wiring 110 instead of 220 electric water heater

Master Brian

Ok, my neighbor bought an electric 30gal water heater for his garage. It was a scratch and dent, so the store pulled the model/serial #'s off so it couldn't be warranted. This brought about some debate since the manual apparently covers several different heaters ranging from 110v to 220v.

In any case, it has a black and red wire, which told me it was a 220v unit, not a 110v. I also pulled it up online and it appeared to be a dual element heater and those are 220v as well. I actually just called American Water Heaters to inquire as well, and they also informed me it was a 220v unit and that wiring to 110v would void the warranty.

In any case, the neighbor had several other friends tell him he'd be ok with 110, because the manual shows 110, which is apparently for 110 models, which again this isn't. Obviously the warranty isn't a factor, since he can't claim it, but I am curious what would happen if he indeed does wire this for 110v? Would it still heat, just not as efficient or would it most likely cause other issues??

I personally am curious, because my understanding is some baseboard heaters and such can be wired 110v or 220v and this is apparently the same 2 wire + ground setup, no neutral.

a7ecorsair

One thing, it might not get the water hot enough so it would be on all the time.

Master Brian

Honestly, that wouldn't upset him, because he doesn't plan on keeping this on all the time anyway. He mainly wanted it because he deer hunts and process's the deer in his garage and he wanted hot water to help clean things up.

His main concern with going with 220 is that he only has 100 amp service to his house and he has a sub panel going to the garage, where he already has a 220v heater wired up. He's afraid he'll overload things. He'd probably take it back, but doubts they'll take it back since it's all but been installed and it was a closeout.

The only 220 that I know of in the rest of his house is two a/c units, which would be off during the winter, a stove, clothes dryer and his garage heater which would probably be used when processing his deer.

I say upgrade to 200amp service, but I don't think that's in his budget. I'm certainly glad I did with my house though....

Scuba_Dave

If the element is running at 1/2 power it may never get to set Temp
If its a 3800w element it will only provide 1900w of power at 120v

And it will take quite a while to get hot
1900w over 1 hour = 6487 BTU's
8.34 BTU to raise 1g of water 1 degree
So in 1 hour it would raise the Temp 25 degrees
Start Temp 55.....2 hours to get to 105
3 hours to get to 130 degrees
Not counting heat loss

So seems it should still work...if my math/calcs are correct
Recovery time however would be 3 hours once the 30g is used up
And once cold water is introduced the heater will not keep pace
So he may end up with less then 30g of hot water
And if its smaller then a 3800w element it will take even longer

Proby

He will not overload anything by using 240V vs 120V. Wire it up correctly.

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Master Brian

Looks like it's a 4500Watt unit and the manual states 20.7gallon per hour recovery @ 90*rise. So, it would take a while at 110v.

I also agree he should wire it up correctly, I just have to get him to realize this!

Thanks for the info, it definately helps!

joed

Open the side panels to gain access to the heaters. They will be stamped with the wattage and voltage. That is the only way to know for sure which voltage it is. You will only need to check one of them.
If you hook 120 to a 240 heater it will take a long time to heat as it will be operating a 1/4 wattage.
If you hook 240 to a 120 unit the heater will burn out very quickly if not instantly tripping the breaker.

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kbsparky

Wiring a 240 volt heating element with a 120 Volt power source won't hurt anything at all. It will heat the water just as hot, and in many cases, you won't even notice anything different. If the elements are 4500 watts, you will get 1125 watts of heat from them.

It will simply take 4 times as long to heat the entire tank to set temperature.

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TimPa

it will work - i discovered a unit wired this way for years. the ho said it always worked fine. i rewired it for 220v, they can't thank me enough.

Red Squirrel

At 120v it may actually end up drawing MORE amps, I would just wire it as 240.

mpoulton

No, it absolutely will not. On 120V, it will draw half the current (which is 1/4 the power). The only devices that will draw more current on a lower voltage are motors and some electronic power supplies.

frenchelectrican

Not on the heating elements and indentscent light bulbs they have fixed numbers of Ohms so if you have 240 volts element or bulb and run on 120 volts the wattage and amparge will drop like big time about 1/4 what you should be on 240 volt.

Like example 4500 @ 240 volts then go with 120 volts supply it will drop down to 1125 watts { note the ohms stay the same regurdless of voltage }

Merci.
Marc

Red Squirrel

My bad then. I was figuring through ohm's law but guess there's more things that apply too. Kinda makes sense now that I think of it. With what I said you'd get infinite current at 0 volts which is impossible.

a7ecorsair

Ohms Law is all you need and the power derivatives:
P=I²*R
P=E²/R

frenchelectrican

here the Ohm Law Chart and it very well knowen Internationally so it used everywhere around the world.



Merci.
Marc