How Defrost Works on a Heat Pump! Explained Step by Step!

[@acservicetechchannel]

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[@saulsanchez9531]

id like you to make a troubleshooting book how to diagnose control boards ,pressure switches ,reveasing valves and all components that the heat pumps , air handle and the funace especially in spanish

[@jeffreybricks2687]

Hey ac Service Tech, if the unit shuts off during the run timer let's say is 40 minutes and it shuts off after 20 and than runs agian will it pick up where it was when the heat turned off?

[@Sam-dc7qp]

Best Teacher hand's down

[@jollyscaria1922]

Systeom not pnp dow no pressar relaszbai

[@jollyscaria1922]

Ok gas revomed need mut pump down peger only down ok big pint

[@NROhvac]

Yes, he is hands down the best

[@falconewk]

Excellent video, simple enough for this electrician trying to develop his HVAC knowledge. Thanks Craig! Your book has been helpful as well.

[@acservicetechchannel]

Wow, thanks!

[@thaitichi]

I've asked this question several times online and nobody ever seems to know the answer. You are amazing!

[@mixtecooaxaqueno6730]

One of the best hvac teacher in youtube, I'm learning a lo from your videos and book.

[@acservicetechchannel]

Happy to hear that!

[@shooter2843]

Another great video. I wasn't ready for the trade after trade school, your videos helped more than I can say.

[@acservicetechchannel]

Great to hear!

[@Joe_Joe_The_HvacMan]

I have been an instructor and in the field for 30yrs. This is an EXCELLENT presentation on time/temp defrost system! GOOD JOB!!

[@acservicetechchannel]

Thank you very much and thanks for teaching techs. It takes passion to teach for 30 years, awesome!!!

[@chesstime356]

I watch and watch over theses videos again and again. Nice

[@bigwhitemeathead7684]

Your series of videos helped me locate and fix a high voltage short in the condenser and a low voltage short in the thermostat wire. This was after the professional hvac techs gave up. Thank you for creating the excellent heat pump videos and for your excellent explanations in each and every one of them!

[@jeffreybricks2687]

You also seem like a very positive and great person, thankyou Craig!

[@acservicetechchannel]

I always say, we are trying!!! Thanks so much!

[@jkbrown5496]

I have adaptive defrost on my system. It failed last year, with a board and thermistors replacement. But I looked into how it is different than the traditional time/thermostat defrost. It has a coil temp sensor (thermistor) instead of a thermostat and an ambient temp sensor (thermistor). It has some algorithm that determines when to defrost based on the comparison. I did learn if the ambient temp sensor fails, the board defaults to a 30 minute time cycle (and uses the same when it is first powered up till it gets a "sense" of the temperature profile). If the coil sensor fails then defrost stops like with a thermostat. Also, the selector pins on the board don't adjust the time, but rather the coil defrost termination temperature. Haven't been able to find much on the why or wherefore of raising or lowering the termination temperature. Testing spare coil and ambient thermistors, I noticed the resistance test current on the meter will cause them to climb reading as it warms them up. So you have to be quick about taking the reading if you want to convert it to a real world temp. Haven't found any good information of field testing for sensor drift. So it is kind of open, shorted, or seems close enough to my outside air temp reading for testing.

[@vnesmuonnam]

Save me a lot time and money on books. Thank you

[@acservicetechchannel]

Happy to help!

[@drprofessor1414]

You’re a wonderful teacher, so eloquent with your words. Very intelligent friend, thank you for your efforts and knowledge!

[@acrepairnearme]

Brilliant! Best teacher on KZbin!

[@acservicetechchannel]

Wow, thanks!

[@tserevenad]

DIYer here, .... wow mind bending. big respect to you pros!

[@jeffreybricks2687]

You make everything so simple man THANKYOU!

[@adamcraig1568]

Great video. Waiting for the communicating systems to be on here

[@brianosegueda3622]

Excellent explanation of what happens in heat pump mode.

[@primusheating1]

Always clear and precise from you my friend.

[@acservicetechchannel]

Much appreciated

[@albotiger7268]

Very good explanation. Great videos as usual!

[@acservicetechchannel]

Glad you liked it!

[@pingpong9656]

Master class teacher - really clarifies the defrost

[@CHOMAHOMA]

Thank you very much for your videos. They always help me to understand HVAC and to improve my skills every time.

[@acservicetechchannel]

Glad I could help!

[@8joh58]

Great explanation Craig 👍

[@HillBillyGaragew]

Good job on explaining easy to understand you!

[@hkhsm359]

Nice video. Great knowledge. Thanks for sharing

[@acservicetechchannel]

Thanks for watching!

[@Demy26]

Great explanation

[@acservicetechchannel]

Glad it was helpful!

[@sharky5570]

Question what is the lowest outdoor temps that these things run in? I have had the things running in temps to mid teens. Ohio.. Also in a pinch I have had the dfs go bad and jumped it out till new one arrived. It would be in defrost for 10 min and go back into hp operation. Carrier did not know if it would work but it does because of the timer. Great video.. subscribed.

[@charlesmorgan2234]

All your vids are great including this one! My only question is when the heat pump turns on electric heating in the air handler does it also turn on the air handler blower?

[@gotchaplumber]

Great explanation!

[@eman3208]

another awesome video.. Thanks!

[@acservicetechchannel]

Glad you enjoyed it!

[@JeanMedard-fh6fj]

Really good video!

[@jesusdelgado2232]

Awesome Vid, I needed this refresher!

[@D2O2]

Turning the aux heat source on also adds energy to the refrigerant raising compressor discharge temp making for a quicker defrost.

[@aaronwynkoop7066]

Awesome job. If you could do a video on furnace and the components and maybe show the wiring that would be awesome

[@walterrisco4236]

Really good explanation very clear am glad that your share all your knowledge of hvac thanks. :)

[@acservicetechchannel]

Glad it was helpful!

[@buddycheck84]

How you have the time to make these great videos and not be in demand to teach in person across the country (all things equal of course) is beyond us,,!!!

[@nickledimez4012]

Buy his book! Great investment

[@MaMa-qh4dy]

YES. You will not be sorry!

[@hanound79]

Useful information 👍

[@acservicetechchannel]

Thanks for liking

[@tecniman356]

You are the best!

[@eternallife721]

Very nice video. Thank you very much.

[@acservicetechchannel]

Glad you liked it!

[@spelunkerd]

When in air conditioning mode, is there a similar defrost cycle to prevent freezing of the indoor coil? Why not? Is it because ambient temp in the home rarely gets so close to the freezing point? If you do see freezing of the indoor coil while in AC mode, do you think of other causes like a dirty filter, low freon charge, or other causes of poor air flow?

[@jjjames5089]

Great detail in your teaching, keep it up. Perhaps you could help, I need a parts catalog for an old Goodman model CPK224-1B heat pump. I'm having trouble finding the right reversing valve coil.

[@campbull_7815]

Great video

[@acservicetechchannel]

Thanks for the visit

[@mjfollrd]

Can the heat pump only go into defrost on a heat call or does the DTS put it into defrost automatically no matter what if heat pump is running of not Great Video Thanks

[@eastboundtrucking]

Thanks!

[@acservicetechchannel]

Thank you very much for your encouragement!!

[@MikeGraham-m9g]

Very helpful, thank you

[@acservicetechchannel]

Glad it was helpful!

[@Ted_E_Bear]

Great information !

[@acservicetechchannel]

Thanks for watching!

[@jollyscaria1922]

Now 6ooofee befor mt no self

[@thisisyourcaptainspeaking2259]

Found my defrost sensor dangling, disconnected from the coil tubing, where should it be mounted, before/after the "evaporator"?

[@omarr.r1448]

Awesome video

[@juancarlossalcitas1690]

We love your videos

[@montes5686]

Good video thx

[@acservicetechchannel]

Glad you enjoyed it

[@thehifiwifiguy]

Why don't they build heating elements into the coils to prevent this? It would potentially use less electricity than the coils in the handler IMO. It would also prevent the excessive reversing valve use.

[@TheUnofficialMaker]

my 24vac fuse is blowing and I have measured 1 ohm to ground on the red/yel Y term connection just above the DFT switch terminals. What should I replace?

[@humbertomacias3239]

Amazing

[@manna5610]

Is there a timer on how long the heat pump will run in heat mode before the elements will turn on? My hp will run to about 88 deg, then temp will start to drop (about 5 min), and the elements will turn on until the set temp is reached. this happens every time I start the hp in heating, even if I continually, adjust the set temp to turn off the hp and them turn it right back on. Service tech told me it is running fine, but could not explain why the elements keep turning on every time. Thanks for any help.

[@mark_Hershey]

During defrost mode is the evaporator getting cold or does refrigerant not reach indoor coil?

[@enduringpromise]

Hello Craig, I know this question is not related to the video. I could not find the answer on you other videos. Two questions... 1. Is there a way to bleed the small air bubble in the BODY of the manifold gauges or is it so minimal that no one worries about that air bubble? 2. If you do not connect the yellow hose to the tank, how do you return the high side refrigerate to the HVAC using a 3 value manifold gauge set? I believe the yellow line would be full of air and there is no valve available to isolate it from the body. Thank you for everything you do. I love listening and watching to all of your videos.

[@sprockkets]

Better solution, don't use archaic manifolds for checking pressures. Use probes. And if you are against electronics, use the analog equivalent, and you won't have to worry about it. And if you are worried about the high side and losing liquid, use this: www.trutechtools.com/Accutools-Shrader-Depressor-Tool-5-16Fx1-4M

[@pinoyamo]

So is it normal for the whooshing noise to occur twice? when it goes to defrost mode and after?

[@craigalan7911]

Hi. I’m a very tech savvy homeowner. My heat pump was diagnosed with a bad defrost board. I would like to do a self install. Other than swapping out the board, does it require any kind of recalibration or anything?

[@MaMa-qh4dy]

No. Just be sure to disconnect power to both the outdoor unit as well as the indoor unit. You don't want to get killed, and you don't want to short-out your low voltage transformer and/or fuse.

[@dkinfishing]

If you don’t have electric heat and natural gas instead, will the natural gas turn on as well?

[@magnito9811]

what happens to the inside coil during defrost ? system basically runny on ac mode wouldn’t the inside could be cold and counter act the electric heat?

[@jasonwee4305]

Hi Craig Thank you for the awesome video and explanation Question : I've come across numerous H/Ps that have had the board and DFT replaced. My question is where do you think the best location for the DFT is, because sometimes I've seen them located right after the outdoor txv, or right (seems to be) the exit for the condensing coil. Thanks in advance

[@acservicetechchannel]

I would like to see them need the middle of the outdoor coil but between the outdoor coil and the metering device works as well.

[@x-man4702]

Subscribed! Thanks for the video, very informative! Quick question: While the system is in defrost mode, does the fan inside the house runs simultaneously? If so, why?

[@MaMa-qh4dy]

Yes it does. In doing so, the fan helps to transfer heat from inside the structure to the outdoor coils to defrost the ice. Additionally, the indoor fan blows air over the resistance strip heaters to heat the "cool" air due the the unit running in a/c mode during defrost cycle.

[@mikesweet9623]

Hi, thanks for a very helpful video that you've shared with us. My question is that when it is difrosting and the gun of thr heat pump stoped working, is it normal that the compressor making a huming noise. should i let it run?; if so for how long it must run to defrost the heat pump. thank you.

[@MaMa-qh4dy]

The hum you hear from the compressor is usually masked by the loud noise of the fan. It is normal noise. Depending on what model unit you have, some defrost according to "time," and some defrost according to demand (outdoor coil and outdoor ambient temperatures). Just let it do its thing.

[@toolemanful]

Off the subject what is a reset relay?? And how is it drawn? Thank u

[@BornToFly4031]

How does a dual fuel (Propane) defrost work (Trane 18xi) if cutout/balance temp is set to 26 degrees? And temp never gets above 26 for a few days?

[@joebar2249]

Hallo My mitsubishi heat pump stops after a half our and unit outside is frozen.. Wher should I look for the problem..Gas is checked and refilled by technician, but no sulution.

[@NOVAServicesLLC]

Any clearer and I’ll see my reflection 😂all jokes aside awesome video and very informative.

[@Ray-wr2wr]

where is 24v coming from to the reversing valve ?

[@elizabethmasih4602]

My AC contensate pump do not start automatic when the reservoir tank is full but the contender outside get shut off and air handler keep running

[@johnconnor7501]

I don’t understand. So the 60 minute timer is just to have the board check one switch every 60 minutes? If it is why not keep it at 30 minutes instead so it check as often as possible since the temperature switch is the one actually making the decision to turn on defrost?

[@OcRefrig]

Good video ! Like #104.

[@acservicetechchannel]

Thanks for the visit

[@mindcreation3591]

Sir there is a Hitachi inverter AC. R-410a has gas. Ampere 4.1. But sir cooling is not happening. What's the problem with that, sir?

[@johndoe-wt4ui]

🙌 the best the 🐐the legend

[@jollyscaria1922]

Got come good

[@chrissauter7501]

How are we supposed to know when to use O or B?

[@sprockkets]

Rhreem and it's brands use B. Almost everyone else does O.

[@charliedc2A]

My defrost is set to 30 minutes will this be ok

[@dymarke]

Can I ask a question about a 4 zone mini split heat hump? I have oddities in my defrost cycle. I have a 4 zone C&H Sophia with ceiling cassettes. Usually all cassettes will defrost together but I have one cassette that will go into a defrost cycle when the other cassettes are still heating. Occasionally that cassette will stay in defrost and not complete the cycle. I have also had two cassettes (only two running at the time) that did not complete the defrost cycle and just didn't start up again. Power cycling returns proper function. This is a new system and my first mini split so I am still learning but this seems like odd behavior. Any thoughts would be appreciated. Thank you

[@acservicetechchannel]

I would contact their tech support to explain what is happening and determine the cause, thanks!

[@dymarke]

@@acservicetechchannel I did email them with no response but I will try again. Thank you

[@HVACRTECH-83]

Or it will power up the gas burners on a gas/dual fuel setup during defrost

[@jkbrown5496]

The defrost board puts power on the W wire (independent of the thermostat) so what ever heat source W controls will come on.

[@tylerlyons8109]

One thing I would correct here, the timer does not start counting run time until the defrost sensor closes, it does not "check" the sensor every 30/60/90 minutes, this is a common misconception that I also thought was the case for years, until I had a debate with another tech about this, we made a bet and bench tested a few different boards, I lost, might make for an interesting video

[@helobeast]

And what you find im curious. Cause im thinking about putting mine on 30minutes or should i leave it at 60 minutes??

[@jkbrown5496]

I traced out a simple Goodman board and was surprised to see that, as you say, the board isn't even powered till the DFT closes. R to the board immediately goes out on the 2nd R terminal (with no other connections on the board) and the DFT terminal is the start of all the circuitry. So the DFT has to be closed to power the board. However, my current system with adaptive demand defrost is has always-on power via R. It even separately monitors the HPS and LPS instead of series wiring.

[@tomozinga2267]

Tyler is correct. This is a common misconception, it’s presented incorrectly in many training videos and books. But that defrost timer does not run unless the defrost thermostat is closed.

[@charliemendez1479]

0:25 when this happens coil in air handle is cooling while aux heating at the same time?

[@DoctorSleep_0]

The heat strips in air handler are energized to produce heat to neutralize the cool air produced from the outdoor unit running in cooling mode. Just while it's defrosting.

[@jeff-w]

Its amazing how refined the operation of these machines is, while at the same time its comical how archaic and sloppy the controls are.

[@kitchenratt]

👍👍👍

[@johndeez2012]

mine pumps cold air when in defrost mode

[@MaMa-qh4dy]

It should do that. But your strip-heaters in the indoor air-handler should turn on to warm the cold air that is blowing over the indoor coil.

[@johndeez2012]

@@MaMa-qh4dy so my strip heaters might be bad

[@throttlebottle5906]

heat pumps work great, without power, just ask Texas! (ok that was an uncalled for low blow lol) I almost feel bad about their overall not expecting the worst and having some form of backup plans in place or at minimum some work-around means. :| sad place of life survival skills and surroundings means to accomplish such the USA has become

[@jakemilkovich1722]

In your given example, if the defrost cycle is a maximum of 10 minutes, why the expense and added complexity for emergency heat? 10 minutes of no heat, for an average building, should not even be noticed.

[@acservicetechchannel]

The problem is that its not that the indoor blower shuts off. It is literally running in air conditioning mode and the refrigerant is absorbing heat from the building in order to move it outside to melt the ice. You can stop the indoor blower because then there will be no heat in the refrigerant to melt the ice outside, thanks!

[@sprockkets]

Indoor creature comfort.

[@enduringpromise]

@@acservicetechchannel FYI, missed the word, "not". Cannot stop the blower...

[@jkbrown5496]

You'd be surprised how pissed off you get when your heat is blowing cold(ish) air. Even though objectively it only reduced the temp 1 degree. I started watching these videos because my system had issues. I finally learned the right questions to ask. My defrost board has two rows of terminals, input and output. When installed they'd put the W wire on the input terminal. I don't cuss the AC guy who installed the system all winter anymore.

[@erichorton1440]

Pause at 6:47 and tell me his thumb isn't fake.

[@sgtfixer]

Does a heat pump make a loud woosh sound during this process? I’m concerned something is wrong with my girlfriends condenser.

[@MaMa-qh4dy]

That is normal when reversing valve goes back to heating mode causing the refrigerant flow to be reversed.

[@sgtfixer]

@@MaMa-qh4dy thanks!

[@realestateservicessaleshea99]

👍🏌 Stay safe. Retired keyboard super tech. Wear your safety glasses.

[@kevinvillal6169]

This nigga can teach

[@yamahasuperbike2202]

I currently have a heat pump at my residence. I'll never own another one again. Piece of shit. Not very warm in the winter and not very cold in the summer.

[@MaMa-qh4dy]

"Not very warm in the winter" -- NORMALLY TRUE. "Not very cold in the summer" -- then, you have a problem with your unit.

[@r410a8]

If a heat pump is air-water the indoor electrical resistances does continue to heat up the water? This doesn't require a nominal electric power comparable to nominal heat power of indoor exchanger element that is working like condenser in normal cylce,producing the heat power of rifrigerant compression plus refrigerant evaporation latent heat? And what happens to total electric power consume for this few minites if the machine has to consume power for compressor + electric power that equals compressor+evaporator (on normal cycle conditions)?,Doesn't this reduce dramaticaly the instant heat cop of heating from a scale multiplicate of 1 ,for instance 4,to a number lower than 1? If a machine gets freeze all the time and gets turn on the defroast cylce frequently for instance 1 time per hour for 10 minist ,the total cop won't be lower than a nominal eventualy? For instance assume a large heat pump with a nominal heat production 1Mbtu/h has a theoritical average hourly cop for a cold outdoor conditions 3,5,then to 1 hour only 1/3,5 Mbtu electrical power has been absorbed by the electrical grid and the rest 1-(1/3,5) has been absorbed as heat by the outdoor unit. If and a defrost 10 min need to be turned on ,the defrost cycle cop is 1 (because heat resistants produce all the demanding work for the defrost time,that equals 1Mbtu/h*(10min/60min) are produced now from heat resistants without having the 3/4 parts to been pumped from outdoor enviroment ) minus 1/3,5 (the theoritical work of compressor that it continues work and consume grid power without producing any good heat work indoor ,that equals 1Mbtu/h*(10min/60min)*(1/3,5) cop) = 10 minites defrost cop 1-0,285 = 0,714.So the total hourly cop isn't 3,5 but 3,5*(50min/60min)+0,714*(10min/60min)=3,035.If my calculations are right then with more time defrost cycle the more less expected average cop will you have in far cold enviromments . Is this a vfm thing taking to account the extraordinery coast of electrical power and the fact that the heat pump is selected for energy and money save?