Duo Therm Heat Pump weirded out

[howardwheeler]

I have a less than two year old Duo Therm Heat Pump that has suddenly started having the compressor run anytime 120 volts is to the unit. Only if I shut off the breaker will the compressor stop running. The fan doesn't run unless I put it in non-automatic mode. I have a five button CCC thermostat. I did lose 12 volt power last night, but the ac worked fine after that. 12 volts are back working now, but the AC compressor runs all the time. It is apparently stuck on heat pump, because when I put the fan on run hot air comes out. It's under warranty but I can't get service to look at it yet and we are using the unit. Any ideas?

[howardwheeler]

Everything has continued to work OK, but I will repost when the relay fails again. I have a spare control box that I'll take with me. My friend who was in the Alpenlite when everything went south said the twelve volt power was basically gone with no twelve volt lights working (It turns out I had a bad battery that drew everything down and even caused the Xantrex inverter/charger to shut down on a low voltage safety). Then two twelve volt lights flickered and the thermostat display suddenly came on and the compressor started running. He realized that the fan wasn't running so he got up, and not knowing what all my breakers were, decided to shut off the main breakers. That of course shut everything down. Then that relay would not release. I started to say that only the compressor would run after that when 120v was supplied, which is true, but I just realized that with the built-in time delay, I probably never let it run long enough for the thermostat to cause the unit to turn back on and start up the fan. I was concerned about pressure build up without a condenser fan running. Anyway, that's the most complete description of the chain of events. My friend said that definitely a small surge of 12v power came back for a short period and that's when the relay stuck (although maybe the cause and effect could be reversed, since all we know is that the events were basically simultaneous). I had come over about an hour before the lights flickered and started the Xantrex back up, but the safety would only let run a few minutes at a time before shutting down. It would go into bulk charging at around 85 amps but then shut down after maybe a minute or so. I did it around five times until I figured there had to be some protection circuit, which I later verified was the case. I've surmised that I got enough charge during that time for the twelve volt system to momentarily come back to life and that's why the lights flickered and the thermostat display came back. I hope this makes sense.

[MEXICOWANDERER]

Frainbart Sorry

RELAY!

[dougrainer]

MEXICOWANDERER wrote:
Doug,

Is this a PC board mount C/B?

C/B (Circuit breaker????) The Compressor RELAY is soldered on the AC control board. Doug

[MEXICOWANDERER]

Doug,

Is this a PC board mount C/B?

[dougrainer]

Low 12 volt voltage will not cause the relay to stick. Low voltage (12 volt)would cause the relay to NOT close. Low or High 120 will not really affect the relay unless the low 120 voltage(under 104 volts consistantly), would cause the points in the relay to arc and pit and that causes the relays to "weld" closed. Your problem is NOT the wall tstat. I cannot remember the last time I replaced a 5 button wall tstat. Doug

[howardwheeler]

I will definitely repost if any further problem happens. And I trust that Doug knows what he's talking about as well, as he's helped me in the past as well. Right before resetting, I did turn the circuit breaker back on and the compressor did start back up with the thermostat on off. But resetting did get everything working. Do you know why a low 12v voltage would cause the relay to stick? I have two ACs but only one is hooked up to the CCC thermostat. Do I need to change thermostats? I thought I'd done whatever was necessary to get everything running right when I bought the new heat pump a year and a half ago.

[dougrainer]

Ivylog wrote:
It will be interesting/educational to see if the unit fails again. Since it was a 12V power failure initially and I know you should not bet against Doug, I'm hoping/betting the problem is solved. Keep us informed.

I hope when it fails again(it will) he posts that it did fail:C Doug

[Ivylog]

It will be interesting/educational to see if the unit fails again. Since it was a 12V power failure initially and I know you should not bet against Doug, I'm hoping/betting the problem is solved. Keep us informed.

[dougrainer]

howardwheeler wrote:
It worked!!The reset on the thermostat brought everything back to normal! Thank you all. It's in the high nineties, so hopefully you can feel my appreciation. It is really strange what happened, though. The compressor alone would run anytime power was to the unit, regardless of what the thermostat was set on, including completely off!

The reset did not fix it. The relay just opened. ALL a reset does is verify the DIP switch settings. THAT IS ALL A RESET DOES. Nothing else. It will fail again. For some reason, people think the Dometic CCC tstats are like a computer and a reset fixes operational problems. It does NOT. What you have is a PENGUIN model that comes with a new control board. But that board is a 12 button CCC board. They installed a 12 to 5 button kit to work with the 5 button CCC tstat. IF you have just one roof top unit, you do NOT install the 12 to 5 kit. You purchase and install the 12 button wall tstat which is about the same price. If you have more than 1 roof AC unit, then you have to purchase the 12 to 5 kit so the other AC units can communicate. Doug

[howardwheeler]

It worked!!The reset on the thermostat brought everything back to normal! Thank you all. It's in the high nineties, so hopefully you can feel my appreciation. It is really strange what happened, though. The compressor alone would run anytime power was to the unit, regardless of what the thermostat was set on, including completely off!

[howardwheeler]

Hello Doug, I did replace the AC unit about a year and a half ago (it's the new style Duo Therm), but they sold me a control unit (the electronic box that fits up in the new AC) that was supposedly designed to make the new AC work with the old five button CCC thermostat. I think I was concerned that there was no way I could run a new thermostat wire up to the unit, as it runs through the wall, and somehow I understood a new thermostat needed a different wire. I really don't remember why I stayed with the old thermo. It has worked great for a year and a half until this morning. My control unit is a 3109226.005. So I'll try the thermostat reset. Otherwise, you think its the control unit., is that right? I wasn't sure whether it would be the thermostat or the control unit. Thank you very much for the info. Duo Therm is impossible to get tech support from.

[Ivylog]

As usual Doug knows his stuff. Since you have a 5 button Tstat and it's defaulted to heat it's a old style unit (like mine) and the control board is 3109229.009.

I would try a Tstat reset although it sounds like a control board:
SYSTEM RESET
a. Turn the ON/OFF switch to (OFF) position.
b. Simultaneously depress and hold the MODE and ZONE
push-buttons while turning the ON/OFF switch to (ON).
FF should appear in the LCD display until the MODE
and ZONE push-buttons are released signalling proper
communication between the Tstat and upper control
board.
If you do not get FF then I would try cleaning the contacts on the phone plugs that connect the Tstat and control board.



$125 on Ebay.

[dougrainer]

howardwheeler wrote:
I have a less than two year old Duo Therm Heat Pump that has suddenly started having the compressor run anytime 120 volts is to the unit. Only if I shut off the breaker will the compressor stop running. The fan doesn't run unless I put it in non-automatic mode. I have a five button CCC thermostat. I did lose 12 volt power last night, but the ac worked fine after that. 12 volts are back working now, but the AC compressor runs all the time. It is apparently stuck on heat pump, because when I put the fan on run hot air comes out. It's under warranty but I can't get service to look at it yet and we are using the unit. Any ideas?

Your Compressor Relay on the Upper control board is stuck CLOSED. This is not a replaceable part(the relay). Replace the 5 button upper control board. Your timeline does not make sense. The 5 button has not been used in almost 5 years. Do you mean the Upper HP was replaced less than 2 years ago? If so, then the upper board was not replaced when they changed out the unit(you do not unless it was bad). Doug