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Old 26-07-2009, 20:16   #1
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Inverter 110vac for Hot Water?

Any one running the inverter to get AC to heat water? Trying to keep hours off the diesel, and I should have a few extra amps when I upgrade my solar array next month. or any other ideas on hotwater?

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Old 26-07-2009, 20:47   #2
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Originally Posted by svDragonfly View Post
Any one running the inverter to get AC to heat water? Trying to keep hours off the diesel, and I should have a few extra amps when I upgrade my solar array next month. or any other ideas on hotwater?
Given the inefficiencies of the charger, the batteries, and the inverter, you'd probably be better off running the diesel (engine, not genset?) to heat water, but every situation is different.

If you have, say, an Isotemp water heater (750 watts) rather than a Raritan (1500W), then you might argue that the beating the battery bank takes from the Isotemp is less than that of the Raritan. I'm guessing your water heater doesn't have a heat exchanger connection for water from the engine cooling system?

If your planned solar panel array is large enough, there's another option: replace the AC heating element in your water heater with a 12V DC version. It would be marginally more efficient than using the inverter - no losses with DC-AC conversion. Not that I'm suggesting you go that route...

Cap'n Jon (KB1HTW)
S/V Beausoleil -1979 Formosa 51 Ketch
"If it's gonna happen, it's gonna happen out there." - Captain Ron
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Old 26-07-2009, 20:59   #3
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You need 10 amphrs to heat 1 gallon from 70F to 120F. Using an inverter probably 12 to 14 AmpHrs.
There are propane hot water heaters that heat the water on demand see Precision Temp Boat Tankless Hot Water Heater. Gas Marine Water Heaters. Propane Boat Hot Water Heater
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Old 26-07-2009, 22:37   #4
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I use an on-demand propane heater to heat water when not at the dock, or running the engine. I have to switch my on-demand water heater into my water system and my tank out, after I use up my tank; and it's an extra procedure to go through, but what the heck.

Then when I start up the engine to power up, or to go to a dock, I reverse the procedure. Then I use the tank on shore power when at the dock.

I have about 650 AH of batteries and a 2500W inverter which would handle the demand, but the draw on the batteries for my tank would probably make the batteries sizzle>

Good luck

Joe S
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Old 27-07-2009, 13:48   #5
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On our previous boat, I made a 2x4 foot solar water heater and integrated it into my arch with the solar panels. I recirculated the water with a March magnetic drive food grade pump powered by 12 volts and controlled by a differential controller. Whenever the panel was hotter than the tank, it ran the pump.

I posted a pic somewhere on this site.

Steve B.
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Old 27-07-2009, 14:11   #6
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sv Dragonfly -- I notice that you have a windgen, too. Have you considered using a shunt to the water heater off of the windgen?

Steve B -- I'd love to know more about that solar water heat set up. I've looked at my boat with a similar notion in mind -- it seems like such a natural way to go.


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