5000W Water Heater

Status
Not open for further replies.

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
I may have an issue. I have 10 residential units that call for water heaters with 5kw elements. Service is 208y/120.

I get as per 422.13:

5000?208=24.038A

24.038?1.25=30.047

Units are wired in NM. As per 334.80 I see 30A in the 60?C column of T310.16 for #10 NM.

Slightly over the allowable ampacity of the 10/2 mn that is installed.

Am I mistaken?
 
Did you read 220.5(B)?

I am not sure if this section number can be applied to 422.13

Good call Pierre. I wouldn't have thought of that seldom used piece of information and pulled 8 copper to the units. You just saved Chris' bacon (or substituted a sirloin steak for his bacon) on that job.
 
220.5(B) applies to branch circuit calcs, because 220.1 says so. :wink:
If you come up with 30.047 amps, you can drop the .047 amps, and use 30 amp conductors.

When doing a load calc I will drop the fraction, when sizing a branch circuit I will follow this:


422.13 Storage-Type Water Heaters.
A fixed storage-type water heater that has a capacity of 450 L (120 gal) or less shall be considered a continuous load for the purposes of sizing branch circuits.
FPN: For branch-circuit rating, see 422.10.
 
Status
Not open for further replies.
Top