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Discussion Starter · #1 ·
My latest design project will have one of these.
My client managed to get his hands on a used Square D I-Line panelboard lineup. From Square D delivery would be well over a year. He will get his in January of the coming year! The shop providing the equipment had been around over 50 years and knows what they are doing. The only negative is I would have ordered one with a cable entry section like I used on previous projects. This one is set up for cable entry behind the main breaker. The bus bars are barely 24” from the floor! Any way you look at it the electrician will need ape arms. My concern is that the likelihood of conductor and primarily insulation damage trying to bend and shape large cables to connect to the bus.

Reference the photo of similar gear.

Originally, I was going to use 10 – 600 MCM per phase with a 3/0 neural. But, coming out of 10 - 3-1/2” PVC conduits from below will be a nightmare. At best, with all the different phases crisscrossing each other, avoiding damage to the insulation will be unlikely. And maintaining equal phase conductor length? HA! The service transformer is a pad mount that is only 20 feet away.
One night when I couldn’t get to sleep, I think I came up with what I thing is a workable solution! How about using 12 - 500 MCM in 3-1/2” PVC conduits and coming up out of the floor directly under the phase bus bars, each conduit with only it’s respective phase conductors! Minimal bending of the conductors to lay onto the bus above. Little chance of damage and no crisscrossing. And maintaining equal phase lengths possible. Each conduit would have 4 – 500 MCM same phase conductors.
The system 3/0 neutrals would be in their own 3 – 3-1/2” PVC conduits and terminate to the neutral bus.
Of course, NO ferrous metal ever between the separated phase conductors!

Thoughts?
Wood Fixture Electrical wiring Composite material Engineering
 

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Discussion Starter · #5 ·
USED?????? Why such a long lead time? How old is this gear?

What documentation is the vendor supplying? Or are you going to pay someone to commission the gear including all of the testing? (meger, hi pot, dlro, coordination study for the breakers)
What breakers and trip units are supplied?

Put the section on a 12" pad if your worried.

You would be much better off if the transformer was farther away. Then you could criss cross the primary conduit under ground. Which makes the cable length much easier to deal with.

I did on primary feed where the shortest and longest conductors where 23' different. I was told to cut the long ones and refused.

I have done 100's of sections like that with the primary conduits in the same section as the MCB.
Just need a good measure of working clearances to pull and make up the conductors.

Who is going to stamp these drawings?


Are you NUTS about putting filling a conduit with ONLY ONE PHASE CONDUCTOR?
or did I mis understand your text?
That is a motor winding looking for a fault. I have seen what happens. It is very expensive to fix and the last guy I know that did it lost his Arizona engineering license.
I have no problem with that. Look up "Iso phase bus duct". The CONCEPT has been around a very long time.
So long as you keep no ferrous metals between the phases, you are fine.

For example, im this case the "A" phase conduits would be right below the "A" phase bus bar. Straight up, connect. No crisscrossing, no sharp bends, etc.
 

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Discussion Starter · #8 ·
Thanks for all your responses!
It's still going to be hard to keep the phase conductors the same length. And to make sure the utility people don't try to cut the ends to the same length!

RC
 

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Discussion Starter · #10 ·
BTW, I am the PE of record on this project. And I will have no issues in stamping the drawings.

The company we are getting the gear from has been in business for over 50 years and we have done business with them before and were very pleased with he product. They have been doing regular testing on my clients electrical equipment for many years. I have used them to test equipment on other projects of mine. Good people. They are members of PEARL and NETA.

I will be doing the coordination study.

The main will have a remote trip located in a KNOX box outside the building, a maintenance mode switch, and ground fault. The existing trip unit will be replaced.

RC
 
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