Roof mounted heat pumps

The Atwood heater does not perform well. Fortunately, I bought the unit mainly for the AC portion. I found that the heater will not reach the temperature I want and will not keep it there, even if it’s not that cold outside.

imgoin4it wrote:
Bob, your right about 4sensors. The one that “measures the temperature is supposed to be on the return somewhere and regardless is not on the room temperature . It acts more like it is on the supply side as when the outlet temp reaches between 100 & 105 degrees the compressor shuts off. The fan then comes on for anout 5 or seconds to “sample” the temp. Then after a few minutes the fan starts again and shortly after the compressor starts again for about 2or3 minutes.until the outlet temp gets to 100 . And that cycle repeats continually. My tech says Atwood doesn’t want to talk to him anymore. I’m reasonably sure that the unit does not work like any other, Atwood , and now dometic, which I believe bought the acnd business from Atwood, knows exactly how it works and that is not like any reasonable person would expect.

It seems like as I watch the exit temp reach 100 degrees the compressor shuts off. I wonder if I could locate this sensor and move it to the return side ? I also wonder what would happen if I took a styrofoam cup and cut it dow to cover the sensor to basically disable it would it make the pump run longer??? I would just figure out how to figure out which and where it was.....

Bob, your right about 4sensors. The one that “measures the temperature is supposed to be on the return somewhere and regardless is not on the room temperature . It acts more like it is on the supply side as when the outlet temp reaches between 100 & 105 degrees the compressor shuts off. The fan then comes on for anout 5 or seconds to “sample” the temp. Then after a few minutes the fan starts again and shortly after the compressor starts again for about 2or3 minutes.until the outlet temp gets to 100 . And that cycle repeats continually. My tech says Atwood doesn’t want to talk to him anymore. I’m reasonably sure that the unit does not work like any other, Atwood , and now dometic, which I believe bought the acnd business from Atwood, knows exactly how it works and that is not like any reasonable person would expect.

Mr Wizzard the compressor only runs for 2-3 minutes at a time then shuts off and the evaporator fan will run for a couple of seconds at a time for about 5 minutes then the compressor will come back on but for only 2-3 minutes. Thus when it is say 50 degrees outside the heat loss is as much as the heat gain thus it will never raise the inside temp. There are 4 sensors on this system and I think one in the plenum may be prematurely shutting the compressor off before the thermostat gets a chance to be satisfied. It is an electronic thermostat so it does not have an anticipator. If it had an anticipator I could adjust that but it does not. I do not think it has a high pressure cut out because if it did it would shut it off when it was in the A/C mode. I have asked Atwood for a wiring schematic but they say one does not exist. Which I think is BS.......A/C tech's would not be able to repair them with out one.....That may be why the repair place that installed it could not fix it.....

I'm sorry, i think i misunderstood what is happening
Didn't you say the compressor, was not running
For temp to get that close, it must be running
2° difference in set point versus measured ? Room temp ?
Sounds like a calibration difference in measuring devices
I would move the thermostat 2 degrees, as long as that got me the room temp i wanted

My hourly test of the temp readings show that no matter what I set the thermostat at the temp will only come to 2 degrees less than what the setting is.....something is more than wrong with the whole Atwood set up....

Our Penguin units will both run until the temp is reached in the front and our back unit. It works down to about 35 degrees and is a bit on the noisey side.

We’ve corresponded on this subject and the answer is “yes” as long as it’s not an Atwood. Every other brand heat pump I’ve had in four other motor homes, the heat pump runs as long as the T stat calls for heat. Atwood is the only brand I know that runs the fan and only starts the compressor once every three minutes or so. Atwood has basically confirmed to me as well that this is the way it is supposed to work. It will not heat any part of me coach. I’ve trashed a new Atwood acnd with heat pump to buy another brand. It was a great acnd but absolute waste of money if you want the heat pump.

As long as the temperature is above 45 degrees my Colmeman heat pump heats the trailer with no problem. Below that I run the gas.

I just got an admission from Atwood that the heat pump I bought from them will not heat my 32' foot fifth wheel. They claim it was not designed to do that. My question is then why do they advertise that it will. With all the money I have spent on buying this unit and getting it installed and the money the service tech charged me to come repair it plus the gas money taking it to the shop now exceeds 1000 dollars...Money that I could have spent buying another brand. The short story is Atwood does not stand behind their products....