Heat Pumps - Do I have them?

[rdownward]

Can anybody tell me a simple way to determine if I have heat pumps in my Dometic A/C units in my '03 36 MDDS? The thermostat shows a "Heap Pump" mode but nothing happens when I turn it to that setting. The furnace is also not coming on when in the Furnace mode but that's probably an issue with the furnace I would suspect. Any help anybody can provide re the heat pumps would be appreciated.

Roger D

[Old Scout]

In a word -- YES--you have heat pumps! Furnance is linked to the front A/C unit so you have to set the furnance with the thermostat set on the front zone only. Strange that neither pump would be working. If they are not working--doing diagnostics on what might be wrong is a bit of a challenge.

[Dave Fernandez]

Roger the problem may be that the thermostat is not set high enough, the furnace should start shortly after the temperature is set on the thermostat. As for the Heat Pumps some time will take several minutes for them to start after you set the thermostat. I sometimes will set the thermostat several degrees higher than normal to start them and then after the interior has warmed I turn them down. The Thermostat is different from the one at home in that they work from thermistor’s one in front and one in the rear. And they are very sensitive to temperature. If one of the vents is pointing at the thermistor the A/C Heat Pump will short cycle.

If I am using the Heater I must set the temperature lower than the Heat Pump because the Furnace heats from the bottom up and the Heat Pump heats from the top down. The Furnace will warm the coach and it takes a long time for the heat to reach the thermistor, Where as the Heat Pump is blowing warm are in the front of the coach and it cycles off sooner than the furnace. It took me a while to find the comfort zone for each.

[Mr_D]

For one thing you don't have "heat pumps" in your A/C's. You either have A/C's OR Heat Pumps. An A/C only puts out cool air, a heat pump puts out both heat and cold and is tied into your furnace.
If the control shows "Heat Pump" then you do have heat pumps. Having had them in stick houses for over 25 years I can say the heat feels different than a furnace. I turn the fan on to either "Low" or "High" and let the compressor cycle. That way the air is flowing all the time. Can you hear the compressor cycling? I know I can with ours.
The air temp is less than your body temp so it feels cold to you. You need to put a thermometer right at the output grate and check the temp.

[Dale777]

Originally Posted by Mr_D

For one thing you don't have "heat pumps" in your A/C's. You either have A/C's OR Heat Pumps. An A/C only puts out cool air, a heat pump puts out both heat and cold and is tied into your furnace.

Mr_D,

For the model year 2003 Alpine Coach, an option was "Duo-Therm 15,000 BTU air conditioner with heat pump option." See page 40 of this Alpine Coach owner's manual at this link:

http://www.alpinecoachassociation.co...2003manual.pdf

On page 40, the description continues with, "As an air conditioner, the heat pump has exactly the same cooling capability as its cool-only counterpart; but its unique, built-in reversing mechanism extracts and concentrates heat from the outdoors to make it an efficient RV heating system."

On both my previous 2001 Alpine Coach and my current 2006 Alpine Coach, I had/have the heat pump option, which works in practice exactly as described.

[Benny367]

Originally Posted by Dale777

Mr_D,

For the model year 2003 Alpine Coach, an option was "Duo-Therm 15,000 BTU air conditioner with heat pump option." See page 40 of this Alpine Coach owner's manual at this link:

http://www.alpinecoachassociation.co...2003manual.pdf

On page 40, the description continues with, "As an air conditioner, the heat pump has exactly the same cooling capability as its cool-only counterpart; but its unique, built-in reversing mechanism extracts and concentrates heat from the outdoors to make it an efficient RV heating system."

On both my previous 2001 Alpine Coach and my current 2006 Alpine Coach, I had/have the heat pump option, which works in practice exactly as described.

I have heat pumps in my HR Admiral SE as well and they work great!

[Benny367]

Originally Posted by rdownward

Can anybody tell me a simple way to determine if I have heat pumps in my Dometic A/C units in my '03 36 MDDS? The thermostat shows a "Heap Pump" mode but nothing happens when I turn it to that setting. The furnace is also not coming on when in the Furnace mode but that's probably an issue with the furnace I would suspect. Any help anybody can provide re the heat pumps would be appreciated.

Roger D

I also have heat pumps and i know that they will not operate if the outside temperature is 40 F or below, this is the normal operation of the heat pumps and instead the furnace will turn on (automatically) to heat the coach.

[bcbowers]

Roger - Since your heat pumps AND the furnace are not coming on, I doubt this will help but you should check the 12V fuses in the bathroom sink cabinet. There is a fuse that feeds the furnace and the water heater. Mine had come loose but only affected the furnace and not the heat pumps.

Also, Dave is correct that if the thermostat is set to a temperature higher than the actaul inside coach temperature the furnace will come on in just a few seconds. Whereas, the heat pumps don't come on for atleast a full minute or two.

[rdownward]

Thanks everybody for your input. Much appreciated. I spent the day yesterday trying to troubleshoot the system and it appears that the problem is most likely either the comfort control unit itself or the wiring coming from the comfort control. I could manually activate the furnace by shorting the thermostat input wires but when connected to the comfort control wiring, no luck. Got my work cut out for me! Thanks again everybody. As always, your opinions and instructions were very helpful and appreciated. RD

[rdownward]

Oh yes, by the way, When testing the system, the temperature on the comfort control unit was set at 99 degrees for both the heat pumps and the furnace and the ambient temperature in the coach was 70. RD

[JohnRR]

Does this post have any bearing on this? In particular replies #6, 7, & 9?

[takepride]

Roger:

I had to replace my thermostat at 5 years. They are readily available at RV supply places, online and Camping World. Just be sure to get the one with five buttons.

Or order the fancy new one (I could send you my old style one....):

[rdownward]

Primarily based on the post by Old Scout, I noticed that the furnace function on the comfort control was set on zone 2, when according to Old Scout, it should have been on zone 1. I tracked down the thermostat wires (unfortunately not shown in the wiring diagrams) and found them in the housing for the front heat pump unit (zone 1). Using the installation manual I found where the dip switches were located and how they should be set. I found that, sure enough, the dip switch on the rear unit was set for "Furnace On" and the one on the front unit had the furnace turned off. So, I reversed those so that the furnace switch was turned on on the front unit and lo and behold, the thermostat worked as it should and the furnace turned on. On a side note, when the furnace turned on, it was vibrating and making a horrible racket. Upon removing the furnace and checking the combustion blower, I found several hornet's nests fouling things up. I have been finding them all over the place (I found 5 or 6 big ones when I removed the refrigerator to install a new cooling unit) so it was really no surprise that they had found their way into the blower unit. After removing all the mud and debris the fan now operates nice and quiet so all is well with the furnace. Also, when I was working on the furnace, I turned on the heat pumps and they worked. Not much in the way of heat coming from the ducts, but they at least turned on. The only thing I can think of that when I tried to turn them on the first time, the ambient temperature may have been below 40 degrees so they wouldn't turn on (and since the furnace didn't work, no heat was available at all). Thanks again to Old Scout and everybody who helped me go the right direction in resolving my latest problem. This is the greatest forum anywhere and invaluable for us Alpine family members!

[Wayne Pryor]

Originally Posted by takepride

Roger:

I had to replace my thermostat at 5 years. They are readily available at RV supply places, online and Camping World. Just be sure to get the one with five buttons.

Or order the fancy new one (I could send you my old style one....):

We have never been able to just replace a 4 button with a 5 button. It has always required changing the P/C boards located in the A/C's. Just because the coach built in front of yours has heat pumps doesn't mean that yours does.