Electric Hot Water Heater 2000 watt 220 volt run on 110 volt

[John1397]

Will a hot water heater element that is rated 220 volt AC by 2000 watts when only applying 110 volt AC just put out 1000 watt instead?

 

[berkeman]

Will a hot water heater element that is rated 220 volt AC by 2000 watts when only applying 110 volt AC just put out 1000 watt instead?

Hard to say, but remember that the power ratios with the square of the voltage, not linearly with it. Plus who knows what the control electronics will do with only 110Vac input. Probably better to just spring for a new heater module or a new water heater. How old is it?

Also, electrical installations in homes or businesses generally fall under local building codes, so replacing an appliance with a different appliance with different ratings may require a building permit and inspection/sign-off. Check with your local building inspection department (at your city's offices) to find out.

 

[Rive]

As a starting point half the voltage means quarter of power, so it'll be only 500W. But things are a bit more difficult, since resistance will depend on temperature, what in this case will depend on power. Most likely the heating element will not be able to reach the usual working temperature at reduced power, resulting in lower resistance. 6-700W might be a good guess, depending on the circumstances.

 

[CWatters]

I think if the element is immersed in water the temperature might not be much different so 500W is probably about right.

 

[russ_watters]

...why would a place with 110V available not also have 220?

 

[jim hardy]

i'd guess he's trying to fight the liming problem that hard water causes.

Reducing watts per inch should reduce the rate at which lime builds up.

I've considered doing that myself.
Of course my water heater controls are old fashioned bimetal thermostat type so are oblivious to applied voltage.

But temperature recovery will be mighty slow at only about one quarter power.see https://elementsofheating.wordpress.com/2013/07/23/how-to-choose-a-water-immersion-heater-2/

that's where i got the image

 

[CWatters]

How hot do you run your tanks? Were running ours at 50-55C which is too cold to prevent legionaries disease but the design allows us to dose the tank with chemicals. Perhaps running yours at 50-55 would be ok if you set up a timer to crank it up to say 80C once a week to kill bugs?

 

[John1397]

A heating element for electric home water heaters is basically a pipe with a special type of material wire on the inside probably not copper filled with ceramic material to transfer heat and keep wire from touching pipe or it would short out. I know they make 2000 watt X 110 volt elements except I didn't want to change elements as the water heater works fine with a 2000 watt 220 volt element. I have solar panels and my inverter does not produce 220 volts only 110 volts. I was thinking a electric element is just a 12 gauge piece of wire approximately 2 feet long if applying only 110 volts to this same piece of wire it just seems to me it would only produce half as many watts. I know that if it put out only 1000 watts it would need to run twice as long. Basically your hooking two 110 volt lines to each side of the element and I only want to hook one 110 volt line and ground to both terminals of the element.

 

[berkeman]

if applying only 110 volts to this same piece of wire it just seems to me it would only produce half as many watts.

No. Power P = V * I = V^2/R = I^2 * R.

Power ratios with the square of the voltage or current, given a constant resistance.

 

[Asymptotic]

I know they make 2000 watt X 110 volt elements except I didn't want to change elements as the water heater works fine with a 2000 watt 220 volt element.

As pointed out earlier, a 2000W rated element operated at half voltage delivers only 500W. It is useful perhaps to work out each scenario using the power formula @berkeman posted.

A 220V, 2000W rated element will measure about 24.2 ohms of resistance. Current is 9.1 amps when operated at rated voltage.
Current is cut in half (to about 4.5 amps) when operated at 110V. Since both voltage and current have been reduced by half (and power=volts times amps) the element will produce only 1/4 of rated power.

A 110V, 2000W rated element would be about 6.05 ohms, and draw 18.2. amps.

The easiest thing for you to do is change over to 110V elements, but with this big caveat, only if the wiring, thermostat and other control devices that may be in the heater circuit are able to withstand this much higher current.

Basically your hooking two 110 volt lines to each side of the element and I only want to hook one 110 volt line and ground to both terminals of the element.

I'm not following your line of thought.

 

[jim hardy]

wow
for heating water i much prefer a flat plate collector

they convert several times more of the collected sunlight into useabe energy (hot water) than does an electric solar cell,

https://www.nrel.gov/docs/fy16osti/66215.pdf

 

[John1397]

well if it puts out 1/4 as many watt it should take 4 times as long to heat water. should work.

 

[berkeman]

well if it puts out 1/4 as many watt it should take 4 times as long to heat water. should work.

Except the controller likely won't work, unless it's super-simple like @jim hardy has on his water heater...

 

[OmCheeto]

well if it puts out 1/4 as many watt it should take 4 times as long to heat water. should work.

I researched yesterday and found that I use about 20 gallons of water a day.
My hot water tank is 50 gallons.
So I'm guessing I use about 1/5 the capacity of my tank each day.
So, I agree, that it should work.
As long as you don't have one of those fancy electronic water heaters, as berkeman mentioned.
Mine is only 10 years old, but quite Neandertalish, as far as electronics go.
Since I don't get enough sun in the winter to support a PV system, but do in the summer, I may abscond with your idea and create a hybrid hot water system.
Upper element: grid powered
Lower element: solar PV powered

That is, until I install my BTES. (Borehole Thermal Energy System) (ETA: 2021!)
As Jim Hardy mentioned, flat plate solar thermal is a lot more efficient, both financially, and energy-wise.

 

[jrmichler]

When the daily usage is less than the tank capacity, fast recovery is not important. If we assume 20 gallons times 80 deg F temperature rise, that's 13,300 BTU. Since 1 kwh is 3412 BTU, recovery will take 13,300 / 3412 = 3.9 kwh. That could be 1 kw for 3.9 hours, 500 watts for 8 hours, or 250 watts for 16 hours. Standby losses need to be added in. Estimating standby loss at about 100 watts, the total recovery would be 3.9 hours for 1.1 kw, 8 hours for 600 watts, or 16 hours for 350 watts.

Set the lower (solar PV) element to a higher temperature then the upper (grid) element may allow near 100% solar hot water during the sunny season.

 

[John1397]

My elements are bigger than I thought as I found a used one on the shelf it says 4500 watt X 240 volt and has a resistance of 12 ohms so under ohms law this would equal 1200 watt running on 120 volts should give some heat.

 

[John1397]

Set the lower (solar PV) element to a higher temperature then the upper (grid) element may allow near 100% solar hot water during the sunny season.

That would work pretty good I think you could just hook solar panel directly to bottom element would not even need to use an inverter only cost you would have for solar panel and piece of wire.

 

[OmCheeto]

That would work pretty good I think you could just hook solar panel directly to bottom element would not even need to use an inverter only cost you would have for solar panel and piece of wire.

That may or may not work, depending on

1. the design of the thermostat
2. your DC input voltage, and
3. the capacity of your PV system.

From a previous thread, where I questioned why my coffee pots had a warning NOT to power them with DC:

The AC only ratings are probably dictated by thermostat switch contact ratings. A typical rating is 250V/10A, 125V/15A for AC, but unrated for DC (or, if it is, it would be limited to 30 volts at the 125 VAC current rating). The arc that occurs when the contacts open extinguishes when AC crosses zero volts, but a DC arc sustains until their separation distance becomes great enough. Not only does this generate a lot more heat, but in a physically small switch like a thermostat the distance between contacts may never open up enough to fully extinguish the arc, and they'll melt in short order.

And on that note:

I may abscond with your idea and create a hybrid hot water system.

I've changed my mind. I will not be doing that this summer.

 

[Rive]

I think you could just hook solar panel directly to bottom element

That's definitely a bad idea. You need 110V DC to have the similar power, but 110V DC is just not a thing you want to play around with at home (especially when water is involved).

Mixing up some new feature into an old system to make a hybrid monster usually a bad idea. You should rather try to get something like this as a backup. These vacuum pipes works well from spring to autumn and they are surprisingly sturdy.
(Also, you get ~ 80% efficiency instead of ~ 15%...)

 

[CWatters]

Here in the UK you don't get paid much/anymore for exporting excess PV generated electricity. So some people install a heating element in their hot water tank to ensure they use any excess themselves instead of paying for gas. The heater is controlled by a device that detects when you are exporting. They are available commercially but I've heard they are/were expensive?

One or two people might have built systems that use DC from the PV array to directly heat the water but I think they are probably DIY installs.

 

[Dullard]

Most 220 VAC water heaters will work (albeit slowly) on 110VAC. As noted above, the power will be reduced by approx 75%. This is precisely how I maintain my water heater (with a 6 KW generator) during that miserable week after a hurricane and before power is restored to my house.