Suction Line Temperature

In this video, Bryan takes a more in-depth look at suction line temperature. He explains why it's "beer can cold" and what it indicates about system operation.
The placement of your temperature probe can have a major impact on your temperature readings. The suction line will be colder near the evaporator and warmer near the compressor. Direct sunlight can also increase the temperature reading via radiant heat. All that said, we typically measure the suction line temperature and check our superheat near the condensing unit.
If you don't connect gauges, you need to know the indoor return temperature. In most cases, the evaporator temperature (boiling temperature or suction saturation temperature/SST) is about 35 degrees below the indoor return temperature. So, if the indoor return temperature is 75 degrees, then you would get the typical rule-of-thumb 40-degree evaporator coil. However, the difference will vary a bit if you're running a lower airflow for dehumidification purposes; colder coils are better for pulling the moisture out of the air.
To calculate the suction line temperature from the SST, we need to know our return air temperature (measured away from the evaporator coil), subtract 35 degrees, and add the superheat (set by the TXV). The total superheat (right before the compressor) is often 20 degrees, though some manufacturers also specify that they don't want suction line temperature to exceed 65 degrees.
Compressors could be more likely to overheat if the suction line temperature exceeds 65 degrees. The superheat at the evaporator outlet on residential systems is typically around 10-12 degrees. The difference between the superheat at the evaporator outlet and the compressor inlet comes from the fact that the suction line picks up extra heat between the two locations. You can take all of these readings and do all of that math without connecting gauges.
Read all the tech tips, take the quizzes, and find our handy calculators at www.hvacrschool.com/

Пікірлер: 78

  • @monteglover4133
    @monteglover41334 жыл бұрын

    Again a great video, I've have 40 years experience in HVAC&R knowing these kind of "tricks " has saved me lots of time and headaches. You have to be able to see and think to be a good technician, most of us had to learn this in the field

  • @hozerhvac4406
    @hozerhvac44064 жыл бұрын

    Bryan it’s not a joke that you are one of the greatest teachers to ever come forth in the HVAC community. What you have done for the industry is amazing. As a fellow technician I want to say thank you. You have made my career that much better with what you have done. 👍 to you my friend.

  • @HVACS

    @HVACS

    4 жыл бұрын

    I’m not sure I deserve all that but I’m thankful for you

  • @SombraLocs
    @SombraLocs4 жыл бұрын

    Understanding temperatures and using it to troubleshoot is a lot easier than trying to troubleshoot with pressures.

  • @shannonhill3356
    @shannonhill33562 жыл бұрын

    Florida tech with on yr in the field, here. I would give my left arm for even just three months with your company to get some serious learning in. Thanks so much for all your videos and podcasts - I discovered the channel while in trade school and have been following along since. You e helped answer so many questions as well as just show me things I wouldn't come across in my day to day.

  • @anthonybielobockie4991
    @anthonybielobockie49914 жыл бұрын

    I was just searching the Internet yesterday to figure out non-invasive AC system performance diagnostics and guessed that suction line temp would be key based on watching suction line temps come down as a system reached a full refrigerant charge. This video confirms that observation with a lot more info. Thank you.

  • @edwinjewell5359
    @edwinjewell53594 жыл бұрын

    Bryan your Awesome Great Videos its sometimes hard to keep up with ya but you really explain it in layman terms. Thanks.

  • @uakzkah6001
    @uakzkah60013 жыл бұрын

    I love my fieldpiece probes, I had a hard time spending that much money on them but they have really been helpful.

  • @corruptedbrain6

    @corruptedbrain6

    8 ай бұрын

    i have them too 😢 they are so good ! 😊

  • @travispoe4401
    @travispoe44014 жыл бұрын

    Great content keep up the good work!

  • @jeanabrea5054
    @jeanabrea50544 жыл бұрын

    awesome video bryan my idol. always watching your videos gotta learn more from you

  • @ronie1337
    @ronie1337Ай бұрын

    Bryan, thanks for the info.

  • @misaelmorenoluna7299
    @misaelmorenoluna72994 жыл бұрын

    Super helpful info. Thank you!!

  • @JamaicaBayRat
    @JamaicaBayRat11 ай бұрын

    Another great hvac video

  • @VeryPersian
    @VeryPersian4 жыл бұрын

    Great video. I would just add that a higher efficiency indoor coil will have a target of 30 vs 35 degrees.

  • @phillipjoy8191
    @phillipjoy81914 жыл бұрын

    Great video

  • @donnierobertson3088
    @donnierobertson30883 жыл бұрын

    Nice job and video like always

  • @GotchaplumberGotchahvac
    @GotchaplumberGotchahvac2 жыл бұрын

    Good tips!

  • @coolezum
    @coolezum4 жыл бұрын

    Spot on presentation. Great job! Just a suggestion brother and you may have already covered it but, I found many HVAC techs do not realize that many TXVs are adjustable especially on commercial equipment. Maybe a vid? Peace

  • @Oopsie223

    @Oopsie223

    3 жыл бұрын

    Pretty sure he has a vid on troubleshooting a TXV. KZread sucks for searching a specific channel for videos though.

  • @oindigenous9990
    @oindigenous99903 жыл бұрын

    Muchas gracias 😊 amigo.

  • @coolezum
    @coolezum4 жыл бұрын

    Good job, just a note : prefer to see liquid line filter drier close to the indoor metering device. Helps keep it out of the weather and from rusting as well. The picture on the outdoor unit just showed it outdoors but, good to see one in he system.

  • @condor5635

    @condor5635

    11 ай бұрын

    So if I get a new system alway tell them to place the dryer close to the TXV instead of outside? I always thought there was a reason it was outside but you make a great point.

  • @coolezum

    @coolezum

    11 ай бұрын

    @@condor5635 ya man👍😎

  • @Oopsie223
    @Oopsie2233 жыл бұрын

    Total credit to Jim Bergman for all this theory.

  • @josephkwon9034
    @josephkwon9034 Жыл бұрын

    hi whole suction line have to be insulated or only outside insulated?

  • @User-be5yj

    @User-be5yj

    Жыл бұрын

    The entire length.

  • @MrNebRebew
    @MrNebRebew4 жыл бұрын

    I wonder if you could do a video/podcast on line set sizes like different diameters on system performance. Everyone knows we should follow manufacturers specifications but I run into many systems where people have reused the line sets and the newer systems is calling for one diameter larger like 7/8” vs 3/4”. Around here many of the systems are installed in attic’s and suction lines are quite often dropping 25 feet. Many times the systems seem to be running fine but could they be running a better delta T, or better electrical efficiency if they have used the larger suction line?

  • @coolezum

    @coolezum

    4 жыл бұрын

    MrNebRebew Hello Brother, just a note from a long time tech here. I have noticed more often than not when going from R22 to R410 that the line sizes are typically the same or less. Also if you go to the Install manual or the Engineering specs often the line sizing has a pretty large margin on line set diameter as well as length before it affects BTU output significantly if at all. Trane and carrier have great design manuals for all this.

  • @AGON17
    @AGON174 жыл бұрын

    How does this apply to a RTU? I've had plenty of instances where I have a perfectly running system with 8-12° of SH at the compressor. Is this due to a lack of a lineset?

  • @jennifercase9306
    @jennifercase93064 жыл бұрын

    Hello, asks a Question I hope you can answer. Is it recommended using TWO different Systems in an AC say Out side is a Goodman, inside is a Rheem. Do these Mix well or should all AC be the same inside and out. The apts i live in they have Non Certified HVAC woking here and none of them even Know the +30 Rule and probably nothing of what you just Discussed they speak little if any English is why.

  • @this_is_9ball
    @this_is_9ball2 жыл бұрын

    please consider adding metric in text overlay. great videos.

  • @UltraHydrophobiccoat
    @UltraHydrophobiccoat4 жыл бұрын

    Today I have two R22 AC in a house which have NO filter driers installed. Fixed piston metering device. Both suction line pressures are around is 90psi (saturated vapor temperatures are around 53F). The suction line temperature at outside condenser service valve are around 73F. So the superheats are around 20F. The liquid line pressures are around 220psi (the saturated vapor temperature is around 108F). The liquid line temperature is 104F. So the sub cooling is 4F. Although the super heat is high, but I don’t want to add refrigerant since the pressure at suction line is already pretty high. Is the metering device clogged? Thank you

  • @Es0ter1ca

    @Es0ter1ca

    4 жыл бұрын

    You have high superheat and low SC. That’s likely just an undercharge situation. It’s unlikely the piston is restricted, but it’s hard to really diagnose without knowing airflow or indoor wet bulb and such

  • @veritasaequitas9875
    @veritasaequitas98752 жыл бұрын

    Can you apply this principle to a domestic refrigerator? I got two pipes emerging from the compressor. One is hot (105F) at the point the pipe meets the compressor and the other is ambient (68F) where it meets the compressor. Which one is the suction pipe? The ambient?

  • @APEX.86
    @APEX.862 жыл бұрын

    Would there be any merit in using indoor suction line temp to tune your blower speed? For example, if you were slowing the blower to remove more water, but didn't want superheat to fall too far.

  • @sbsaircon

    @sbsaircon

    2 жыл бұрын

    Suction and condensing temp Of compressor.

  • @johnd4348
    @johnd43482 жыл бұрын

    The company I work for sticks to ridget rules on temperatures and pressures. You cant talk to these guys and explain to them that not all systems are created equally. Some are just bad installs or worn out equipment. Me I just use my gut feeling on what works . its worked for me for 30 years. Not an expert just a service man.

  • @bryontharp5790
    @bryontharp5790 Жыл бұрын

    Is 15 degree drop good in humid hot weather 104 outside from return air to vent bryan.

  • @haroldcouch4168
    @haroldcouch4168 Жыл бұрын

    I'm having a problem I need help with.5ton 410a Txv.Subcool about 10.Sat temp 48.(High right)Delta T 15(low)Suction temp at evap 63 and hunting.I see however suction temp hotter at evap than at service valve.Capacity for crap high elec bills air gets hotter by the day with inside home at a muggy 80.Is there a restriction,bad txv,non condensibles,bad coil distribution?HelpShould I remove refrigerant to get lower sat temps.Its 79 indoor temp at return plenum which I thought sat temp should be about 44.Air supply is 63

  • @paulchristian8271
    @paulchristian82713 жыл бұрын

    A dirty ID coil, or fan running low speed, can screw this all up, even with a TEV, depending on how bad an airlflow problem is. I’ve seen plenty of iced up coils (back to the compressor)with TEVs, with a warm space temp, and t-stat setting in normal range.

  • @gorankoleznik1
    @gorankoleznik13 жыл бұрын

    Can you talk more about how to properly set up the probes and do the measurement on some modern air-water heat pump with ETXV like Mitsubishi PUHZ or PUD or Daikin or Panasonic or, Hitachi. This videos are too much of an US type air-air conditioners not heat pumps. Im really interested how would you measure the system with Testo smart probes, read the data from it and use that data to diagnose the system. Most of the times the heat pumps like Mitsubishi comes precharged and with inverter technology. Can you even diagnose the system on inverter heat pump? Where do you plug in the probes(at the service valves or at the valves at exit from the heat pump? How do you know if the system is charged good if you have inverter heat pump?

  • @coldfinger459sub0
    @coldfinger459sub04 жыл бұрын

    Beer cold 🍺 draft please. Don’t like beer in can cold. 👍 Fieldpiece probes + MeasureQuick + Bluvac PRO + NAVAC NRD16T vacuum pump + Accutools TruBlu Evacuation pro kit. 👍👍👍 loving life. I don’t work I just have a cool hobby.

  • @MrDougfunny7

    @MrDougfunny7

    4 жыл бұрын

    t lech that’s awesome dude. I’m in property maintenance and I’ve learned everything HVAC from this channel and his podcast. I use measurequick and the fieldpiece probes too. Hoping to move to HVAC when I know enough to not have a lower wage when I transition. Love when I get an AC call! Lol.

  • @zacharyreed45
    @zacharyreed45 Жыл бұрын

    (DBIAT - 35 + TSH = SLT) +- 3

  • @leehancock2782
    @leehancock27824 жыл бұрын

    My suction line is cold as hell by compressor. 120000 btu furnace and only 8 vents on 6 inch duct in house. Is it possible im not moving enough air. Unit runs non stop above 90 degrees

  • @davejohnsonnola7908

    @davejohnsonnola7908

    3 жыл бұрын

    There is a phrase that may apply here. "ABC" = AIRFLOW BEFORE CHARGE. Too many "techs" start passing gas before eliminating airflow problems at both evaporator and condensor.

  • @AlexMW-1
    @AlexMW-13 жыл бұрын

    I enjoy your videos but sometimes you overlook or don't state the effects that ventilation issues can have on these numbers. I am in the controls and data analytics software business (my co). To use an example, I decided to hook our sensor system on my own home. I didn't expect to find much but I was instead very surprised. My home is zoned up and downstairs with a Honeywell controls system. After running the diagnostics on my home, it blew me away when I discovered that my bypass showed "open." When I examined the system in the attic, I discovered that these fools never installed a bypass and it was wide open. Now this causes the extreme heat or cooling in the return (depending on what stage is running). As for the suction line, it shows very cold when the system is cooling. That might cause some errors in a tech's judgement when only considering LL to SL etc. My point is that the big picture matters greatly. We deal with commercial applications with bypasses and fairly complex setups too. However, even the small split systems can get complex when they've gotten fancy with Honeywell zoning and bypasses.

  • @scottwebber652
    @scottwebber652 Жыл бұрын

    Boy that’s a lot of info for me so if I was going to get someone to check out my unit how/what do I need to do/ask for this n what /how much time is expected for the eval. I get repairs r separate. I gotta ask tryin not to get hosed as I can see $$$$.

  • @maness2112
    @maness21124 жыл бұрын

    I like my ipa at 55f.

  • @zesty2023
    @zesty20234 жыл бұрын

    Can someone explain clearly why the suction line is colder then the liquid line? I mean the liquid line is subcooled liquid, but the suction line is saturated boiling gas.. it's holding all the heat from inside the house so how is the line so fricken cold?

  • @davejohnsonnola7908

    @davejohnsonnola7908

    3 жыл бұрын

    Behold the magic of pressure and temperature relationships and the movement of heat from where we no longer want it to somewhere else. ¡ Namaste !

  • @satratey
    @satratey4 жыл бұрын

    Sir, what is the capacity of a refrigerant compressor, how is it calculated, and why do we measure it in term of a heat transfer unit like BTU/hr or TR?

  • @vetta17

    @vetta17

    4 жыл бұрын

    sandeep satratey I can kind of answer that I think?!.. capacity is the stroke, bore and size of piston, if I remember right from school lol. And you use btu because thats the heat rejection, like 1 ton of cooling is 12,000 btu of heat rejection and 15,000btus of cooling.. or something like that haha my numbers might be off but the idea is close

  • @davidycedo1606
    @davidycedo16062 жыл бұрын

    Try data for Arizona 110 to 119 inside day temp 80 .

  • @JulesODwyer
    @JulesODwyer4 жыл бұрын

    Still try and look at your suction line at the Compressor and see if it is sweating all the way to the Compressor and maybe a small ring past the Point of entry into the Compressor is somewhat a good indication of over or under charge of a system .

  • @HVACS

    @HVACS

    4 жыл бұрын

    That depends on outdoor dewpoint

  • @JulesODwyer

    @JulesODwyer

    4 жыл бұрын

    HVAC School I agree live in Louisiana but plenty of times you can see the sweating will Stop a few inches from Compressor which is a sign but I always do Superheat and Subcooling no matter if fixed office or Txv and if it’s a change out or New System I always put Fittings by evap Coil with shraders lil expensive but can check my pressures and temps entering and leaving evap Coil also with liquid dryer at Coil . I’m 63 yrs old still working and learning every day

  • @Es0ter1ca

    @Es0ter1ca

    4 жыл бұрын

    Here in AZ we very rarely have sweating suction lines because it’s so dry out here. Careful sharing that method with others.

  • @davejohnsonnola7908

    @davejohnsonnola7908

    3 жыл бұрын

    Jules, we sweat in January in Louisiana! Not everyone lives in a swamp!

  • @duanesee3430
    @duanesee3430 Жыл бұрын

    Yel

  • @BigSad49702
    @BigSad497025 ай бұрын

    My instructor did not teach this

  • @MatthewsDre
    @MatthewsDre4 жыл бұрын

    Second

  • @maness2112
    @maness21124 жыл бұрын

    Remember to have clean filters before measuring suction sht.

  • @johnszymanski548
    @johnszymanski5484 жыл бұрын

    First

  • @eliorios9420
    @eliorios94204 жыл бұрын

    What do you mean we don’t know that beer can cold is cold 🥶 just because it’s cold beer can cold doesn’t mean we’re drunk while we’re Measuring the temperature with our hands!😅😅

  • @billr7096

    @billr7096

    4 жыл бұрын

    He made the case in this vid that beer can cold is a good measurement. With all the variables he put out there it comes down to nothing over 65 degrees. So who cannot feel that? Beer can cold has a place to b used. Might not b spot on but is close. If u look at the makers specs they give temp "ranges" usually 5 degrees. The temp probes also have a plus or minus degrees of accuracy. Remember we are not working on the space shuttle!!! B 4 anyone gets panties in a bunch I do have Associate Degree in Air Conditioning and Refrigeration and years of field experience. I know the highly technical shit as well as rule of thumb shit. Just sayin both have their place.

  • @FlyEaglesFly19111
    @FlyEaglesFly191114 жыл бұрын

    Ductboard.. that's a bad example. It was intended to use as wrapping metal duct. It is a bad product..causes mold, fiberglass constantly in airstream, and so on. I cannot stand scabs that can't be real men and do a job right.

  • @HVACS

    @HVACS

    4 жыл бұрын

    Then you won’t like the entire state of Florida 😂

  • @matttzzz2
    @matttzzz2 Жыл бұрын

    I love u and all but i hate all this Fahrenheit shit. Please at least put the proper temperature measurement underneath the improper one. Its very frustrating having to convert it every time!

  • @mickc6926
    @mickc69262 жыл бұрын

    Awesome videos...but heavens above SLOOOOW down when explaining your theory on these videos...its like listening to a horse race commentary..🥴

  • @tqt5413
    @tqt54133 жыл бұрын

    Well knowledge doesn't mean good teacher. You talk like a robot - Too fast and too monotone.. (bored)

  • @TheWilferch

    @TheWilferch

    2 жыл бұрын

    You can play-back at less than normal speed. Look for the gear tooth on the bottom edge of the vid....click....and run at 0.75 speed. I have the same issue...BUT.....I appreciate the shortness of the vid at regular speed and to get the big picture....yet be able to play back at 0.75 or even slower speed if I need to....to absorb the details. You gotta admit, the content is technically excellent. Hei s a good teacher and uses screen text to good effect too.... 👍

  • @User-be5yj

    @User-be5yj

    Жыл бұрын

    Damn I thought I was the only person

  • @cengeb
    @cengeb3 жыл бұрын

    Talk slower!!! And stop waving your hands, I think it is giving me sea sickness!

  • @Dale37
    @Dale374 жыл бұрын

    I love my fieldpiece probes, I had a hard time spending that much money on them but they have really been helpful.

  • @cu27rotary70

    @cu27rotary70

    4 жыл бұрын

    I am getting SMAM for a hundred bucks and my boss will pay the difference. My Yellow Jacket probes were 278.