How to Test Heat Pump Defrost and How Defrost Works

[@MRXDS1989]

How you deliver this info is hands down the best on KZbin....the cuts to what your referring to is EXTREMELY helpful....so many vids just ramble on and on segwaying into unneeded info

[@daniahalnuaimi82]

يًًث ى

[@yodamanrulz176]

Absolutely concur. Thank you for your efforts 👍🏻👍🏻 Helping newer technicians is always commendable ❤ You guys are top shelf no doubt 😎🥸

[@kevinknight777]

I've been doing this work 20 years and I'm ashamed to say that defrost boards I have always given me an issue and I always leave aggravated that I didn't feel comfortable with understanding them. I just listened to this on the way to my next call for Frozen heat pump there will not thaw out, now I know exactly how to do it and if not, where to find the answer.

[@charleswashington7576]

I have seen a few different techs and these guys are good too. Heat pumps cause of the defrost boards, reversing valves,by-passes and two metering devices. Makes heat pump a challenge. Straight cooling is simple now. I hope heat pump become as easy one day.

[@Nine_883]

Metering devices are not bypassed. There is one for heating and one for cooling. The heating metering device may look different, but it’s there. If they bypassed a metering device it would wash out the compressor and if it’s a reciprocating compressor it would slug the piston with liquid.

[@tinymanthebeast]

Thank god. The information in this video is worth thousands. I've worked on dikan and York .

[@wk6927]

BRAVO ! Excellent and concise description of the subject as well as sharing detailed useful information essential for the task in hand. Thank you and please keep up your great contributions to KZbin community. If I may suggest, please add or emphasize that Carrier defrost switches are normally-open, and as they approach freezing temperature (32F), it closes the internal contacts. So a simple continuity check on the sensor at temps above 32 degrees F should show an open circuit and this is why you need to use a jumper on the defrost board sensor pins to simulate a closed defrost switch at 32F. I think you have eluded to this concept in your video. However, emphasizing it could provide further clarification. Again, an excellent video and God's blessings.

[@harrystrohm7614]

Thank you Jesse,Bill&Bryant wish their was KZbin &you fellas around back in the 80"s I went to &graduated from two trade schools and this was never explained as easy to understand as you Guys explained.

[@eracismm]

Great video guys...Keep up the amazing work, the industry desperately needs this........Thx John

[@Sctronic209]

Good info now if I can remember it when needed that will be a plus.

[@Tetarkall]

Thank you for the tutorial!

[@geraldschilli8870]

It sure is nice that over many years now defrost controls are solid state. When I got into the service business back in ‘74 defrost controls were all mechanical & somewhat a pain in the rear to troubleshoot. Since they were replaced with solid state boards, it’s a lot easier the test & initiate a defrost cycle.

[@Oldthesis]

Trane uses the two temperatures (the outdoor ambient and coil temperature) to calculate a delta-T in order to execute a defrost cycle. This algorithm effectively prevents the unit from entering a defrost when warm outside, thus extending run time. After initial startup in heating mode, the defrost board begins a learning routine to find the nominal coil temp for the clean coil conditions. The control then will decide to initiate defrost when: The delta-T is 1.9 times greater than the clean coil conditions The outdoor temperature is < 52°F The coil temperature is < 34.5°F or The first stage heating operates for three hours continuously at < 28°F or eight hours continuously > 45°F, which can be reset by a defrost or a five minute second stage cycle. Long story short, you can't trick this algorithm into defrost with "dumb" methods, which is why the control has a built in TEST function.

[@yodamanrulz176]

Now that’s good explanation technique. Thank you for taking time to thoroughly explain. As if we, the students, can’t read your mind. And torturing us with fingers in the way and mumble/stumble speak. Using a thin pointer and practicing verbal delivery is paramount. Obstructive hand gestures are bad, distracting and a show of rookieism to be avoided. OTT, they did a mediocre job. Yes, I could do better. Peace out ✌️

[@gfriedman99]

Thanks for the info on the backup heat. Now i know why it blows cold inside during defrost.

[@philipwall1025]

Your heat strip is 2 small,increase the kw.You actually shouldn't know when your in defrost, and if your heat strip was little bit bigger (in kw) u wouldn't know.

[@gfriedman99]

@@philipwall1025 That's a possibility but it actually was because the W2 low voltage wire was not connected to the heat pump board. Emergency heat worked fine when called for at the tstat but it never turned on when defrost cycle kicked in.

[@philipwall1025]

That would do it gene,also some guys like to wire each kit seperate,while other guys wire both kits together. Regardless you were able to rectify the situation, and thats what its all about!

[@hozerhvac4406]

I love this content. Keep it up

[@surfingfrenchman]

Now, this was a good video. Thank you!

[@edilsonserafim4784]

Very well explained

[@jaredbailey1494]

I noticed your carrier is equipped with a sensi predict. Very nice!

[@ABCJKE]

Thanks for your efforts. Maybe a good idea to show the Trane equipment like this vid showed the Carrier unit, and a little more explaining for the demand defrost operation and sensor testing and the voltage going to those sensors from the pins.

[@MaMa-qh4dy]

The resistance values for the sensors at specific outside temperatures is posted online.

[@williamswan7779]

very helpful stuff guys,thanks

[@kylemarshall6217]

Great directions!

[@erickalief]

i appreciate yall, good info! i thought the 30 60 90 was the delay on the condenser.

[@lancerudy9934]

Nice video. Thanks

[@Bobherry]

Love the content!

[@earlscott1923]

Thank you, I understand now. Big help !

[@Tc-gt5vm]

During a maintenance, or on a broken system, I will pull the outdoor fan motor wire from the relay and and let the outdoor coil frost over to test the sensor on a system that is not demand defrost. Board will sometimes be good and just the sensor has failed.

[@sknight0391]

Your doing it exactly right TC 👍 And a "rub" on those defrost sensor wires can also be one of the most notorious and hard to find low-voltage shorts in the winter time.

[@philipwall1025]

Good idea dawg! Never tested the sensor myself, only the board going into defrost. Those ambient sensors go all the time.

[@Cplcrab]

If you jump the defrost tstat, how are you testing to ensure that it actually works? You're completely taking it out of the defrost scenario by jumping it. I like to pull the fan lead, let the coil get cold and ensure the defrost tstat closes on its own. Then i verify that the unit comes out of defrost when the tstat opens back up without tripping the heat pump on high head pressure.

[@sknight0391]

Keep in mind, they're in Florida so that could take a very very very very long time to freeze that coil up and close the DF sensor.

[@peepeepoopoo1399]

@@sknight0391 this is exactly it. Can’t do this in CA

[@brandnewage1]

30,60,90 defrost???, might wanna rethink that, more like 30,60,90 time until defrost, keep makin those vids,lol

[@chrisswofford5757]

Thank you!

[@DoctorSleep_0]

It would be helpful to know where to find this information for different brands

[@rogerf3622]

On Carrier I believe there is a temp probe down by the service valves that measures ambient. Does this probe also affect the defrost?

[@marcusdarnell3348]

Great video! The 90 to 100 degrees above outside temperature on the discharge line. Can that rule apply to any manufacture

[@georgeian3243]

60 minutes of accumulated run time with the dft closed has been selected. Thus, on the 61st minute of run time with dft closed the unit will defrost. With Trane, you can measure the DC volts the board is reading from the sensors, compare your 0 to 5 vdc readings with the chart in Service Facts and thus verify if the sensors are reading accurately or not. Otherwise, the board may be bad.

[@minnesotasalamander5913]

Nice report.

I thnk u for all the info that u put out there. I am having an issue and hope u can assist here. My Rheem heat pump, not getting any voltage at the COIL of the contactor, which is connected to the defrost board. I checked between, the R and C terminals coming from the indoor unit and I DID have the 24v going to the R and C terminals on the board. I am thinking that the DEFROST BOARD is defective, but, I am not sure. Could there be any other reason, that could have caused this contactor coil NOT to be getting THIS 24V in my case? Or can any time say?

[@5822huron]

Good knowledge.. i have only seen 2 heat pumps in 6 years.. im in chicago lol

[@calskywalker8293]

Good video but one mistake that gets alot of technecians into more trouble. 30, 60, 90 minutes AFTER the defrost thermostat calls for defrost. The unit will then preform defrost functions. Then time up to manufacturers maximum or temperature of thermister or snap disc will cause system to once again perform heating function. The board is always checking and listening to the defrost thermostat.

[@bishal509]

Around 1:38 you mentioned auxiliary heat, my system doesn't shut down that auxiliary heat even after the unit reaches the set temperature, the only way I manage to stop it is by switching to AC. I have a tech come over and suggest replacing the defrost board but I would like to know the real cause for this. Any help?

[@dalejustice9207]

I just had mine fixed switched from r22 to 407b. It worked fine for 2 weeks n then started freezing up bad 2 inch ice on the condenser. Do y think the board went out? The guy who fixed it unplugged the emergency heat bc of it running with the pump also. Thanks

Thnx for ur videos. Maybe you guys can assist me here. What is a "high pressure lockout"? And could a defective thermostat caused the defrost board to show this code. My heat pump board is currently showing this code. The OUTDOOR unit DOES NOT, start up at all, in heating or cooling. There is 24v on the R and C terminals. In the "emergency" mode, I am not getting enough heat. It only heats up to 72degrees only, and runs all night. And never shuts off. This is a RHEEM system. 6yrs old. I am really frustrated now, because i am having all these issues at the same time. I am thinking the thermostat is mal functioning, then I think its the defrost board. then i think the heat strips has issues. I am a wreck with these issues. The indoor unit runs fine, but NOTHING from the OUT DOOR UNIT. I just can't figure it out. Hope you or any other can assist me.

[@mickkassem]

We have a Trane XL20i. It has always gone through a tremendous number of defrost cycles. It is in defrost at least 10 to 15% of the time the unit is running. Getting this info from the XL950 stat. Trane actually replaced the outside unit a couple of years back because they could not figure out why it was have so much cycles. The outside temp sensor always reads high. It is anywhere from 2 t o10 degrees higher that actual outside temp. If the defrost board is looking at the delta temp (coil vs outside temp sensor), would that make the board more likely to go into defrost more often? Our installer has ordered a new outdoor temp sensor and it should be installed next week. When the outdoor temp is around 24 to 26 degrees, the inside vent (closest to the air handler) air is at 80 to 82 degrees without an auxiliary heat strip cutting in so I don't think we are low on refrigerant. Does the delta temp make sense as an explanation and perhaps replacing one or both sensors help?

[@caru3257]

a

[@Wrexxxx]

My Carrier froze over. Doing the speed up test you showed (thanks a million btw) it sounds as if it goes into defrost mode, but the outside fan will not stop. Then every 30 seconds or so later it does the same sound again with the same result..fan will not stop. Am I looking at a possible faulty fan relay on the defrost board?

[@jaycee6639]

Im having the same problem did you get it figured out?

[@Wrexxxx]

@@jaycee6639 crazy you commented today. I just worked on it again TODAY! I replaced the board in hopes that was the issue..it was not. Still freezing up. I can hear it go into defrost mode, yet the ice doesn’t melt off the fins. Idk if my pressure is low or what. Something is definitely keeping it from heating up to melt the ice.

[@jaycee6639]

@@Wrexxxx thanx for the reply im stumped on this issue. Its getting annoying because it vibrates my house when the unit goes into defrost. Good luck!

[@motoman9944]

Great video! How do you determine if the defrost problem is caused by a bad defrost sensor or a bad defrost board? Thanks!

[@truthmatters6719]

I guess you check the sensor for resistance and then you check the incoming voltage of the board, that's just my guessing. If there are any visual problems with the board such as burn marks replace it. Overall if the sensor is good then it should be the board, make sure your charge of refrigerant is good cause that could be a problem too.

[@harrypezzi9901]

I like this thank you

[@TheMarbo74]

Question... If I understand correctly. Will frost on on the heat pump coils happen only when it's used as a heat pump and not in A/C mode? If ye,s then frost can only happen when in A/C mode on the coils inside the house correct?... In other words, in A/C mode we should never see frost on condeser coils on the outside unit.

[@u2ooberboober]

Correct

[@N.N.77]

Are heatpumps common heating and cooling option in the US?

[@jakobpollard4146]

Yes very common

[@lancerudy9934]

Thanks!

[@trackman174]

My heat pump system is backed up by propane. When the unit goes into the defrost mode the propane burners do not fire up, thus blowing cold air from the registers. Would the defrost board be the problem or a internal furnace problem?

[@adamradley4407]

Get access to the propane heater terminals. If is receiving 24v then its the heater. If it is not receiving 24v then most likely the control

[@franciscojavierestrada7585]

yes. i jumped the defrost sensor, however, the Carrier package unit/heatpump, still freezes over. If the Carrier system does not detect it needs defrost, while the jumper is on , what else could it be?

[@christiananderson9027]

So if i just topped my Freon off and pressures are good but my coils are still freezing up do you think my defrost board needs to be replaced?

[@lancerudy9934]

How often should defrost kick in?

[@texture6]

At 8:00 minute into the video. The resistance he is talking about is affected or influenced by the temperature. Temperature affects how electricity flows through an electrical circuit by changing the speed at which the electrons travel. Similar to having the right resistance in an antenna. So if the wire or sensor is cold the resistance is off?

[@chuckdearruda6271]

texture6 Search thermistor.

[@Oldthesis]

Trane (and most manufacturers) use NTC (negative temperature coefficient) thermistors . What that means is that as the temperature increases, the resistance decreases. Google up "Trane thermistor resistance chart" for reference on 10k ohm thermistors.

[@texture6]

Thank you

[@MaMa-qh4dy]

Before I condemn the defrost board part number Trane CNT 02941. Split unit heat pump. Two defrost temp. sensors (ambient and coil). Defrost is auto "demand". Condenser ices-up. I short out force-defrost pins, unit enters defrost mode, OD fan cuts out, but ONLY 5VAC to reversing valve. Should be 24VAC in order to switch-over refrigerant direction. Reversing valve coil Ohm checks good. Both sets of sensor pins on defrost board show proper voltage at 5.5VDC. Both outdoor temp. sensors ohm out good relative to outdoor ambient temp. LED flashing normal. I had to melt the ice by shorting out force-defrost pins and temporarily jumpering R-O wires at condenser which sends 24VAC directly through defrost board to activate reversing valve. So, reversing valve is not automatically receiving proper voltage during defrost cycle. Any suggestions for other tests prior to condemning defrost board? Thanks.

[@snoopy0039]

Hi how are you!! Can you help me out with some tips ! I had a carrier heat pump brand new and when the outside temp go down more then 37 F the outside coil get frozen and I replace the control board 2 times already and the temp sensor to!!

[@ronc2047]

Trane Pub. No. 34-4101-07 says defrost will terminate in 10 min OR when coil temp is 55 or 70 depending on type installed .. read somewhere that cutting Jumper J2 would make it 70 (vs 55). I'd be interested in what the experts say about this .. using board #02940. If true, the extra defrost time may what I need when ambient is

[@hozerhvac4406]

This whole time bill frisbee works for kalos!!!!! Never knew that

[@Selftops]

30 60 90 minutes of defrost? How about 30 60 90 minutes between DEFROST cycle?

[@HVACS]

Yes that is correct, does he say 30 60 90 of defrost?

[@marcoalvarez1276]

HVAC School he corrects himself later on while he’s talking to the trane guy. 👍🏽

[@richardburchett]

It’s how often the system checks the thermostat, not necessarily how often it goes into defrost.

[@Marty1911]

@@HVACS Still not correct. it is 30, 60 or 90 min of "cumulative" compressor run time not simply time between defrost cycles.

[@robvoyles]

@@HVACS ​ Are all defrost termination switches typically supposed to be normally open then close to initiate defrost because my switch is brand new and it is 50 degrees today and it is closed.....and when i put my board in test mode it does test fine but will only hold the test mode for a few seconds then goes right back to normal operation....it is freezing up and not defrosting....any thoughts...it is an Armstrong air 2.5 ton standard heat pump package unit.....any info would be helpful.

[@mudcrew2924]

You failed to say what two out of the three pins you jumper on the Trane defrost board.

[@adamcraig1568]

“Common” and “forced defrost” pins. Pins should be labeled

[@abazism]

But just because it goes to defrost manually, it doesn’t mean that it dose it by itself, right ? It just means that the reversing valve shifts.

[@ralph9987]

hi i have a rheem mpi 325l heat pump hot water system unit that only runs in boost mode the two LEDs dont light up and there is no pump, fan or compresor running can you please help to get a service manual and circuit diagram for the control board please. thanks guys

[@GOOCHIElicker]

Sounds like you have a loss of voltage somewhere

[@dilboteabaggins]

Pretty sure the time settings on the carrier board are for how often the board checks to see if the coil needs defrosting and not the length of defrost. Further, I do believe the defrost terminates when the defrost thermostat makes.

[@HVACS]

Yes we say both of those things

[@dilboteabaggins]

I must have misunderstood what you were saying. Bryan Orr never gets it wrong

[@officerkrupke4966]

On Carrier, T1 is energized when system is running, this powers the defrost timing function if dft tstat is closed. Timer resets if dft tstat opens before defrost is initiated. There is no checking.Its total cumulative time system has operated with dft tstat closed.

[@patrickhutchins6935]

8:10 the 30,60 or 90 minute time frame is not "real time" it is cumulative run time of the compressor. If the compressor runs for 15 minutes, off for 10 minutes then back on for 15 minutes it will take 40 minutes of real time for the 30 minute setting to be satisfied

[@undaya]

r valve energized heat or cool?

[@philipwall1025]

The only company inthe industry that energizes the rv valve in heat mode is rheem ,ruud.EVERYBODY AND I MEAN EVERYBODY ELSE energizes the rv in cooling mode.

[@hectoribarra8473]

Does anyone know why is my heat pump freezes up when the temperature are below 34. It works find above otherwise. I call a tech and he added refrigerant assuming that was the problem. It still the same its cover in ice.

[@sknight0391]

Hector, your defrost cycle is not working properly. That is why the unit is freezing up. You're going to need a qualified HVAC technician to repair that for you. You're wasting tons of money on your electric bill with that thing frozen up like that. The repair will pay for itself in your power bills. 👍

[@ParabellumX]

(5:27) 🧐Did he say, '...90-100° above ambient?' 😆

[@kckc6578]

If the sensor closes at 30F to start defrost does that mean the heat pump doesn't actually work at temperatures lower than 30F sense the outdoor coil needs to be colder than the surrounding air to collect heat? Anyone know?

[@MaMa-qh4dy]

HP work at very low temps. They just extract more heat out of the air when the outside temp is higher. The ice build-up on the outside coils is due to humidity in the air. That needs to be removed (defrost cycle) so that air can move easily through the outside coils during normal heating operation.

[@brahimabdelsadek5815]

Hi master.if u can speak slow english pls.i love your videos.big salute from algeria

[@philipwall1025]

Heat pumps have comealong way.I remember the first time my uncle took that big York box from out of the trk ,he would connect to the unit initiate rv,drop out the cfm,initiate thisand that.Heat pump seemed overwhelming and sophisticated. You would have a psi switch in the condenser section that would initiate defrost when a vacuum was created because of the build up ice on the coil.Newbies dont know anything about those set ups,SOON ENOUGH, THERE WONT BE aux,or it will be strictly emergency. They'll defrost like mini without blower motor operation.

[@tttota5421]

What might cose the outdoor fan to stop running and compressor still working or has this weird noise Anyone ever had this kind of problem, bc it’s a new unit ,I just installed it,it works for an hour and then the fan stops working but the compressor still running If anyone anyone sees this and have had sort out something like that ,l would lone to hear ?

[@craftman5632]

When your outdoor fan turns off and makes that weird noise, it's in defrost mode and then your auxiliary heat will kick on, when the frost melts off your heat pump when it's in defrost mode, then your outdoor fan will kick on and turn off the auxiliary heat.

[@tttota5421]

@@craftman5632 spot on, I watched for a while and that what exactly happened,appreciate it

[@georgespangler1517]

He could have showed what test pins to jump on Trane

[@MaMa-qh4dy]

Jump the DFT and Common pins in order to force defrost

[@keithcorbin477]

Explain to me bypass and check valve

[@mackenziegray2090]

Don't you need to be mindful that low refrigerant charge can also increase in discharge temperature? Because of the high super heat plus the heat also given off by the compressor when doing the 90-100F above ambient rule for discharge temperature.

[@twisted8956]

Probably should of explained how to test a bad sensor vs a bad board a lot of guys I talk to have no idea and just change both 🤬

[@twisted8956]

If unit not defrosting and you jump sensor and it goes into defrost change sensor first

[@marktaylor2141]

If I have a bad board I always change the stat, but I don't change the board if I have a bad stat but I always check the stat first.

[@lancerudy9934]

Defrost yes

[@THEJIG-IS-UP]

Yup

[@Nine_883]

Trane is the spelling. In your chapters you spelled it wrong and it’s not exactly impressive. On that Carrier that is not a defrost temperature sensor. It’s a simple bimetal switch. It’s a klixon type thermostat. Normally open. You guys make some good basic content, but then there are some simple things that are terms that should be correct. And obviously Train is not the name of the manufacturer. Trane is. As an engineering employee at a manufacturer I am a stickler.

[@copkhan007]

Camera man sucks. He should be showing the components and what to disconnect and where to make adjustments. Instead, he is showing us the guy's face who is talking. Take a class on camera skills first.

[@HVACS]

Thanks for your kind feedback.

[@johnyoukhanna8397]

explain what defrost means in Hvac first before ranting about how to jump the board

[@iansimpson419]

Sorry mid-roll ad so stopped watching. Enjoy your videos but protesting KZbin's mid-rolls by not continuing to watch any videos they interrupt.

[@HVACS]

Cool, so long as you also shut off the TV when commercials come on in the middle then you are consistent.