water heater

[domnic]

I have a 4500 watt water heater can i use #12 wire.

 

[Dennis Alwon]

simple No. #10 is required with either a 25 amp or 30 amp breaker.

 

[Dennis Alwon]

A water heater such as that is considered continuous-- art. 422.13.

4500 watts/240 volts = 18.75 amps
18.75 * 1.25= 23.5 amps.

OCP cannot exceed 150% 422.11(E)(3)

18.75 * 1.5 = 28 amps-- you may go to the next higher breaker size 422.11(E)(3)

 

[charlie b]

The question cannot be answered without knowing the voltage. Dennis used the most probable value of 240. But if the heater were three phase, 480 volts (do they make such things?), the current would be under 7 amps, and a #12 would be acceptable.

 

[mivey]

But if the heater were three phase, 480 volts (do they make such things?),

They do, at least 6kW for sure (208, 240, or 480 three phase)

 

[Dennis Alwon]

The question cannot be answered without knowing the voltage. Dennis used the most probable value of 240. But if the heater were three phase, 480 volts (do they make such things?), the current would be under 7 amps, and a #12 would be acceptable.

4500 watt is a standard size resi. water heater so I used that as the basis. You are correct if it is 3 phase the situation would be different.

 

[mivey]

They do, at least 6kW for sure (208, 240, or 480 three phase)

Here are specs for a light-duty commercial Rheem having 3, 4, 4.5, 5, & 6 kW elements:

http://globalimageserver.com/fetchDocument.aspx?id=903e08f3-297c-43a0-a587-e0fae55a8801

 

[LarryFine]

On the other hand, a 4500w 240v water heater used on 208v would pass 16.25a and use 3380w.

 

[mtfallsmikey]

They do, at least 6kW for sure (208, 240, or 480 three phase)

I have Lochinvar 40 gal. htrs. in my buildings, 4500 wt. 277v.

 

[yankj]

Do you know how difficult it is to get 277volt heaters?

 

[LarryFine]

Do you know how difficult it is to get 277volt heaters?

No, but, if you hum a few bars . . .

 

[Sierrasparky]

I have seen many a condo or apartments wired with # 10 Al. serving water heaters. How did that pass?

 

[One-eyed Jack]

I have seen many a condo or apartments wired with # 10 Al. serving water heaters. How did that pass?

Don't know which code cycle that was in. Today #10 Al has a 30 amp rating. This is code compliant for a the 24 amp load of a 4.5 kw water heater. I would not do it. There was a time when the max ocp for a 4.5 kw water heater was 25 amp. Sometime in the 80's.