30KW electrical water heater wiring

[zemingduan]

Hi guys. I am an electrical designer working on a restaurant project that needs to supply a 1ph 240V 30KW electrical water heater from a 1PH 240V 600A electrical panel.

30,000W / 240V = 125A 125A X 125% = 156.25A the next higher level breaker size is 175A.
Below is the water heater front view and wiring diagram from the installation manual. The model is BRADFORD WHITE CEHD120.


It seems that the wiring diagram calls for oen 175A 2P breaker on electrical panel and 2/0 copper to feed the terminal block. But NEC 430.11(F)(3) says that you need to subdivde the heating element into circuit not more than 120A. Is this talking about the interior circuits within the water heater or also applying to the cirucits from the electricala panel to the water heater?

The 30KW wate heater has 6 heating elements. And from the layout above, they do have fuse block to subdivde the interior circuits. If I use oen 175A 2P breaker on electrical panel and 2/0 copper to feed the terminal block, it that a code violation?

 

[texie]

It is not likely that this WH qualifies under 422.11(F)(3) as it is not likely a ASME vessel. It's a moot point anyway as the manufacturer has sub divided the load to less than 48 amps per 422.11(F)(1). You just supply it with one branch circuit as you described.

 

[petersonra]

It is not likely that this WH qualifies under 422.11(F)(3) as it is not likely a ASME vessel. It's a moot point anyway as the manufacturer has sub divided the load to less than 48 amps per 422.11(F)(1). You just supply it with one branch circuit as you described.

would it be a BC or a feeder?

 

[LarryFine]

would it be a BC or a feeder?

I'd say a BC because the internal OCPDs are not part of our work.

 

[texie]

Yes, it is a branch circuit.