My pair of heated tanks are protected by a 30aDC (thirty) fuse in the electrical panel. One circuit. Obviously don't draw that much but that's the fuse size.
Never measured the draw in freezing temperatures -- never been convenient or I keep forgetting. They draw 1.24 amps just On -- the indicator light.
Anyone know how many amps the tank heaters draw? Gonna be COLD in the desert this weekend and will want to turn them on. Also adapting one to a LiFePo battery heater and need to fuse it
While not all are like mine, they're usually similar.
There should be a DC fuse in the distribution panel for ~30 amps.
On my TT there are two low watt, small pads on each holding tank at the discharge tube. They have no thermostats built in and are constantly on when the tank heater switch is on. Current draw (via Victron BMV-712) is ~2 amps.
The larger tank heater on the FW tank is thermostatically controlled by a built in thermostat that switches on around 35 degrees TANK TEMP, not outside temp. Since my tank is covered by the belly cover the tank is receiving some heat that "leaks" down through the floor and is also shielded from wind so it's slow to cool. The heater will shut off when the tank temp reaches as much as 60+ degrees. This of course depends on the tank heater manufacturer.
If worried whether heaters will work when temps are freezing, first check to see if power is actually reaching the tank by checking voltage at wires just before heaters. Use a needle probe and pierce insulation to obtain readings with switch on If power is there and still worried there's always the piece of dry ice applied to the tank heater itself. Look for the "bump" near the wire inlet and freeze the bump (which is where the thermostat is ). That should get power flowing even on a warm day.
The heaters have a thermostat on them. Chances are they might not have turned on while you were paying attention. Unless you have a recording battery monitor?
To check mine I've measured my black tank temp with an infrared thermometer, easy enough to do. Almost has always been around 60 degrees.
My fresh water tank was always around 50 degrees or so putting a thermometer in a glass of water. I filled the tank to full a week ago and it went up to 60. Not sure why it took a full tank to have it get to the higher point. Must have always just taken a temp reading after the heaters shut off.
No way to measure the grey tanks unless I want to chance getting soaked.
I guess I cold pull the handle briefly with the cap on and then catch that in a bucket.
As for current draw, 2-6 amps on my AC ammeter coming in seems like what I see after plugging in after a move. That would correlate to the DC current getting closer to 25-30 amps at the higher end. I pay a bit more attention to current draw after a move. Everything has cooled down and can not flip everything on at once.