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Old 10-13-2018, 10:02 PM   #1
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Grey/Black tank heaters

I have a Thor Four Winds with Grey and Black tank heaters. Besides turning the switch to on how can you tell if the heaters are actually working? Should the bottom of the tanks feel warm. Is there a thermostat that turns them on?

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Old 10-13-2018, 11:11 PM   #2
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Typically the heat pads are 12V DC powered and have built in t-stat that energizes the heater when the liquid in tank drops below 40*F (off when liquid temps is above 60*F)

On the pad should be a 'lump'...that is where the t-stat/control is located.
You can place a 'freezer pack'/zip-lock bag of ice etc over that lump cooling t-stat down to test if pads heat up

Turn the pads ON when ambient air temps are going to be below 32*F and WITH Liquid in the tanks....otherwise OFF

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Old 10-13-2018, 11:50 PM   #3
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Yup! What Old Biscuit says.

On mine (self installed) the instructions say to have at least 2" of water in the tanks........to prevent rapid/excessive cycling of the tstats in the pads.

Instead of crawling under the rig, I measure the current. Each of my tank pads draw "about" 5 amps at 12vdc (pretty typical, I'd wager.) When the temp is cold enough, I measure the current being drawn by the coach batteries as a baseline and then have the DW throw the tank heater switch on and I read the increase. The increase is the current being drawn by the pads. In my case I have one "elbow" heater also (no tstat in the small elbow heaters.....they don't cycle.) Anyway, I see about 12 amps total for the pads. The power ckt for mine is fused at 15A. Might be a viable option for you ...... to verify operation. I know I want to ensure the heaters are working so I can take quick action if needed and avoid a costly freeze up.

I used to have a small hands-on A/C business, so I have a lot of meters ..... but, I bought the small Sears meter below (on sale, of course) just for the clamp on DC current measuring capability. Not a lab quality instrument by any means, but good enuff for this dude..........and I find I use it a lot. Amazon, HD and lots of others have meters of this type.

Safe travels..............
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Old 10-19-2018, 04:10 AM   #4
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OP, I have the tank pads, but cannot directly answer your question, but I found out on mine that with ambient temps in the 20's, my pads heated the tank to about 42, BUT, (really big but), the gate valves were still in mid 20's.
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black tank, heat, heater, tank

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