Low Outdoor Temp, "CHECK THE REFRIGERANT CHARGE" in the Cold!
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- เผยแพร่เมื่อ 25 ธ.ค. 2021
- In this HVAC Training Video, I Show the Method for Checking the Charge when the Outdoor Temp is between 37°F to 70°F. Restricting the Outdoor Unit Airflow Allows the Liquid Pressure to Rise High Enough to Measure Superheat and Subcooling Correctly. Supervision is needed by a licensed HVACR Tech while performing tasks as Experience and Apprenticeship garners Wisdom and Safety.
If you want to see this Method Measured with Digital Gauges and Using a Charging Jacket, see this video: • Checking the Charge of...
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⚠️ Disclaimer:
Information in this video is intended for educational purposes only. Any work related to the topics in this video should be performed by licensed technicians or by apprentices under the supervision of licensed technicians. AC Service Tech LLC is not responsible for any possible damages or injuries caused by the use or misuse of any information provided.
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The total superheat was a little high especially with the low heat load. I will need to check the charge again during the beginning of summer to investigate why the TXV isn't allowing more refrigerant into the evaporator. The bulb was mounted correctly. I did see that. The superheat should be lower such as below 16 degrees but preferably closer to 10 degrees. Any time you check the charge this way during low outdoor ambient temps, it is only in a worst case scenario and the technician should schedule another service to measure the charge again when there is an adequate heat load on the building such as 85 degrees or higher outside and 74 dry bulb or higher inside temp and a 60 degree or higher indoor wet bulb temp. Realistically, the indoor and outdoor dry bulb temps both must be above 70 degrees before and during the measuring process. Thanks!
Many thanks
Been using this method for years on micro channel condensers. Works great.
Great video - I often refer new guys to your videos PERFECT explanations with VISUALS that make the concepts stick.
..great use of 'stub gauges', even though I have wireless probe sets, digital gauges, and manifolds - stub gauges are my go-to for initial diagnosis.
Another great video. Thanks for making this one.
Thanks Craig
I love you Ace Service tech . . . Your the Best!
Great video. Thanks for sharing.
Great Tech info, Thanks Craig.
Thank you sir. Excellent video
Excellent explanation 👍🏿I can remember back in the day if a system was overcharged the hvac guy would just release some out the unit into the open air🤷🏿♂️
Back when I got into the Trade (1979) refrigerant tanks allowed you to add gas back into the tank.
The guy I worked for had two 15 pound tanks ( I not sure but I believe the 15# are no longer made)with red paint that he used as service tanks. He bought 50 pound tanks to reduce cost I think $19 per tank was the price 40 plus years ago. When a small tank was empty he would pull a vacuum and stick it in the freezer and use the 50 pounder to refill it the next morning.
Great guy to work for but taught me to add gas till the suction came back cold and several other bad habits that I thought was correct until I went to School for HVAC two years later. Ours is a great Trade to have because you have to have knowledge of multiple trades to be qualified to do our trade. Which translates into rarely hiring someone to make a repair on your home.
GREAT VIDEO! it helped me a lot. Thank you guys for sharing this valuable content!
Great job
WoW! Great video.
Craig you're awesome!
Very Good Video.
Nice jacket too!
I have the Fieldpiece charging jacket for TXV metered systems. I'll also use cardboard around the inlet of the condenser to drive up head pressure
Thanks for the video =)
Great video thank you very much Craig and happy new year. If you can please explain Aprilaire automatic humidifier wiring with smart thermostat ( Nest, Ecobee)
Best clips on the internet for this topic. Well done. You said, "don't remove too much refrigerant this way or it can remove oil from the system." How much is too much? Also, how low on charge were you?
nice video
Great video thank you very much. Craig I have a question. Does your quick reference cards just cover R-410A or more?
I do this all the time on road equipment.
Thank you for the video Greg I love your videos. I was wondering how do you check the charge in cold weather with an orifice piston metering device and also what if you have 2 systems. One for the downstairs and one for the upstairs how do you check the charge then? Thank you and God bless you sir.
Great video, I learn a lot from you. Please make a video explaining bubble point and dew point in detail. I understand it, but can’t explain. Thank you
You know it when you can explain it
Can you please upload a link for the thumb depressor cores? Appreciate it, keep up with good work as usual.
I already know SC and SH. But I had to watch because your videos are so enjoyable and clear. Idk if I learned anything new. I still feel like I did tho lol.
That's great to hear though, thanks!
Hi Greg what was the heat pump symptom leading to check in the charge?
Thank you
so what is a good super heat reading i was told to focus on the superheat for a more accurate charge
Does this matter if indoor metering device is txv or piston? Your other video I watched, u said it has to be only txv.
What happens/how if it is piston?
What if this is way below 37* outside? How do u charge? Heat mode?
Also, I’ve been looking at your videos trying to find stuck reversing valve, how to bypass and test etc… 😢
Do you need to have the indoor air temperature above 70 degrees to accurately check subcooling or can subcooling be measured effectively just by using a charging jacket outdoors without having to heat the indoor space to above 70 degrees?
What about shutting off the condenser fan? Like a head pressure control does in the colder weather
The pressure spikes make it difficult to test operation and get proper readings. Being in control of condenser airflow makes this still better
What's the coldest conditions you can test this?
What is the best affordable thermal meter
Hi, do you have your book in metric system, im from europe.
Great video, as usual, many thanks, by the -way, I didn't see any direct link to the Gauge you use on this video, can you please add a link, thanks and happy new year.
Links in video description.
@@Jeff9202 Many thanks.
What would happen to td of supply and return?
Here is my question, instead of pulling out charge could we adjust the txv to be more open? Wouldn't this lower superheat and lower subcooling?(assuming it's adjustable)
That makes sense to me. I think it would just be a little more time consuming - labor costs are expensive, might not be worth it to the customer. Also, depending on how long the vapor line is, 20°F superheat might not be that high - in a longer vapor line removing refrigerant seems like a better idea. Just my thoughts.
What kind of temperature sensor is that?
Would this work if it was 35-40 out
Can you do that with a piston metered system?
My opinion yes but not the best. I run the unit to see how much above ambient my head pressure is. Then start restricting it and compare my simulated head pressure and ambient vs wet bulb to get a target superheat. If it looks low I ramp the head pressure up more and then check it again. If you go this route you have to monitor the superheat carefully to make sure you don't slug the compressor. Works best on cool calm days. Add rain or high wind and you're better off coming back on a different day.
So I'm curious. Why are we driving up the pressure to simulate a warmer day in order to check the charge? Just because the sub cooling is naturally gonna be higher with lower temperatures?
To simulate actual working conditions /design conditions. I believe you are correct - in low ambient conditions, the refrigerant condenses much faster so it will subcool much more. The ratings given, like 10deg F ideal subcooling are for specific conditions. Conditions, as he mentioned in the video of approx 72-74 deg F inside and maybe 70-80 deg F outside (I can't remember what numbers he used. Most condensers run at approx. 20-30 deg F above outside temps so to put the system into "design-ish" conditions we have to get the head pressure up to a saturation temperature somewhere between approx 90 and 110 deg F.
I would be weary to use that method to check the change, I mean what if you move the board on top? The pressure is gonna change right? How do you know where to put the board or how much to block off? I just feel it's a "fire from the hip" scenario where you don't truly know what the charge would be because you moving the board blocking the airflow will have a major effect on your pressure. I'm jaded cuz I work in South Florida and its only cold for a month outta the year but I wouldn't hang my hat on that method. Thank you and your videos are great
It's pretty much a good ballpark figure, but you're right not 100%. As an installer in NW Louisiana we have way more cold weather start ups, we always schedule a follow up return visit when the weather warms up to recheck. No additional charge to the client, and saves the extra cost of an unexpected callback for a tech at 10 o'clock at night lol. Gotta love weather in the south..
This is making the best of an non-ideal situation. Anytime you have to check charge outside of design conditions is technically not ideal... Which is almost always by definition. This method is not perfect but if you have a thorough understing of the system and this method, you can be fairly confident with your results. Many people that do this if they need to in cooler weather, will try and come back in warmer weather just to double check.
I have the exact same unit. Mine is manufactured in 2008 so 15-year-old. It is not cooling. I called an HVAC company and technician hooked up gauges and said it has low refrigerant. They dont add refrigerant because it is R22. I am immediately connected with a salesman to get a quote of 10-20k AC replacement. It is so frustrating to experience all of these especially this time where I am looking for my first job after getting my PhD.
Anyways the tech measured the pressure when it was 50-60 outside. He didn’t do any heating method as you described. I wonder the measurement he did was false
What about if you had a fixed metering device.?
This...
What are your thoughts on refrigerant below the oil in the compressor when the outdoor ambient temperature is low and the compressor hasn't run for days or weeks? Wont it boil up through the oil, thus not allowing the oil to reach the parts of the compressor that it's supposed to be lubricating?
Crankcase heaters
@@HVACRDUDE only are installed on heat pumps. Not AC only. He was working on gas with AC.
I've seen crankcase heaters on AC-only compressors, circa 90's.
Unfortunately these days, be careful a new heat pump comes with a crankcase heater else it can't be operated under 50F ambient.
@@thisisyourcaptainspeaking2259 everything is customizable these days.
@@Brokefootchuck Hopefully it has an accumulator, or does the field tech need to design that as well?
My minisplit is a 12,000 btu unit. Unit indoor and outdoor are running there is no error code appearing so I let it run all night about 12 hours straight, indoor not heating or cooling? indoor fan is turning but only getting ambient room temperature coming out of head unit was installed by licensed hvac teck 2 years ago can anyone help thanks.
👍
I'm waiting for the "charge without gauges" video.
It was the board
I believe your temps kept changing because you were losing your heat load in the house.
Yep. Cooler and cooler evaporator means less and less refrigerant in the low side. That refrigerant ends up waiting in the high side, so high side pressures increase and subcooling increases.... In a perfect world you would throw a bunch of electric portable heaters on in the house close to matching the AC capacity - or you would adjust charge on a hot day. Then you would have nice even running. Have to be relatively quick when doing this type of charging and hopefully can keep an eye on indoor returns air temps. A very slow drop in temp is fine but if you are dropping a degree every couple mins you probably would never reach a stable charging condition.... just my thoughts
2:00 how is that silver stem on the depresser not leaking refrigerant? I don’t understand what’s keeping that sealed
Just a compressed gasket or oring. There is a packing but you can tighten if it ever starts to loosen up. You tighten that nut and it further compresses the sealing material. Exactly the same idea as any water gate valve.
Or what we do is we (outdoor temp-saturated temp) if we get 12 to 16 degrees of difference it’s ok
In this scenario, 10 degrees manufactured design, like the teacher said, +/_ 3 degrees it’s fine you good, if you have more than that, the system is overcharged, if less is undercharged
If you take refrigerant out then your superheat is going even higher than 20 and with no heat load does not justify over a 20 superheat. Thoughts?
TXV's job is to maintain superheat (within a reasonable pressure range). Removing a relatively small amount of refrigerant will remove total amount in the system. TXV basically maintains the same amount in the low side so the refrigerant pooling in the high side is reduced... Lowering the subcooling. *With any fixed metering(piston or cap tube) device you would see superheat increase and subcooling decrease.
@@sbitschy ... Just for reference...36 years in the trade and teach worldwide. Standard txv will not maintain superheat no matter what occurs. It will only maintain with within certain parameters. 👍 You can absolutely have a super high/low superheat and subcooling.
@@burtminshew4812 I don't understand what you are saying. I am here to learn. I said that a TXV can only maintain superheat in specific pressure range. I feel like we said the same thing. I am well are that you can have high superheats and low subcooling in certain circumstances. It seemed like he removed a negligible amount of refrigerant, I didn't feel that it was enough to start messing with the TXV superheat control. Can you explain what part you disagree with?
What valve core tool/ connector did you use?
Thumbscrew core depressor.
@@yoshitoons113 Got a brand , thanks
Hi, why can't we use this method with a fixed orifice metering device? Thanks
Because to check superheat you need the outdoor dry bulb temperature while “simulating” a warmer day. Basically would be guessing
What if it's a piston instead of a thermal expansion valve
Same way
Just charge and check in the summer... That's risky,. You could easily overcharge I think.... Also what if there is no txv and has a piston? Then you can't do this method?
To my knowledge, you can do the same method, just because that one has TXV, you have to check it from high side for sub cooled, and piston, for superheat.
I find you can't muck about, the room will reach setpoint pretty quick and shut off before you're ready.
Btw I'd definitely flip it over to heating to recheck the pressures
That’s if it’s a heat pump otherwise you can’t check the pressures in heating mode
I use a contractor garbage bag as a charging blanket. Simple light weight multipurpose. Easy to adjust and no risk of the plywood flying off and causing injuries to a newbie tech.
Wouldn't a bag fly off faster than a board
Wouldn’t moving the plywood change your values ?
That’s EXACTLY what I was thinking. Like, how can you REALLY tell it’s overcharged or not… If you cover it all up or not at all the values change… so which is right? Doesnt seem consistent and or accurate.
The entire point of this is that your values change depending on how much air you block off. The 10 deg F Fahrenheit subcooling target is given for a specific set of conditions. We can't raise the outdoor temperature to these specific conditions but we can block off enough air to get our pressures and saturation temperatures up to these conditions. Your condenser simply rejects heat from refrigerant. Since the condenser rejects more heat at lower outdoor temps and the same airlow, we can start to block off airflow on a lower temp day until we are rejecting heat at the same rate as it would on a warm/hot day(the specific conditions where the 10 deg subcooling is the target.)
Sorry tough to explain in a TH-cam comment... Anyways, the concept of what he is doing is perfectly legit.
At the 6 minute and 40 second mark you said something that doesn't sit well with me. Not sure if it was a mistake.
Why would the subcooling be lower when it's cooler outside and higher when it's hotter outside?
I would think it would be the opposite.
The cooler it is outside, the more the condenser will be able to condense... More subcooling... and the hotter it is outside the less the condenser will be able to condense.... Less subcooling.
What am i misunderstanding?
I just looked this up and this is a copy and paste from online....
"As the ambient temperature increases, the condensing pressure also increases, resulting in a higher pressure differential across the orifice. This will increase the flow rate of refrigerant in the system, resulting in less liquid remaining in the condenser and correspondingly lower subcooling."
The sub cooling ends up being low in cold weather because the refrigerant isn’t flowing properly out of the condenser . The condenser is so cold that the refrigerant wants to remain stationary in it. You end up getting small bursts of liquid refrigerant leaving instead of a solid column of refrigerant. The temperature of the leaving refrigerant is not accurately sensed which manifests in low sub cooling.
Sounds like the quoted text is speaking about a fixed metering device. And in that case I would agree that the flow of refrigerant through the metering device would increase. The low side pressure would also increase. I think that a tev would only briefly exhibit that behavior and then would pinch down to correct the super heat.
Now that does not answer your original observation, but I thought it may be helpful to say something about the flow statement from the quoted material. Seems to me that increasing the condenser temperature while still maintaining a cool temperature outdoors would present a larger subcool reading than if the OD temp was much warmer. Reason for this is the condensing temp same but colder air being drawn across the coil, and that would be accurate if the same amount of air flow of the colder air were in the equation. In this case the airflow across the coil is reduced. So what I am saying is that with this method it is kinda self correcting to a major extent and the subcooling should be a reliable number to determine if the charge is set. So it was overcharged. The only thing I do differently is push the condenser temperature a little higher to between 110° and 115° depending on the equipment design for most modern equipment I see. Reason is that is a 95° day plus the condensing differential. Not it may not be able to hit that high and maybe that was the case here or the instructor had some other reason to replicate a milder day.
Hope this helps, and keep watching this channel.
This want work on a piston metering device?
You’d use superheat
@@jrenna07 same concept, just with super heat?
@@floyddavis2095 yes. Restrict airflow like in video. Fixed metering device you use superheat. TXV you use subcooling since it is a “constant superheat device”
@@jrenna07 thanks
Usually I love your videos but I'm a little confused in this one. With the valve core remover, you were not removing the Schrader core so why were you spinning it as though you were loosening it? Those just push in and out. You usually push in and then turn while it's pushed in.
That's not a Schrader valve remover. It's a low loss called thumbscrew core depressor.
@@yoshitoons113 oh ok. Thank you so much
@@yoshitoons113
Couldn't you just use this every time you put your gauges on regardless of using hoses or the stubbies?
@@biblebloopers946 yes you can use it
Why is superheat high if you claim to be overcharged?
I was thinking the same thing. Might have a TXV that isn't opening as dar as it should or is slightly restricted
Since the system has TXV, we should use sub cooling method, we don’t have to focus on superheat, because, we need just to adjust sub cooling to manufacture design degree,
@@bill98778 you don't fine tune the charge with superheat if you have a txv, but you still need to see if it is within range to detect if there are any other problems. But Craig said SH is high, therefore it is overcharged. And I'm wondering how did he get that conclusion.
@@realSamAndrew well, if the system is overcharged, could damage the compressor, or since the superheat is high could be the TXV is not working properly even he said is doing his job
Why do all the H fat companies wanna check my heat pump once a year in the fall and my air handler in the Spring and not make it simple and check both products once a year add a good time when the temperature is right
To many variables that can give you a false reading and no actual humidity load to simulate wet coil condition techs will be recovering charge in winter and recharging in summer wait for adequate testing temperatures.
A contractor garbage bag blocking the intake of air would be easier.Easily and safely adjust the amount of air that is moving across the outdoor coil. No wood or recovery tank to deal with. Also less stress on the fan motor. Cheaper than a charging blanket and it serves two purposes.
Totally mis-leaded information and could be led to refrigerant mis-charge and equipment damage. 10F sub-cooling on name plate is equipment factory design sub-cooling at 95F ambient and 73F indoor wet-bulb temperature. I didn't see author did put indoor wet-bulb temperature into account. The truth is, if indoor wet bulb or outdoor ambient temperature or both below equipment design temperature the sub-cooling going to increases, if above the sub-cooling will decrease.
For example: at 80F ambient and 70F indoor wet bulb temperature the sub-cooling will be about 17.5F.
You are correct. The little paper attached to the electrical cover called service facts would tell him that. What he is simulating is a ODU with an airflow restriction running in low ambient. This is not how it should be done.