Calculaton questions

[SideshowBob]

I embarrassed that don't remember this but swallowing some pride is sometime good for a person. I am wiring a 3 phase in-line water heater and the manufacturer lists the current draw at 177A. at 480 volts, (144kw). Would that be per phase rating or would that be just the total. I was thinking it was just the total and i needed to calculate the phase current at 48kw/(480v x square root of 3)=58A. Unfortunately, I've started to doubt myself. Thanks for the help.

 

[pc1966]

That would be the per-phase current, assuming when you say 480V you mean L-L so around 277V L-N.

144kW at 277V = 520A, so split over 3 phases you have 173A/phase.

That sure is a big heater! I'm guessing for a hotel or some industrial site?

 

[snowhead]

Confirmed by the fact for a typical heater of that rating they suggest a 200amp 3ph breaker

 

[SideshowBob]

That would be the per-phase current, assuming when you say 480V you mean L-L so around 277V L-N.

144kW at 277V = 520A, so split over 3 phases you have 173A/phase.

That sure is a big heater! I'm guessing for a hotel or some industrial site?

Thank you for your help. It is a pretty good sized heater. We use it to heat the water in a safety shower system.