Wire sizing for parrelle

[KELLY YOUNG]

I HAVE A BIDDING SOFTWARE. I BID A JOB WITH A 600 AMP SERVICE AND IT SHOWED TO DO IT IN 300 PARALLEL AND I DID NOT LOOK AND I SENT THE BID. LATER WHEN I WAS GOING BACK THROUGH MY NOTES, I NOTICED IT WAS IN 300'S. WHEN i LOOKED UP 300 & 75C, i NOTICED THAT IS ONLY GOOD FOR 285 AMPS. IS THIS BIDDING PROGRAM WRONG OR IS THERE A RULE WHEN USING PARALLEL, YOU CAN USE 90C?:-?:-?:-?
THANKS,

 

[chris kennedy]

Welcome to the Forum. The software is assuming a calculated load of 570A or less. 240.4(B) allows the use of a 600A OCPD.

Check your caps lock.

 

[infinity]

You cannot use the 90 degree C ampacity simply because these are parallel conductors. Chris gave you the answer when applying the next standard size rule in 240.4(B) so it may or may not work depending on your calculated load. Please turn off your CAPS lock. It makes your post harder to read and is construed as shouting.

Welcome to the Forum.

 

[augie47]

Hopefully that is your only problem I didn't see in your OP if the parallel conductors are in 1 conduit or paralleled in 2 conduits.
De-rating will introduce another possible problem.