Did you do a cold soak at -27? For how long? Where are you getting the 100W power to heat the tanks for 24/7? We're talking 10A continuous! You'll need more than 24H/4H * 100W = 600W of solar just to run the 100W tank heater! You'll need greater than 400 AH battery bank (10A * 20H * 2 = 400AH) just to run the tank heater!!!
To boot, I seriously doubt you can keep the water going to shower from freezing.
Sal
pianotuna wrote:
Hi,
I've tested the tank heater to -27 C with no other source of heat (i.e. RV not heated in any way, just the tank heater active), using 100 watts from a fan based heater. It would be easy to add more wattage should that prove necessary. There will be at least some radiant heat from the interior of the RV.
The fresh water tank is within the area heated by the propane furnace.