# Retrofit Demand Defrost goodman clpt42



## carlb23 (Jun 22, 2008)

Hi I am a homeowner and I have a goodman clpt42 which i installed in 2006. While the heatpump and the GMV 95 furnace have been problem free since the installation I always disliked the timed defrost feature since even set at 90 minutes my heatpump defrosts much more often then necessary. This has spurred me to change out the time defrost to a demand defrost board. Because of cost i decided to go with a White Rodgers 47D40-801 demand which i purchased from Amazon for 44 dollars. The wiring was pretty straight forward except that the white rodgers board was designed to energize the reversing valve during heat while the Goodman energizes the coil on cooling. To rectify this i just added a spdt relay to circuit so that when the board energizes the relay the relay removes power from the reversing coil, this causes the reversing valve on the Goodman to operate properly. On the original setup the yellow wire coming from the T-stat went directly to the compressor contactor, this had to be moved to the new board then the yellow out from the board to the contactor so that the board could shutdown the compressor for 5 seconds on defrost initiation. While electrically everything is working correctly, I wanted to make sure that i placed the outdoor coil temperature sensor in the correct location. I placed the sensor on the vertical liquid tube coming from the outdoor metering device just before it goes into the coil at the top. So far I haven't seen any frosting on the coils but that doesn't mean it isn't defrosting too often. I have not had the time so far to really determine how often it is defrosting but i will do that in the near future. After i am all done i will draw a schematic of the wiring Also the brown wire from the Tstat must be used to energize the defrost circuit rather than the orange wire as this board wants to see 24vac on call for heat rather than cool. If anyone has any suggestions as to the placement of the outdoor coil temperature sensor I would love to hear them. Thanks  Carl.


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## carlb23 (Jun 22, 2008)

Update

Well it has been just about 5 days since i installed the Demand Defrost Board in my Goodman heat pump. 

I also installed two electronic counters so that i could determine how long and how many times the heat pump has gone into defrost. 

One is a cumulative timer / hour meter that keeps track of the time the aux heat is energized during defrost the other is an event timer and it just counts the number of times the aux heat is energized during the defrost mode. 

Note in my setup, when the heat pump goes into defrost is energizes a 10kw heat strip, when the t-stat calls for aux heat because the temp is below the balance point temp it only energizes a 5kw heat strip.

The white rodgers board will automatically do a short defrost cycle every 6 hours of compressor run time and so far it has logged 8 events each lasting only about 30 seconds. 

So far I have not seen any frosting on the coils and while it has been dry here the temperatures have been quite cold. 

yesterday the low was 18 and the high was 25 this morning it was 10.5 degrees and it is not only 20 degrees out at 11 am. 

I go out and check the coil for frosting at least 4 times a day but so far no icing or frosting to the coil is present and no defrost events have happened.

The cumulative timer has only logged about 3 minutes of aux heat from calls from the heat pump for aux heat during defrost which only represents the 8 events which the board automatically does at 6 hours of compressor run time.

The demand defrost board has cut the daily energy usage from aprox 120kwh a day in 26 degree weather to less than 80kwh a day even in these cold temps. 

The addition of the demand defrost is a huge energy savings at least as of now. I suspect when it gets a little warmer and a little wetter it will ice up and actually need to go into defrost but as of now i have avoided the dreaded 90 minute unnecessary defrost cycles.

With the old defrost board it would have defrosted 35 times unnecessary, based on the 53 hours of heat pump run time in the last 5 days, resulting in much less wear and tear on the compressor / reversing valve / heat strips and lastly savings huge amounts of electricity.

This simple change will pay for itself in about 1 month of usage.:thumbup:


Carl


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## Done That (Apr 28, 2011)

I would have placed the coil temperature thermistor in the same location as the original snap-disc thermostat for the time/temp board.

The air temperature sensor is also important for demand defrost. Make sure it is hanging "free" in the unit, not touching sheet metal for example, and not near anything generating heat that would give it a false reading.


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## carlb23 (Jun 22, 2008)

The ambient thermocouple is routed to the outside of he heat pump and out of direct sunlight. The original snap disk was mounted to one of the 90 degree tubes near the bottom of the condenser coil. The new sensor is not designed to be mounted to a curved surface. So far so good, I guess I will have to wait until it actually gets some frost / ice on it to be sure the placement is ok. If not i will move it down to where the original one was but it wont fit properly.


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## carlb23 (Jun 22, 2008)

Update.

I need to move the coil temperature sensor two times since i did the install (this takes about 10 minutes to remove the fan move the sensor and replace the fan). When i located it in the original location where the snap disk sensor was located it would not go into defrost. I then moved it to the bottom of the coil on the opposite side and this caused it to defrost a little too often (when only a light frost was appearing on the coils and very little loss in performance). I have since moved it up to the center of the coil from the bottom and it has been working fine for the last month and a half. 

With the sensor in this location it will only defrost when there is a fair coating of frost on the coils and the performance has dropped about 20%. The only times it has gone into defrost is when it is cold and raining or snowing or if the humidity is very high which is not often in the wintertime here when the temp is below 40. In the last month and a half it has defrosted a total of 13 times for a total time of 109 minutes. In those 45 days it would have normally have defrosted no less than 225 times for a total time of aprox 1350 minutes.

The side benefit aside from the wear and tear on the equipment and enormous energy savings the house stays more comfortable with the fewer defrost cycles.


I couldn't be happier with the modification :thumbsup::thumbsup::thumbup::thumbup:
Carl


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## Done That (Apr 28, 2011)

Thanks for taking the time to share your experiences with this project, good info.


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## bobinphx (Nov 25, 2011)

Thanks.... Now I have to go and measure how often mine is going into defrost!!! thanks... thanks a lot!!! LOL (hope you see this is my attempt at a joke)... 

in all honesty, WOW is all I can say... that and great job for a non professional. Goes to show you that common sense is alive and well in the USA. 

so the question comes up why didnt the MFGR do this in the first place??? why the timed defrost. Heck even my fridge does not do timed defrost... oh... I know seer rating never takes defrost into account!!!! 
LOL


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## beenthere (Oct 11, 2008)

3 to 4 inches after the OD metering device should work pretty good for sensing liquid line temp.


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## vhehn (Sep 7, 2006)

hi carlb23 are you still around? i have a question.


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## arg3670 (Oct 13, 2012)

I'm thnking about doing the same to my goodman. I have a wiring question what happens when your on ac how does does the reversing valve get its power? 


Thanks


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## beenthere (Oct 11, 2008)

The O terminal.


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## arg3670 (Oct 13, 2012)

HI

I'm wondering if you could post wiring diagram for your retrofit on a Goodman.

Thanks


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## beenthere (Oct 11, 2008)

A diagram should have come with the board you bought. I don't have any.


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## dmet (Nov 20, 2012)

*Retrofit Demand Defrost goodman*

I have been down about the same path as Carlb23. I used an older version (47-182684-83) and made a couple reroutes on the circuit board and glued a relay to the top to take care of the Goodman logic on the "O" pin of high on cool/ low on heat. All of this was done on the board itself, so if I ever had the Goodman dealer out, I could put the original board back in quickly (10 year warranty).
Seems to work good except that for some reason in freezing weather it will start a defrost on call for heat. It should wait for things to stabilize.
For anyone contemplating doing a conversion, there is a PDF on the internet written by Ranco. Do a search for "ranco ddl 01-03" Seems to be some you have to buy, but others post it free. Also, Rheem and Ruud and others have installation instructions with wiring diagrams.

I have wired in a switch, which is in the house where I can disable defrost altogether. I have run for days in freezing weather with no frost buildup (lo humidity), and therefore did not let it defrost. Now, I have seen things on the internet that defrosting is still necessary in cold weather to be sure lubricant is returning to the compressor. Anyone know anything about this??

My system is a DSZ18 4 ton Goodman


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## etona58 (Dec 31, 2012)

Dmet,
I bought the same demand defrost board as you.I want to change my timed defrost board to demand defrost. Unit is a Goodman package heat pump. Can you provide a schematic or wiring diagram of what you did to the new board?

"Now, I have seen things on the internet that defrosting is still necessary in cold weather to be sure lubricant is returning to the compressor. Anyone know anything about this??" From what I've read, some boards do a "forced defrost" every 6 hours of run time below 35* to ensure adequate oil return to the compressor.Not sure if this particular defrost board does it or not.Maybe someone with more knowledge can chime in.


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## beenthere (Oct 11, 2008)

All on demand defrost boards do it.


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## dmet (Nov 20, 2012)

etona58;
I will have to clean up some hastily written schematics, but here are some jpegs of the changes I made to the board. Obviously neatness means nothing to me.

Although is seems to work fine (except for the startup defrost) I would advise you to verify the logic and wiring as I have made mistakes before and I will make them again.


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## mrairflow (Oct 25, 2009)

im thinking about bootlegging a trane defrost control on my carrier


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## dmet (Nov 20, 2012)

*Goodman Demand Defrost Conversion*

Here are some (crude&hasty) drawings to show changes I made in the Demand defrost Board. Changes were made on the board (instead of elsewhere) so that it is a direct plug in, and the original board could be reinstalled easily.

The location of the taps to board components is shown as viewed with the text reading normally. 

An earlier post by me was of an older board, and I had made some changes since then. 1) power thru the add on relay comes from R (24vac) instead of the Y terminal. 2) Power to the on-board relay for the reversing valve comes from R also.

Always learning from this, so I welcome comments and/or ideas


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## etona58 (Dec 31, 2012)

*Goodman Retrofit*

Good job Dmet:thumbsup:
I did the first revision wiring changes to the board.Happened to have a dpdt relay on hand,so I used it.I may change it to a spdt relay if I run across one.
The "Y" terminal from the thermostat went through the low charge switch,then to the contactor.I rerouted it from the low charge switch to the "Y" teminal on the defrost board.The "Y OUT" terminal controls the contactor.
Have not experienced the startup defrost you mentioned earlier as of yet.
So glad I don't have to hear the unit go into defrost when it's 50+ degrees outside.


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## dmet (Nov 20, 2012)

Glad it is working out for you. I know what you mean about the annoying defrost at 50 degrees.... wonder how Goodman ever thought that was acceptable.

I realized that I labeled the relay as a Double pole when it was a single pole. 

I have not mentioned it before, but the demand defrost board will also provide for a delay of the compressor when switching modes. Use the CC terminal and connect it to the Compressor contactor grounded(C) side. Lift all the other grounds and tie them together. This will keep all the other grounds working normally, but allow the cc terminal provide the ground to the relay thus allowing the defrost board to de-energize the contactor .


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## sammy37 (Dec 9, 2008)

carlb23 said:


> Hi I am a homeowner and I have a goodman clpt42 which i installed in 2006. While the heatpump and the GMV 95 furnace have been problem free since the installation I always disliked the timed defrost feature since even set at 90 minutes my heatpump defrosts much more often then necessary. This has spurred me to change out the time defrost to a demand defrost board. Because of cost i decided to go with a White Rodgers 47D40-801 demand which i purchased from Amazon for 44 dollars. The wiring was pretty straight forward except that the white rodgers board was designed to energize the reversing valve during heat while the Goodman energizes the coil on cooling. To rectify this i just added a spdt relay to circuit so that when the board energizes the relay the relay removes power from the reversing coil, this causes the reversing valve on the Goodman to operate properly. On the original setup the yellow wire coming from the T-stat went directly to the compressor contactor, this had to be moved to the new board then the yellow out from the board to the contactor so that the board could shutdown the compressor for 5 seconds on defrost initiation. While electrically everything is working correctly, I wanted to make sure that i placed the outdoor coil temperature sensor in the correct location. I placed the sensor on the vertical liquid tube coming from the outdoor metering device just before it goes into the coil at the top. So far I haven't seen any frosting on the coils but that doesn't mean it isn't defrosting too often. I have not had the time so far to really determine how often it is defrosting but i will do that in the near future. After i am all done i will draw a schematic of the wiring Also the brown wire from the Tstat must be used to energize the defrost circuit rather than the orange wire as this board wants to see 24vac on call for heat rather than cool. If anyone has any suggestions as to the placement of the outdoor coil temperature sensor I would love to hear them. Thanks Carl.


So for the 45 bucks they get for this kit, does it work well? In reading several posts on another professional site, guys over there said it was too expensive to do and would require hundreds of dollars in parts. 
So who's right here?

Everything he had to do seems pretty straight foward, along with the relay for the RV. Is he saying that the O wire gets replaced with the B at the thermostat? That would also require going into the stat menu and changing the setting internally o/b. I assume it would be permanent and nothing would have to be changed come summer?

As long as I'm stuck with using our heat pump this kit would work great here, as we get very little humidity and truly only need a real defrost very few times during the heating season.


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## dmet (Nov 20, 2012)

*Who is right?*

We are. Mine has been going 2 years. Carlb23 did a great job modifying and documenting his results. The concepts is simple, but implementing it has its risks. 

First is personal safety. You can get electrocuted working inside the unit. There is 120 volts waiting for you(get unlucky and you can get across 240).

Second, you can damage the unit with a misplaced wire. 

Third, If you have warranty on the unit, and have the serviceman out for repair, they could deny warranty since you modified the unit. 

Aside from the above, the White Rodgers 47D40-801 is a kit that consists of a board and 2 temperature probes..thats all,,, no instructions for what we have done. But on the other hand, the board will match the mounting holes of the original, and most of the input wiring is the same. The connectors are the same. Carlb23 apparently made the logic corrections external to the circuit board, while I made them on the board. That will allow me to swap back to the factory setup in minutes. 

there are 2 logic corrections needed...
1) reverse the "o" logic to make the whiterodgers board happy. That means a relay.
2) Reverse the output of the whiterodgers board to the reversing valve. this means a relay, OR as I have done cut and jump traces on the board itself. Whitesrodgers uses a double throw relay. It is simple to change it so it does the opposite of what was intended.

When all of this is done, there is nothing needed to be done outside the board. Thermostat stays the same. Cooling mode will not be affected.

Of course there is always the risk of something going wrong. You have to wary of that. That will be up to you. Are you willing to take the chance that you will be out there in 20 degrees putting the old board back in so that it will defrost? Small chance, but you have to think about it.

Good luck


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## sammy37 (Dec 9, 2008)

dmet said:


> We are. Mine has been going 2 years. Carlb23 did a great job modifying and documenting his results. The concepts is simple, but implementing it has its risks.
> 
> First is personal safety. You can get electrocuted working inside the unit. There is 120 volts waiting for you(get unlucky and you can get across 240).
> 
> ...


I installed the unit 6 years ago and plan to eventually go back to gas but for now, this kit looks like a neat way to avoid all the useless defrost cycles that our unit goes through.
I just ordered the defrost kit and an Evergreen blower motor. The motor can be transfered to the next unit when the time comes.


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## Jesuitson (Jan 28, 2013)

I recently made this mod on a Carrier unit. Replaced the timed defrost with a Rheem 47-102685-85 defrost board from Amazon. I found a way to wire the board without using another relay. I feel this mod is much simpler and could be more reliable due to not adding any other parts to the board. All I had to do was scrape away two terminals on the changeover/defrost relay and jumper them elsewhere.

Remember, this board receives power from the B terminal of your thermostat. This means that the board expects the changeover solenoid to be energized in heating mode. When the B wire sends 24v to the board, the board then knows that the system is in heating mode and will then begin sensing defrost conditions. The B wire energizes the IC on the circuit board. If you hook the orange wire up, then the board will not know that there is a call for heat. You can reverse the relay, but without a B signal, the board will never initiate a defrost.



If your thermostat features an O and a B terminal like mine, then you can use both and bypass adding any relays. This is a simple mod to the board and only takes a few minutes. Scrape away the B terminal from the relay so that you don't send power to the changeover during heating. Then solder a new wire for the O terminal. Anyway, pictures are worth a thousand words. 

Note: I added a jumper wire to the front because this Carrier does not have a low pressure switch so I had to bypass it on the board.


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## bronzemaxell (Jan 28, 2013)

Hi, Jesuitson

i have 3m50 thermostat, and it has both B and O, my thermostat cable has 8 wires inside, and i have a gibson heat pump, no low port switch on my old defrost board either.

can you explain more, or show another picture about the two scrapes.
i think i see where the B scrape is, but not sure about how you cut the RV.
thanks


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## beenthere (Oct 11, 2008)

bronzemaxell said:


> Hi, Jesuitson
> 
> i have 3m50 thermostat, and it has both B and O, my thermostat cable has 8 wires inside, and i have a gibson heat pump, no low port switch on my old defrost board either.
> 
> ...


Why not just get the Gibson on demand defrost board. no fuss no muss.


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## bronzemaxell (Jan 28, 2013)

beenthere said:


> Why not just get the Gibson on demand defrost board. no fuss no muss.


mainly cheaper, comfortguru.com sell this demand defrost kit with sensors only $37, and seem like easy hack to add the o wire


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## bronzemaxell (Jan 28, 2013)

ahh, i see it now, better picture when i looked at your picture on iphone than big lcd monitor
it looks like at the right of Rv marking


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## Jesuitson (Jan 28, 2013)

bronzemaxell said:


> ahh, i see it now, better picture when i looked at your picture on iphone than big lcd monitor
> it looks like at the right of Rv marking


Yes, that is correct. Sorry about the blurry picture. I couldn't get the camera right. I labeled the board at the relay. It says from top to bottom, B, O and RV. This is not what these circuits went to originally. This is what they become once you make the mod. All you have to do is cut the trace at the "B" and "RV" on the relay, jumper them and then add your "O" wire. Hook up the O and B to your thermostat, ensuring that O is energized in Cooling mode and B is energized in Heating mode.

The way this works is that in heating mode, the thermostat sends voltage through B to the IC which kicks in the demand defrost sensing. This tells the board that the system is calling for heat. But then you cut the output so that it doesn't send voltage to the reversing valve (RV). When the system calls for a defrost, it will then switch the relay and send voltage to both the RV and the heat strips through the D terminal. Once defrost completes, the relay switches back, de-energizing the RV and the heat strips.

In AC mode, voltage is supplied through the O terminal. With the modded board, the O terminal will energize the RV. As these are normally closed when the relay is not active. With no voltage going to the B terminal, the board knows that it is in cooling mode and will not attempt a defrost.

One other thing... When installing the board I covered the back with electrical tape to prevent any possibility of shorting. When you solder in new connections you do have an increased risk of a short because you have removed the protective coating from the board...The board is mounted on plastic stand-offs and I don't think shorting is likely but it's always best to play it safe.


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## beenthere (Oct 11, 2008)

bronzemaxell said:


> mainly cheaper, comfortguru.com sell this demand defrost kit with sensors only $37, and seem like easy hack to add the o wire


The Gibson board is 38 bucks. At least thats what it cost me.


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## beenthere (Oct 11, 2008)

> In AC mode, voltage is supplied through the O terminal. With the modded board, the O terminal will energize the RV. As these are normally closed when the relay is not active. With no voltage going to the B terminal, the board knows that it is in cooling mode and will not attempt a defrost.


An on demand defrost board doesn't go into defrost in heating mode when the outdoor temp is above X degrees(X varies with manufacturer). Pretty much has nothing to do with weather the board knows its in heating or cooling mode.


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## Jesuitson (Jan 28, 2013)

beenthere said:


> An on demand defrost board doesn't go into defrost in heating mode when the outdoor temp is above X degrees(X varies with manufacturer). Pretty much has nothing to do with weather the board knows its in heating or cooling mode.


Normally, yes. Unless you are dealing with low outdoor ambient conditions. I have run the AC in the wintertime before. Sometimes we will have a day that gets up in the 70's (like right now) and then down in the 20-30s at night. When I come home late the house might still be hot and so I'll turn on the AC sometimes to bring it back down to where it should be. I also run a head pressure control so I don't flood back to the compressor.

My parents Carrier, who I installed this board on have Christmas parties with 50 or so people over. It's not uncommon for them to run the AC in the winter either.

In both cases, while the board will never sense frosting conditions, it will initiate a defrost every 6 hours to re-oil the compressor if the board does not know it's in cooling mode. That's why it is important not to hook up the O wire to the B terminal on the board. You could get nuisance defrosts while in AC if the board gets voltage to the B terminal...


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## bronzemaxell (Jan 28, 2013)

Hi, Jesuitson, i saw your note that you only bypassed Low pressure contact, how about the high pressure contact?


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## Jesuitson (Jan 28, 2013)

bronzemaxell said:


> Hi, Jesuitson, i saw your note that you only bypassed Low pressure contact, how about the high pressure contact?


On this particular heat pump there is a high pressure switch and so I did not bypass it on the board. The high pressure switch on the heat pump is hooked up to the board in my setup. If the heat pump had a low pressure switch I would have installed it too, but it didn't. I didn't want to bypass any of the safety features that were on the heat pump.


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## beenthere (Oct 11, 2008)

Jesuitson said:


> Normally, yes. Unless you are dealing with low outdoor ambient conditions. I have run the AC in the wintertime before. Sometimes we will have a day that gets up in the 70's (like right now) and then down in the 20-30s at night. When I come home late the house might still be hot and so I'll turn on the AC sometimes to bring it back down to where it should be. I also run a head pressure control so I don't flood back to the compressor.
> 
> My parents Carrier, who I installed this board on have Christmas parties with 50 or so people over. It's not uncommon for them to run the AC in the winter either.
> 
> In both cases, while the board will never sense frosting conditions, it will initiate a defrost every 6 hours to re-oil the compressor if the board does not know it's in cooling mode. That's why it is important not to hook up the O wire to the B terminal on the board. You could get nuisance defrosts while in AC if the board gets voltage to the B terminal...


Worse that could happen when running it in cooling in the winter as far as going into defrost. Is it stops the outdoor fan for 15 to 30 seconds. The defrost it temp terminated. So it shouldn't be able to go into defrost in cooling mode since the coil is above termination temp.


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## Jesuitson (Jan 28, 2013)

beenthere said:


> Worse that could happen when running it in cooling in the winter as far as going into defrost. Is it stops the outdoor fan for 15 to 30 seconds. The defrost it temp terminated. So it shouldn't be able to go into defrost in cooling mode since the coil is above termination temp.


Well regardless it's hooked up properly as the board manufacturer intended. We can just agree to disagree on the logic of the circuit.


As an update, I too had to move the coil temp sensor. I originally hooked the sensor up where the original bi-metallic thermostat was located for the timed defrost. It was defrosting way too often. I moved the thermocouple half way up the evaporator and that solved the problem. I figure that the bottom of the coil is colder and carrier put the original thermostat there so that it would keep the defrost circuit engaged for the timer. It defrosts too often when the new system reads from this location. About half way up and everything works great...


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## beenthere (Oct 11, 2008)

Jesuitson said:


> Well regardless it's hooked up properly as the board manufacturer intended. We can just agree to disagree on the logic of the circuit.


The manufacturer didn't intend for a rely to be added, nor any alterations to the board, or wiring deviations.

It works.


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## bronzemaxell (Jan 28, 2013)

thank you jesuitson again
i retrofited the Rheem 47-102685-85 demand defrost board today on my gibson 13 seer 4ton

I have dual fuel furnace and heat pump, 
from my 3m-50 thermostat, I use W wire for heat pump, and W2 for furnace aux, as well as O, Y, C, R wires,
i wired the gibson outdoor unit "W2" (really it is the W wire from thermostat) to B to energize the rheem board, gibson wire T1 and C to high pressure switch, also need to bypass the low pressure switch on rheem board, gibson T2 Blue wire to Y (compressor), O to O to Reverse valve.
the gibson DFT and R (red wires) not used.
amazingly, it works, 
so far i run the heat pump continunouly over 2 hours, sunny, and outdoor temperature is 28F and dropping, no defrost cycle kick in yet, and no frosting on outdoor coil either.


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## taxmantoo (Jun 11, 2013)

beenthere said:


> The Gibson board is 38 bucks. At least thats what it cost me.


So this board is a drop in for Goodman without changing the reversing valve logic like you'd need to do with a Rheem board?

What's the part number?


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## carlb23 (Jun 22, 2008)

Wow, I haven't checked into this thread for quite a while. I see that many very bright people and taken my crude yet effective demand defrost board retrofit idea to a new level. Great work guys. As far as my original installation is concerned, everything is still working great, defrost only comes into play when necessary. I have gone weeks in sub 30 degree weather with no defrosts when humidity is low. Every six hours of run time the board goes into defrost for about 1 minute to make sure there are no oil issues. Great work guys. carlb23


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## etona58 (Dec 31, 2012)

Same here Carl.I hear it go into defrost on a few occasions during the daytime when the six hour timer has been reached.
Glad there are people like you on this board.:thumbup:


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## RSWAFFER (Feb 24, 2015)

Question....My Hunter Model Number 44428 Auto Temp II Heat Pump Thermostat has a 3 position switch concerning the reversing valve inside the thermostat. It has RO to energize O in cooling mode.....RB to energize for heating mode....And NR which does nothing to the reversing valve. Could I install one of these Rheem Demand Defrost Boards and the sensors, switch the 3 position switch to RB (Heating Mode) and not have to make any of these modifications to the board? My present time/temperature defrost system has the switch set to RO (Cooling Mode).


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## zappa (Nov 25, 2011)

It's the signal coming from the defrost board that is the problem.


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## RSWAFFER (Feb 24, 2015)

Thank You ZAPPA for your comment.....I am attempting to modify a Rheem P/N 47-21517-14 Demand Defrost Board. Would one of your fellows please share with me what to "Scrape" and where to run a wire to solve of the problem of the signal coming from the defrost board. Am I correct that I can switch my Hunter 44428 Auto Temp II Heat Pump Thermostat to "RB" to send a signal to the board to energize in heating mode?


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## RSWAFFER (Feb 24, 2015)

Jesuitson said:


> Yes, that is correct. Sorry about the blurry picture. I couldn't get the camera right. I labeled the board at the relay. It says from top to bottom, B, O and RV. This is not what these circuits went to originally. This is what they become once you make the mod. All you have to do is cut the trace at the "B" and "RV" on the relay, jumper them and then add your "O" wire. Hook up the O and B to your thermostat, ensuring that O is energized in Cooling mode and B is energized in Heating mode.
> 
> The way this works is that in heating mode, the thermostat sends voltage through B to the IC which kicks in the demand defrost sensing. This tells the board that the system is calling for heat. But then you cut the output so that it doesn't send voltage to the reversing valve (RV). When the system calls for a defrost, it will then switch the relay and send voltage to both the RV and the heat strips through the D terminal. Once defrost completes, the relay switches back, de-energizing the RV and the heat strips.
> 
> ...


After studying the information Jesuitson provided I think I better understand the wiring. However I do have a question.

My Hunter Model 44428 Auto Temp II Thermostat has a Selector Switch.
1. O activates in cool mode (RO Position)
2. B activates in heat mode ((RB Position)
3. W connection made internally, no terminal at thermostat instead, there 
is a separate connection for 1st stage heat.

The switch is presently is RO position (Cool Mode)

Their is a orange wire in the O/B connection in the thermostat.
Their is a blue wire that goes to common.

What do I need to do concerning the "B" connection on the RHEEM P/N 47-21517-14 Demand Defrost Board?

I understand that the "B" terminal on the board needs 24 Volts for Demand Defrost Sensing.

Am I missing something here?

Thank You....Anyone For advice/information.


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## Done That (Apr 28, 2011)

Shameless plug, Moderator may certainly delete this if inappropriate, however due to the interest and discussion I just wanted to make some folks aware:

White-Rodgers is currently releasing a Universal Heat Pump Defrost Board kit, part number 47D01U-843. It will likely be a bit before it starts popping up at HVAC wholesalers and other points of distribution.

Bottom line is that it can be easily configured to run EITHER Time/Temp or Demand Defrost, and it can be also be easily configured to energize EITHER an "O" or "B" reversing valve system. Includes the two needed thermistors and other parts. Many other configurable features to make it work with most 1-stage heat pumps having PSC fan motors. Has a RV shift delay that can be turned on for folks that may not have that feature and have a noisy unit.

No need to hack up existing controls. Hope this might help some folks.


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## Bob Sanders (Nov 10, 2013)

Done That said:


> White-Rodgers is currently releasing a Universal Heat Pump Defrost Board kit, part number 47D01U-843. It will likely be a bit before it starts popping up at HVAC wholesalers and other points of distribution.


That's a pretty good idea. It looks like it'll fit the majority of the more simplistic single stage models.


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## zappa (Nov 25, 2011)

Done That said:


> Shameless plug, Moderator may certainly delete this if inappropriate, however due to the interest and discussion I just wanted to make some folks aware:
> 
> White-Rodgers is currently releasing a Universal Heat Pump Defrost Board kit, part number 47D01U-843. It will likely be a bit before it starts popping up at HVAC wholesalers and other points of distribution.
> 
> ...


Thank you for that model number. I spent a lot of time searching for this board just a few days ago and came up blank. I couldn't even find it on White Rodgers site.


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## zappa (Nov 25, 2011)

From a thread here I heard that the old boards shut the compressor down when shifting the valve, something I definitely don't want. The OP easily bypassed it (lost some features IIRC) but I wonder if it's an option on this board. They mention a shifting delay but nothing about keeping the compressor running.


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## Bob Sanders (Nov 10, 2013)

zappa said:


> From a thread here I heard that the old boards shut the compressor down when shifting the valve, something I definitely don't want. The OP easily bypassed it (lost some features IIRC) but I wonder if it's an option on this board. They mention a shifting delay but nothing about keeping the compressor running.


That shift delay has indeed been EXTENDED on the newer goodman boards to try and minimized the noise complaints goodman was getting. It was 5 seconds but now a board revision has extended it to 30 seconds... and the compressor does turn off. The system now has 30 seconds for a bit of equalizing before the valve is shifted.

I'm not sure how hard it is on the system in an instantaneous reverse but one would figure it can't be good.


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## Done That (Apr 28, 2011)

The 47D01U-843 can have the RV shift delay set to: 0, 12, or 30 seconds by the installer. If you don't want a shift delay just set it to 0. 

Many older units with recip compressors had no shift delay. It exists today mostly because scroll compressors exhibit noise going into/out of defrost.....and the delay resolves this.


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## Bob Sanders (Nov 10, 2013)

For those interested there is a Youube video on installing the new White Rodgers universal demand defrost board on the older single stage Goodman's


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## kent_a (3 mo ago)

Sorry to revive this thread, but it's one of the only ones I could find on this retrofit so I wanted to add a potential contribution for future DIYr's.

I modified the control of a Goodman GSZ-16 heat pump (RV controlled by "O") without the use of a "B" thermostat output or an external relay to reverse any signals. I'm using a White Rogers/Emerson 47D43-811 Demand Defrost Board with OCT and OAT sensors (1/3 the cost of the universal control board) which seems to have similar relay logic as the 47D40-801 but with the addition of High and Low Pressure Cutout.

I also landed on the same logic modification that Jesuitson posted using half of the onboard DPDT relay (triggered when the board determines a defrost cycle is needed): RV output from the common terminal, thermostat "O" on the N.C. terminal, and an arbitrary 24 VAC signal on the N.O. terminal). This works because the "RV" circuit board output carries the thermostat's "O" signal unaltered during normal operation, but is switched to 24 VAC on defrost = cooling mode for non-Ruud/Rheem.

However, my approach is different because I jumped "Y" to the board's "B" input trace, so every time the compressor turns on (heating OR cooling) the board will THINK it's in heating mode. Based on the Racho DDL Training Bulletin shared in this post "the coil temperature must be below 35*F for defrost to occur" which I'm relying on to prevent a defrost attempt during cooling season. Amazingly "Defrost Function" item #13 also states that defrost functions are suspended if the coil temp is higher than the air temp so theoretically this could even work when using the system for cooling in ambient temperatures below freezing (but I have no intention of testing that). As an added benefit, this frees up the board's "B" input spade so I repurposed it as an "O" terminal to simplify board connections and keep everything looking stock (red wire soldered to the backside in my image, on the front side I scratched off "B" and proudly drew an "O").

One unique side effect of switching from the Goodman time/temp defrost board is that the Emerson 47D43-811 demand defrost board controls the compressor by interrupting the Contactor Common "CC" terminal whereas my Goodman PCBDM133S stock control board interrupts the "Y" signal using a Contactor "CNT" output. I'm sure this varies based on brand, but on the Goodman it was simple enough to lift the common node as recommended by dmet (previously the contactor coil was used as a junction point), so now common goes straight from the thermostat wiring to the Emerson board and the "Yout" and "CC" terminals are the only things connected to the contactor coil. Also, on my unit High Pressure Cutout switch is wired inline with the "Y" signal so I jumpered the "HPC" terminals on the Emerson board since the inline connection functionally accomplishes the same thing.

Hope this helps someone! I'll report back if this configuration fails. It seemed to work fine when I tested it in both heating and cooling mode.


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