33 years in the HVAC trade and I’d say this was the best explanation I’ve heard. Too many companies are trying to promote IAQ through the furnace and I don’t agree with that method, the way I see it is in order to use the furnace for IAQ you need to add more returns to the system and it can get silly in a house. IAQ is all about air changes and being able to move the air throughout the house not just one section of the house. I’v actually been recommending a MERV 8 or less and tell people to use room HEPA air filtration. Don’t get me wrong I can design an air cleaning system for a house but most people aren’t willing to pay for it.
Great Channel! Thank you for sharing from your wealth of experience. Great to hear from someone not trying to sell you a new HVAC System or some unnecessary & expensive Parts Replacements. The major problem I have is with DUST accumulation inside the house, yet we keep windows/doors closed always. I have tried all grades & efficiency-levels of filters. As you said, the higher the grade & more expensive, the more they impede air-flow & blower-fan, and causing so much noise through the return-air plenum, loud 😂bough to disrupt sleep. The dust-problem is a nuisance - one day, you dust-clean the whole house and the next day or two, everywhere is covered with dust again. Any ideas on how to deal with dust problems? Thank you. - Nigel
Doesn't get cold there, so you can get away with that. Try that crap filter living on the prairies in 6 months of real cold. You'll have 4 inches of dust all over your house.
All is perfectly explained. I would add two things: 1. It doesn't matter, which MERV you use, if it's clogged, you are running at MERV 20 pressure or higher )) 2. It really matters, which filter system you have. If you have 1 inch filter, sure, it matters, merv 8 or merv 13, because it's not much of profit from ribs added. BUT if you're at 4-5 inch system, it doesn't matter, because the static pressure is really low at those filters.
Thank you for this video. Your explanations are quite clear and concise. As for my experience, I put in a Merv 10, and my furnace worked improperly. I have a new house with one of the cheapest Trane furnaces available. Works fine with no filter. Now I’m going to try a Merv 5. Thanks, again, for your expertise.
The thickness of the filter is also relevant. My Bryant unit had an insert that could be removed to allow a 2-inch filter. That will lower static pressure due to the increased surface area, and they will last three months.
Excellent information!! Perfect explanation for us less knowledgeable individuals about an important subject. I’m going to build a box fan filter with a Merv 13 to save my furnace but still get good air filtration. Maybe 2 or 3 once I make 1 or 2 for the shop
I live in central Idaho and every year there are forest fires either here in Idaho (most of Idaho is BLM forest) and/or Washington state and the far reaching smoke sneaks into the house making for unpleasant smelling air. My furnace calls for MERV 8 with strong caveats against anything higher which is fine the rest of the year. With some trepidation I started using 3M Filtrete MERV 11 filters during these fire events and they cleared the air perfectly for me. However in the back of my mind was the fear of furnace damage. This gentleman's fine presentation has removed most of my angst over the occasional use of MERV 11 furnace filters for interior smoke mitigation. Thank you sir!
My take - I have a 2-story colonial, 2150 sq ft, no pets, non smokers, no kids, well insulated home in upstate NY. I change furnace filters depending on the season. During the winter heating season (Oct - March) the furnace filter (FulterBuy MERV 8) is changed every 2 months since it is running more often but the house is closed so there are limited outside contaminates. In the spring (April - June) I use a MERV 11 when the pollen and cottonwood are flying everywhere. The HVAC is not running as often and is off most of the time, just a few heating and cooling days depending on the weather but with the windows open stuff gets in. I change the filter (back to MERV 8) for the summer cooling season and the AC runs about 5 hours a day for 25 days at the most. My goal: maximize air flow, minimize the time HVAC is running and reduce wear and tear on the HVAC system. My last HVAC system lasted over 24 years without a single problem and was only replaced because of other factors.
I agree with every thing you said except the part about the blower using more energy with a restrictive or dirty filter. A PSC motor will use less energy with higher static pressure. I am not saying thats a good thing in any way. If its not moveing air its just free spinning and pulling less amps. This however does not apply to an ECM moter because it will just keep ramping up till it reaches its limit in an attempt to move more air. Under sized duct work is way more of an issue in most HVAC systems. And I always tell customers unless its newer duct work designed to move the cfm modern furnaces require to never put in anything bigger that an merv 8 and that applys to 5 in filters if it a one inch filter even less. Checking your temp split is the best way to find out how high of a merv you can get away with. And always make sure all your registers are open and your returns are not blocked. Shutting registers will not save you money. A furnace is sized to heat your whole house. Your furnace does not now or care if you dont use all your bedrooms cus your kids moved out. A simple temp rise will let you know how many you can get away with closing. I know most of what i just said has nothing to do with filters but in most cases more important.
Very insightful observations. What should the temperature difference be between the air going in and the air going out, for heating or cooling ? I see the furnace maintenance technician measure this but never thought to ask why he did that. I’ve got a small digital probe thermometer and I’ll check mine out.
@@lanarkwanderer I don’t know why that is measured. When my unit is serviced for summer the tech checks the temp at the register in the room to be sure it is cooling enough. Maybe some techs on here can provide some insight?
Place more load on ANY motor and it uses more energy. You cannot get more Nm of force at no cost. Bicycle, EV, heat pump or furnace there is NO free ride my friend
Good practical explanation thank you. I bought a 3 pack of higher MERV filters, but when those are gone I will go back to the MERV 7 true blue. About $3.00 apiece at Menards.
Well done ! I try to tell people to compare this to wearing two mask because of fear of Covid and how that would filter out the potential bad air and virus but then the side affect of leaving you gasping for air and making your lungs and heart work harder.
I just got some 10's, but I only run my system in the winter months (three months for a few hours max a day). The two filters never turn color but replace them once a season.
Nicely Done Good Sir! Was about to pull the trigger on buying a MERV 13 lifetime washable filter as it obviously sounds good. But now listening to your great tech advice, given the cost, the load on the motor and that I dont have the issues to need such filtering. There famous cold air auto filter company makes a Lifetime Merv 11 as well so Ill see if that works. Nicely Done, Very Nicely Done, thank you!!!!!
This is so helpful!! I've spent so much time trying to figure this out, and I really appreciate your insight as a professional and someone who's worked in the industry. Thank you!!
I always recommend to my clients to use a MERV 8 and not more than a MERV 10. I explain to them that if they truly want air cleaning quality that the filter is not what does that. I recommend HEPA systems with UV lighting . Your explanation is one of the better that I’ve heard , thank you.
I use a particle counter, dylos 1100 pro. Pleated filter was good for 18 months. One day it was filtering fine, next day not at all. It was ugly, but working fine. No issues with a/c.
3M Merv 5 here. The fiberglass in my opinion allows too much small dust, even when changing every 30 days. The Merv 5 seems to be the best balance for dust capturing and air flow. I used Merv 13 filters in a separate air filtration device.
I have some seasonal allergies. I tried a merv 11 filter but the ductwork whistled. Bought a magnetic dwyer utube manometer. I was running .8" !!! Furnace was cycling on high temperature cutout. Installed a 5" filter frame and a merv 11 filter. Allergies all good, filter DP at 6 months was .3". I wouldn't recommend any more restrictive filter unless you can see the DP it creates. Cheap Utube manometers are about the price of a good pizza, and are always showing a reading so you know how restrictive your filter is getting.
I just bought an fpr 7 hdx air filter. We have a carrier system installed in 2012 with 1 cat and 1 dog. It says this is equivalent to a merv 10-11. Thoughts? Just dont want to harm the system
i use a regular cheap figerglass filter and i change it every month is that ok or am i hurting my hvac system ...i dont have pets or smoke or dust or alergies .....the reason why i use the cheap ones is because i find that with the cheap filter my vents in the house are able to blow more air and circulate the ac or heat better thruout the house and when i instal a nerv 8 or 13 my ducts barely push air ,,but with the cheap filter my house stays cooler and hotter depends on the season ...am i hurting my system by using a cheap fiberglass filter ?
Under the conditions you describe you are not going to hurt your system. Keep changing your filter monthly. If you do want more dust capturing 3M Filtrete has a MERV 5 on Amazon. I have a video on my channel.
3M is a highly static charged filter. U of M turned them down after test showed efficiency dropped 33%. MERV A rating is what counts for efficiency. I work for Camfil
My furnace shut down and would not restart on the lowest range pleated Merv. I had forgotten to change it for 2-3 months. HVAC guy had to tap the auto reset to get it to work again and told me to get the Merv 4 fiberglass for the best results. Said it was even ok to use for 2 months instead of 1. Fine by me! He recommends that kind to most of his clients.
I have a Aprilaire 2210 whole house filter - which has a 20x25x4 replaceable filter. Can you speak to the restrictiveness of these deep filters and how a typical 1 inch (at say Merv 7) might compare to a 4 inch deep filter (at, say Merv 11)?
@@FurnaceFilterTalk That's right, a1inch filter needs changing ounce a month, while the 4 inch filter will be good for 3 to 4 months. The yearly cost of replacing the filters is about the same for both.
This must be why my house has a 2000cfm return grill on a 1200 cfm system. I was very confused on why it was so large. Nice idea with the builder though as you can do a merv 13 filter 5"thick no problem.
First, people need to understand that a furnace filter is there to protect the furnace blower and heat exchanger/air conditioner evaporator. It wasn't originally intended to be a whole house air cleaning system. The filter companies created the higher priced filters to expand their product line and generate more profits. If you really need much cleaner room air due to medical conditions, consult with an expert who will most likely recommend a stand alone HEPA system. That being said, I've always found that the standard fiberglass furnace filters don't keep the blower and heat exchanger/air conditioning evaporator coils clean enough. They might strain out small rocks, but plenty of fairly large particles don't even slow down going through one of those "filters". Merv 8 is the minimum I consider acceptable. Just my humble opinion based on my personal experience.
I disagree with you. I worked my whole life for filter manufacturers and companies put a lot of money to develop higher Merv filters that won’t hurt a furnace. Things have evolved.
Residential furnaces TOTAL static is .5”. That is .25 on the return and .25 on the supply. You also have to figure static loss of the ductwork, which leaves very little for filter pressure drop.
My hvac says 1” filter but the space is so big that I have fit a 4”. Wouldn’t a 1” be floating in the space with the air pressure reducing the filtration ?
Man thank you on this. I bought some massive 3M 2200s that were a lot of money but I was worried. I haven't opened them yet - going to return them and buy just a 3M 1000. My house is super dusty and I sneeze a lot so I need something more than a basic filter but I clearly went overkill.
Hi thank you for your video. I would like to comment on your thought that a restricted furnace filter requires more energy. I’m speaking strictly about the furnace blower fan. It is a fan, not a positive displacement pump and as such, it draws its maximum power (amperage) when its moving the maximum amount of air it can. The less air it moves, the less it’s energy requirement. In other words, the more you restrict its income air, the less air it moves and that equates to less energy required. Thanks
But the longer your system operates due to a more restrictive filter the more energy is used to cool the house down and shortening the life of the system.
This is incorrect. Most homes operate at 300 FPM and a dirty filter causes the blower to work harder and use more energy. Take a look at www.energy.gov/energysaver/maintaining-your-air-conditioner for more info.
Added comment, "True, I am a mechanical engineer". I am referring to the comment that "less air flow requires less energy". This is true. Based on fan curves and fan laws.
That’s true, a centrifugal fan powered with a permanent split capacitor (PSC) motor will unload (use less energy) as the filter becomes more restricted by dirt or is operating in a poorly designed and/or installed duct system. However, some newer furnaces have electronically controlled constant volume fan motors (ECM). These motors are low wattage by design and use less energy than a PSC, all things being equal. But, when an ECM detects the airflow it’s programmed to maintain is falling off, it ramps up (speeds up) in an effort to maintain programmed airflow. When the filter is dirty or too restrictive or the duct system is wonky or all of these things combined, the ECM will use as much or even more power than the PSC motor. Not only that, the system becomes louder…perhaps a good indication the air handling system is in distress. In the end, an air handing system should be properly designed for restrictive in-line filters. Consider using a bypass filter like Amaircare, uses a bit more power but has no restrictive effect on the air handling system.
I have five filters in ceiling returns. 2 20X20 and 3 14X14. Really only the two in the more lived in area ever look dirty when I change them. If they will fit would it make sense to use 2 or 4 inch filters to have more serface area with the higher MERV at least in the two areas that collect more debris? Thanks.
If your unit is in a closet with one of those louvered closet doors with the slots you can put the more restrictive air filter on the back side of that door (the air handler side)
Would using a 5" Nordic MERV 13 help with the pressure drop? I use the 5" one with the really deep V pleats and I always thought the increased surface area helped with that. Never had a problem and I change them every 60-90 days. I used to use 2" filters and I realized the box would take a 5", no looking back.
2 high efficiency furnaces in 3 homes I bought in past 7 years are baked in with the thick filter slot (5 inches!). HVAC guys just seem to install the thick slot standard now. So us homeowners are being forced into thicker filters.
Not sure if you're not liking them, or liking them. The poster of this video didn't explain that part very well though he mentioned pleats for a bit. Those thick filters are way better than the skinny ones. The filter material is folded into pleats. If you unfold them, you'll see a much larger filter. More surface area = more filter material = longer life, better flow. So per month your cost should be lower, not higher. I wish mine had a 4 or 5 inch filter. Instead mine is 24x24x1.
@@Gersberms No argument here. And yea, there's more media in thicker filters. I'm just parroting that lots of folks keep saying "thick filters kill furnance fans". No they don't. Very high MERV -- at whatever thickness -- could kill any fan.
@@Gersberms I have the same size filter as you do in my home. I now purchase a Practical Pleat 24 X 24 X 5 filter from discount filters. A tremendous difference in air flow and IAQ. I pay approx. $60 a piece but they last 6+ months.
Which filter would be less restrictive: 16 X 20 X 4 MERV 11 or: 24 X 12 X 1 MERV 5? I can put the large filter in my A/C unit in the attic or put the smaller filter in the hallway ceiling. Thanks for any assistance.
Our electronic air filter stopped working, I was told to buy a filter 20 x 25 x5 filter. Still now I did not know Merv. The filters are meth 13 ,after 4 or 5 for heat I can still see light thru them. Am I messing up?
Very Interesting 🤔 most of the 3M MERV 5 filters I have seen have .47” pressure drop or “intial resistance” published right on the filter. What is your opinion on that?
I put in a 20x30 oversized return air box so i am not using 20x20 filters inside unit and i got 5 inch thick filters that fit inside the air return box so it has almost no air restriction
Would you say it's fair to stay that one should give a month of usage per inch thickness of a MERV 13 filter? So for the typical 2 inch filter, change it out every 2 months, for a 4 inch filter, change it out every 4 months and so on?
I always wonder what to do, i have 2 returns and a filter space right before the fan/evaporator, right now i have 2 merv 5 in the returns and 1(4inch) right before the evaporator but don’t know exactly what is the best combination
Sounds like a good setup. Maybe use a higher MERV before the evaporator based on if you have pets or allergies or just want less dust. Consult your HVAC tech to be sure.
If you have a woodstove or fireplace, change filter every month if you run merv 10 or higher. Or twice a month if you burn alot. Protect your hvac system.
Yes I change my filter monthly for our daughter's allergies. Using a 13 currently but when I check my filter with a manometer it starts at a 1.23. I feel that two high for my furnace with a listed max on the data plate being .7. What are your thoughts?
I have a merv 4 ez flow in our townhome and it the heater blower is so strong that you have to turn up the volume on the tv. The air flow is so strong through our filter that it sucks freezing cold air from our fireplace and cracks through our doors and windows. It heats up stairs really well but the downstairs is freezing cold. Ironic part is the thermostat is downstairs 😅
If you use a Merv 13 that’s a whole home 4 inch filter rather than 1 inch could you go longer between changing? We would like to use as high of a merv as possible for allergies, and have the ability to do a 1 inch or 4 inch filter. We have been informed 4 inch will last longer, but we’re also told not to go above merv 9 for air pressure reasons.
4 “ will definitely go longer than 1”. A MERV 11 would be a good choice. My opinion is use the 1” and change it every month or use the 4” and change it every 3 months. You should inspect it monthly.
@@FurnaceFilterTalk you’re forgetting, that you can get a higher merv with the thicker filters, because you have more surface area. You can get the same air into a 5 inch merv 13 as a 1 inch merv 8. And don’t have to change them as often
I'm using a MERV 5 because if I go to an 8 or more my burner cycles while the blower is still running. That tells me it's restricting so much that it's overheating the combustion chamber.
I have a question. Does static pressure on the input side directly correlate to air flow through the system? I'm asking because if the exhaust side of the blower (heat exchanger, duct work) restricts air flow (which I'm sure it does) would a slight decrease in air pressurre after the filter due to a slightly more restrictive filter be directly proportional to the output volume of air. My thinking is that there is nearly 14 PSI of available atmpsopheric pressure pushing air throught the filter so as long as the blower can create enough pressure drop after the filter so flow equals the maximum volume of air the fixed power blower is capable of pushing through the system it should not make much difference. I am assuming the blower motor would have enough slip to allow it to spin slightly faster in the less dense air created by the filter restriction until it reaches exhaust side pressure equlibrium caused by the blower's power limitation and restriction of the ducts and heat exchanger. I don't think I explained myself well so I hope you understand what I mean.
This question is beyond my expertise. I do know higher MERV or even lower MERV when the filter gets dirty enough it will increase resistance to air flow. Will it be enough to cause damage? Very dependent on each household.
@@FurnaceFilterTalk Hi thanks for the speedy reply. I have bad allergies in the fall and noticed a significant improvement with a 3m Merv 14 filter I tried vs a cheapy. I counted 72 pleats for the Merv 14 vs 18 pleats for the Merv 11 which is quite a difference. The clean flow rating is similar but I have no idea how they would compare after a few months of use or whether I'm stressing the system with over kill filtration. I should check the price of a cheap windspeed meter and compare the blower output with different clean and dirty filters. Not knowing is like an itch I have to scratch.
Your over all static pressure should be .5 inches of water column as stated on your furnace data plate .8 is usually more of a realistic real life number and any thing 1 inch WC or over that is not good. The chart in your furnace manual will not even have blower speeds and cfm calculations for any thing over that. If you have anything close to a psi you need to call a professional. Your blower is not a vacuum. its a fan. Over all static is measured after the filter for one reading and after the heat exchanger but before your ac coil for your second reading. One number will be negitive (return side) and one will be positive (supply side). Add those two togeather ignoring the -/+. Thats your over all static. The measurement After your filter is the static we are concerned with here that includes the filter and return duct work. Although if the supply side is high that means you have undersized duct work or closed heat registers. And needs to be adressed cus the blower cant move air of there is nowhere for it to go. So getting back to the filter. If you measure before the filter that will tell you the static of just your return duct work if that number is high it means you need more return air. Bigger ductwork or adding return registers. The measurement before the the fitler subtracted form our original after the filter will tell you the statc resistance of your filter. Unless you change your duct work your stuck with using a filter that doesn't add to much resistance to the over all static. If your total static pressure is 1 inch of WC or more your furnace will run so hot that it will short cycle on high limit. The high limit is a thermally actuvated switch that opens to protect your when furnace when it reaches unsafe teampatures when it cant get rid of the heat it is makeing. And will not close untill the blower has cooled the heatexchanger down to it set limit. These number are differant for all furnaces. This is not good and will destroy your heat exchanger. And is also very inefficient. So in a nut shell high static means less cfm of air moved. Cfm is cubic feet per minute. If the blower cant move air it cant move heat. The positve and negitive pressures that you were talking about are very important and if they dont work togeather or are to high your blower will just freespin and do nothing. Blowers move air they dont suck or blow. They work on pressure equipment to you sucking water .5 inchs or less up a straw. Hope this was healpful. Furnace blowers also dont move much with no restance. Thats irrelevant here and only applys to using an old one for a garage fan.
@@TheDeadheadable Thanks for that detailed and clear reply. What I wasn't getting is pressure measurement being used as a proxy for CFM. If the static pressures check out the CFM through the system must also check out because the system is designed to work within that pressure range with that particular blower and that particular heat exchanger. In theory, you could swap out the blower for a more powerful unit with a restrictive filter and the static pressures could be way out of spec but there would still be plenty of CFMs of air moving through the heat exchanger for the furnace to function correctly without over-temping.
I have a merv 12 filter and my plenum is building up water with just a little on the Unit as well. My soffit vents are not pulling much air for some reason. My thinking is my roof is very tall in the attic some points are 20ft above the soffit. Do you think attic vent fans would clear up my moisture?
Good overview. Was wondering how the new Micro Guard Power filters from Dial One work. They claim they filter to .003 micron and do not have a hard draw on the HVAC system if changed on a regular schedule.
HVAC help Hello my name is Jr. I have recently installed my first HVAc system and I can tell you it’s a blessing going from window units to HVAC. I’m 6 months into my system and I am having problems with it. I have a 5 ton 2 stage system installed on my house. Currently I have 1600 sq feet cooling off with 2 return ducts and 11 vents. In a couple of months I am building an upstairs area of 600 sq ft that should take another return vent and 3 more supply vents. I also have a 5” filter on the air handler. The upstairs is currently blocked off. After the first 3 months the pipes going to the condenser outside started freezing so at that time I panicked and was wondering why this was happening. I turned the system off and let it run for an hour and I changed the 5” merv 11 filter and the system started working fine. Here we are 2 months later I’m thinking the air filter I stepped down from the merv 11 to merv 8 would work better and not restrict more air, but the system is not getting cool for the second time. I change the 5” filter again after an hour of being turned off and letting the fan run and the system starts working normal again. Is my system not liking the 5” merv filter that was installed or what is going on. I know I’m throwing a bunch of information out there and the best way is to physically check the system but anything information would help. Thanks in advance.
james goudeau why not install a magnahelic gauge downstream from the filter, monitor the gage and when the pressure reaches a predetermine level change the filter.
I have a Space-Gard 2200 model Aprilaire Purifier that is upgraded with the Aprilaire 1213 kit to accept Aprilaire 213 filters. The 213 filters is a merv 13. I can't find anything lower than Merv 13 for that set up. Does anyone know it there is a lower Merv for that upgrade kit on the Space-Gard 2200? Edit: Aprilaire tech services informed me that the 213 filter at Merv 13 was less restrictive than the old 201 filter that I previously had installed. According to him there is a 210 filter that is Merv 11. He also said that they recommend yearly replacement for both. According to the chart he sent to me the Merv 13 increases from .18 to .4 pressure drop IWC versus .13 to .35 IWC for the Merv 11 filter over 12 months.
@@FurnaceFilterTalk Glasfloss. I'm kind of stuck with them at the moment because we had a whole new system installed. But when they constructed the housing for the air handler, it was built exactly to the specs of the filter which instead of it being exactly 16X20X1, its 151/2 X 19 1/2 X 7/8. Almost nothing at local stores or hardware have any filter that is 19 1/2 long. Even though most of them are a bit shorter, they all come in just a tad longer than what will allow for the little door to close and lock in place. So I just order them online. And my apologies. Its every 90 days, not 60.
@@Playitstraight44 You might try Nordic Pure. Theirs are the exact size you said. 15.5x19.5. You can use this link to connect directly to their page. shrsl.com/3pz6n
Interesting. We bought a house that had a Honeywell electric air cleaner attached to our furnace with a media type merv 16 filter. Says it lasts one year so we recently replaced with a merv 13. Do we really need to change as frequently as monthly. If so, why does the manufacturer say they last up to 1 year?
Are you talking about a 4” or 5” filter? Those can go longer because they have lower resistance to air flow. Everything I am discussing is a 1” filter and there is no 1” disposable filter that will go a year. Most 1” filter makers say 2-3 months. HVAC techs say every month. Of course every household is different due to pets, smokers, allergies, etc.
This is all true, but even if you have allergies are good air quality is important, how much of your home's air is going to get run through the air filter? In most homes wouldn't it be not a lot? If so, is it worth filtering 90% of the particles in 20% (let's say) of the air that gets run across your furnace filter? Willing to learn here, but it seems to me if the filter is there to protect the gear there's not much benefit to high Merv filters. Thoughts?
@@FurnaceFilterTalk - I didn't say what I wanted to say. Wouldn't dust settle in the home when the fan isn't even on? If you've ever maintained a swimming pool, you know that stuff settles away from the flow that the filter catches. One strategy is just to stir the water and suspend the stuff so the filter will get it. But that'll never happen with air in a home. It just seems to me merv filters aren't going to do what people think they will.
Without a filter, my unit can take in 3400 CFM. With a MERV 5 3M Basic, that drops to 1800 CFM. Yikes. I'm thinking about switching to the cheap green ones...
In HVAC (heating, ventilation, and air conditioning) systems, static pressure refers to the resistance to airflow in the ductwork and other components of the system, such as air filters, coils, and dampers. It is a measure of the pressure drop that occurs as air moves through the system, due to frictional losses and other forms of resistance.
What if you have an old furnace/ac unit? Ive got an old Bryant system from the mid 80s, 2 cats and 2 dogs. My wife and I dont have much allergy troubles and we dont smoke cigarettes but I will have an occasional cigarillo 4-5 times a week. My wife also enjoys her scented candles. Ive been using MERV 4 up to this point but Id like to get as much filtration as possible without overly taxing my ancient furnace. Any advice on what MERV rating would fit that bill?
For your system anything MERV 5 to 8. For your health it is up to you. Petroleum based candles are very bad which is what most every candle is made of. Look through my videos and find the one about burning candles.
MERV 13 1" Deep is a lot different than MERV 13 12" Deep. . I rum a MERV 14A 12" DEEP Change it every 2 years. deltaP is .18". stay with the 1" track MERV 8. It's fine for the coil. Add a UV lamp to remove viruses and keep your coil clean
Project Farm did a test of furnace filters recently. It's not just about MERV rating, it's design too. I use a 1" 3M 2200 filter (or 1900) and as he shows in his tests, the static pressure is relatively low for the level of filtration you're getting. I've never seen a furnace with a greater than 1" allowance for a filter in 36 years of home ownership. If you're in an actual cold climate (i.e. here on the Canadian prairies), those low MERV filters will leave your house full of tons of dust. All of the forest fire smoke these days also makes it necessary to use a better filter. I've been using these filters in my house (built in 2012, high efficient NG furnace) since new and have never had an issue. I keep an eye on usage, don't let my wife control the thermostat(!), and change the filter every 3 months, unless we are having a cool summer.
Looking at your chart, the MERV 12 seems to be the best fit for me. What range of MPR ratings should I look for? I like the 3M Filtrete filters - have used them for years.
Check your temp rise. If its with in the range that is on your furnaces data plate usualy 35 to 65 but some times its less like 35 to 55 then your probualey good. You should be at least 5 less than the max with a new filter.
I switched from a 1 inch MERV 4 to a 4 inch MERV 11 and use the cheapest 1 inch MERV 4 in front of the 4 inch to catch the larger particles. Is this a viable setup or should I change some aspect?
@@FurnaceFilterTalk Thank you for responding. I assume by air restriction, you mean the filter area size, which is 16x25. There are 13 pleats in the filter, each having 2 sides, 2x3.68x24.4/pleat gave me approx. 2300 sq. in. plus the 1-inch fiberglass MERV 4 filter.
If you have a Cat, don't bother with the high numbered Merv filters. They will clog up even faster. Remember to just change the filter every month with any filter, because of Cat Hair.
3ms will kill your furnace. Merv 8 is the absolute most for a 1inch thick filter. Anything higher and you should really look into having a contractor install a 4-6 inch filter box to go up in merv ratings and keep the static pressure happy.
@@FurnaceFilterTalk Years of experience taught me this. I've done tests with a merv 4 3m filter vs my old companies merv 8 1 inch filter and the merv 8 had better static readings.
It depends on your particular household. If you have pets, and smokers in the house and how frequently you have windows open. You are correct that the dirtier the filter gets the higher the MERV becomes.
I have a Merv 16, but it’s a 5” filter, I believe he is referring to the standard 1”. Since 5” has much more surface area you get more airflow even with higher Merv.
I have a Merv 16, but it’s a 5” filter, I believe he is referring to the standard 1”. Since 5” has much more surface area you get more airflow even with higher Merv.
I had to shell out $1200 for a damn blower motor a couple of years ago. They aren't cheap to replace. The builder that built my house told me 9 years ago to run it 24/7. That it is more efficient that way. What a bunch of crap. I did that for a few years and when I stopped my bill went down $20 a month. I think running it 24/7 for years led to early failure.
Hmm, if only there was a way to measure when the filter is getting plugged but that would save a lot of furnaces from premature failure so who in their right mind would do that? Its all about sales and that's what makes this country a horrible place to live.
Yes Merv 13 is wayyy too much filter for your furnace ......A merv 8 is plenty fine .... Your furnace is not designed to be an air filtration system ..... The furnace filter should not restrict air flow and was designed for catching larger particles not microscopic ones .... The Merv rating for furnace filters is mainly marketing to sell more expensive filter that you don't need. Buy a separate system if you are concerned about air filtration.
Just don't use the furnace as a high quality air filter for breathing. Size the density of the filter for the needs of the furnace, then buy a seperate air filtering machine for breathing needs.
"Your air filter in your system is to protect your system, not really intended to protect your air and what you breathe. That's not the primary purpose of an air filter." That's news to me; says WHO? If you want to "protect" your system just TAKE OUT THE FILTER. If you want to slow down the squirrel fan just put in circuitry to slow it down. Your statement sounds preposterous.
You can’t run a furnace without a filter, especially if you have a cooling coil. The filter protects fine dirt and lint from plugging up the coil, the blower wheel, and the motor. If you have no filter, the coil becomes the filter, which is something you don’t want
Not to be rude, but I think this explanation was dumb. With a filter you are trying to accomplish two things. One is to keep the purity of air circulating through your home at its best and the second is having your system operating at peak efficiency. The goal of filter manufacturers is to accomplish both task. They are not going to make a filter that is so restrictive it would damage your system. The higher the merv, the better the air quality. Using a merv 5 is next to nothing. If you are worried about filters being too restrictive don't use anything.
Agree to disagree. A MERV 5 is better than a fiberglass panel filter but it doesn’t help allergy sufferers nor filter out smaller particles. The danger of higher MERV is if it isn’t changed regularly. The fact is MERV 13 starts out at a higher resistance. I have no issues with using a higher MERV but change it every 2 months. By the way saying not to be rude and then being rude just means you meant to be rude all along.
I assume you want to do this to extend the filter life. I would be worried that it would not remove the imbedded particulate and your air flow resistance would not go down. If the resistance is not reduced it would serve no purpose. I have never tried it so I can’t say for sure. I have a 3M Merv 11 in right now and when it is time to change it I will measure the resistance, vacuum it and measure it again. Then we will have some actual proof.
Only one “chink in your armor”. As the flow of air becomes restricted and the furnace blower wheel starts to run out of air to grab, you’ll notice the amp draw on the motor actually go down as it runs out of “load”. Less amp draw equals less energy consumed. Not good for overall performance but still the accurate answer is “not to site an increase in energy consumption. Otherwise great video. Very helpful. Wish I’d have done it.
33 years in the HVAC trade and I’d say this was the best explanation I’ve heard. Too many companies are trying to promote IAQ through the furnace and I don’t agree with that method, the way I see it is in order to use the furnace for IAQ you need to add more returns to the system and it can get silly in a house. IAQ is all about air changes and being able to move the air throughout the house not just one section of the house. I’v actually been recommending a MERV 8 or less and tell people to use room HEPA air filtration. Don’t get me wrong I can design an air cleaning system for a house but most people aren’t willing to pay for it.
Thanks. I appreciate the feedback.
Last spring we had a new HVAC system installed with a 20x25x4 filter. The contractor recommended MERV8, replace every 6 months. Seems to work well.
Great Channel! Thank you for sharing from your wealth of experience. Great to hear from someone not trying to sell you a new HVAC System or some unnecessary & expensive Parts Replacements.
The major problem I have is with DUST accumulation inside the house, yet we keep windows/doors closed always. I have tried all grades & efficiency-levels of filters. As you said, the higher the grade & more expensive, the more they impede air-flow & blower-fan, and causing so much noise through the return-air plenum, loud 😂bough to disrupt sleep. The dust-problem is a nuisance - one day, you dust-clean the whole house and the next day or two, everywhere is covered with dust again.
Any ideas on how to deal with dust problems? Thank you. - Nigel
Correction/
*** … loud enough to disrupt sleep.
Thank you for sharing your valuable input. Much appreciated.
Excellent explanation. I currently use a Filtrete MPR 300, MERV 5. Thanks for sharing and Greetings from Nova Scotia Canada
Doesn't get cold there, so you can get away with that. Try that crap filter living on the prairies in 6 months of real cold. You'll have 4 inches of dust all over your house.
All is perfectly explained. I would add two things:
1. It doesn't matter, which MERV you use, if it's clogged, you are running at MERV 20 pressure or higher ))
2. It really matters, which filter system you have. If you have 1 inch filter, sure, it matters, merv 8 or merv 13, because it's not much of profit from ribs added. BUT if you're at 4-5 inch system, it doesn't matter, because the static pressure is really low at those filters.
Well said.
Great reply. That agrees with what Aprilaire told me.
Thank you for this video. Your explanations are quite clear and concise. As for my experience, I put in a Merv 10, and my furnace worked improperly. I have a new house with one of the cheapest Trane furnaces available. Works fine with no filter. Now I’m going to try a Merv 5. Thanks, again, for your expertise.
The thickness of the filter is also relevant. My Bryant unit had an insert that could be removed to allow a 2-inch filter. That will lower static pressure due to the increased surface area, and they will last three months.
Excellent information!! Perfect explanation for us less knowledgeable individuals about an important subject. I’m going to build a box fan filter with a Merv 13 to save my furnace but still get good air filtration. Maybe 2 or 3 once I make 1 or 2 for the shop
Awesome! Thank you!
I live in central Idaho and every year there are forest fires either here in Idaho (most of Idaho is BLM forest) and/or Washington state and the far reaching smoke sneaks into the house making for unpleasant smelling air. My furnace calls for MERV 8 with strong caveats against anything higher which is fine the rest of the year. With some trepidation I started using 3M Filtrete MERV 11 filters during these fire events and they cleared the air perfectly for me. However in the back of my mind was the fear of furnace damage. This gentleman's fine presentation has removed most of my angst over the occasional use of MERV 11 furnace filters for interior smoke mitigation. Thank you sir!
Your welcome.
My take - I have a 2-story colonial, 2150 sq ft, no pets, non smokers, no kids, well insulated home in upstate NY. I change furnace filters depending on the season. During the winter heating season (Oct - March) the furnace filter (FulterBuy MERV 8) is changed every 2 months since it is running more often but the house is closed so there are limited outside contaminates. In the spring (April - June) I use a MERV 11 when the pollen and cottonwood are flying everywhere. The HVAC is not running as often and is off most of the time, just a few heating and cooling days depending on the weather but with the windows open stuff gets in. I change the filter (back to MERV 8) for the summer cooling season and the AC runs about 5 hours a day for 25 days at the most. My goal: maximize air flow, minimize the time HVAC is running and reduce wear and tear on the HVAC system.
My last HVAC system lasted over 24 years without a single problem and was only replaced because of other factors.
Sounds like you have things under control.
I agree with every thing you said except the part about the blower using more energy with a restrictive or dirty filter. A PSC motor will use less energy with higher static pressure. I am not saying thats a good thing in any way. If its not moveing air its just free spinning and pulling less amps. This however does not apply to an ECM moter because it will just keep ramping up till it reaches its limit in an attempt to move more air. Under sized duct work is way more of an issue in most HVAC systems. And I always tell customers unless its newer duct work designed to move the cfm modern furnaces require to never put in anything bigger that an merv 8 and that applys to 5 in filters if it a one inch filter even less. Checking your temp split is the best way to find out how high of a merv you can get away with. And always make sure all your registers are open and your returns are not blocked. Shutting registers will not save you money. A furnace is sized to heat your whole house. Your furnace does not now or care if you dont use all your bedrooms cus your kids moved out. A simple temp rise will let you know how many you can get away with closing. I know most of what i just said has nothing to do with filters but in most cases more important.
Interesting.
Very insightful observations. What should the temperature difference be between the air going in and the air going out, for heating or cooling ? I see the furnace maintenance technician measure this but never thought to ask why he did that. I’ve got a small digital probe thermometer and I’ll check mine out.
@@lanarkwanderer I don’t know why that is measured. When my unit is serviced for summer the tech checks the temp at the register in the room to be sure it is cooling enough. Maybe some techs on here can provide some insight?
Place more load on ANY motor and it uses more energy. You cannot get more Nm of force at no cost. Bicycle, EV, heat pump or furnace there is NO free ride my friend
Good practical explanation thank you. I bought a 3 pack of higher MERV filters, but when those are gone I will go back to the MERV 7 true blue. About $3.00 apiece at Menards.
Well done ! I try to tell people to compare this to wearing two mask because of fear of Covid and how that would filter out the potential bad air and virus but then the side affect of leaving you gasping for air and making your lungs and heart work harder.
I just got some 10's, but I only run my system in the winter months (three months for a few hours max a day). The two filters never turn color but replace them once a season.
Nicely Done Good Sir! Was about to pull the trigger on buying a MERV 13 lifetime washable filter as it obviously sounds good. But now listening to your great tech advice, given the cost, the load on the motor and that I dont have the issues to need such filtering. There famous cold air auto filter company makes a Lifetime Merv 11 as well so Ill see if that works. Nicely Done, Very Nicely Done, thank you!!!!!
This is so helpful!! I've spent so much time trying to figure this out, and I really appreciate your insight as a professional and someone who's worked in the industry. Thank you!!
You are welcome.
I really appreciate the breakdown.
I always recommend to my clients to use a MERV 8 and not more than a MERV 10. I explain to them that if they truly want air cleaning quality that the filter is not what does that. I recommend HEPA systems with UV lighting . Your explanation is one of the better that I’ve heard , thank you.
Thanks.
I use a particle counter, dylos 1100 pro. Pleated filter was good for 18 months. One day it was filtering fine, next day not at all. It was ugly, but working fine. No issues with a/c.
3M Merv 5 here. The fiberglass in my opinion allows too much small dust, even when changing every 30 days. The Merv 5 seems to be the best balance for dust capturing and air flow. I used Merv 13 filters in a separate air filtration device.
I also was a 3M MERV 5 user but they changed their design. I just switched to a MERV 8 Aerostar. I will do a video on it soon.
I have some seasonal allergies. I tried a merv 11 filter but the ductwork whistled. Bought a magnetic dwyer utube manometer. I was running .8" !!! Furnace was cycling on high temperature cutout. Installed a 5" filter frame and a merv 11 filter. Allergies all good, filter DP at 6 months was .3". I wouldn't recommend any more restrictive filter unless you can see the DP it creates. Cheap Utube manometers are about the price of a good pizza, and are always showing a reading so you know how restrictive your filter is getting.
Good job!
I just bought an fpr 7 hdx air filter. We have a carrier system installed in 2012 with 1 cat and 1 dog. It says this is equivalent to a merv 10-11. Thoughts? Just dont want to harm the system
i use a regular cheap figerglass filter and i change it every month is that ok or am i hurting my hvac system ...i dont have pets or smoke or dust or alergies .....the reason why i use the cheap ones is because i find that with the cheap filter my vents in the house are able to blow more air and circulate the ac or heat better thruout the house and when i instal a nerv 8 or 13 my ducts barely push air ,,but with the cheap filter my house stays cooler and hotter depends on the season ...am i hurting my system by using a cheap fiberglass filter ?
Under the conditions you describe you are not going to hurt your system. Keep changing your filter monthly. If you do want more dust capturing 3M Filtrete has a MERV 5 on Amazon. I have a video on my channel.
I’m with you. Once I switched to the basic fiberglass filters, I was amazed at how much more air blew out of my vents.
Best review on the internet. Thank You for sharing your expertise.
Thanks for the feedback.
3M is a highly static charged filter. U of M turned them down after test showed efficiency dropped 33%. MERV A rating is what counts for efficiency. I work for Camfil
My furnace shut down and would not restart on the lowest range pleated Merv. I had forgotten to change it for 2-3 months. HVAC guy had to tap the auto reset to get it to work again and told me to get the Merv 4 fiberglass for the best results. Said it was even ok to use for 2 months instead of 1. Fine by me! He recommends that kind to most of his clients.
I’m glad you didn’t get any damage. I change mine every month and I use a Aerostar MERV 8. I could probably go 2 months but why take the chance.
I have a Aprilaire 2210 whole house filter - which has a 20x25x4 replaceable filter. Can you speak to the restrictiveness of these deep filters and how a typical 1 inch (at say Merv 7) might compare to a 4 inch deep filter (at, say Merv 11)?
A deeper filter will have lower airflow resistance than a 1” and it will last longer because it has a larger square footage of media.
@@FurnaceFilterTalk That's right, a1inch filter needs changing ounce a month, while the 4 inch filter will be good for 3 to 4 months. The yearly cost of replacing the filters is about the same for both.
This must be why my house has a 2000cfm return grill on a 1200 cfm system. I was very confused on why it was so large. Nice idea with the builder though as you can do a merv 13 filter 5"thick no problem.
Sounds like a good setup.
Been using a MERV 13 and now switching over to a MERV 11 by Aprilaire. I was told to change this so ill see how much of a difference it makes
I also have an Aprilaire system, 4" depth. Who advised you to change from 13 to 11?
First, people need to understand that a furnace filter is there to protect the furnace blower and heat exchanger/air conditioner evaporator. It wasn't originally intended to be a whole house air cleaning system. The filter companies created the higher priced filters to expand their product line and generate more profits. If you really need much cleaner room air due to medical conditions, consult with an expert who will most likely recommend a stand alone HEPA system. That being said, I've always found that the standard fiberglass furnace filters don't keep the blower and heat exchanger/air conditioning evaporator coils clean enough. They might strain out small rocks, but plenty of fairly large particles don't even slow down going through one of those "filters". Merv 8 is the minimum I consider acceptable. Just my humble opinion based on my personal experience.
I disagree with you. I worked my whole life for filter manufacturers and companies put a lot of money to develop higher Merv filters that won’t hurt a furnace. Things have evolved.
Residential furnaces TOTAL static is .5”. That is .25 on the return and .25 on the supply. You also have to figure static loss of the ductwork, which leaves very little for filter pressure drop.
Agree. This is why changing the filters are so important.
If my unit has room for two do I put two? Or is it always just one? Thanks!
My hvac says 1” filter but the space is so big that I have fit a 4”. Wouldn’t a 1” be floating in the space with the air pressure reducing the filtration ?
Man thank you on this. I bought some massive 3M 2200s that were a lot of money but I was worried. I haven't opened them yet - going to return them and buy just a 3M 1000. My house is super dusty and I sneeze a lot so I need something more than a basic filter but I clearly went overkill.
Glad I could help
Don’t listen to him. Use the filter. I use and have been using mine for years with ZERO issues
@@jamesbizs which one do you use, j p?
Hi thank you for your video.
I would like to comment on your thought that a restricted furnace filter requires more energy. I’m speaking strictly about the furnace blower fan. It is a fan, not a positive displacement pump and as such, it draws its maximum power (amperage) when its moving the maximum amount of air it can. The less air it moves, the less it’s energy requirement. In other words, the more you restrict its income air, the less air it moves and that equates to less energy required.
Thanks
But the longer your system operates due to a more restrictive filter the more energy is used to cool the house down and shortening the life of the system.
This is incorrect. Most homes operate at 300 FPM and a dirty filter causes the blower to work harder and use more energy. Take a look at www.energy.gov/energysaver/maintaining-your-air-conditioner for more info.
True.
I am a mechanical engineer.
Added comment,
"True, I am a mechanical engineer".
I am referring to the comment that "less air flow requires less energy". This is true. Based on fan curves and fan laws.
That’s true, a centrifugal fan powered with a permanent split capacitor (PSC) motor will unload (use less energy) as the filter becomes more restricted by dirt or is operating in a poorly designed and/or installed duct system. However, some newer furnaces have electronically controlled constant volume fan motors (ECM). These motors are low wattage by design and use less energy than a PSC, all things being equal. But, when an ECM detects the airflow it’s programmed to maintain is falling off, it ramps up (speeds up) in an effort to maintain programmed airflow. When the filter is dirty or too restrictive or the duct system is wonky or all of these things combined, the ECM will use as much or even more power than the PSC motor. Not only that, the system becomes louder…perhaps a good indication the air handling system is in distress. In the end, an air handing system should be properly designed for restrictive in-line filters. Consider using a bypass filter like Amaircare, uses a bit more power but has no restrictive effect on the air handling system.
I have five filters in ceiling returns. 2 20X20 and 3 14X14. Really only the two in the more lived in area ever look dirty when I change them. If they will fit would it make sense to use 2 or 4 inch filters to have more serface area with the higher MERV at least in the two areas that collect more debris? Thanks.
If your unit is in a closet with one of those louvered closet doors with the slots you can put the more restrictive air filter on the back side of that door (the air handler side)
Interesting idea!
Would using a 5" Nordic MERV 13 help with the pressure drop? I use the 5" one with the really deep V pleats and I always thought the increased surface area helped with that. Never had a problem and I change them every 60-90 days. I used to use 2" filters and I realized the box would take a 5", no looking back.
2 high efficiency furnaces in 3 homes I bought in past 7 years are baked in with the thick filter slot (5 inches!). HVAC guys just seem to install the thick slot standard now. So us homeowners are being forced into thicker filters.
Not sure if you're not liking them, or liking them. The poster of this video didn't explain that part very well though he mentioned pleats for a bit. Those thick filters are way better than the skinny ones. The filter material is folded into pleats. If you unfold them, you'll see a much larger filter. More surface area = more filter material = longer life, better flow. So per month your cost should be lower, not higher. I wish mine had a 4 or 5 inch filter. Instead mine is 24x24x1.
@@Gersberms No argument here. And yea, there's more media in thicker filters. I'm just parroting that lots of folks keep saying "thick filters kill furnance fans". No they don't. Very high MERV -- at whatever thickness -- could kill any fan.
@@vap0rtranz Got it.
@@Gersberms I have the same size filter as you do in my home. I now purchase a Practical Pleat 24 X 24 X 5 filter from discount filters. A tremendous difference in air flow and IAQ. I pay approx. $60 a piece but they last 6+ months.
@@andresdelgado5698 Nice, thanks for the tip.
Our 1964 furnace takes room 16x20x1 filters. The Merv13 filters do not seem to significantly reduce the airflow.
The airflow doesn’t reduce but the blower works harder using more electricity and if it gets restrictive enough damages could happen.
Which filter would be less restrictive: 16 X 20 X 4 MERV 11 or: 24 X 12 X 1 MERV 5? I can put the large filter in my A/C unit in the attic or put the smaller filter in the hallway ceiling. Thanks for any assistance.
Our electronic air filter stopped working, I was told to buy a filter 20 x 25 x5 filter. Still now I did not know Merv. The filters are meth 13 ,after 4 or 5 for heat I can still see light thru them. Am I messing up?
Very Interesting 🤔 most of the 3M MERV 5 filters I have seen have .47” pressure drop or “intial resistance” published right on the filter. What is your opinion on that?
I put in a 20x30 oversized return air box so i am not using 20x20 filters inside unit and i got 5 inch thick filters that fit inside the air return box so it has almost no air restriction
Smart.
Would you say it's fair to stay that one should give a month of usage per inch thickness of a MERV 13 filter? So for the typical 2 inch filter, change it out every 2 months, for a 4 inch filter, change it out every 4 months and so on?
I always wonder what to do, i have 2 returns and a filter space right before the fan/evaporator, right now i have 2 merv 5 in the returns and 1(4inch) right before the evaporator but don’t know exactly what is the best combination
Sounds like a good setup. Maybe use a higher MERV before the evaporator based on if you have pets or allergies or just want less dust. Consult your HVAC tech to be sure.
Now about going from a 1in thick to a 4in filter? wouldn't this reduce restriction allowing a higher merv?
Yes, a thicker filter has less resistance. Most systems won’t accommodate a different filter thickness but maybe your HVAC tech can change it.
If you have a woodstove or fireplace, change filter every month if you run merv 10 or higher. Or twice a month if you burn alot. Protect your hvac system.
Yes I change my filter monthly for our daughter's allergies. Using a 13 currently but when I check my filter with a manometer it starts at a 1.23. I feel that two high for my furnace with a listed max on the data plate being .7. What are your thoughts?
I have a merv 4 ez flow in our townhome and it the heater blower is so strong that you have to turn up the volume on the tv.
The air flow is so strong through our filter that it sucks freezing cold air from our fireplace and cracks through our doors and windows.
It heats up stairs really well but the downstairs is freezing cold. Ironic part is the thermostat is downstairs 😅
This issue should be addressed with a heating and air technician. Assuming you have put in a clean filter this doesn’t sound filter related.
If you use a Merv 13 that’s a whole home 4 inch filter rather than 1 inch could you go longer between changing? We would like to use as high of a merv as possible for allergies, and have the ability to do a 1 inch or 4 inch filter. We have been informed 4 inch will last longer, but we’re also told not to go above merv 9 for air pressure reasons.
4 “ will definitely go longer than 1”. A MERV 11 would be a good choice. My opinion is use the 1” and change it every month or use the 4” and change it every 3 months. You should inspect it monthly.
@@FurnaceFilterTalk you’re forgetting, that you can get a higher merv with the thicker filters, because you have more surface area. You can get the same air into a 5 inch merv 13 as a 1 inch merv 8. And don’t have to change them as often
@@jamesbizs more surface area does not mean higher MERV. It does mean lower resistance though.
I'm using a MERV 5 because if I go to an 8 or more my burner cycles while the blower is still running. That tells me it's restricting so much that it's overheating the combustion chamber.
Interesting.
I have a question. Does static pressure on the input side directly correlate to air flow through the system? I'm asking because if the exhaust side of the blower (heat exchanger, duct work) restricts air flow (which I'm sure it does) would a slight decrease in air pressurre after the filter due to a slightly more restrictive filter be directly proportional to the output volume of air. My thinking is that there is nearly 14 PSI of available atmpsopheric pressure pushing air throught the filter so as long as the blower can create enough pressure drop after the filter so flow equals the maximum volume of air the fixed power blower is capable of pushing through the system it should not make much difference. I am assuming the blower motor would have enough slip to allow it to spin slightly faster in the less dense air created by the filter restriction until it reaches exhaust side pressure equlibrium caused by the blower's power limitation and restriction of the ducts and heat exchanger. I don't think I explained myself well so I hope you understand what I mean.
This question is beyond my expertise. I do know higher MERV or even lower MERV when the filter gets dirty enough it will increase resistance to air flow. Will it be enough to cause damage? Very dependent on each household.
@@FurnaceFilterTalk Hi thanks for the speedy reply. I have bad allergies in the fall and noticed a significant improvement with a 3m Merv 14 filter I tried vs a cheapy.
I counted 72 pleats for the Merv 14 vs 18 pleats for the Merv 11 which is quite a difference. The clean flow rating is similar but I have no idea how they would compare after a few months of use or whether I'm stressing the system with over kill filtration.
I should check the price of a cheap windspeed meter and compare the blower output with different clean and dirty filters. Not knowing is like an itch I have to scratch.
Your over all static pressure should be .5 inches of water column as stated on your furnace data plate .8 is usually more of a realistic real life number and any thing 1 inch WC or over that is not good. The chart in your furnace manual will not even have blower speeds and cfm calculations for any thing over that. If you have anything close to a psi you need to call a professional. Your blower is not a vacuum. its a fan.
Over all static is measured after the filter for one reading and after the heat exchanger but before your ac coil for your second reading. One number will be negitive (return side) and one will be positive (supply side). Add those two togeather ignoring the -/+. Thats your over all static.
The measurement After your filter is the static we are concerned with here that includes the filter and return duct work. Although if the supply side is high that means you have undersized duct work or closed heat registers. And needs to be adressed cus the blower cant move air of there is nowhere for it to go. So getting back to the filter. If you measure before the filter that will tell you the static of just your return duct work if that number is high it means you need more return air. Bigger ductwork or adding return registers. The measurement before the the fitler subtracted form our original after the filter will tell you the statc resistance of your filter. Unless you change your duct work your stuck with using a filter that doesn't add to much resistance to the over all static. If your total static pressure is 1 inch of WC or more your furnace will run so hot that it will short cycle on high limit. The high limit is a thermally actuvated switch that opens to protect your when furnace when it reaches unsafe teampatures when it cant get rid of the heat it is makeing. And will not close untill the blower has cooled the heatexchanger down to it set limit. These number are differant for all furnaces. This is not good and will destroy your heat exchanger. And is also very inefficient. So in a nut shell high static means less cfm of air moved. Cfm is cubic feet per minute. If the blower cant move air it cant move heat. The positve and negitive pressures that you were talking about are very important and if they dont work togeather or are to high your blower will just freespin and do nothing. Blowers move air they dont suck or blow. They work on pressure equipment to you sucking water .5 inchs or less up a straw. Hope this was healpful. Furnace blowers also dont move much with no restance. Thats irrelevant here and only applys to using an old one for a garage fan.
@@TheDeadheadable Thanks for that detailed and clear reply. What I wasn't getting is pressure measurement being used as a proxy for CFM. If the static pressures check out the CFM through the system must also check out because the system is designed to work within that pressure range with that particular blower and that particular heat exchanger. In theory, you could swap out the blower for a more powerful unit with a restrictive filter and the static pressures could be way out of spec but there would still be plenty of CFMs of air moving through the heat exchanger for the furnace to function correctly without over-temping.
@@TheDeadheadable And when I said more powerful blower I meant a blower than could also generate more static pressure not just more volume.
I have a merv 12 filter and my plenum is building up water with just a little on the Unit as well. My soffit vents are not pulling much air for some reason. My thinking is my roof is very tall in the attic some points are 20ft above the soffit. Do you think attic vent fans would clear up my moisture?
This is not something I can answer. Maybe one of the HVAC techs on here can?
Good overview. Was wondering how the new Micro Guard Power filters from Dial One work. They claim they filter to .003 micron and do not have a hard draw on the HVAC system if changed on a regular schedule.
I have never heard of them. Where do you buy them?
@@FurnaceFilterTalk Dial One
Or one hour heating and air
Good explanation but in Canada higher merv 13-14 is cheaper than lower 11-12
HVAC help
Hello my name is Jr. I have recently installed my first HVAc system and I can tell you it’s a blessing going from window units to HVAC. I’m 6 months into my system and I am having problems with it. I have a 5 ton 2 stage system installed on my house. Currently I have 1600 sq feet cooling off with 2 return ducts and 11 vents. In a couple of months I am building an upstairs area of 600 sq ft that should take another return vent and 3 more supply vents. I also have a 5” filter on the air handler. The upstairs is currently blocked off. After the first 3 months the pipes going to the condenser outside started freezing so at that time I panicked and was wondering why this was happening. I turned the system off and let it run for an hour and I changed the 5” merv 11 filter and the system started working fine. Here we are 2 months later I’m thinking the air filter I stepped down from the merv 11 to merv 8 would work better and not restrict more air, but the system is not getting cool for the second time. I change the 5” filter again after an hour of being turned off and letting the fan run and the system starts working normal again. Is my system not liking the 5” merv filter that was installed or what is going on. I know I’m throwing a bunch of information out there and the best way is to physically check the system but anything information would help. Thanks in advance.
I am not a HVAC technician but maybe someone on here can offer you advice.
my lennox hvac system came with a merv 16, its getting that time to replace it, can i downgrade and replace it with a merv 11 without any issues?
I can’t think of any reason that would be an issue but that would be a question for your HVAC company.
How do lower air flow damage any system? Is it just because they have to work harder to suck the air through?
Correct
THE WEBSITE link appears to be non-functional now.
james goudeau
why not install a magnahelic gauge downstream from the filter, monitor the gage and when the pressure reaches a predetermine level change the filter.
Great idea
I have a Space-Gard 2200 model Aprilaire Purifier that is upgraded with the Aprilaire 1213 kit to accept Aprilaire 213 filters. The 213 filters is a merv 13. I can't find anything lower than Merv 13 for that set up. Does anyone know it there is a lower Merv for that upgrade kit on the Space-Gard 2200?
Edit: Aprilaire tech services informed me that the 213 filter at Merv 13 was less restrictive than the old 201 filter that I previously had installed. According to him there is a 210 filter that is Merv 11.
He also said that they recommend yearly replacement for both.
According to the chart he sent to me the Merv 13 increases from .18 to .4 pressure drop IWC versus .13 to .35 IWC for the Merv 11 filter over 12 months.
I would try Nordic Pure. Just go to this link. www.shareasale.com/r.cfm?b=680763&u=2904244&m=56823
@@FurnaceFilterTalk thanks 👍
Thank you!
Your welcome.
I use MERV10 and change them out about every 90 days to keep the system healthy and happy.
What brand do you use?
@@FurnaceFilterTalk Glasfloss. I'm kind of stuck with them at the moment because we had a whole new system installed. But when they constructed the housing for the air handler, it was built exactly to the specs of the filter which instead of it being exactly 16X20X1, its 151/2 X 19 1/2 X 7/8. Almost nothing at local stores or hardware have any filter that is 19 1/2 long. Even though most of them are a bit shorter, they all come in just a tad longer than what will allow for the little door to close and lock in place. So I just order them online. And my apologies. Its every 90 days, not 60.
@@Playitstraight44 You might try Nordic Pure. Theirs are the exact size you said. 15.5x19.5. You can use this link to connect directly to their page. shrsl.com/3pz6n
@@FurnaceFilterTalk Thank you!
Interesting. We bought a house that had a Honeywell electric air cleaner attached to our furnace with a media type merv 16 filter. Says it lasts one year so we recently replaced with a merv 13. Do we really need to change as frequently as monthly. If so, why does the manufacturer say they last up to 1 year?
Are you talking about a 4” or 5” filter? Those can go longer because they have lower resistance to air flow. Everything I am discussing is a 1” filter and there is no 1” disposable filter that will go a year. Most 1” filter makers say 2-3 months. HVAC techs say every month. Of course every household is different due to pets, smokers, allergies, etc.
@@FurnaceFilterTalk I believe so. Our size is 20 x 25 x 5. Good to know, thank you!
Check out this article . It has a chart for filter life. furnacefiltertalk.com/how-often-to-change-a-furnace-filter/
This is all true, but even if you have allergies are good air quality is important, how much of your home's air is going to get run through the air filter? In most homes wouldn't it be not a lot? If so, is it worth filtering 90% of the particles in 20% (let's say) of the air that gets run across your furnace filter? Willing to learn here, but it seems to me if the filter is there to protect the gear there's not much benefit to high Merv filters. Thoughts?
In general, a properly functioning HVAC system should be able to filter a significant portion of the air in a home, typically between 80% and 90%.
@@FurnaceFilterTalk - I didn't say what I wanted to say. Wouldn't dust settle in the home when the fan isn't even on? If you've ever maintained a swimming pool, you know that stuff settles away from the flow that the filter catches. One strategy is just to stir the water and suspend the stuff so the filter will get it. But that'll never happen with air in a home. It just seems to me merv filters aren't going to do what people think they will.
What about 4 inch filters? I’ve been running 4 inch Merv 13 filters, changing them every six months.
I think that is fine.
What about a Honeywell Merv 8 filter?
My experience with Honeywell tells me they are excellent filters. I have not used or tested them due to size constraints of my system.
Without a filter, my unit can take in 3400 CFM. With a MERV 5 3M Basic, that drops to 1800 CFM. Yikes. I'm thinking about switching to the cheap green ones...
What is mfg spec and static pressure measurements?
In HVAC (heating, ventilation, and air conditioning) systems, static pressure refers to the resistance to airflow in the ductwork and other components of the system, such as air filters, coils, and dampers. It is a measure of the pressure drop that occurs as air moves through the system, due to frictional losses and other forms of resistance.
Merv 11 is fine. My 2 stage furnace runs 90% of the time at stage one so the Pressure drop is fine.
Converting my AC to accept 4-5 “ thick filter. Solves the problem. Going with a merv 16
What if you have an old furnace/ac unit? Ive got an old Bryant system from the mid 80s, 2 cats and 2 dogs. My wife and I dont have much allergy troubles and we dont smoke cigarettes but I will have an occasional cigarillo 4-5 times a week. My wife also enjoys her scented candles. Ive been using MERV 4 up to this point but Id like to get as much filtration as possible without overly taxing my ancient furnace. Any advice on what MERV rating would fit that bill?
For your system anything MERV 5 to 8. For your health it is up to you. Petroleum based candles are very bad which is what most every candle is made of. Look through my videos and find the one about burning candles.
@@FurnaceFilterTalk Thx
No problem
What about 5” filters? Way more surface area so higher Merv would not impact airflow as much as 1”
5” filters have lower resistance and will be able to last longer than 1” filters. Higher MERV’s in a 5” will do much better than a 1”.
MERV 13 1" Deep is a lot different than MERV 13 12" Deep. . I rum a MERV 14A 12" DEEP Change it every 2 years. deltaP is .18". stay with the 1" track MERV 8. It's fine for the coil. Add a UV lamp to remove viruses and keep your coil clean
Project Farm did a test of furnace filters recently. It's not just about MERV rating, it's design too. I use a 1" 3M 2200 filter (or 1900) and as he shows in his tests, the static pressure is relatively low for the level of filtration you're getting. I've never seen a furnace with a greater than 1" allowance for a filter in 36 years of home ownership. If you're in an actual cold climate (i.e. here on the Canadian prairies), those low MERV filters will leave your house full of tons of dust. All of the forest fire smoke these days also makes it necessary to use a better filter. I've been using these filters in my house (built in 2012, high efficient NG furnace) since new and have never had an issue. I keep an eye on usage, don't let my wife control the thermostat(!), and change the filter every 3 months, unless we are having a cool summer.
Beyond the effect on your lungs, higher MERV filters can reduce dust on horizontal surfaces in your house.
Looking at your chart, the MERV 12 seems to be the best fit for me. What range of MPR ratings should I look for? I like the 3M Filtrete filters - have used them for years.
MPR 1500
Check your temp rise. If its with in the range that is on your furnaces data plate usualy 35 to 65 but some times its less like 35 to 55 then your probualey good. You should be at least 5 less than the max with a new filter.
I switched from a 1 inch MERV 4 to a 4 inch MERV 11 and use the cheapest 1 inch MERV 4 in front of the 4 inch to catch the larger particles. Is this a viable setup or should I change some aspect?
I think it depends on your air restriction. Only way to know is measure it.
@@FurnaceFilterTalk Thank you for responding.
I assume by air restriction, you mean the filter area size, which is 16x25. There are 13 pleats in the filter, each having 2 sides, 2x3.68x24.4/pleat gave me approx. 2300 sq. in. plus the 1-inch fiberglass MERV 4 filter.
If you have a Cat, don't bother with the high numbered Merv filters. They will clog up even faster. Remember to just change the filter every month with any filter, because of Cat Hair.
Oct to April.
3ms will kill your furnace. Merv 8 is the absolute most for a 1inch thick filter. Anything higher and you should really look into having a contractor install a 4-6 inch filter box to go up in merv ratings and keep the static pressure happy.
Interesting thought.
@@FurnaceFilterTalk Years of experience taught me this. I've done tests with a merv 4 3m filter vs my old companies merv 8 1 inch filter and the merv 8 had better static readings.
A merv 8 filter will turn into a merv 13 filter after about a 1 months use after all the particles it captures😅
It depends on your particular household. If you have pets, and smokers in the house and how frequently you have windows open. You are correct that the dirtier the filter gets the higher the MERV becomes.
❤
Assume u r not talking 4 inch filters right?
Correct.
I have a MERV 16. Think it's overkill. Going with a 13.
I have a Merv 16, but it’s a 5” filter, I believe he is referring to the standard 1”. Since 5” has much more surface area you get more airflow even with higher Merv.
I have a Merv 16, but it’s a 5” filter, I believe he is referring to the standard 1”. Since 5” has much more surface area you get more airflow even with higher Merv.
I had to shell out $1200 for a damn blower motor a couple of years ago. They aren't cheap to replace. The builder that built my house told me 9 years ago to run it 24/7. That it is more efficient that way. What a bunch of crap. I did that for a few years and when I stopped my bill went down $20 a month. I think running it 24/7 for years led to early failure.
My builder did tell me to buy the cheap filters. I guess that was good advise but that 24/7 stuff wasn't a good idea
I have only heard one person say run 24/7 and it was an allergy doctor. Always sounded like a bad idea.
Hmm, if only there was a way to measure when the filter is getting plugged but that would save a lot of furnaces from premature failure so who in their right mind would do that? Its all about sales and that's what makes this country a horrible place to live.
Yes Merv 13 is wayyy too much filter for your furnace ......A merv 8 is plenty fine .... Your furnace is not designed to be an air filtration system ..... The furnace filter should not restrict air flow and was designed for catching larger particles not microscopic ones .... The Merv rating for furnace filters is mainly marketing to sell more expensive filter that you don't need. Buy a separate system if you are concerned about air filtration.
high limit in heating will let you know
Thanks.
Just don't use the furnace as a high quality air filter for breathing. Size the density of the filter for the needs of the furnace, then buy a seperate air filtering machine for breathing needs.
There is no difference between a super high efficiency filter, and a very dirty cheap filter.
I respectfully disagree.
Nerve 13 is too much for your furnace, you want to get the cheapest filter, like Merve 3, When you use Merve 13, your choking the system.
Thanks for the input.
A lot of baseless claims made here.
Thanks for your input.
"Your air filter in your system is to protect your system, not really intended to protect your air and what you breathe. That's not the primary purpose of an air filter." That's news to me; says WHO? If you want to "protect" your system just TAKE OUT THE FILTER. If you want to slow down the squirrel fan just put in circuitry to slow it down. Your statement sounds preposterous.
Read the next comment.
You can’t run a furnace without a filter, especially if you have a cooling coil. The filter protects fine dirt and lint from plugging up the coil, the blower wheel, and the motor. If you have no filter, the coil becomes the filter, which is something you don’t want
Russian bot has spoken. Slow down fan LOL!
Not to be rude, but I think this explanation was dumb.
With a filter you are trying to accomplish two things. One is to keep the purity of air circulating through your home at its best and the second is having your system operating at peak efficiency. The goal of filter manufacturers is to accomplish both task. They are not going to make a filter that is so restrictive it would damage your system.
The higher the merv, the better the air quality.
Using a merv 5 is next to nothing. If you are worried about filters being too restrictive don't use anything.
Agree to disagree. A MERV 5 is better than a fiberglass panel filter but it doesn’t help allergy sufferers nor filter out smaller particles. The danger of higher MERV is if it isn’t changed regularly. The fact is MERV 13 starts out at a higher resistance. I have no issues with using a higher MERV but change it every 2 months. By the way saying not to be rude and then being rude just means you meant to be rude all along.
Do you recommend using the sweeper on a filter to pull back out some dust etc on the "in" side of the filter
I assume you want to do this to extend the filter life. I would be worried that it would not remove the imbedded particulate and your air flow resistance would not go down. If the resistance is not reduced it would serve no purpose. I have never tried it so I can’t say for sure. I have a 3M Merv 11 in right now and when it is time to change it I will measure the resistance, vacuum it and measure it again. Then we will have some actual proof.
th-cam.com/users/shortsGY6PJnf7l9k?feature=share
Only one “chink in your armor”. As the flow of air becomes restricted and the furnace blower wheel starts to run out of air to grab, you’ll notice the amp draw on the motor actually go down as it runs out of “load”. Less amp draw equals less energy consumed. Not good for overall performance but still the accurate answer is “not to site an increase in energy consumption. Otherwise great video. Very helpful. Wish I’d have done it.
Thanks for the input.