mnicholet
April 28, 2010, 12:44am
1
Ok I have a 284 Litre (75 Gallon) HWT tank on a 240V 20 AMP breaker. The hot water heater states 3800/4500W upper and 3800/4500W Lower with 4500W Max Load. It is a GSW.
OHMS LAW comes up with 18.75 AMPS
This needs a 30 AMP breaker right?
mgratton
April 28, 2010, 1:16am
2
mnicholet:
Ok I have a 284 Litre (75 Gallon) HWT tank on a 240V 20 AMP breaker. The hot water heater states 3800/4500W upper and 3800/4500W Lower with 4500W Max Load. It is a GSW.
OHMS LAW comes up with 18.75 AMPS
This needs a 30 AMP breaker right?
Right and 10 gauge wiring!
rmeier2
April 28, 2010, 9:04am
3
The load is as you’ve stated 4500 watts:
4500w/240v=18.75 amps
The NEC considers a HWH a continuous load therefore the circuit must be sized at 125% of the nameplate value:
18.75 amps * 125% = 23.4 amps.
This could be on a 25 amp OCPD with #10 AWG conductors.
II. Branch-Circuit Ratingsshall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load .
mgratton
April 28, 2010, 12:30pm
4
Robert,
Correct but 25 Amps breakers are not common so the 30 Amps are used.
rmeier2
April 28, 2010, 7:58pm
5
That is true, but 25 amps is considered a standard size OCPD by the NEC.
I just wanted to point out that using a 25 amp OCPD in this application would be code compliant and that a 30 amp is not required.