I am not sure of your setup.
@@Balticblue93 yeah I'm Texas and a lot of homes have the whole system in the unfinished attic with a ceiling filter box in the living space. Of course mine is on a 10ft ceiling so need a ladder to change. It's a pain and it's an odd 24x36. Just found the ones with the lip but they are pretty expensive and almost none for my size. I look into one of the replacement boxes after taking some measurements on my system, maybe it's fine.
Nice video. Very true that most don't check sp. Got a kick out of the 'giant fan' comment! I travelled 9 states for an institutional and industrial sheet metal company living out of a service truck and suitcase. Crane and helicopter picks to get equipment on to rooftops and equipment suites. You could actually crawl into the fans I worked with and pretend you were a gerbil if you were so inclined. Our systems that were designed during the tuberculosis period were set up to bring in 100% outside air, heat it, deliver it to the rooms, and then exhaust it through big vents on the roof. In the 80's and 90's we spent days with saws, Jack hammers, drills, the infamous, back breaking 'wacker', and hammers and chisels opening up primary return air chases, and individual room chases to provide return air - and required smoke and fire dampers. There were variable pitch sheaves and vortex dampers to adjust volume (often upgraded from wooden sheaves and flat belts) Million+ btu burners, oil nozzles (sometimes triplex) that drank gallons per hour, even coal stokers (ever had to clear a coal room to get to an auger's shear pin?), early geo- well water circulated through cooling coils, enormous compressors for DX or chillers, huge pneumatic or motorized outside air, mixing, and exhaust dampers, Chai pull, pneumatic, and now ddc controls, and single draft inducer bearings at power plants that weigh more than an entire residential furnace and dx cooling system combined. Had two boilers in a school in Ashtabula ohio that had come OUT of a great lakes steamer in the 1930's. Had to convert them to gas. The last boiler man in the district that knew anything about coal was retiring-- had that scenario at schools all over as coal was being phased out. Remember back in the 80's when one of our sheet metal guys dropped a tinners hammer from a catwalk from duct big enough to drive through at the Ohio Theater in columbus ohio. Just missed the organ. I was often serenaded by Dennis James on their 'Mighty Morton' while performing pm there (35' × 16' filter area with electronic cells and automatic static pressure controlled feed for oiled prefilter rolls {talk about an itchy job!!}) The low notes on that organ would make your innards quiver like the bass guitarist Chris Squire's low notes in Yes's Starship Trooper!! We subcontracted companies that came in to confirm the balance numbers that our engineers had come up with. Our company had been founded in 1867. After merging with a pipe fitting company it took less than 3 years for the new rape and run business model to run it into the ground. They didn't like that I objected to their business approach. Have worked on that little stuff from time to time-- got cut on one of those itsy bitsy zip screw points or a rough cut sliver of metal just about every time I had to try to squeeze my hands into that stuff or work around that light gauge (aluminum foil!!) duct! Lol. Put some give a damn in your work and you'll build friendships that last a lifetime. Was a great trade.
Thank you for this helpful video. I am a homeowner looking to learn. On those pressure probes, it looks like they just face into the airflow and it doesnt matter if the hole is "sealed" by the base of the probe where it enters the ducts or am i wrong on that?
Hey, just a heads up from someone who checks static pressure often on gas furnaces, there is a hole into the heat exchanger available after the blower that the manufacturers make for us, just remove the primary limit switch, I prefer NOT to drill holes into equipment if it is unnecessary.
+Sightthrough, if you test at the high limit switch hole you will get a higher than actual TESP reading, since you're also picking up the top of the heat exchanger.
Hello Corbett, First off, way to nail it, great presentation, period! Please bear with me on my question... I hope it does not appear ignorant. How would I check down flow ( mobile home furnace ) filters are attached to backside of door and in this particular case, this unit is about 22 yrs old and does not have central air. There is an exterior independent a/c unit. The back of the Furnace obviously is in the cabinet ( closet ) all ignition, flame sensor, are internal and completely enclosed. Blower is in your face and completely exposed. Thanks, Jerry
Wow, Jerry, good question, but I don't have an answer for you. No experience with this type of unit. Check out this vid to find a way that might work: th-cam.com/video/9vwmP1T2ReI/w-d-xo.html
Great job Corbett! You are extremely articulate and able to convey complicated subject matter in an easily understandable manner. You could easily be a TV personality on one of the DYI channels! I’m assuming the drilled holes should be sealed using metal tape?
I'm curious. Why do you have a $1500 manometer, but only a Ryobi drill? (Kidding.) Thanks for the video, I'm new to the field, just finished A/C season and I'm heading into furnace season.
Haha, and I still have a few shirts from 15 years ago too. Welcome to the whole house practice, hope you get your hands on a blower door and start showing up the competition!
I have been doing this for years in the memphis area, I am not only a contractor, but an Instructor at a tech school as well. I try to teach my students these principles to commission units and use a blower performance chart to set proper airflow for A/C. The sad part is the majority of homes run .8 or higher. Those 1" pleated filters are horrible for static. I recommend nothing less than a 2" pleated for single filters at the furnace base. Jack Rise from ACCA taught a class here years ago and called Memphis the land of no return. He was right! After seeing very nice homes with 2x4x16" wall stacks and builders trying to get 2 tons of return in two cavities! The installers in the area have no clue, the builders want the cheapest, and the homebuyers say look at the granite countertops and saltwater inground pool. Next thing I'm telling them the ductwork was done by a doofus because they aren't comfortable.Keep educating! I just replaced a 7 year old system on a new house because the plenum had a 4"x22" hole in it in the attic where it was never sealed! Keep calling out the shoddy work! It's not opinion if there is verifiable performance! Oh, sometimes I can't drill an old furnace in a closet, I normally take out the limit switch for my probe, not ideal, but works!
+Jesse Johnson you rock brother. Keep up the great work in TN- the world needs you calling out doofus work! See you around I hope- we're not far, in Atlanta now!
PS +Jesse Johnson : my 6-week mastermind course might be useful to your students or colleagues HomePerformance.training Starts 4/1 and registration begins 3/1
Jesse Johnson I'm in Nashville and I see a lot of the same. I actually got cussed out the other day by another inspector of all people because I wrote up a 5 ton system pulling from one 20x30 return filter and a 10x15 run. The static pressure on the return alone exceeded .5" which is the max on the system allowance. You just have to walk away and shake your head at some people.
Usually I'll pull the limit if the hole is too big I'll put metal tape to make up the space for the magnetic static probe and of course for accuracy . Not all but alot of times in California at least drilling on the side is a real task sometimes the limit is the only answer . Great video
Great video. I've done some drilling into plenums and ducts before for testing but never into a unit and below the coils. Any rule of thumb as to where the coils sit in most units so hitting them when drilling into the units can be avoided?
Question, when measuring the pressure across the coil you subtracted .07-.21=.14. When measuring across the furnace .38 + .21= .59 for the furnace you added your two different pressures but across the coil you subtracted. Not sure why you subtracted one and added the other.
I agree with so many others on here that this was one of the best, easy to understand explanations and demonstrations for basic testing of static pressure with some great references to industry standard measurements such as drop across filter and A-coil etc. Thanks for sharing! I'm actually trying to determine airflow in CFM for my 3-ton heat pump system to see if it is meeting the required 400cfm per ton which would be a total of 1200cfm to work properly & efficiently. I'm finding that determining airflow accurately without expensive testing equipment can be a very difficult thing. And the results of low cost instruments can vary widely. So, what I might share for those on this elusive hunt, are 2 things: 1 is figuring airflow by using a similar probe but with additional tubing connection (Pitot tube). It works the same but collects 2 measurements simultaneously static and velocity. To get an accurate test a series of holes (travers) are drilled across a section of ductwork at predetermined spacing and a timed and averaging is done and then a bunch of tedious conversion mathematics which seems like a lot of trouble. The alternative using this instrument is a single hole in center and an averaging multiplier of .9 is used to get within +/-5%. Another method listed below blew me away and I'd like to hear comments on this. It utilizes a simple formula using volts, amps draw and temperature rise to determine airflow. I've included a link to the article library.coburns.com/HVACTechTips/Calculating%20CFM%20Coburns.pdf
So how do you know what the pressure drop is supposed to be across an evaporator coil if it is not part of the furnace itself? Also how do you know what the pressure drop across any filter should be?
I tell what man. You're a mentor to industry! Dang ole truth is we're all idiots! What we know we inherited. Inheritance requires discern you know what I'm saying man. Calling out the kind from the swag and tossing the bunk under a bus. There may have been a TESP performed on an AH w/out a hole. Some techs remove the limit switch, and testing from there, but doing this will give you a higher reading because of resistance (top of heat exchanger) I try to replace the filter before I test. 4" media filters w/higher or lower merv values also tweak your #'s. Dang ole beer can cold vets deserve respect, but after 20yrs thinking your right when you were actually wrong. I'd respect the man who pointed out this reality proving to me why I had been mistaken. Corbett I think in the future your name may be as recognized as Bob Vila's was 10yrs ago. So if you become the TV host for this new house? I'm applying for a job!
Great video!!! now i understand a little more. I will appreciate your advice though. So, i have a new air handler and new ac condenser unit (replaced).Since the installation 2 weeks ago, air flow has decreased noticeable in the third level of the house only (it's very weak). I have it checked (no testing as shown here whatsoever) but the response of the technician is that it's normal. Now, i wake up in the middle of the night sweating, and I also have two fans in my bedroom. Finally, another company is coming this Saturday to check the "blower" (after doing some research that's how i explained the problem). Which should i "demand" from this other company in order to have the unit properly inspected and diagnosed? Thanks in advance!
Hi Priscilla- sorry you’re having trouble, but glad you found us! You should try and find a diagnostics company that won’t have an agenda of selling you HVAC equipment. Go to: HomeDiagnosis.tv/pro to learn to find these companies in your area.
You said if you dont see a hole on the side of the furnace your contractors are bad. What about removing the high temperature limit? Everyone I know uses that when they can to avoid drilling holes.
Yes, that can work, but it’s guaranteed to give you a higher than actual reading of TESP. And based on my testing history with hundreds of systems, I feel confident most contractors are never testing this. If they ARE, they should be showing that they pass on the unit, alongside all the other stickers on there.
Thank you, bravo , excellent job at explain in layman's terms so our consumers can get a better understanding of what should be done on every installation. It's too bad the majority of technicians installing furnaces do not even know this, at most they just seen pictures in literature but never had their bosses actually run them through it and explain it to them so it never gets done and the customer usually ends up with an inferior install. Thank you for all your effort and passion to educate people about the subject.
i got a 4ton for 1300sqft thats 350ft per ton in southern Nevada easy 115 degree days, i aim to get 1600cfm and my filter is 20x20x1 side by side for a total of 20x40 filter return. i currently use the honeywell HD merv 11 filters but i think ill start using the 3m 1200 merv 11 because of the more surface area on the filter to help decrease static pressure if that doesnt help ill try to use 4in filter
Hey Corbett. Great video!! I hope you can answer me this though. Every video on you tube shows how to measure static pressure and that it should be at about .5"wc for most residential units. However, I cant find any material on What just the return pressure should be. Or what just the supply should read. In other words, what if I have a read of total static pressure of .7"wc. All I know is that it's high. What pressure should I target in the return or what pressure should I target in the supply? You briefly touched in that .14 is average for the a/c coil and that the filter should be at .1"wc. And then you mentioned that at .19 the return was high and .07 the supply was low. But again I dont know what to target. If you could help me understand this I would really appreciate that. Or point me to material that I can read to further my knowledge in the matter. Thanks!!
Sure- ductwork is designed to pressurize to 0.1” or .08”, that should be ret and sup. And you don’t want TESP to be .5”, you want it UNDER .5”. So .1 for ret duct + .1 for filter + .1 for coil + .1 for sup ducts = .4”
I've been in the industry for a year, I was told that yes you shouldn't have more TESP than what the manufacture says but was told by my seniors that you're allowed a little wiggle room (.1-.15 more than the static pressure) because of the filter. Some customers prefer certain types of air filters that will increase the static pressure. Are my seniors right and what do you do to compensate for the thicker filters?
+Kyle Rae great question! Just think about the fact that it’s a pass/fail test. If you’re over .5 even a little, you risk another pro telling your client you don’t know what you’re doing. The old school guys are used to nobody checking their work, but once your client thinks you lied to them one time, they will never hire you again. Remind them that TESP includes the filter- the filter doesn’t get added later as fudge factor. If a homeowner wants a higher MERV filter, they have to go wider media or upsize the return. Keep up the great work challenging the old rules of thumb!!!
I’m conflicted if I can move up to a MERV 13 furnace filter. I believe I have a 2 ton gas/AC furnace. Any suggestions would be great. Hell, I’d also like for someone to test my system’s static pressure. Any certifications I should look for in company? Cheers, great video.
Sorry Pete, no certifications for this one, but you can search google for it and maybe find somebody who’s trying to be better than the rest. If you go with a 4” pleated filter then absolutely you can.
@@HomePerformance I actually have a 20x25x5 inch pleated MERV 10 furnace filter right now, but I’d like to move up. I think I should be ok. I’ll tell you something crazy though, I just found significant water vapor damage inside of my wall from the microwave “range hood” over the stove, which some how is blowing inside of the wall. I can hear the wind in the wall from the other side when it’s running. I look at the best mold inspectors in the nation’s reports for a living and I have not seen this source area to date yet. Talk about negative pressure lol Thanks for the reply btw.
Great video, my question is: when you check for static pressure do you run ac or only the blower fan, can it be check when the heat is on?, the reason i’m asking this is because multiple speed blowers won’t work on a full speed if you just run the blower by itself, thanks for your time...
+Diego Lopez great Q. In the appendix of my book, there are a few methods for tricking the blower to run in AC mode, which you’re right is generally the highest speed. Important in my opinion to know the performance at different speeds, but if your goal is TESP no higher than 0.5, then yes, always test on high speed.
Hi, I'm a homeowner that just had a new packaged unit installed and replaced the duct work as well. I noticed the return vents whistling and pulling more air. I contacted the installer and they wanted to change the type of filter or return grill. I'm concerned that the duct work may be improperly designed. I'm going to ask them to perform the test but I want to understand if changing the blower speed setting is important because they recommended changing it.
I disagree with the point you made about not calling a company just because there are not holes driven into the furnaces.There are a static pressure readers into the new furnaces
There are a lot of hard working companies that have been providing exceptional service and hard work and you are telling people not to call them back.It not true
how much should i pay to get this test done, since i dont know how well the 25 year old ac unit is performing. reason is i will be getting a brand new unit and i want to see before and after performance results.
Just make sure it’s in the contract for your install, and they can test the old one before taking it apart. It takes only 10 minutes, as you see. Maybe $100 if they know what they’re doing, maybe $10,000 if you’re scaring them.
Is the best way to measure pressure across the filter if you have wall grill filters, to measure the room pressure and make that the delta? Or is it better to remove the filter?
Don’t you have a book for sale? Also, my unit is in my attic with a 4 ton coil but I want to install my new unit in my garage 9 foot below. 18” Return with a 14” and a 12” Supply coming off the plenum. Any thoughts?
Yes, my book is at: buildingperformanceworkshop.com/homeperformancediagnosticsbook And your ductwork can easily be redesigned if needed, to put the equip in the garage.
Thank you and I look forward to getting your book. My other question is when dealing with existing ductwork then when you find problems how would you suggest we correct them without creating a huge cost to the consumer?
The consumer gets what they pay for- if they see the benefit, they won’t need a lot of convincing on cost. Several ways to seal ducts, depending on situation.
-Fan stops blowing about once a year. -Techs change out Emerson controller board. Problem goes away for about a year each time. -New tech actually tested total static pressure. He reported the the total is .7. Unit label says .3. -He says the static pressure is damaging the board and recommends 10k duct work. -We can temporarily work around the issue and get the fan to run again by disconnecting power from the controller board for a few minutes. Does this make sense that the circuit board can be damaged by incorrect static pressure? What do you think?
Ok so after I get static pressure reading? What do I do with that info? Is there something to adjust if we are low or high on static pressure? I guess you would want to check airflow before adding refrigerant.
It’s a forensic look at whether the ducts were designed properly, and if you have problems in one particular area. Surgery would be required generally.
Sorry, I do have one more question if you are nice enough. Out here we have our airhandlers (furnace and A coil and ductwork) in our attics. There is a movement when they are replaced to move the unit to the garage so maintenance is easier. How would you suggest setting up ductwork to have the proper pressures? The original ductwork would remain in the attic but the unit would be about 9 foot lower and 6 foot away from where it was? Also, most attic ductwork is flexible but metal would be run to the garage. Probably too much but at least I tried….and thank you.
Thank you for this most informative video. I am NOT hvac saavy,but my understanding of it's basic principles,has now been thoroughly upgraded from OH?,to I understand what your saying. Life is good! Be well,friend.
I am working on a tenant complaint about AC cooling not being good enough. This is for a an upstairs duplex apartment unit. The evap is getting nice and cold-maybe too cold. I think the fan speed for the cool is too low. Right now the cool for the motor is on the BLUE (Med-Low). And the heat is on YELOW (Med-High). I alway heard that the cool speed should generally be faster than the heat speed, so Im going to switch the two so the cool is Med-High and the heat is Med-Low. Will this help solve my cooling issue?
Good q, but you have only one data point. I’d want to know temp and RH in the apt, actual airflow thru the indoor coil, whether the unit is sized properly, air leakage of the apt walls, ceiling and floor. You could mess around there for years, or solve the problem in one visit if you test. Check out my interview on the HVAC School Podcast: www.hvacrschool.com/blower-door-testing-building-performance-w-corbett-lunsford-podcast/
So when you said balancing the system,the total should not exceed .5 But to be there or under. So my interpretation is not that supply is .25,nd return is .25 but that what the combination is should not exceed the manufacturer s Number?? If I got that right,your tutorial was excellent. Please let me know 🤔
Good explanation. I just had to fight with my installer to do the commissioning testing shown in the Lennox installl manuals. Lennox's detail shows one test hole in the A/C coil compartment and the other between the filter and the fan for total static pressure. The installer chose to use the supply plenum ( after coil) instead. I would think he's missing the restrictions caused by the A Coil and would get a lower reading. How important is it to be before the coil?
I may be misunderstanding what you're saying at 9:20: in this setup it appears that the filter is After the furnace blower fan. Shouldn't the filter be on the suction side of the blower fan?
I am planning to use the pressure drop across my air filter to determine when the correct time to change it is. I have a set of pitot tube and required hardware to install them. I plan to but 1 on each side of the filter. That said, this mean one pitot tube will be located in the blower assembly of my HVAC system. Based on where I have seen in your video and others, the static pressure should be somewhat constant. Since this is a home unit, I do not expect a large variation in pressure across the duct and plan to use only 2 pitot tubes. With one on each side side of the air filter, located in the center (side-to-side) of the duct and about 6" into the air flow. Other than ensuring I am on the correct side of the blower fan, is the location of the pitot tube in the blower compartment important for measuring the static pressure?
+Grover D first, I assume you mean just static pressure probe when you say 'pitot tube'- a pitot tube also measures total pressure, which you won't need. I'd sample a few places in the cabinet and all different directions for pointing the probe, but yes, it shouldn't matter much.
Hope you can point me in the right direction. Just checked my furnace, heat only no AC, and I am getting .07 on supply side, and .48 on return side. Total is a little above .5, but the fact that I only have .07 on the supply side seems very wrong to me. Where should I start looking for issues?
Replace the filter first. Heating mode is often low speed on an air handler, so don’t be too concerned with the supply reading for now. You’d also want to take temps in rooms and airflow out of vents and thru system to get the big picture.
@@HomePerformance Thanks for the quick reply. I replaced the filter before even checking. I am pretty sure a ton of junk fell into the floor returns when the previous owner opened the walls up and the blown insulation fell out everywhere. I'm guessing that is why the return side is so high. Is there a way to force the air handler to blow in a higher mode to make sure I am able to get higher supply pressures?
Hi Corbett just makin sure now, the friction rate is on each manual of the air handler depending on the speed of the blower? And we have to match that friction rate based on how we calculate sp, pressure drop, equivalent length, etc after the design is complete correct?
Hi Corbett, so basically just wanted to confirm static pressure is the resistance of the air inside the ducts and pressure drop is? If you can just summarize the two meanings for me I would appreciate it.
Cobett, hey I have some questions. 1. Do you have a "field cheat sheet" on this? 2. What state is this test supposed to be run. ie; start up, steady state etc...? What about negative pressure or positive pressure is that a factor here?
Hey Michael- APT Reports has an automated section for this test. No need to run for any length of time, as long as the fan is running at the speed you want to target (usually high). House pressures are insignificant generally compared to blower induced pressures.
Hey Michael- APT Reports has an automated section for this test. No need to run for any length of time, as long as the fan is running at the speed you want to target (usually high). House pressures are insignificant generally compared to blower induced pressures.
Thanks for the video it was very educational and helpful. I have a Carrier 58mca-060-16110 furnace with air conditioning installed in a small room at the center of the house with grates in all the walls to the surrounding rooms(house is on a slab and doesn't have return ducting). The filter is mounted on the side of the furnace(one side exposed to the room) and sucks the air directly from the room.I have a digital manometer and want to check pressures on the furnace. I have a few questions if you don't mind. 1. Does the one probe need to be held in front of the filter or just anywhere near the furnace. Or is it needed at all, at least for the filter drop. 2. Does the probe inserted above the heat exchanger and below the evaporator coil need to be anywhere specific in the space. My coil is offset to the left side directly over the heat exchanger (no room to insert it) but there is a lot of open space to the right of it that's probably not directly in the airflow. Thanks
Hi Norman, thanks for following. The pressure in the room at large (before the air hits the filter) will be zero. No need to measure that one. And you must insert the probe BELOW the evap coil's drain pan for sure, but it shouldn't matter if you're in the air path or not, static pressure is like a balloon's pressure, it should be pretty even everywhere in there.
good question everyone, so if you have a roof top packaged unit and want to calculate its external static pressure, do you consider internal pressure drops due to filters and coil? Or do you only calculate the pressure drop due to duct system?
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You're the first person to actually explain what static pressure is clearly. Thank you.
High praise- thanks man
I've been doing research on static pressure to understand it better, and this is the best video I've seen on the subject. Highly recommended to HVAC people.
Hey, thanks David! Nice to hear!
Same here & I agree!
Thank you other David!
Great for non hvac professional too
Can the testo be use without the probes.
Such a great video of clearly explaining static Pressure. We get static pressure readings on every call our techs go on. Keep up the great work!
33 year HVAC guy, who started in Air Balance for 3 years. Your videos rock, and you're an effective communicator. I've attended many classes with brilliant instructors who couldn't instruct. That's not you.
WOW, thanks a lot my man! Really appreciate it! You know I get trolled for this stuff sometimes too, so it’s nice to hear the opposite.
As a retired service and training manager for a major brand and an instructor of manual J & D, I ground your video to be excellent, correct, and very well explained. Great job!
Airflow and air duct testing is so important as many system failures are traceable back to a faulty duct system.
A “ tip” if I may. When drilling into a furnace or air handler beware that there’s insulation ( in many cases) that’s only glued on and any excess pressure from the drill may loosen the insulation causing an eventual failure of adhesion allowing the insulation to start flopping around with some ending up on the evaporator coil.
Another way, on furnaces, would be to remove the high limit and go in there. You’ll be between heat exchanger cells right above the blower and get a accurate reading too. This way you will not damage the insulation.
Just of course be aware that one leg on the limit is hot with 24 volts, so as not to blow the fuse on the board. Real bummer 😖
This video has very valuable information guys, please use it.
Thanks Wayne! And yes, limit switch hole is better than nothing, but the reading obtained there will be higher than actual. If they can pass ESP with that spot, great, but in my experience installers need every 0.1” wc they can get to be at .54” and round down.
@@HomePerformance - What is the best way to deal with the holes after you have run all the tests?
@darriuscole8544 they make metal plugs, or plastic if you prefer.
I've been searching for a good static pressure explanation video all over TH-cam and none of them are as thorough and precise as yours has been! Thanks for taking the time to explain this procedure step by step.
So glad it helps you, +Cesar Aquino !
helped me too. thanks!
+Jose Marcano glad it helped!
Home Performance hey so is a wet coil .07? Or is that dry?
Def dry
This guy does the best Tutorial I've ever experience, and I have been watching him for a good while...
Aw, geez, thanks Yozy!
My instructor gave us topics to research before discussing it, and static pressure is one of them. This cleared up a WHOLE LOT for me! Great explanation! Thank you!
+mike martinez wonderful! So glad to have helped.
There are a lot of videos and web sites that address static pressure. This video is the best of all of them.
Damn, Louis! Thank you buddy.
Well done 👏
The pressure drop of coil + filter called internal static pressure .
The pressure drop of the duct called external static ptessure .
Well done SIMPLE video. We use this in our training (for a few years now) when we are onboarding new team members. Thanks for the content, keep it coming brother.
Hell yeah man, thanks for the high five!
I paid thousands of dollars to go to college for HVACR in order to become an HVACR Technician, and my instructor didn't teach us any of this. We either learned (almost) everything from an online educational program (Cengage Learning) or our book. Our teacher often took days off in order to go fishing.
I'm pissed; I learned more from this guy about static pressure (and other sections of HVACR from other people here on TH-cam) than I have from my 'teacher'. 🤬🤬🤬
Thank you, Corbett. I actually just watched this video about five times back-to-back.
After all, repetition is the basis of all teaching. 😏
Hey man, sorry to hear. I suspect your experience is not uncommon.
@@HomePerformance I agree.
I think the teachers' philosophy at school is, "We're just giving you enough to get you started. If you really want it bad enough, you'll go get it."
And that alone cost $10,000.
Next time, I'll just rely on Google and TH-cam, and treat myself to another brand new bike.
@@ParabellumXdefinitely not uncommon it's crazy how little real life education you get from these schools
Anyone else notice how nice that install is.
Thank you. Finally a Static Pressure video that was clear and concise. Answered all the questions that i should have already known the answers to.
Hey, great to hear- thanks!
This is invaluable… I want to incorporate this because very few tradesman take this into consideration in the field, and comfort problems are the hardest things for me to solve. I can fix anything that’s broken but when it comes to humidity issues and the refrigerant levels look good… oh boy I start scratching my head
Nice! I'm an HVAC student and its been a while since my first class. This material is refreshing. Thank you.
That’s great- glad you found us. Hope you subscribe and find all our other stuff too!
Awesome! By far the most clear explanation of static pressure I've seen! It's been a while for me and I need to do it next week, so I appreciate the refresher!
A few notes:
1. That is a quiet AHU, I couldn't hear it in the video!
2. Don't forget the low limit for TESP, 0.08" WC. I've been finding 0.12" is the bottom on some systems - the second floor doesn't cool for squat below that.
3. The positive/negative thing still messes with me. (I'm a little slow sometimes...) Perhaps talk about the difference or spread between the two? The spread -.38 and +.21 is .59. Like I said, I'm a bit slow sometimes...
Thanks again for the refresher, I get to freak out once again while I drill holes in a perfectly good furnace next week!
+Energy Smart Home Performance glad to help my friend. Easiest way to calc the spread is just drop the neg sign at the get-go and add the two together.
Much better explanations and demonstration for the layman than most other videos 👍😎
Thanks Bob buddy
Wow think I might actually understand it now. This was much better explanation than others teachings.
Awesome Chris!
Great presentation. This helped me get more involved in air flow testing a few years ago. Hence to name, static pressure nerd. I would be interested to see the pressure drops in the return drop!
Love it! Thanks my friend! More testing courses coming up, both in person and virtual: BuildingPerformanceWorkshop.com
First: thank you for the descriptive and informative video.it was very helpful.
I have been doing hvac for 30 years and believe it or not I never considered evaluating static pressures. UNTIL one day I did a change out and removed a zoned damper system including the bypass per customers request and was unable to get my subcooling or super heat correct. It was a nightmare. I called the manufacturer technician support and discovered just how important static pressure truly is. It's not enough just to replace a system without verifying that the ductwork was seized correctly. Now I ALWAYS check static pressures on every job including surveys for new accounts. Be safe everyone
Keep on rocking, William!
Thanks for your clear, concise explanations! I am a residential remodeling contractor. I am having trouble explaining some of these concepts to a client, who thinks that simply closing off vents to half the house in the winter will save energy, that the furnace burns less fuel/gas when vents are closed, and that static pressure can/will damage the furnace components. They have a single stage unit, no AC.
Do you have a video that might explain these concepts? My analogy of "getting 10 pounds of sugar in a 5 pound bag" is not getting the point across 🙂
Thank you!
You might try this one first, Scott- it’s shorter and simpler: Static Pressure Testing for Home HVAC: What, Why, and How in 2 Minutes
th-cam.com/video/Ks55DcS1ZgQ/w-d-xo.html
Very clear demonstration, thanks for posting. I've just determined that my furnace (which was installed by previous owner in 2012) is staved for return air. I found that the heat limit switch was tripping every time the system was kicked into 2nd stage heat. When I remove the panel before the blower the limit switch doesn't trip -- I posit that this allows enough airflow to keep the furnace in operating temperature range. I think the installers never fully tested their installation and now I have to figure out how to solve this inadequate return issue for them. My furnace installation does not have any of the ports you called out as needed in order to make TESP measurements.
Excellent diagnostic work, Greg!!! Once enough homeowners are like you, the HVAC industry will be a different beast!
Greetings
Just wanted to let you know that I appreciate the video’s you make. I’m sure you get push back from businesses that, in reality, should be thanking you for the information you provide but instead “they” just want things how “they” want them and not to be checked or questioned.
Please don’t get discouraged. Just keep on keeping on. Know that you have thousands of guys that appreciate knowing how things are supposed to be.
Hope you and your family are well.
Grace and Peace
Slick
Hey, thanks Slick- very thoughtful of you to take the time, and always nice to hear.
You are very good at explaining and your teaching is very straight forward and easy to understand, thank you very much
So glad to hear, Yama Zaheer
Great Video. You are a gifted speaker and teacher.
Thanks very much, my friend
Thanks, I learned something and I've been doing a/c for 25 years...
Awesome! Thanks for watching and commenting, Steve!
I know isn't it crazy how slow the growth is working for someone compared when going out on your own. Thats why I'm out here learning a few things, my employer refrained from me to keep me from fully independent lol well here I come! 😂
That is the best explanation of this subject that I have heard. Thank you for sharing this excellent video.
Hey, thanks do much Michael! Happy to hear- hope you’ll dubscribe, lots more where this came from.
You got it right! The .59 TESP should and does total your other 4 SP readings. SA duct -.07, Coil - .14, Filter -.19, RA duct -.19 = .59 TESP. As you mentioned, the other readings clearly show where the problem of too high TESP is. Thanks
Well explained and after watching several times and mapping my system which is different than most, I finally understand the pressures and meanings. Thanks.
Absolutely fantastic explanation! Love it!
Thanks +Stephen!
Stephen Rardon hey Stephen can bad total static pressures cause adnormal refrigerant pressures?
IMon Airflow does effect refrigerant pressures, in my opinion "bad static" is high static which means poor Airflow
To clarify, all A/C is just refrigerant and airflows. The refrigerant PERFORMANCE is affected by airflow, but the pressures in the lines and the ducts don't talk directly to each other.
Always thought the probes need to go with the airflow for accurate readings, what are thoughts Steve?
We always did static pressure, temperature rise and gas pressure tests on all of our start ups, then recorded the readings and put them in a customer file. If you don’t do this you are not determining if the furnace is running properly and under design conditions
We do it on every start up, every single maintenance just to ensure the system is operating properly and nothing has changed within the system. I love it
My hero
Keel up the good work!
Best video for furnace system. Would be awesome if you did a video for heat pump systems. Thanks for through easy to understand video.
Thanks Chris, I’ve added it to the list.
Super clear & enthusiastic presentation!
Thanks man!
Corbett,
This is a rare find! A superior instructional tool...
Thank you much!
Thanks for enjoying it, Romell!
Great video. Thankfully it confirms they way I test static. That is typically ow I test TESP. One slight difference I usually pullout the high limit switch to get the post-blower pre-coil number.
Thanks, Nate! The high limit switch is not ideal- you get a higher than actual TESP. You will pick up some of the pressure induced by the top half of the heat exchanger- which they do not want you to include in the TESP.
I conformed that in our shop with a live unit.
Its a pretty consistent .18-2 higher in the heat exchanger.
If you study anything from ACCA, you will know now in 2022 with the Air handlers, furnaces and package units, the static pressures can exceed 0.5 without causing any issues. Is it ideal to be 0.5 or below, sure I suppose so. But I have seen systems run just fine at 0.9-1.1 without an issue. Variable speed ECM blowers were practically designed for that. But a properly built system with the right amount of return air, a large filtration system 4-6" filters with good air flow, a good variable speed system properly matched with the ducting design and system functions with be most likely below 0.5 but can safely run much higher. For the homes that are completely finished, and ducting cannot be upgraded, the HVAC system can still be spec'ed properly that could be running 0.5-0.9 without a single hiccup. There are just too many variables to say 0.5 is the maximum these days, but this is a 6-7-year-old video and the 80%-98% units have come a long-ways. This is an outdated video but still has some validity for older systems. Like, don't put in a Filtrete 1900 1" in a single stage 20-year-old 80% system, sure you will have problems. But anything with an ECM blower will run fine but I still don't recommend that ridiculous filter. But also, stop putting on those no MERV rated filters that you can see through that cannot even stop flour. Depending, a MERV 8 is a good average for older systems. If you want to pay a $1 a filter and change it monthly with very little filtration, so be it. It is your stuff, but a MERV 5-6 would be fine for that use. Anyone can add a 5" filtration box to their system and have reduced static pressure and better filtration, no matter what year it was built. Just make sure you have good return air, good intake air and generally you will have a pretty healthy system, if serviced yearly and cleaned properly on your coil, condenser and blower. Maintenance is just like a car, after all, they do cost as much to replace! But these days, you can get some amazing systems for a decent price. I sell my clients the best system possible at the best price. Find a small HVAC company that has good reviews, and you will get better service than some big-name company who advertises on TV or mailers. You get to pay for all their advertising, fancy vans/trucks etc. Make sure they do a full manual J, S and D and get 4-5 quotes and ask neighbors and friends on social media for referrals to friends and family. I promise, if you follow some of these rules, you will have success and be happy. Have a great day!!
What is the location of where you work? I'm sure people reading your comment might be interested in your HVAC services.
How would one go about replacing a 1in filter box in the ceiling with a 5in? They dont seem to exist or i'm just not looking in the right place.
@wojtek-33 you can get a 4” Aprilaire I know
@@wojtek-33 Do you mean your furnace or AHU is in the attic? You can buy Honeywell, AprilAire, Trion Bear and many other filter boxes. Or are you talking about return air ducts. You can buy filters that have a lip and the filter extends up into the cavity. One brand is Flow Right. And you get get filters at Filterbuy in the custom sizes. So many options available but I am not sure of your setup.
@@Balticblue93 yeah I'm Texas and a lot of homes have the whole system in the unfinished attic with a ceiling filter box in the living space. Of course mine is on a 10ft ceiling so need a ladder to change. It's a pain and it's an odd 24x36. Just found the ones with the lip but they are pretty expensive and almost none for my size. I look into one of the replacement boxes after taking some measurements on my system, maybe it's fine.
Great video. Most installers might be aware of the pressure drop from the filter- if that. They don't know about the other factors such as ductwork.
Thanks as always, Matt
Excellent video!! is ti more important to have a higher static pressure on the supply or the return?
Great work Corbett, one simple line from you cleared up my head. Thanks.
+Kamal Hassan so glad to hear!
Nice video. Very true that most don't check sp. Got a kick out of the 'giant fan' comment! I travelled 9 states for an institutional and industrial sheet metal company living out of a service truck and suitcase. Crane and helicopter picks to get equipment on to rooftops and equipment suites. You could actually crawl into the fans I worked with and pretend you were a gerbil if you were so inclined. Our systems that were designed during the tuberculosis period were set up to bring in 100% outside air, heat it, deliver it to the rooms, and then exhaust it through big vents on the roof. In the 80's and 90's we spent days with saws, Jack hammers, drills, the infamous, back breaking 'wacker', and hammers and chisels opening up primary return air chases, and individual room chases to provide return air - and required smoke and fire dampers. There were variable pitch sheaves and vortex dampers to adjust volume (often upgraded from wooden sheaves and flat belts) Million+ btu burners, oil nozzles (sometimes triplex) that drank gallons per hour, even coal stokers (ever had to clear a coal room to get to an auger's shear pin?), early geo- well water circulated through cooling coils, enormous compressors for DX or chillers, huge pneumatic or motorized outside air, mixing, and exhaust dampers, Chai pull, pneumatic, and now ddc controls, and single draft inducer bearings at power plants that weigh more than an entire residential furnace and dx cooling system combined. Had two boilers in a school in Ashtabula ohio that had come OUT of a great lakes steamer in the 1930's. Had to convert them to gas. The last boiler man in the district that knew anything about coal was retiring-- had that scenario at schools all over as coal was being phased out. Remember back in the 80's when one of our sheet metal guys dropped a tinners hammer from a catwalk from duct big enough to drive through at the Ohio Theater in columbus ohio. Just missed the organ. I was often serenaded by Dennis James on their 'Mighty Morton' while performing pm there (35' × 16' filter area with electronic cells and automatic static pressure controlled feed for oiled prefilter rolls {talk about an itchy job!!}) The low notes on that organ would make your innards quiver like the bass guitarist Chris Squire's low notes in Yes's Starship Trooper!!
We subcontracted companies that came in to confirm the balance numbers that our engineers had come up with. Our company had been founded in 1867. After merging with a pipe fitting company it took less than 3 years for the new rape and run business model to run it into the ground. They didn't like that I objected to their business approach.
Have worked on that little stuff from time to time-- got cut on one of those itsy bitsy zip screw points or a rough cut sliver of metal just about every time I had to try to squeeze my hands into that stuff or work around that light gauge (aluminum foil!!) duct! Lol.
Put some give a damn in your work and you'll build friendships that last a lifetime.
Was a great trade.
Thank you for this helpful video. I am a homeowner looking to learn. On those pressure probes, it looks like they just face into the airflow and it doesnt matter if the hole is "sealed" by the base of the probe where it enters the ducts or am i wrong on that?
Hey, just a heads up from someone who checks static pressure often on gas furnaces, there is a hole into the heat exchanger available after the blower that the manufacturers make for us, just remove the primary limit switch, I prefer NOT to drill holes into equipment if it is unnecessary.
+Sightthrough, if you test at the high limit switch hole you will get a higher than actual TESP reading, since you're also picking up the top of the heat exchanger.
Hello Corbett,
First off, way to nail it, great presentation, period!
Please bear with me on my question... I hope it does not appear ignorant. How would I check down flow ( mobile home furnace ) filters are attached to backside of door and in this particular case, this unit is about 22 yrs old and does not have central air. There is an exterior independent a/c unit. The back of the Furnace obviously is in the cabinet ( closet ) all ignition, flame sensor, are internal and completely enclosed. Blower is in your face and completely exposed.
Thanks,
Jerry
Wow, Jerry, good question, but I don't have an answer for you. No experience with this type of unit. Check out this vid to find a way that might work: th-cam.com/video/9vwmP1T2ReI/w-d-xo.html
Hello Corbett!
Thank you for taking time out to respond and thank you even more for taking additional time with further assistance. Have a great day!
Anytime, Jerry- thanks for following!
@@HomePerformance You bet!
Thanks for this video! Very informative, especially after my boss asked me what external static pressure is 😁
PERFECT FORM, ZAMBONY
Great job Corbett! You are extremely articulate and able to convey complicated subject matter in an easily understandable manner. You could easily be a TV personality on one of the DYI channels!
I’m assuming the drilled holes should be sealed using metal tape?
+Paul Mac thanks! We actually are releasing a TV show called Home Diagnosis in 2018! Yes, metal tape works, or metal plugs.
great video lets see more on static pressure
You tart how to test that furnace really good and I thank you for that.
Tanks Tommy
very good descriptions in common language that help visualize airflow...
+hvac01453 so glad you liked it!
I'm curious. Why do you have a $1500 manometer, but only a Ryobi drill? (Kidding.) Thanks for the video, I'm new to the field, just finished A/C season and I'm heading into furnace season.
Haha, and I still have a few shirts from 15 years ago too. Welcome to the whole house practice, hope you get your hands on a blower door and start showing up the competition!
I have been doing this for years in the memphis area, I am not only a contractor, but an Instructor at a tech school as well. I try to teach my students these principles to commission units and use a blower performance chart to set proper airflow for A/C. The sad part is the majority of homes run .8 or higher. Those 1" pleated filters are horrible for static. I recommend nothing less than a 2" pleated for single filters at the furnace base. Jack Rise from ACCA taught a class here years ago and called Memphis the land of no return. He was right! After seeing very nice homes with 2x4x16" wall stacks and builders trying to get 2 tons of return in two cavities! The installers in the area have no clue, the builders want the cheapest, and the homebuyers say look at the granite countertops and saltwater inground pool. Next thing I'm telling them the ductwork was done by a doofus because they aren't comfortable.Keep educating! I just replaced a 7 year old system on a new house because the plenum had a 4"x22" hole in it in the attic where it was never sealed! Keep calling out the shoddy work! It's not opinion if there is verifiable performance! Oh, sometimes I can't drill an old furnace in a closet, I normally take out the limit switch for my probe, not ideal, but works!
+Jesse Johnson you rock brother. Keep up the great work in TN- the world needs you calling out doofus work! See you around I hope- we're not far, in Atlanta now!
PS +Jesse Johnson : my 6-week mastermind course might be useful to your students or colleagues HomePerformance.training Starts 4/1 and registration begins 3/1
Jesse Johnson I'm in Nashville and I see a lot of the same. I actually got cussed out the other day by another inspector of all people because I wrote up a 5 ton system pulling from one 20x30 return filter and a 10x15 run. The static pressure on the return alone exceeded .5" which is the max on the system allowance. You just have to walk away and shake your head at some people.
What a great video, thank you so much. The furnaces in both of my houses had no ports for measuring?? but they do now.
+john clark you are officially one of the illuminati. Welcome.
Usually I'll pull the limit if the hole is too big I'll put metal tape to make up the space for the magnetic static probe and of course for accuracy . Not all but alot of times in California at least drilling on the side is a real task sometimes the limit is the only answer . Great video
Agreed, if the limit access is the only way, do it!
Great video. I've done some drilling into plenums and ducts before for testing but never into a unit and below the coils. Any rule of thumb as to where the coils sit in most units so hitting them when drilling into the units can be avoided?
With all of these tests, would you have pressed the “diff” button on the manometer to see the pressure drop from any one location to another?
Great video! Thanks for educating! It made all the pieces fall into place! Sometime a video makes sense when the books dont!
Question, when measuring the pressure across the coil you subtracted .07-.21=.14. When measuring across the furnace .38 + .21= .59 for the furnace you added your two different pressures but across the coil you subtracted. Not sure why you subtracted one and added the other.
I agree with so many others on here that this was one of the best, easy to understand explanations and demonstrations for basic testing of static pressure with some great references to industry standard measurements such as drop across filter and A-coil etc. Thanks for sharing! I'm actually trying to determine airflow in CFM for my 3-ton heat pump system to see if it is meeting the required 400cfm per ton which would be a total of 1200cfm to work properly & efficiently. I'm finding that determining airflow accurately without expensive testing equipment can be a very difficult thing. And the results of low cost instruments can vary widely.
So, what I might share for those on this elusive hunt, are 2 things: 1 is figuring airflow by using a similar probe but with additional tubing connection (Pitot tube). It works the same but collects 2 measurements simultaneously static and velocity. To get an accurate test a series of holes (travers) are drilled across a section of ductwork at predetermined spacing and a timed and averaging is done and then a bunch of tedious conversion mathematics which seems like a lot of trouble. The alternative using this instrument is a single hole in center and an averaging multiplier of .9 is used to get within +/-5%. Another method listed below blew me away and I'd like to hear comments on this. It utilizes a simple formula using volts, amps draw and temperature rise to determine airflow. I've included a link to the article
library.coburns.com/HVACTechTips/Calculating%20CFM%20Coburns.pdf
+Tie Dye thanks for sharing! Here are a bunch of other airflow test techniques: th-cam.com/video/45gX7Jb60JM/w-d-xo.html
So how do you know what the pressure drop is supposed to be across an evaporator coil if it is not part of the furnace itself? Also how do you know what the pressure drop across any filter should be?
Manufacturers put that info in the install manual, for both coils and filters.
I tell what man. You're a mentor to industry! Dang ole truth is we're all idiots! What we know we inherited. Inheritance requires discern you know what I'm saying man. Calling out the kind from the swag and tossing the bunk under a bus. There may have been a TESP performed on an AH w/out a hole. Some techs remove the limit switch, and testing from there, but doing this will give you a higher reading because of resistance (top of heat exchanger) I try to replace the filter before I test. 4" media filters w/higher or lower merv values also tweak your #'s. Dang ole beer can cold vets deserve respect, but after 20yrs thinking your right when you were actually wrong. I'd respect the man who pointed out this reality proving to me why I had been mistaken. Corbett I think in the future your name may be as recognized as Bob Vila's was 10yrs ago. So if you become the TV host for this new house? I'm applying for a job!
+MrTommytabasco wow, thanks for the kind words brother! You made my day!
Never thought I'd learn as much from Jeff Goldblum as I've learned today
Life finds a way
Great video!!! now i understand a little more. I will appreciate your advice though. So, i have a new air handler and new ac condenser unit (replaced).Since the installation 2 weeks ago, air flow has decreased noticeable in the third level of the house only (it's very weak). I have it checked (no testing as shown here whatsoever) but the response of the technician is that it's normal. Now, i wake up in the middle of the night sweating, and I also have two fans in my bedroom. Finally, another company is coming this Saturday to check the "blower" (after doing some research that's how i explained the problem). Which should i "demand" from this other company in order to have the unit properly inspected and diagnosed? Thanks in advance!
Hi Priscilla- sorry you’re having trouble, but glad you found us! You should try and find a diagnostics company that won’t have an agenda of selling you HVAC equipment. Go to: HomeDiagnosis.tv/pro to learn to find these companies in your area.
@@HomePerformance Thank you so much!!!
Wow!What a great teacher you are. Thanks.
Hey, what a nice thing to say! Thanks!
Fantastic job. I now know what to look for to resolve my problem.
So glad to have helped!
You said if you dont see a hole on the side of the furnace your contractors are bad. What about removing the high temperature limit? Everyone I know uses that when they can to avoid drilling holes.
Yes, that can work, but it’s guaranteed to give you a higher than actual reading of TESP. And based on my testing history with hundreds of systems, I feel confident most contractors are never testing this. If they ARE, they should be showing that they pass on the unit, alongside all the other stickers on there.
Thank you, bravo , excellent job at explain in layman's terms so our consumers can get a better understanding of what should be done on every installation. It's too bad the majority of technicians installing furnaces do not even know this, at most they just seen pictures in literature but never had their bosses actually run them through it and explain it to them so it never gets done and the customer usually ends up with an inferior install. Thank you for all your effort and passion to educate people about the subject.
Thanks so much for your message, +t lech, I'm happy to be helping the world move forward. Back atcha!
i got a 4ton for 1300sqft thats 350ft per ton in southern Nevada easy 115 degree days, i aim to get 1600cfm and my filter is 20x20x1 side by side for a total of 20x40 filter return. i currently use the honeywell HD merv 11 filters but i think ill start using the 3m 1200 merv 11 because of the more surface area on the filter to help decrease static pressure if that doesnt help ill try to use 4in filter
Absolutely the best explanation I've seen on TH-cam!!!
Thanks Parnell! Glad you found us!
Hey Corbett. Great video!! I hope you can answer me this though. Every video on you tube shows how to measure static pressure and that it should be at about .5"wc for most residential units. However, I cant find any material on What just the return pressure should be. Or what just the supply should read. In other words, what if I have a read of total static pressure of .7"wc. All I know is that it's high. What pressure should I target in the return or what pressure should I target in the supply?
You briefly touched in that .14 is average for the a/c coil and that the filter should be at .1"wc.
And then you mentioned that at .19 the return was high and .07 the supply was low. But again I dont know what to target. If you could help me understand this I would really appreciate that. Or point me to material that I can read to further my knowledge in the matter.
Thanks!!
Sure- ductwork is designed to pressurize to 0.1” or .08”, that should be ret and sup. And you don’t want TESP to be .5”, you want it UNDER .5”. So .1 for ret duct + .1 for filter + .1 for coil + .1 for sup ducts = .4”
I've been in the industry for a year, I was told that yes you shouldn't have more TESP than what the manufacture says but was told by my seniors that you're allowed a little wiggle room (.1-.15 more than the static pressure) because of the filter. Some customers prefer certain types of air filters that will increase the static pressure. Are my seniors right and what do you do to compensate for the thicker filters?
+Kyle Rae great question! Just think about the fact that it’s a pass/fail test. If you’re over .5 even a little, you risk another pro telling your client you don’t know what you’re doing. The old school guys are used to nobody checking their work, but once your client thinks you lied to them one time, they will never hire you again. Remind them that TESP includes the filter- the filter doesn’t get added later as fudge factor. If a homeowner wants a higher MERV filter, they have to go wider media or upsize the return. Keep up the great work challenging the old rules of thumb!!!
Your fan motor doesn't care about anything other than the TESP, filter or not.
Couldn’t have explained it any better. Thank you!
Hey, thanks Ronald!
Excellent presentation on subject.
Thanks
I’m conflicted if I can move up to a MERV 13 furnace filter. I believe I have a 2 ton gas/AC furnace. Any suggestions would be great. Hell, I’d also like for someone to test my system’s static pressure. Any certifications I should look for in company? Cheers, great video.
Sorry Pete, no certifications for this one, but you can search google for it and maybe find somebody who’s trying to be better than the rest. If you go with a 4” pleated filter then absolutely you can.
@@HomePerformance I actually have a 20x25x5 inch pleated MERV 10 furnace filter right now, but I’d like to move up. I think I should be ok. I’ll tell you something crazy though, I just found significant water vapor damage inside of my wall from the microwave “range hood” over the stove, which some how is blowing inside of the wall. I can hear the wind in the wall from the other side when it’s running. I look at the best mold inspectors in the nation’s reports for a living and I have not seen this source area to date yet. Talk about negative pressure lol Thanks for the reply btw.
Yikes! Sounds like they forgot to cut a hole in the sheathing- half a job done is much worse than none at all in that case.
@@HomePerformance I thought there was an exhaust line out the top of my roof. None. Just blows right in the wall…
Great video, my question is: when you check for static pressure do you run ac or only the blower fan, can it be check when the heat is on?, the reason i’m asking this is because multiple speed blowers won’t work on a full speed if you just run the blower by itself, thanks for your time...
+Diego Lopez great Q. In the appendix of my book, there are a few methods for tricking the blower to run in AC mode, which you’re right is generally the highest speed. Important in my opinion to know the performance at different speeds, but if your goal is TESP no higher than 0.5, then yes, always test on high speed.
Home Performance Diagnostic book?
+Diego Lopez bingo! HomePerformanceBook.com
Hi, I'm a homeowner that just had a new packaged unit installed and replaced the duct work as well. I noticed the return vents whistling and pulling more air. I contacted the installer and they wanted to change the type of filter or return grill. I'm concerned that the duct work may be improperly designed. I'm going to ask them to perform the test but I want to understand if changing the blower speed setting is important because they recommended changing it.
Its late 2019, and this video is still wonderful !! Do you plug the little drill holes when not testing so they won't whistle?
Thanks Bruce! Yep, you can get metal or plastic plugs, or just cover with metal tape.
If the whistle, that's another sign you might have static pressure too high!
I disagree with the point you made about not calling a company just because there are not holes driven into the furnaces.There are a static pressure readers into the new furnaces
There are a lot of hard working companies that have been providing exceptional service and hard work and you are telling people not to call them back.It not true
So you’re saying that most HVAC companies are testing and tracking this? Why do almost all readings exceed the limit?
Have you ever watched How It's Made? It would take a lot to add that whole to the manufacturing process.
Exactly!
how much should i pay to get this test done, since i dont know how well the 25 year old ac unit is performing. reason is i will be getting a brand new unit and i want to see before and after performance results.
Just make sure it’s in the contract for your install, and they can test the old one before taking it apart. It takes only 10 minutes, as you see. Maybe $100 if they know what they’re doing, maybe $10,000 if you’re scaring them.
Is the best way to measure pressure across the filter if you have wall grill filters, to measure the room pressure and make that the delta? Or is it better to remove the filter?
Don’t you have a book for sale? Also, my unit is in my attic with a 4 ton coil but I want to install my new unit in my garage 9 foot below. 18” Return with a 14” and a 12” Supply coming off the plenum. Any thoughts?
Yes, my book is at:
buildingperformanceworkshop.com/homeperformancediagnosticsbook
And your ductwork can easily be redesigned if needed, to put the equip in the garage.
Thank you and I look forward to getting your book. My other question is when dealing with existing ductwork then when you find problems how would you suggest we correct them without creating a huge cost to the consumer?
The consumer gets what they pay for- if they see the benefit, they won’t need a lot of convincing on cost. Several ways to seal ducts, depending on situation.
-Fan stops blowing about once a year.
-Techs change out Emerson controller board. Problem goes away for about a year each time.
-New tech actually tested total static pressure. He reported the the total is .7. Unit label says .3.
-He says the static pressure is damaging the board and recommends 10k duct work.
-We can temporarily work around the issue and get the fan to run again by disconnecting power from the controller board for a few minutes.
Does this make sense that the circuit board can be damaged by incorrect static pressure? What do you think?
Now we're getting somewhere. Excellent explanation. That's the stuff most AC guy's don't want you to know.☺
Thanks Will
Ok so after I get static pressure reading? What do I do with that info? Is there something to adjust if we are low or high on static pressure? I guess you would want to check airflow before adding refrigerant.
It’s a forensic look at whether the ducts were designed properly, and if you have problems in one particular area. Surgery would be required generally.
Sorry, I do have one more question if you are nice enough. Out here we have our airhandlers (furnace and A coil and ductwork) in our attics. There is a movement when they are replaced to move the unit to the garage so maintenance is easier. How would you suggest setting up ductwork to have the proper pressures? The original ductwork would remain in the attic but the unit would be about 9 foot lower and 6 foot away from where it was? Also, most attic ductwork is flexible but metal would be run to the garage. Probably too much but at least I tried….and thank you.
Thank you for this most informative video. I am NOT hvac saavy,but my understanding of it's basic principles,has now been thoroughly upgraded from OH?,to I understand what your saying. Life is good! Be well,friend.
Awesome to hear, buddy! Thanks for your feedback!
Great breakdown of Total static pressure. Thanks for the video!!
Rock on, +Michael Simi !
I am working on a tenant complaint about AC cooling not being good enough. This is for a an upstairs duplex apartment unit. The evap is getting nice and cold-maybe too cold. I think the fan speed for the cool is too low. Right now the cool for the motor is on the BLUE (Med-Low). And the heat is on YELOW (Med-High). I alway heard that the cool speed should generally be faster than the heat speed, so Im going to switch the two so the cool is Med-High and the heat is Med-Low. Will this help solve my cooling issue?
Good q, but you have only one data point. I’d want to know temp and RH in the apt, actual airflow thru the indoor coil, whether the unit is sized properly, air leakage of the apt walls, ceiling and floor. You could mess around there for years, or solve the problem in one visit if you test. Check out my interview on the HVAC School Podcast:
www.hvacrschool.com/blower-door-testing-building-performance-w-corbett-lunsford-podcast/
Excellent content and delivery! Thanks.
Thanks for watching, Chuck!
Very informative video. Does “away from the fan” mean on the side for which the fan is blowing towards? Thank you.
It applies to both sides of the fan.
@@HomePerformance got it! Thank you. Makes sense now.
So when you said balancing the system,the total should not exceed .5
But to be there or under. So my interpretation is not that supply is .25,nd return is .25 but that what the combination is should not exceed the manufacturer s
Number??
If I got that right,your tutorial was excellent.
Please let me know 🤔
Exactly, James. Thanks for watching, glad you enjoyed
Good explanation. I just had to fight with my installer to do the commissioning testing shown in the Lennox installl manuals. Lennox's detail shows one test hole in the A/C coil compartment and the other between the filter and the fan for total static pressure. The installer chose to use the supply plenum ( after coil) instead. I would think he's missing the restrictions caused by the A Coil and would get a lower reading. How important is it to be before the coil?
Very
I may be misunderstanding what you're saying at 9:20: in this setup it appears that the filter is After the furnace blower fan. Shouldn't the filter be on the suction side of the blower fan?
I am planning to use the pressure drop across my air filter to determine when the correct time to change it is. I have a set of pitot tube and required hardware to install them. I plan to but 1 on each side of the filter. That said, this mean one pitot tube will be located in the blower assembly of my HVAC system. Based on where I have seen in your video and others, the static pressure should be somewhat constant. Since this is a home unit, I do not expect a large variation in pressure across the duct and plan to use only 2 pitot tubes. With one on each side side of the air filter, located in the center (side-to-side) of the duct and about 6" into the air flow.
Other than ensuring I am on the correct side of the blower fan, is the location of the pitot tube in the blower compartment important for measuring the static pressure?
+Grover D first, I assume you mean just static pressure probe when you say 'pitot tube'- a pitot tube also measures total pressure, which you won't need.
I'd sample a few places in the cabinet and all different directions for pointing the probe, but yes, it shouldn't matter much.
Hope you can point me in the right direction. Just checked my furnace, heat only no AC, and I am getting .07 on supply side, and .48 on return side. Total is a little above .5, but the fact that I only have .07 on the supply side seems very wrong to me. Where should I start looking for issues?
Replace the filter first. Heating mode is often low speed on an air handler, so don’t be too concerned with the supply reading for now. You’d also want to take temps in rooms and airflow out of vents and thru system to get the big picture.
@@HomePerformance Thanks for the quick reply. I replaced the filter before even checking. I am pretty sure a ton of junk fell into the floor returns when the previous owner opened the walls up and the blown insulation fell out everywhere. I'm guessing that is why the return side is so high. Is there a way to force the air handler to blow in a higher mode to make sure I am able to get higher supply pressures?
Hi Corbett just makin sure now, the friction rate is on each manual of the air handler depending on the speed of the blower? And we have to match that friction rate based on how we calculate sp, pressure drop, equivalent length, etc after the design is complete correct?
Whoa Ando, you’re losing me- but I will have some HVAC design courses coming online soon.
Hi Corbett, so basically just wanted to confirm static pressure is the resistance of the air inside the ducts and pressure drop is? If you can just summarize the two meanings for me I would appreciate it.
Resistance to the inside of the ductwork. And p drop is the differerence in static on both sides of an obstruction.
Cobett, hey I have some questions. 1. Do you have a "field cheat sheet" on this? 2. What state is this test supposed to be run. ie; start up, steady state etc...? What about negative pressure or positive pressure is that a factor here?
Hey Michael- APT Reports has an automated section for this test. No need to run for any length of time, as long as the fan is running at the speed you want to target (usually high). House pressures are insignificant generally compared to blower induced pressures.
Hey Michael- APT Reports has an automated section for this test. No need to run for any length of time, as long as the fan is running at the speed you want to target (usually high). House pressures are insignificant generally compared to blower induced pressures.
Thanks for the video it was very educational and helpful. I have a Carrier 58mca-060-16110 furnace with air conditioning installed in a small room at the center of the house with grates in all the walls to the surrounding rooms(house is on a slab and doesn't have return ducting). The filter is mounted on the side of the furnace(one side exposed to the room) and sucks the air directly from the room.I have a digital manometer and want to check pressures on the furnace. I have a few questions if you don't mind.
1. Does the one probe need to be held in front of the filter or just anywhere near the furnace. Or is it needed at all, at least for the filter drop.
2. Does the probe inserted above the heat exchanger and below the evaporator coil need to be anywhere specific in the space. My coil is offset to the left side directly over the heat exchanger (no room to insert it) but there is a lot of open space to the right of it that's probably not directly in the airflow.
Thanks
Hi Norman, thanks for following. The pressure in the room at large (before the air hits the filter) will be zero. No need to measure that one.
And you must insert the probe BELOW the evap coil's drain pan for sure, but it shouldn't matter if you're in the air path or not, static pressure is like a balloon's pressure, it should be pretty even everywhere in there.
good question everyone, so if you have a roof top packaged unit and want to calculate its external static pressure, do you consider internal pressure drops due to filters and coil? Or do you only calculate the pressure drop due to duct system?
Thank you for this great video ❤. Very informative