Some of this might be useful and maybe not. It dropped to 32 for the first time this week.
If it freezes ……
Our motorhome is stored under a roof with 30 amp power in a commercial storage facility. The HydroHot electric element, refrigerator, battery charger and a dehumidifier are on. The furnace is set to 50. Monitoring the Aladdin indicates that power consumption can vary from about 8 amps to about 22 amps if everything decides to run at once.
It normally stays above freezing here, but occasionally can get as low as 20 degrees.
I could winterize with the pink stuff. It is reliable, cheap and I’ve done that. Instead, I like to keep the motorhome ready to go and hope for opportunities to head out.
There is a risk that the power could fail, the circuit breaker could trip, the shore plug could unplug or the Hydro Hot electric element could fail. In fact, all that has happened, but I’ve caught it in time to prevent buying a new $8k furnace.
Gradually I came up with a plan to cover what I think are the primary risks. It’s complicated. Stop reading if you are in a hurry to do something.
We live near Tacoma. To keep the interior dry and free of mold and mildew we always have a dehumidifier running. I keep it in the shower with the shower door open. Attached is an “optional” hose so that the water drains into the shower drain. A byproduct of the dehumidifier is a little heat for the interior. Even after 9 years, out motorhome always has a 'fresh' smell when we walk in.
I bought a 200 watt ceramic heater to back up the Hydro Hot element. To do that, I installed a “utility” outlet in the HydroHot bay. The outlet is wired into the 120volt feed to the existing electric element. The heater is plugged in with a thermostatic freeze cube intended for and made by a plumbing heat tape company found at Lowes. The heater does not come on, unless the temperature in the bay drops to near freezing. That shouldn't happen unless the HydroHot element fails (again).
I did the same thing with another additional utility outlet behind the “hidden” tank bay door where access to the wiring for the “basement” outlet is accessible. Now, if the HydroHot element, the tank bay heat exchanger or its thermostat fails, the freeze cube will turn on the second 200 watt heater.
A third 200 watt heater is plugged into the existing “basement” outlet with a freeze cube. That area is normally kept warm by heat coming off the inverter/charger. Should the power to the motorhome fail and the inverter stop “glowing”, the extra 200 watt heater will come on and keep the bay above freezing.
If the shore power is disrupted at the plug or there is a general power failure, the Onan is set to auto start when the batteries are only moderately low. Because the dehumidifier will be running off the inverter, the batteries will draw down quickly enough that the generator will start before anything gets very cold. The genset is not set for auto shutoff. That serves as an “alarm”. I expect that the manager at the storage center would call ifhe hears it running.
No plan beyond a complete “pink stuff” winterization is perfect. I think I have improved my odds against freeze damage, reduced single point failure modes and made it easier to use the motorhome in the winter. The cost for the three small heaters, freeze cubes and utility boxes was about $100.