750's in 3" conduit.

[Cow]

Two 750's and one 350 in 3" pvc/rigid. Two 90's(that I know of), 150 feet long, existing conduit under parking lot and concrete slab.

Can I do it or am I doomed to fail? Conduit fill ratio works, but jamming is the concern. Only ever put 750's in 4 inch.

I need more than a 400 amp single phase service according to a quick manual load calc. Thinking about getting to 475 amps with the 750's wire ampacity and then using the round up rule to allow a 500 amp main breaker or use a combination of service disconnects/panelboards. Haven't decided yet, just trying to figure out if the wire size in the conduit will work to get the ampacity I need.

Thanks for the help.

 

[infinity]

Have you considered parallel conductors like 300's? Two sets gets you to a full 512 amps. (320*2*80%=512 amps)

 

[Cow]

I hadn't. Probably should of slept on it first. May have a had a bit of tunnel vision when I posted since we don't typically parallel in the same conduit. This being a different situation than the usual, I'll run it through the way you suggested and see where we end up. Thank you.

 

[electrofelon]

I would stay away from that bad jam ratio, it will be nothing but a headache. I like the parallel's Idea. You could even do three sets of cheap 4/0 AL and and because its single phase still have a .8 derate and gets you 492 amps. Three sets might make terminating a hassle and not worth it however.

 

[qcroanoke]

If it's PVC you'll need an equipment ground.

 

[infinity]

If it's PVC you'll need an equipment ground.

He stated in the OP that is a service.

 

[qcroanoke]

He stated in the OP that is a service.

Missed that.