Tank heater power requirements

 While boondocking at a Pilot travel center in below freezing weather, I turned on the tank heaters for the night. The next morning I noticed that my batteries were mostly discharged.
I had been worried about the drain on my batteries due to the compressor fridge but I forgot about the tank heaters -- you have to remember that I am a newbie to RVs. The compressor fridge draws 3.2 amps while running and given how cold it was I doubt it was on more than 50% of the time -- so say 5 hours of run time X 3.2 amps (12V) = 16 amp/hours -- not enough to draw down my batteries.
I have a feeling that the tank heaters draw a lot more power -- does anyone know how many tank heaters would be on a 2351 and how much current they draw?

Hi 4x4Diversion,

Welcome to our world of power management and the challenges associated with it.  Your particular situation with your fridge is a new dynamic which places you in a very unique category all your own.  I am the last person to discuss the effects of tank heaters on batteries when boon-docking because I have never used our tank heaters in the many years we have owned our PC.  I wonder if they work???

I assume a new PC has the same setup as our 2007 with regards to tank heaters.  Our gray and black waste tanks each have one tank heating pad adhered on the outside bottom.  Afterward the tanks are wrapped with an insulation blanket.  The last time I studied our tanks, I recall seeing a ghost of an outline of the heating pad through the blanket.

Phoenix could tell you the brand and model heaters they install so you can look up their power consumption.  Phoenix might even have the specs handy for you.  Phoenix might install a smaller heating pad for the smaller tank so be sure to ask for the specs on each one installed.

The picture below is an example of what PC waste tank heaters "might" look like which appears to use the same technology used in heated seats.

Ron Dittmer

Just got home from Florida. Last night had to stay in a rest area in West Virginia on I-81 as there were no campgrounds open. When we went to bed temp was 40 but forecast to go into the teens overnight. turned the tank heat on and used the heater all night.  When we got up, it was 15.  Don't have anything other than the PC panel but it showed one red LED and batteries started the generator for breakfast.