Calculation Single non motor appliance 422.11(E)

Hi, I'm a little confuse with 422.11(E)--Overcurrent protection for non motor appliance.

If a have a non-motor appliance rated at 32 amps (example water heater less than 120 gal) then

1) 422.13- says it is a continuous load 125%-----(1.25)(32)=40 amps-----------conductor #8 rated at 40amp
2) 422.11(E)--If the appliance is rated over 13.3 amp then the max Overcurrent Protection is 150% of the appliance and if the 150% doesn't correspond to a standard size then the next higher standard size can be used..so.....
------ (1.5)(32)=48 amp. There is no 48 so we can use a Breaker of 50 amp.

So We could use a Breaker 50 amp with a #8 rated at 40 amp.

Is this correct?
 

iwire

Moderator
Staff member
So We could use a Breaker 50 amp with a #8 rated at 40 amp.
No, article 422 is only concerned with the appliance and not the conductors.

So the water heater in your example could be supplied from a 50 amp breaker but your would have to use a conductor rated 50 amps. Or at least 41 amps so 240.4(B) could be used.
 
Top