# What is meaning of "standard" and "maximum" wattage for electric hot water heater?



## eitnum (Aug 14, 2014)

*What is meaning of "standard" and "maximum" wattage for electric hot water heater?*

The specs for the AO Smith ProMax EJCT-20 electric water heater say that the element wattage is 2500 for "standard" 240V and 6000 for "maximum" 240V.
What is the meaning of "standard" and "maximum"?

I am trying to determine if this water heater is a possibility for the power that's in my house, but don't have much electrical savvy.


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## gregzoll (Dec 25, 2006)

Exactly what you stated. Standard is another way of stating "Minimum Voltage". Min. amp's is 15, Max amps is 25 at 240 vAC.


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## eitnum (Aug 14, 2014)

In other words, the water heater would operate over the range of 2500 - 6000 watts?

But at 2500 watts, wouldn't the amps be just 10.4, instead of 15?
(2500 divided by 240 = 10.4.)


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## gregzoll (Dec 25, 2006)

You have to go by the max for what size breaker to use. 25 or 30 amp will suffice.


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## Protocol. (May 31, 2012)

Manual states 2500 w is for standard 120v configuration and 6000w is for 240v configuration. I guess it all just depends on what voltage you have available.


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## chitownken (Nov 22, 2012)

Protocol. said:


> Manual states 2500 w is for standard 120v configuration and 6000w is for 240v configuration. I guess it all just depends on what voltage you have available.


Not quite. A 6000W element at 240V only generates 1500W at 120V.

Greg has it right. The water heater has 2 elements. The lower element is 2500W. It comes on first and in low demand situations (standard) it is the only one that comes on. In high demand situations, the upper element will be energized as well for a total of 6000W.

If you are sizing your electrical connection, it must be sized to handle 6000W.


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## eitnum (Aug 14, 2014)

Protocol--you are right. I misread the spec sheet. "Standard" is 120V, not 240.

Chitownken, I have just discovered another document that says this water heater has only a single heating element. And the 6000 wattage is for 240V, not 120V. 

To repeat: Wattage is 2500 at "standard 120V" and 6000 at "maximum 240V".

I'm still wondering what the "standard" vs. "maximum" means. Is it really OK to run a 240V appliance on a 120V circuit?


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## gregzoll (Dec 25, 2006)

eitnum 240 vAC is just two 120 vAC legs to the appliance. You are really over thinking this way too much. Just get the job done and move on. Also make sure you install Earthquake strapping and follow the code on the intake & output for the water.

I personally would use AC or MC between a junction box and the water heater, vs. Romex. It gives a little more flex if you do have any tremors. Plus more protective of the wiring feeding the water heater.


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## Protocol. (May 31, 2012)

chitownken said:


> Protocol. said:
> 
> 
> > Manual states 2500 w is for standard 120v configuration and 6000w is for 240v configuration. I guess it all just depends on what voltage you have available.
> ...


You're misreading what I'm staying. Im just quoting what the manual states, not an ohms law calculation based on wattage at 240v vs 120v.


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## nap (Dec 4, 2007)

when I go to AO Smith's website all I see concerning this model is it is a 20 gallon compact water heater rated at 2500 watts. 

http://www.hotwater.com/water-heate...pact-electric-water-heater-ejct-20-200/#specs




> Tech Specs
> 
> Gallon Capacity:	20
> Recovery Gallons:	11
> ...




while it doesn't list a voltage at the AO SMith site that I could find, at a Fastenal website it listed it as a 120 volt appliance.


is there some reason you would want a little bitty water heater? 

Oh, my mistake. It actually has this posted on AO SMith's site:




> With a 19.9-gallon tank and 1 element delivering 2500 kilowatts,


man o man, that would vaporize 20 gallons of water instantly. That is 2,500,000 (or 2 1/2 
MILLION watts) I don't think your service can handle it. :laughing:


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## eitnum (Aug 14, 2014)

And the water isn't the only thing that would be vaporized.

Obviously, A.O. Smith is not doing a very good job of presenting accurate info. on their website. So far we have three stories:

Specs turned up by nap: 
"Upper element wattage 2500" (which implies there is a lower element)
"Maximum wattage 2500" (which contradicts presence of second element)

Document I printed out last Sept: "single heating element".

Specs I printed out last Sept, which agree with what Protocol found in manual:
2500 watts for "standard 120v", 6000 watts for "maximum 240V".

I can no longer find online the documents I printed last Sept.


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## nap (Dec 4, 2007)

i think the "upper element" statement is just a generic thing. It was stated there is only one element. Again, poor editing on AO Smith's part.


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