Instantaneous water heater circuit breaker sizing

faresos

Senior Member
Hello All:

Reading the brochure of several instantaneous water heaters it appears they size the beaker based on 100% of the load not 125%. Does this mean they consider this to be non-continuous load? I have been sizing it at 125% but should I follow the manufacturer recommendation which is 100% of the rating?

Thanks,
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Unless the heater is running at full load for 3 or more hours it is not considered a continuous load according to the NEC. Storage type water heater require the 125% factor because is an NEC requirement. I would follow the manufacturers instructions.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Instantaneous heaters are not considered continuous. it would be a very unusual circumstance when the heater would run for 3 hours. In a residential setting, I doubt that would ever happen.
 
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