The Arctic Pack works off the 12 volt system. When it is turned on and the water temperature in the tanks drops to 44 degrees the heat pads kick in and heat the tanks to about 66 degrees. There must be water in both tanks (Black & Grey) or it will damage the unfilled tank. The furnace will heat the basement of the coach to prevent freezing of the pipes there. On my 30 DS if you open the access port behind the door that covers the water compartment with the water heater you can see that the plumbing, hot water heater, fresh water, black water and grey water tanks are in a sealed and furnace heated compartment. Unless you have a way to keep the coach from going below the freezing point during winter storage you need to drain the fresh water tank, water heater, blow the water out of water lines and put RV anti freeze in the drain traps. If your plugged into external power you can leave water in the black and grey tanks but you need to leave the arctic pack turned on.