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Old 20-03-2015, 21:26   #1
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Running 220v water heater on 110v supply

Hello. Is this safe to do so? I believe the water heater element is 1200W so what happens if it receives 110V instead of 220V. I'm thinking the heater and element would be fine but the wiring from the water heater to the power supply would be undersized?
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Old 20-03-2015, 21:33   #2
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Running 220v water heater on 110v supply

You will have a 600 watt heater. Half the current so the original wire size would be ok.


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Old 20-03-2015, 21:55   #3
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Running 220v water heater on 110v supply

No, you will have a 300 watt heater. It will take 4 times longer to heat the water. The wiring will be fine unless you change out the heater element for a 110V version.
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Old 20-03-2015, 22:01   #4
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Re: Running 220v water heater on 110v supply

I = P/V
So
1200/220 = 5.5
1200/110 = 11

So, double the amps to run the same appliance. What am I missing there.
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Old 20-03-2015, 22:11   #5
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Re: Running 220v water heater on 110v supply

Recheck what you are doing. There is no 110v in Australia if you are here!! 240v into a 110v heat not good!!
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Old 20-03-2015, 22:13   #6
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Re: Running 220v water heater on 110v supply

In sunny BVIs.
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Old 20-03-2015, 22:16   #7
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Re: Running 220v water heater on 110v supply

Quote:
Originally Posted by monte View Post
I = P/V
So
1200/220 = 5.5
1200/110 = 11

So, double the amps to run the same appliance. What am I missing there.
Any understanding whatsoever of the physics involved.

P is not fixed. The formula to be used is P=V^2/R. R is the resistance of the element. You get a quarter of the power, at half the current.
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Old 20-03-2015, 22:50   #8
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Re: Running 220v water heater on 110v supply

Ok thanks again. Reason I ask is because I have plugged my 220v wired boat into a 110v outlet, primarily to equalise the batteries, which I did today using the solar and victron controller. All went well and Sg is back up. I did t select the shore power at the panel and left the invert on, although I did turn off everything including fridges during equalisation.
I also turned on the water heater at the panel, assuming no damage could be done. Tonight after running out of water during a shower, I put some clean water in the tank and ran the water through the faucet to clear the air blockages. All good till I turned the faucet to hot and brown water came out of the faucet for about a minute, before running clear again. I don't really think the brown water was sludge in the water tank as they are clean and the water in the hose was clean. We spent so e time using it to clean the boat earlier and it was fine.
I also noticed the water was hotter than usual, really hot, which led me to rethink the 110v.
So it's possible the shower used up all the water in the water heater, and the brown water was some sludge coming from that. It's also possible the water heater did get a lot hotter than it should have and was hot enough to clean off some internal corrosion. The water heater is less than a year old so I doubt it would be very corroded.
I've since turned off the water heater.
Which brings me to another question. What happens when the water runs out when you are showering. Does the water heater empty, but the element continues to heat? Perhaps the brown water was the water being pumped back in and when it hit the element if steamed and steam cleaned the inside if the water heater? The brown water was accompanied by steam.
Any thoughts or ideas and explanations much appreciated! Especially what happens with the waterheater when the water tank runs dry. FYI the waterheater is probably 1m below the water tank.
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Old 20-03-2015, 23:16   #9
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Re: Running 220v water heater on 110v supply

Look at the Raritan water heater installation instructions, here :

http://raritaneng.com/pdf_files/wate.../L206v0911.pdf

There should be a backflow preventer, that stops the hot water from draining back into the cold water tanks, if they empty. All that should happen is that the pressure pump runs dry, no more hot water, the water heater sits there full of hot water you cant use. If it was correctly installed, that is.
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Old 20-03-2015, 23:44   #10
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Re: Running 220v water heater on 110v supply

The element will burn up if not submerged and the heater will / should be plumbed to prevent it.
Max temp is controlled by a Klixon mounted on the tank.

Watt - unit of electrical energy or power - one watt is the product of one ampere and one volt - one ampere of current flowing under the force of one volt gives one watt of energy
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Old 21-03-2015, 07:45   #11
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Re: Running 220v water heater on 110v supply

Ok thanks again for the feedback and link to the waterheater. Most useful. Still having trouble getting my head around how the waterheater manages to not suck air as it is used in the event of an empty tank. I imagine the pump would continue to pump air though the system and cause air locks and spluttering. But perhaps it can only do this on outlets above the pump and water tank height.
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Old 21-03-2015, 09:10   #12
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Re: Running 220v water heater on 110v supply

Quote:
Originally Posted by monte View Post
Hello. Is this safe to do so? I believe the water heater element is 1200W so what happens if it receives 110V instead of 220V. I'm thinking the heater and element would be fine but the wiring from the water heater to the power supply would be undersized?
I'm pretty puzzled by you posting this question because according to your other post, you've already done this.

No, you won't hurt your water heater connecting it to a lower voltage than it's designed for but it won't work very well.

Some other appliances on your boat may well be damaged by low voltage. Anything with a motor for sure.

Connecting a boat to the wrong electrical service is not a great idea. If you plan on doing this in the future, you should have the boat fitted with a transformer to change the voltage to what it needs to be.
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Old 21-03-2015, 09:30   #13
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Re: Running 220v water heater on 110v supply

Quote:
Originally Posted by monte View Post
I = P/V
So
1200/220 = 5.5
1200/110 = 11

So, double the amps to run the same appliance. What am I missing there.
Nothing! just the cremated wires to the heater.
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Old 21-03-2015, 09:55   #14
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Re: Running 220v water heater on 110v supply

Am I missing something here? If you change from 220 to 110 you increase amperage by 2. Also your wiring to the water heater, if made for 220 apps. will heat up exponentially, and cook, because you are now forcing more electrons through the same narrow wire. , also your cycles are higher, though this should only affect some electronics? Also when you run your water tanks down to the point of pushing air, you will be pushing air into the water heater, which is detrimental to the elements, if they are on. When air hit air bubbles hit the elements, it will cause hot spots. If you have only air hitting the elements the elements will over heat and burn out.!!!!!!!!
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Old 21-03-2015, 09:59   #15
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Re: Running 220v water heater on 110v supply

Quote:
Originally Posted by MarkSF View Post
P is not fixed. The formula to be used is P=V^2/R. R is the resistance of the element. You get a quarter of the power, at half the current.
This is correct.
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