Unscientific Heated Holding Tanks Report

[Ottosails]

Test of battery usage of the heated holding tank pads on the Mag/SV34 - Last night the temps in the desert were down to 34 degrees. They were 38 to 34 for 9 hours at least. Not enough to worry about freezing but good enough for a baseline test of battery usage. Coach was in outside storage with everything off except for the Inverter and heating pads. I turned the heated pads on at sunset and checked 12 hours later at sunrise, they used roughly 83.4 Ah from start to finish. The wet bay was definitely warmer than outside and the pads were warm to the touch when I checked this morning. The pic was taken at sunrise after the pads being on for 12 hours. My theory now is that even if the temps were in the 20’s and battery usage was 3 times my test usage - The pads would consume roughly 250Ah’s of my available 540Ah. As you can see, not much to do here in the desert this weekend… Happy New Year!

[DavidEM]

I don't think that they are thermostatically controlled. If not, the current will be the same no matter the temperature.

So 84/12 = 7 amps, a little lower than what I would have expected.

David

[taylorbob1]

“Designed and engineered to protect holding tanks up to 50 gallons, it is thermostatically controlled. Once it is switched to "on", when the tank temperature drops to 45°F, the heater will activate and will continue to heat the tank until it reaches 65°F, shutting itself down. It will cycle as needed as long as it receives constant electrical power and until you turn it off”

Note…when the tank temp drops to 45 degrees
Not when the outside temp drops to 45 degrees

[Ottosails]

Originally Posted by taylorbob1

“Designed and engineered to protect holding tanks up to 50 gallons, it is thermostatically controlled. Once it is switched to "on", when the tank temperature drops to 45°F, the heater will activate and will continue to heat the tank until it reaches 65°F, shutting itself down. It will cycle as needed as long as it receives constant electrical power and until you turn it off”

Note…when the tank temp drops to 45 degrees
Not when the outside temp drops to 45 degrees

Very interesting - I did notice when I placed a hand under each tank the black tank pad was warm and the grey was not. I wondered if they were thermostatically controlled separately? Maybe the grey was off when I hand tested…

[blw2]

The newer pads might be different, but I doubt it....
As I understand it, the pads on my rig do have a thermostat, but only to turn them on only below a certain temperature so while I think he's wrong about them not having a thermostat, I think DavidEM is correct in that once they are heating, that's what you'll get....it's only if the temp rises above whatever that set point is, then they would automatically switch off.

I don't recall what the temp is for my pads, I've had them below freezing but never in a situation where I was worried about tanks freezing up..... so I've never actually used my pads.

[DavidEM]

Well, that sounds like a thermostat, set at 38 degrees to turn on, with a broad dead band. Just like the thermostat on electric heat tapes for pipes. Which is a good idea for waste lines, because on most RVs they are exposed and may not get protected by the tank pad.

David

[Scubawise]

Originally Posted by Ottosails

Test of battery usage of the heated holding tank pads on the Mag/SV34 - Last night the temps in the desert were down to 34 degrees. They were 38 to 34 for 9 hours at least. Not enough to worry about freezing but good enough for a baseline test of battery usage. Coach was in outside storage with everything off except for the Inverter and heating pads. I turned the heated pads on at sunset and checked 12 hours later at sunrise, they used roughly 83.4 Ah from start to finish. The wet bay was definitely warmer than outside and the pads were warm to the touch when I checked this morning. The pic was taken at sunrise after the pads being on for 12 hours. My theory now is that even if the temps were in the 20’s and battery usage was 3 times my test usage - The pads would consume roughly 250Ah’s of my available 540Ah. As you can see, not much to do here in the desert this weekend… Happy New Year!

What do you use for battery Tester and the app?

[gte534j]

I have found that the valves tend to freeze first before the tanks due to the low volume. I put a extra heating pad on the tank elbows and in the valve box itself to help with this.
You can measure power consumption if you have the hughes autoformer with the app or a sense home monitor power app. I have progressively added more heating pads on my Thor vegas grey and black tanks as required so i dont get frozen tanks. I am now good to about 10F or so.
I have about 360W of total heating tank power consumption on black and gray tanks, elbows, and valve box.

[DavidEM]

How about using these 12V heating pads on the grey and black water pipes just before the dump valves: https://www.amazon.com/Facon-Elbow-P...1N6N721Y&psc=1

They are only 7.5 watts or 0.6 amps, so it will also require wrapping the pipes with aluminum covered fiberglass to insulate them. With insulation, even 7.5 watts can provide protection down to maybe 15 deg F.

Along with the 12V tank heating pads, all water heating will be DC so you can use this while dry camping. It will draw significant DC current so make sure you have a way of recharging when necessary if dry camping.

David