600Amp. 120/240v service entrance

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frengija

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Is it allowable to use 250 MCM THHN cable(parallel run/two sets)in two 4" EMT conduits from 600A/3R
Disconnect as a main breaker to the distribution panel which is 40' (feet) away inside the building
 

charlie b

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Location
Lockport, IL
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Retired Electrical Engineer
Re: 600Amp. 120/240v service entrance

If the total calculated load is 510 amps or lower (i.e., twice the 255 amp rating at 75C), yes. Otherwise, no. Furthermore, if you don't have a calculation (or other evidence) that shows the load to be below the 600 amp setpoint of the overcurrent protection, then you need conductors rated for every bit of that 600 amps. That would be a minimum of a pair of 350's.
 
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