[TAKPAK]

Originally Posted by cwestl

I can see we don't have any AC Guys in the forum. Any heat pump will ice up the outside coil while heating. Same with you home unit if you have a heat pump. Sensors will sense this condition and put it in a defrost mode to melt the ice off the coil. Then it should go back to heating. Of course Home heat pumps will work below 32 Deg. Of course the units on Travel Trailers have a lot smaller coils and are not as good collecting heat from outside air.

Well cwestl, I'll have to beg to differ about AC guys. I was in the industry for 32 years. You are correct that a heat pump will ice up, under the right conditions, and if it IS low on charge, it will ice up sooner. We could get into enthalpy, latent heat, dew point and all that, but for this forum it's not needed. I have not checked personally, and there may be a "defrost mode" on the RV heat pump but not observed it in operation yet. My observation on when the heat pump ceases to be practical was based on taking measurements of the return air and the discharge air temps, and observing the outside air temp. What I found was at around 45 degrees OSA, the insided return temp and the discharge temp were virtually the same, therefore for the work the heat pump was trying to do, there was no gain. No sense in "working it to death." And the RV heat pumps to my knowledge don't have an electric (or supplimental) backup heat source, like the home units do. I guess you could always turn on the electric fireplace or heater inside, but that kind of defeats the purpose, and possibly could blow the breaker! Live and learn, eh?