400A panel feed

[Hfalz1]

I am needing to feed a 400A panel single phase. Would it be better to feed it with 2 sets of 3/0 or one set of 500MCM?

 

[charlie b]

Two sets of 3/0 have a total ampacity of 400. A single set of 500 MCM only has 380. So if you calculated load is under 380 amps, you can use the 500s. But if the calculated load is between 380 and 400, or if you don't have a load calculation, then you can't use 500s. I suspect that pulling two sets of 3/0 would be easier than pulling 500s, but someone else will have to confirm ths.

 

[infinity]

How long is the run? You would need to weigh the cost of running two conduits instead of one and terminating twice as many conductors on both ends and setting up and pulling two pulls instead of one. IMO one set of 500's is better unless you need the full 400 amps as Charlie stated

 

[Hfalz1]

I'm looking at the code book and it says 500 thhn is rated for 430A, has it changed in the new code book?

 

[construct]

I'm looking at the code book and it says 500 thhn is rated for 430A, has it changed in the new code book?

If underground, would it not be a wet location? 75C, THWN, 380A

 

[infinity]

I'm looking at the code book and it says 500 thhn is rated for 430A, has it changed in the new code book?

Nothing has changed regarding ampacity for decades. You're are looking at the 90° C ampacity. The terminals you're connecting it with are only rated for 75° C so you must use the 75° C ampacity.

 

[blkmagik21]

Nothing has changed regarding ampacity for decades. You're are looking at the 90° C ampacity. The terminals you're connecting it with are only rated for 75° C so you must use the 75° C ampacity.

So many times I’ve wished manufactures would use 90 degree rated terminals. But alas that shall probably never happen.


Sent from my iPhone using Tapatalk

 

[infinity]

So many times I’ve wished manufactures would use 90 degree rated terminals. But alas that shall probably never happen.

Not likely to happen any time soon because it's not only the terminals it's also the equipment that the terminals are connected to. The equipment would also need to be designed for use at 90° C. You can buy 90° terminals now but if you slap them on some 75° C equipment you still can only use the conductors at 75° C.

 

[electrofelon]

If underground, would it not be a wet location? 75C, THWN, 380A

Pretty much academic. Most of us say "thhn" regardless if the location as everything is thwn-2

 

[Adamjamma]

Not likely to happen any time soon because it's not only the terminals it's also the equipment that the terminals are connected to. The equipment would also need to be designed for use at 90° C. You can buy 90° terminals now but if you slap them on some 75° C equipment you still can only use the conductors at 75° C.

But couldn’t you do this by running the splices outside the breaker boxes to transition from 75 degree to 90 degree for the long run, then back to 75 degree just for the new 400 amp box? Like the video and such I was asking about yesterday! Just butting in, trying to learn better..lol.

 

[infinity]

But couldn’t you do this by running the splices outside the breaker boxes to transition from 75 degree to 90 degree for the long run, then back to 75 degree just for the new 400 amp box? Like the video and such I was asking about yesterday! Just butting in, trying to learn better..lol.

Yup, using the 75 degree C rating sounds easier.