Water Heater calcs

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toomunsch

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I'm wiring a commercial water heater and would just like confirmation that this is correct : 36kw, 100A rated current, 3 ph, 208V. 422.11(E) states use 150% so I need a 150A breaker and would use 1/0 to feed it. No overcurrent protection is listed on the unit. Thanks.
 
Storage type 422.13 makes it "continuous", 100 amp x 125% = 125, so, as jumper says 125 and #1 should be sufficient. Your 422.11(E) would limit it not to exceed 150, but keep 422.11(F) in mind also so you can subdivide the circuits if the manufacturer has not.
 
also a wiring diagram label on the cover of the unit says to use 1/0 and a #6 egc. Do I have to size it at 1/0 because of the label? It has 3 lugs for field wiring and it splits off 4 conductors from those into internals.
 
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Mfg. instructions normally trump all else. Just max sure it doesn't say 1/0 max.
 
It actually says " 0 " so I assume that's 1/0, and it says "1" for lower currents and voltages. The other problem I have is that it's fed from a CH panel and I think 100A is the largest 3 pole CB available... None of this was in the plan so it's all extra anyway.
 
toomunsch said:
It actually says " 0 " so I assume that's 1/0, and it says "1" for lower currents and voltages. The other problem I have is that it's fed from a CH panel and I think 100A is the largest 3 pole CB available... None of this was in the plan so it's all extra anyway.
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That is a problem with many panel boards butt usually 125 amp is the largest size breaker that can be installed on the buss. It should be labeled on the panel.
 
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