IMO, those "Arctic Pack" heat pads are a ridiculous design. I have them on the rig we bought from the original owner. I expected them to be similar to the "Frost Tape" used on vulnerable waterlines in S&B houses, which switch on at about 34 degrees and off again at 37 or so.
According to the user's manual, the thermostats on these pads are non-adjustable and are set to switch the heat on at 40F and not to switch it off again until the tank contents reach 60F. Who the heck wants to heat up the poop in the black tank to 60 degrees?
Also, each pad draws 7 amps at 12 volts, so a drain of 28 amps with all four pads on would run your house batteries down PDQ. I'm also concerned about the risk of the heat, concentrated over a fairly small area, causing damage to the plastic tank material.
I've disconnected mine and stowed the wires so there's no risk of them coming on.
Frank Damp -Anacortes, WA,(DW- Eileen)
ex-pat Brits (1968) and now ex-RVers, as of 08 Dec 14.