Hey Mike, There's one small detail missing from this video. DFT = Defrost Thermostat. It's a SPST NO switch that closes on a drop in temperature. It's located on the outdoor coil to sense the temperature of the outdoor coil during heating mode. Typical setting is 30-35ºF with a differential of 20-30ºF. The actual rating depends on manufacturer. The Defrost control will only accumulate compressor run time while the DFT is closed. If the DFT opens in between cycles due to outdoor temperature, the defrost control will start accumulating compressor run time (starting at zero) during the next cycle after the DFT closes. The defrost control will add up the cycles only if the DFT remains closed in between cycles. If the DFT remains closed long enough to accumulate the selected minutes on the defrost control (Typically 90 minutes in North America) a defrost cycle will be in initiated. One of two things will terminate defrost. The DFT opens due to the coil warming up, or a maximum defrost time is reached. This is a common Time & Temperature Defrost control...
I teach HVAC in a high school in the Boston area. Stumbled upon your videos and the students really enjoy them. Some of the videos we find are too vulgar or too boring. We have not seen you on the videos so everyone tries to describe what you look like. The common theme is that no matter what you look like they all say you are an HVAC BOSS!!! and this is from your Boston area rivals!
I’m in the south, hot weather, rarely when I get a heat pump call. Trying to learn. I lost it a bit but will watch it again, and again until it clicks. Thanks Mike.
Thank you Sir, for this awesome video. You have cleared up quite a few "cob webs" for me. I was able to find the answers for myself after your explaining. NOW, I really understands completely the electricals on heat pumps systems. I literally visualize testing this circuit, with an 'ampbrobe", and correctly got EXPECTED results. Now I am really confident, to tackle these monsters now. WOW!!! Thanks again so much, God bless you Sir.
Best HVAC channel/instructor on RUclips hands down, the current on the diagrams is so helpful I can’t thank you enough. I wish more students would take advantage of your resources, extremely helpful.
First time in my life subscribed to u tube channel , this is best explanation out there . I have no doubt in my mind you will grow big . Explaning how power flows from point A to point B with schematics really clicks . Thank you for all this good work .
Great video. This, combined with being at the actual ODU and physically following each wire from the DCB to each component makes it all so simple and clear. I’ve shared this with my techs, great visual guide and clear explanations.
absolutely amazing how much effort you put into this video. visual is so much better. Great Idea......Now if you could make one for economizers next.......
hi, wanted to say that i've watched alot of your videos, very helpful & thanks alot for putting them out there. Some of them i had to watch a couple times to digest it. You explain things very well, not rushed or meandering around, good diagrams that are color coded to show the electrical flow. Ps - glad you don't use foul language and keep things decent!
Hey Mike thanks for the amazing video. I have a few questions if you don't mind taking the time to clarify a few things. 1. When the unit is in defrost mode, how does the low voltage defrost relay get pulled in to pass 24v to the reversing valve? In the video you just state that the relay gets energized but I'm uncertain how that happens. Is there something internally that's happening? 2. Likewise how does the high voltage defrost relay open during the defrost cycle? 3. Finally just a general question but I'll reference the video as an example. When the Y terminal is pulled in and it sends 24v through the control board and through the pressure switches, how do you know that the 24v then goes to the M terminal? If I were to look at this on my own for the first time, I would have no idea that the 24v will come back to the PS terminal and internally to the M terminal. Obviously you've been doing this for many many years so you know by experience but how would a novice like me be able to figure that out?
Both defrost relays are activated by the 24v signal passed on by the defrost timer taken from the R power. As for the M terminal, that one I just had to figure out by talking to other technicians or checking schematics of similar systems that laid it out a little better. It didn't come easy.
5:45 i didnt realize 120/240 ran through the fan relay on the defrost board. I thought it was control / low voltage that powered the relay, similar to a contactor.
Hello Mike. I was working in the field and ran across a thermostat that the voltage on the R and Y was 16 volts, it also showed 16 volts in the air handler and 16 volts in the condenser. Testing the Red with green, and Red with white both registered 27 volts. What could be causing the voltage drop? The contactor does not show voltage on the coils, but when testing the coil for ohm it shows 12.8 ohm and it also has continuity. What could be the problem? Thanks for your input.
Asking for a friend..... My friend had a company come inspect they found no 24V on the yellow at the outside unit. it was a open float switch because of a clogged drip line. they fixed that and everything was fine for 3 days...... fast forward 3 days and the AC is blowing heat. the Copper lines in and out of the outside unit was way too hot to touch, my friend pulled the cover off the unit to check for 24v on all wires and if the contactor works. what my friend found was the O wire spade had fallen off the defrost board. My friend plugged it back in, BUT AC is only matches outside/Ambient air. The guys that "Fixed" it say the outside is "dead" (6 year old Goodman) would running the system in "A/C" with the "O" off the defrost board "kill" the outdoor unit? It's my opinion they yanked the O wire loose on the defrost board checking for 24V. ?????
The O wire just controls the reversing valve to put it in heating or cooling mode. It was blowing hot air because the RV wasn't getting the signal during cooling mode. Basically, having the O wire disconnected is just heating mode and shouldn't "kill" the outdoor unit. My question is was the O wire touching anything when disconnected? Could have created a short when powered up in cooling mode. Does heating mode still work normally or is it the same ambient result? If heat works, try to jumper Y and O at the defrost board in cooling mode. If ac works then, problem could be a burnt out switch on the thermostat from the short. If not, could have damaged the defrost board or possibly the reversing valve is stuck. At 6 years that could be a warranty repair.
Mike, do you have an Instagram? I have a low voltage company and the alarm systems we install are now probinding low-level automation features suck as lighting and thermostat controls. Your provided understanding of HVAC has now gone unappreciated. Thank you from Arizona.
I have a similar problem with the letter O. I have a Rheem 3.5 Ton AC. I have the following wires coming out of the defrost board. Brown = Common (letter C), Red = Power (leter R), Purple = ?? (Letter D)Blue = ??(Letter B) and Yellow = Y (letter Y) which is for they is for the AC. My problem is the Blue and the Purple. Blue is connected to letter B on the board and Purple to D. The thermostat am using is a Nest Thermostat and it has letter B. It also has W1 and W2 adn from the board in the attic, I have w1 = white and blue wire and W2 white and brown wire. Assuming I connect Blue to B on the thermostat, what do I do with purple? I read some answer below and it suggest to connect Purple to W1 and W2. Once I do that, it will be like placing a jumper from W1 to W2, correct? If am wrong can you please correct me on all and everything.
For clarity, when I said W1/W2, I didn’t necessarily mean place it on both and jumper them. I just mean it should go to one of those terminals depending on how it’s wired based on the configuration of the equipment available, which is information I don’t fully have. There may be 2 stages of backup heat in which case W1 and W2 are wired to each activate one of two heat strips or a 2 different stages of a gas valve in a furnace. All that purple wire off of D does is allow the condensing unit to activate whatever that backup source of heat is. So it will land on the same terminal that calls in the secondary source of heat such as heat strips, which is usually W1. In some cases W2 might do exactly the same thing, just at a different time and it might not make a difference if you place the purple on w1 or w2 or both. Normally it will just land on W1.
@@JerseyMikeHVAC Never worked on an AC of any kind. Your video was a great help, not only that, you answer my questions prompt and to the point. Today I got my ac running, well my heat. Since I have a Nest Thermostat and the temperature outside was below 55 it won't let me turn on the AC but, I guess that will be another question for the summer. Thank you
I need help. I have a Rheem system 3.5 ton, 20kW heat strip. From the control board I have the following wires going out of the cabinet Yellow connected on the thermostat at Y1. White and blue to W2. White and black to W1. G to Green. C to brown and R to red. On the defrost board outside I have the following letter and cable wires Y with yellow wire, B with blue wire, D with purple wire, Red with red wire and C with brown wire. I don't have "O" in the blower or on the defrost board nor orange wire. The thermostat am using is Nest Thermostat. What am I missing? The AC and or the Heat has never worked. No need to rush since the house is vacant but, I will be moving in this summer. What can I do? I see the RV and C on the defrost board connected but, I haven't follow the wires. I also see 2 flashing red lights for about 2 minutes after that, they start alternating on and off for another minute or 2 and start flashing at the same time. Flashing at the same time is normal. Alternative is High and Low pressure lock out. At this moment I just need help with the "O" wire and or terminal that I don't see anywhere. CORRECTION. I got the heat strips to work
On Rheem systems the reversing valve is energized in heating mode off of the B terminal. So there is no O terminal used here. That blue wire on the B terminal on the defrost control board needs to be powered by the B terminal on the thermostat and this connection from B to B happens inside the air handler at the control board. That blue wire in B at the defrost board should go to B in the control board which goes to B on the thermostat.
Also, the purple wire off of D on the defrost board should go to W1 W2 at the air handler. That is your heat strip activation during defrost cycles. Here's a wiring diagram you should be working off of: www.doityourself.com/forum/attachments/thermostatic-controls/54963d1440259155-connecting-thermostat-rheem-heat-pump-system-rheem-thermostat-wiring-diagram.jpg
I have no letter “B” on the control board. All I have is: Y1 = yellow wire W1 = white and black wire W2 = white and blue wire G = green wire C = brown wire R = red wire But no letter “B” or letter “O”
WTF.... HVAC technicians are not engineers this explanation is too long and detailed. I'm going to watch it a few more times to see if I can follow along. And mind you I have a B.S. degree.
Your lack of education is exactly why we have HVAC techs changing parts all day that are not bad, you need to know this information to correctly diagnosis the defost system. If you are not constantly willing to learn yoru trade in great detail i believe you have picked the wrong trade to be in and i recommend that you please move to another profession that allows you to not have to know what your doing edwardlara1011
Hey Mike, There's one small detail missing from this video.
DFT = Defrost Thermostat. It's a SPST NO switch that closes on a drop in temperature. It's located on the outdoor coil to sense the temperature of the outdoor coil during heating mode. Typical setting is 30-35ºF with a differential of 20-30ºF. The actual rating depends on manufacturer.
The Defrost control will only accumulate compressor run time while the DFT is closed. If the DFT opens in between cycles due to outdoor temperature, the defrost control will start accumulating compressor run time (starting at zero) during the next cycle after the DFT closes. The defrost control will add up the cycles only if the DFT remains closed in between cycles.
If the DFT remains closed long enough to accumulate the selected minutes on the defrost control (Typically 90 minutes in North America) a defrost cycle will be in initiated.
One of two things will terminate defrost. The DFT opens due to the coil warming up, or a maximum defrost time is reached.
This is a common Time & Temperature Defrost control...
Thanks for the added detail. I'll pin this to the top of comments so people can see it. 👍
these neon colors/effects really make the information stick. holy shit. Thanks
I teach HVAC in a high school in the Boston area. Stumbled upon your videos and the students really enjoy them. Some of the videos we find are too vulgar or too boring. We have not seen you on the videos so everyone tries to describe what you look like. The common theme is that no matter what you look like they all say you are an HVAC BOSS!!! and this is from your Boston area rivals!
When I was talking about vulgar or boring I was talking about other videos I find on the internet, not yours.
Thank you! You know, I used to live up there for many years. Some family still does. North Shore. You guys are alright in my book.
@@PaulRiordan-bt3nuif vulgarity bothers your students they aren’t built for the trades… I’m sorry
I’m in the south, hot weather, rarely when I get a heat pump call. Trying to learn. I lost it a bit but will watch it again, and again until it clicks. Thanks Mike.
No problem. I know it's a lot to take in, but it's mostly all there.
Oh my GOD ,this is one of the best explanation and example of the sequence operation for heat pump I ever watched thanks Mike.
Awesome! Thank you.
Well done! 40+ year tech here, awesome video for young people in the trade. thanks for such a great explanation and fantastic graphics.
Thanks!
Thank you Sir, for this awesome video. You have cleared up quite a few "cob webs" for me. I was able to find the answers for myself after your explaining. NOW, I really understands completely the electricals on heat pumps systems. I literally visualize testing this circuit, with an 'ampbrobe", and correctly got EXPECTED results. Now I am really confident, to tackle these monsters now. WOW!!! Thanks again so much, God bless you Sir.
Excellent!
Best HVAC channel/instructor on RUclips hands down, the current on the diagrams is so helpful I can’t thank you enough. I wish more students would take advantage of your resources, extremely helpful.
Excellent. Thank you!
This is my new hvac bible for the next 2 months, amazing explanation thank you thank you!!!
This is a perfect explanation. It explains the principle in the simplest words.
Great video!! I'm only a third of the way into it and already feel like I've learned something.
Great to hear!
Thank you Mike, just fantastic explanation
Very welcome
this vedio is remarkable, love your visual. Thanks for the info and making easy to understand. awesome
You're very welcome!
Exceptional quality, is no accident. Thank you for your hard work
Great video. Please make more like this.
Thank you. I have a playlist with several videos like this: ruclips.net/p/PLzqK-0xeBEzXzIz9eZAf9xTU8mnhbqXHz
You got the best videos on YT for hvac wiring schematics. THANK YOU
Glad to help
First time in my life subscribed to u tube channel , this is best explanation out there . I have no doubt in my mind you will grow big . Explaning how power flows from point A to point B with schematics really clicks . Thank you for all this good work .
Thank you. Honored to have you!
I truly love this animated video and it has helped me immensely.
Glad it helped.
this PCB schematic stuff is awesome: augmented techno-vision !
Making this video even helped me figure a thing or two out. ha.
Like the animation. Now I can really explain it now to my students
Another phenomenal video. The animation is great. I know that I learn better when I see a process.
Thanks. Glad it's helping you understand it better.
Great video. This, combined with being at the actual ODU and physically following each wire from the DCB to each component makes it all so simple and clear. I’ve shared this with my techs, great visual guide and clear explanations.
Thank you
Thank you so much for this detailed info i understand my system so much better
Nice job , well explained.
Thanks!
absolutely amazing how much effort you put into this video. visual is so much better. Great Idea......Now if you could make one for economizers next.......
Such a great explanation, keep them coming! Grettings from Tx
Great video thanks you 😊
Love this video! Makes things very clear! Subscribed!
Awesome, thank you!
hi, wanted to say that i've watched alot of your videos, very helpful & thanks alot for putting them out there. Some of them i had to watch a couple times to digest it. You explain things very well, not rushed or meandering around, good diagrams that are color coded to show the electrical flow. Ps - glad you don't use foul language and keep things decent!
Absolutely phenomenal!! Thank you! Best schematic video I have seen EVER!!
Good explanation!
Great animation. Thanks for sharing
You're welcome.
Thank you for your lesson ❤I am lov’in it!
Thanks great videos & explaining.
Glad you enjoyed it!
Mike you are best thank you for this type of videos!!!😊
You're welcome!
Thank you sir 🙏 I am new in canada 🇨🇦. And sir watching your every vedeo . Thank you for explaining with schematic diagram ❤ awesome
Great stuff! It makes it so much easier to understand.
Glad to hear it!
Great video!
Thank you so much for sharing. Tony from Houston
Any time!
Downloaded this 🫡
Great job and video Mike. Thank you.
You're welcome.
Perfect video and explanation. Thanks for sharing!
No problem!
Uh oh, my customers are gonna stop calling me after seeing this!
Best explanation ever!!!!
Great video, and explanation!
Thank you!
Excellent video MIKE!! Thanks for sharing !!
great vid
Thanks!
Amazing video considering he's communicating through time from a helicopter in Vietnam.
...as a double agent...
I subscribed your channel and shared your vedeo
Thank you!
This is great.
excellent, love the animation
***strongly dislike Google Nest***
Me too
Hey Mike thanks for the amazing video. I have a few questions if you don't mind taking the time to clarify a few things.
1. When the unit is in defrost mode, how does the low voltage defrost relay get pulled in to pass 24v to the reversing valve? In the video you just state that the relay gets energized but I'm uncertain how that happens. Is there something internally that's happening?
2. Likewise how does the high voltage defrost relay open during the defrost cycle?
3. Finally just a general question but I'll reference the video as an example. When the Y terminal is pulled in and it sends 24v through the control board and through the pressure switches, how do you know that the 24v then goes to the M terminal? If I were to look at this on my own for the first time, I would have no idea that the 24v will come back to the PS terminal and internally to the M terminal. Obviously you've been doing this for many many years so you know by experience but how would a novice like me be able to figure that out?
Both defrost relays are activated by the 24v signal passed on by the defrost timer taken from the R power.
As for the M terminal, that one I just had to figure out by talking to other technicians or checking schematics of similar systems that laid it out a little better. It didn't come easy.
This is awesome...Is there a place I can find schematic on specific model...old Heil in particular.
5:45 i didnt realize 120/240 ran through the fan relay on the defrost board. I thought it was control / low voltage that powered the relay, similar to a contactor.
Low voltage does control that relay.
Can you make a video with a due fuel system. Oil furnace/heat pump with a 2 zone system Honeywell please 🙏
Hello Mike. I was working in the field and ran across a thermostat that the voltage on the R and Y was 16 volts, it also showed 16 volts in the air handler and 16 volts in the condenser. Testing the Red with green, and Red with white both registered 27 volts. What could be causing the voltage drop? The contactor does not show voltage on the coils, but when testing the coil for ohm it shows 12.8 ohm and it also has continuity. What could be the problem? Thanks for your input.
So what would blow the low voltage fuse in heat mode but not in cool assuming no bad wires?
Asking for a friend..... My friend had a company come inspect they found no 24V on the yellow at the outside unit. it was a open float switch because of a clogged drip line. they fixed that and everything was fine for 3 days...... fast forward 3 days and the AC is blowing heat. the Copper lines in and out of the outside unit was way too hot to touch, my friend pulled the cover off the unit to check for 24v on all wires and if the contactor works. what my friend found was the O wire spade had fallen off the defrost board. My friend plugged it back in, BUT AC is only matches outside/Ambient air.
The guys that "Fixed" it say the outside is "dead" (6 year old Goodman) would running the system in "A/C" with the "O" off the defrost board "kill" the outdoor unit?
It's my opinion they yanked the O wire loose on the defrost board checking for 24V. ?????
The O wire just controls the reversing valve to put it in heating or cooling mode. It was blowing hot air because the RV wasn't getting the signal during cooling mode. Basically, having the O wire disconnected is just heating mode and shouldn't "kill" the outdoor unit.
My question is was the O wire touching anything when disconnected? Could have created a short when powered up in cooling mode.
Does heating mode still work normally or is it the same ambient result?
If heat works, try to jumper Y and O at the defrost board in cooling mode. If ac works then, problem could be a burnt out switch on the
thermostat from the short. If not, could have damaged the defrost board or possibly the reversing valve is stuck.
At 6 years that could be a warranty repair.
I can't see the hole picture
Mike, saw a nest thermostat, yet Rh & Rc were not jumpered. Is this done in background on these thermoststs?
Yes, all Nest thermostats have internal jumpers and will alter function based on what wires the thermostat detects.
This video could take you a long way to finding the problem. Careful about touching things if the breaker is on.
Mike, do you have an Instagram? I have a low voltage company and the alarm systems we install are now probinding low-level automation features suck as lighting and thermostat controls. Your provided understanding of HVAC has now gone unappreciated. Thank you from Arizona.
Do you have a website, do you offer an online course?
Not yet but I'm trying to find time to work on all of that. Eventually.
I have a similar problem with the letter O. I have a Rheem 3.5 Ton AC. I have the following wires coming out of the defrost board. Brown = Common (letter C), Red = Power (leter R), Purple = ?? (Letter D)Blue = ??(Letter B) and Yellow = Y (letter Y) which is for they is for the AC. My problem is the Blue and the Purple. Blue is connected to letter B on the board and Purple to D. The thermostat am using is a Nest Thermostat and it has letter B. It also has W1 and W2 adn from the board in the attic, I have w1 = white and blue wire and W2 white and brown wire. Assuming I connect Blue to B on the thermostat, what do I do with purple? I read some answer below and it suggest to connect Purple to W1 and W2. Once I do that, it will be like placing a jumper from W1 to W2, correct? If am wrong can you please correct me on all and everything.
For clarity, when I said W1/W2, I didn’t necessarily mean place it on both and jumper them. I just mean it should go to one of those terminals depending on how it’s wired based on the configuration of the equipment available, which is information I don’t fully have. There may be 2 stages of backup heat in which case W1 and W2 are wired to each activate one of two heat strips or a 2 different stages of a gas valve in a furnace.
All that purple wire off of D does is allow the condensing unit to activate whatever that backup source of heat is. So it will land on the same terminal that calls in the secondary source of heat such as heat strips, which is usually W1. In some cases W2 might do exactly the same thing, just at a different time and it might not make a difference if you place the purple on w1 or w2 or both.
Normally it will just land on W1.
@@JerseyMikeHVAC Never worked on an AC of any kind. Your video was a great help, not only that, you answer my questions prompt and to the point. Today I got my ac running, well my heat. Since I have a Nest Thermostat and the temperature outside was below 55 it won't let me turn on the AC but, I guess that will be another question for the summer. Thank you
I need help. I have a Rheem system 3.5 ton, 20kW heat strip. From the control board I have the following wires going out of the cabinet Yellow connected on the thermostat at Y1. White and blue to W2. White and black to W1. G to Green. C to brown and R to red. On the defrost board outside I have the following letter and cable wires Y with yellow wire, B with blue wire, D with purple wire, Red with red wire and C with brown wire. I don't have "O" in the blower or on the defrost board nor orange wire. The thermostat am using is Nest Thermostat. What am I missing? The AC and or the Heat has never worked. No need to rush since the house is vacant but, I will be moving in this summer. What can I do? I see the RV and C on the defrost board connected but, I haven't follow the wires. I also see 2 flashing red lights for about 2 minutes after that, they start alternating on and off for another minute or 2 and start flashing at the same time. Flashing at the same time is normal. Alternative is High and Low pressure lock out. At this moment I just need help with the "O" wire and or terminal that I don't see anywhere.
CORRECTION. I got the heat strips to work
On Rheem systems the reversing valve is energized in heating mode off of the B terminal. So there is no O terminal used here.
That blue wire on the B terminal on the defrost control board needs to be powered by the B terminal on the thermostat and this connection from B to B happens inside the air handler at the control board.
That blue wire in B at the defrost board should go to B in the control board which goes to B on the thermostat.
Also, the purple wire off of D on the defrost board should go to W1 W2 at the air handler. That is your heat strip activation during defrost cycles. Here's a wiring diagram you should be working off of:
www.doityourself.com/forum/attachments/thermostatic-controls/54963d1440259155-connecting-thermostat-rheem-heat-pump-system-rheem-thermostat-wiring-diagram.jpg
I have no letter “B” on the control board. All I have is:
Y1 = yellow wire
W1 = white and black wire
W2 = white and blue wire
G = green wire
C = brown wire
R = red wire
But no letter “B” or letter “O”
How do you use one of the WORST thermostats ever made, especially for a heat pump?
Because 8000 people will ask me how to hook up a Nest with it, so I just did it with a Nest.
Hi how are you i contac you i live in mew jersey
My contact info is on my channel page
WTF.... HVAC technicians are not engineers this explanation is too long and detailed.
I'm going to watch it a few more times to see if I can follow along.
And mind you I have a B.S. degree.
It's true, nobody looks at us HVAC technicians as engineers, but this is the level of understanding that is required to diagnose these things.
Your lack of education is exactly why we have HVAC techs changing parts all day that are not bad, you need to know this information to correctly diagnosis the defost system. If you are not constantly willing to learn yoru trade in great detail i believe you have picked the wrong trade to be in and i recommend that you please move to another profession that allows you to not have to know what your doing edwardlara1011