800A Feeders

[sunelectricbx]

Can I run parallel 500kcmils out of an 800A fused disconnect with double lugs approximately 200' linear into 2 seperate 400A MLO panels, or do I have to reconnect the parallel runs in a wireway with some Polaris terminal blocks above the panels before going into the 400A MLO panels?
Is this against code?
Its a new tanning salon install and we can get both panels pretty close to being perfectly balanced.
Someone told me I need to rejoin them before they go into the panels and I cant find that in the code book.
Any advice?

 

[mdshunk]

If they are not rejoined, then you have a tap rule violation.

 

[JohnJ0906]

If they are not rejoined, that is not a parallel run. See 310.4

 

[sunelectricbx]

Thats what I originally thought, but when I read the section it talks about feeder taps without overcurrent protection.
Is it because it really becomes 2-400A feeders with 800A protection? Now its making sense.
You could actually overload the 500kcmils in 1 conduit at 600A and never blow the fuse if the other conduit is only drawing 100A.
Got it!

 

[sunelectricbx]

Thanks again, sometimes you think and your brain just farts.

 

[infinity]

I'm curious, so how will you do the job?

 

[sunelectricbx]

I will come out of the disconnect with 2-3" conduits, both with 500kcmil conductors then rejoin them with 4 terminal (2-500's in and 2-500's out) polaris blocks in a wireway above the 2-400A panels.

 

[infinity]

You will not be able to use MLO panels with this setup. Since your 400 amp conductors will be taps you will need OCPD for them at the 400 amp panels. If I remember correctly, if you use a 400 amp OCPD at each panel your tap conductors would have to be rated for at least 400 amps. 500 kcmil THHN is only good for 380 amps.

 

[sunelectricbx]

What about the next size up rule? Doesnt it apply 800A and under?

 

[don_resqcapt19]

Rob,

What about the next size up rule? Doesnt it apply 800A and under?

It doesn't apply to taps.
Don

 

[sunelectricbx]

Awesome, now I get to pull 600kcmils for 200'
Thanks for the advice, I really appreciate it. I have done 6 of these salons already, but they usually have an 800A MDP and 3 sub-panels, and they are usually back to back with the CT/meter.
I thought I was slick.

 

[sunelectricbx]

What if change everything!
I will come out of the transformer into an 800A CT/meter. Then from the CT cabinet I will double lug out to 2-400A disconnects and then run the 200' to the 2 seperate 400A panels. No wireways, no taps, no 600's
Can you have 2 disconnects for 1 tenant location?

 

[don_resqcapt19]

Rob,

Awesome, now I get to pull 600kcmils for 200'

Actually the parallel 500s are not taps and are ok on an 800 amp breaker. You would only need the 600s from the wireway to the panels.

I will come out of the transformer into an 800A CT/meter. Then from the CT cabinet I will double lug out to 2-400A disconnects and then run the 200' to the 2 seperate 400A panels. No wireways, no taps, no 600's
Can you have 2 disconnects for 1 tenant location?

That is fine too.
Don

 

[sunelectricbx]

That is what I was thinking but it doesnt make much sense. The taps will only be 2'-3' long.
What a relief, I priced the job with 500's