I have a trouble light with a 100 watt light bulb. Put this into the
water and sewer compartment. Provides plenty of warmth. Also you can
let the furthest faucet drip. This can keep the water moving enough to
prevent freezing. If cold is extreme--down into the 20's I always unhook
the hose from the water source.
Have been in Central Florida 4 years at Tanglewood in a 2005 Newmar Kountry Star.
I have 3 electric heaters in the basement each with a low thermostat setting and a remote Radio Shack thermometer that tells me what temperatures exist.
1. In water hook up bay half seting at 750 watts
2. In water pump/heater bay half seting at 750 watts
3. in water tank area that is 200 watts and external thermostat set at 45 degrees.
These normally don't run unless the outside temperature becomes low.
Found two water lines that run in a narrow space above the fender and they would freeze. Sprayed in foam with an extension tube and now they are OK.