Hwt amps

[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?

[Marcel Gratton]

Originally Posted by 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!

[Robert Meier]

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.

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.

II. Branch-Circuit Ratings
210.19 Conductors — Minimum Ampacity and Size.
(A) Branch Circuits Not More Than 600 Volts.
(1) General. Branch-circuit conductors shall have an ampacity not less than the maximum load to be served. Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum branch-circuit conductor size, before the application of any adjustment or correction factors, shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load.

[Marcel Gratton]

Robert,

Correct but 25 Amps breakers are not common so the 30 Amps are used.

[Robert Meier]

Originally Posted by mgratton

Robert,

Correct but 25 Amps breakers are not common so the 30 Amps are used.

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.