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Turning an Electric Water Heater Back On

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Eric Johnson, Jan 8, 2008.

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  1. Eric Johnson

    Eric Johnson Mod Emeritus

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    A couple recent threads concerning domestic hot water strategies made me remember that turning an electric hot water heater back on after heating your DHW with wood for awhile can involve more than just flipping the breaker.

    Electric hot water heaters have several safety mechanisms built in. One is a heat-activated breaker on the thermostat module. If you exceed the setpoint, which I believe is around 190 or 200 degrees, the beaker opens, cutting power to the heating elements. If you managed to trip that breaker at some point while heating the tank with the wood boiler, then you will need to reset the breaker on the thermostat by removing the cover and pushing the little round button (firmly) with a screwdriver until it clicks.

    Or, you can be like me, and tear your whole water heater apart looking for the problem and blowing an element in the process......

    The other thermal safety feature is a temp sensor built into the pressure relief valve. At a certain (pretty high) temp, it will cause the relief valve to open, generally resulting in a wet, steamy floor. If this is a problem for you, there are ways around it, but I'm not going to discuss them in a public forum, because this is an important safety feature that shouldn't be overridden.

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  2. barnartist

    barnartist Minister of Fire

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    Thanks Eric. I'll know not to dig too far this spring.
  3. wdc1160

    wdc1160 New Member

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    As much as I like hearing plumbing horror stories about how high hot water heaters can shoot into the air. Or, what amount of material they can pierce with their energy -- I don't want to be indirectly responsible for the that stuff either.
  4. Eric Johnson

    Eric Johnson Mod Emeritus

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    Thanks for pointing that out, Bill.

    Just to clarify I'm certainly not suggesting that a solution would be to block or otherwise restrict the pressure relief valve in any way. That would be just plain stupid and against every fundamental safety precaution I can think of. NEVER OBSTRUCT OR RESTRICT A PRESSURE RELIEF VALVE IN ANY WAY. PERIOD.

    You'd want to check the code in your area. In some jurisdictions, the thermal trigger may not be required. In many, it is. That's all.
  5. jebatty

    jebatty Minister of Fire

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    Mythbusters on Discovery ran a segment on an over-heated HWH -- seems to me it rocketed through the roof.
  6. Eric Johnson

    Eric Johnson Mod Emeritus

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    I've been running at my boiler's max temp of 80 degrees C. all winter and I turned my water heater on today, with no need to reset the thermostat breaker. So it takes pretty hot water to do it. And I ran a lot higher boiler temps (at times) with my old boiler for 4 seasons and never opened the pressure relief valve, so it's not a common occurrence. But when I used to run the old Marathon Logwood at 210 or 220, it would happen from time to time. ABGWD4U is the only one I know of who likes to run their system at those temps.

    Hot water heaters will launch through floors and walls under certain circumstances. It's always important to periodically check your pressure relief valve and replace it if it leaks or doesn't work when you try to open it. They're pretty cheap and easy to replace.
  7. wdc1160

    wdc1160 New Member

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    Eric, I don't think you said anything that exposed others to risk or even marginal.

    But, thank you for the breaker info, didn't know that sucker was in there.
  8. Eric Johnson

    Eric Johnson Mod Emeritus

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    I don't think it will hurt anything, but that's an odd way to pipe it, IMO. What kind of hx are you using? Do you get enough hot water doing it that way? Why use the tank at all?
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