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post #1 of 16 Old 07-26-2014 Thread Starter
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Powering hot water heater with dedicated 12v

All summer long we don't hook to shore power. It would be nice to have even warm water for showering. And we have 540 watts of solar power, more than we need, actually.

Does anyone know if Raritan hot water heaters can be powered by 12v instead?

After doing some measuring, it looks like the 1100 watt heating element is a 13 ohm resistor. I could invert 12v to 120v AC and then step down 2:1 to 65 volts AC to drive the heating element at 277 watts. But solar panels can drive even low resistance loads, so it would be much simpler to go direct from panel to heater (or charge controller dump load to heater).

How about it, anyone know if there's a limitation that precludes this?

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Brad

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post #2 of 16 Old 07-26-2014
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Re: Powering hot water heater with dedicated 12v

It would work on direct 12v however I would think rather poorly just like the old travel mate coffee pot I had in a truck had an adapter that the 120ac cord plugged into and went direct to he old CIG lighter it worked but rather poorly the may answer your questions better and provide an alternate that would work better 6 Inch 12 Volt DC Submersible Water Heater Element

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post #3 of 16 Old 07-26-2014
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Re: Powering hot water heater with dedicated 12v

There are 12 volt water heater elements made specifically as dump loads for windgens which might serve your needs. A quick search should find you the info.

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post #4 of 16 Old 07-26-2014
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Re: Powering hot water heater with dedicated 12v

Solar shower works ok.
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post #5 of 16 Old 07-26-2014
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Re: Powering hot water heater with dedicated 12v

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There are 12 volt water heater elements made specifically as dump loads for windgens which might serve your needs. A quick search should find you the info.
Agreed. Some even have both a 120VAC and 12VDC element. Call John at SVHotwire Enterprises Alternative Energy Products ? svHotwire - 727-943-0424 | svHotWire . IIRC there are elements for Raritan. I think Isotherm is a problem.

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post #6 of 16 Old 07-26-2014
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Re: Powering hot water heater with dedicated 12v

Not what you asked for, but it could be an option. Portable cheap on demand propane heater. Plumb it to a big tank and leave the unit outside (because of CO concerns).

Coleman - Hot Water On Demand? Portable Water Heater

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Re: Powering hot water heater with dedicated 12v

Brad, someone posted a conversion formula for 120<>12v resistive heating loads, either here on on a certain other forum, a week or three ago. Basically, it is NOT just a matter of driving loads and resistance, the heating element wants to see a certain wattage and if you drop the voltage, you've really got to up the amps in order to still get heat out of the heating element.

In practical terms, you either want to apply the rate 120V or ideally, find a 12V heating element for it. There may be one, targeted for the RV market, that bolts right up. Raritan might know. If not, you might be able to have an adapter threaded up to make one fit.
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post #8 of 16 Old 07-26-2014
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Re: Powering hot water heater with dedicated 12v

build a solar water plate to heat the H20 should be easy enough Or just route black tubing in a loop. but fill it to the top, it should move via gravity/temp difference. It won't "Flow" if there is air in the plate or tubing.

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post #9 of 16 Old 07-26-2014
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Re: Powering hot water heater with dedicated 12v

Was going to express my concept but thought ,'no ,they wouldn't be interested' But Denise is on a similar tract. My plan is to bypass the hot shower water up thru the deckhead into a black solar tank on deck. Tank heats and overflows back to shower head mixing with cold for optimum temp control. This assumes a pressure water system and a desire to wash.
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post #10 of 16 Old 07-26-2014
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Re: Powering hot water heater with dedicated 12v

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Originally Posted by hellosailor View Post
Brad, someone posted a conversion formula for 120<>12v resistive heating loads, either here on on a certain other forum, a week or three ago. Basically, it is NOT just a matter of driving loads and resistance, the heating element wants to see a certain wattage and if you drop the voltage, you've really got to up the amps in order to still get heat out of the heating element.

In practical terms, you either want to apply the rate 120V or ideally, find a 12V heating element for it. There may be one, targeted for the RV market, that bolts right up. Raritan might know. If not, you might be able to have an adapter threaded up to make one fit.
Here is a dedicated direct replacement 12 v heating element that meets all of Brad's requirements and a lot cheaper han a new heater 6 Inch 12 Volt DC Submersible Water Heater Element

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