3ph 480v wrt htr

G

garbo

Senior Member
A 3,500 watt heating element feed from 480 volts three phase would draw approximately 4.207 amps. So a 15 amp circuit breaker would easily handle it. I never came across a 6,7 or 10 amp three pole circuit breaker that would fit into conventional 480 volt three phase panels. I used to use a cheater multiplier for ruff field three phase 480 volt calculations by multiplying the KW by 1.2 . example 3.5 KW × 1.2 =4.2 Amps.
 
kingpb

kingpb

Senior Member
Location
SE USA as far as you can go
Occupation
Engineer, Registered
garbo said:
A 3,500 watt heating element feed from 480 volts three phase would draw approximately 4.207 amps. So a 15 amp circuit breaker would easily handle it. I never came across a 6,7 or 10 amp three pole circuit breaker that would fit into conventional 480 volt three phase panels. I used to use a cheater multiplier for ruff field three phase 480 volt calculations by multiplying the KW by 1.2 . example 3.5 KW × 1.2 =4.2 Amps.
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Use the smallest breaker you can get, then put a fused disconnect at the water heater.
 
kwired

kwired

Electron manager
Location
NE Nebraska
422.11(E) says this unit could be on up to a 20 amp overcurrent device. If using 14 AWG conductors then the conductor is what would limit you to 15 amp overcurrent devcie.
 
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