Cold Weather Concerns

Bill and Mister P, excellent suggestions. How cold do you think it has to get before the items in the interior are in jeaprody? I'm assuming one keeps the interior "comfortable" and follow these suggestions. A bit of an academic question because of all of the variables I admit, but what have people experienced using these methods?
I always though if I were going to camp in below freezing conditions I'd just use water in my aqua tank, but I do understand how following these suggestions would extend use of interior unit plumping below freezing.

[scrubjaysnest]

We ran into some temps in the low 20's this trip. Not a problem once the inside temps get into the low 40's or upper 30's we set the heater to cycle at about 48. Did have a night at Joshua Tree and another at Stubblefield where we ran the small Mr Heater quite a bit. For CG's with elec we have a small ceramic space heater.