be advised that the arctic pac in the 24M does not include the fresh water tank.
There is a furnace heater duct that sends some warm air to the fresh water tank surround but only when the furnace is actually putting heat into the interior. If it is below freezing outside and you have your furnace turned off while you are sleeping in your nice cozy murphy bed, your fresh water might be freezing.
Also, if you turn the furnace off while you are away or while you are on the road, there is no thermostatic control to provide heat from the furnace tot he fresh water tank and, again, your fresh water might freeze.
In addition to this, whenever you have your furnace on with the outside temperature above freezing, you are wasting the propane that heats the air going to the fresh water tank.
I have ordered another tank heater just like the ones on the holding tanks and I will install it on the fresh water tank and I will connect it to the arctic pac circuit and close the duct from the furnace to the fresh water tank surround to conserve propane. With shipping, the additional heater is about $135 which I think is a reasonable price for protecting the fresh water tank from freezing and saving propane.