Possible solutions to a bad design

[gaylen]

I have a situation where there is a 120/208Volt 3 Phase 600 Amp safety switch with double lugs (which is the max that is manufactured for a 600 Amp. per the manufacture) which is going to a 600 Amp. MDP, which also only comes with Double lugs. However the designer had planned on paralleling (3) 3/0 CU. and had installed (already installed under concrete) (3) runs of 2 1/2" PVC however with the situation of double lug max it will be difficult to run (3) conductors and will need to run a (2) wire system and that is with 350 MCM CU. and that runs into a problem of conduit fill. 2 1/2" PVC conduit only allows (4) 350 MCM and that doesn't account for the ground. Any suggestions would be appreciated.
Tx Gaylen

 

[MarkyMarkNC]

I would pull the 3/0's in the conduit, and then use Polaris taps to change over to 350 inside the disconnect and MDP.

I'm sure you've already thought about swapping out the existing lugs for ones that will take 3 wires, and I've seen that done many times, but I would try to avoid that.

 

[hardworkingstiff]

I would pull the 3/0's in the conduit, and then use Polaris taps to change over to 350 inside the disconnect and MDP.

It seems this would be crowded in that disconnect. I would try to install a box below the disconnect and make the connections there.

I'm sure you've already thought about swapping out the existing lugs for ones that will take 3 wires, and I've seen that done many times, but I would try to avoid that.

If the manufacturer has designed this for 2 conductors maximum, you might void the listing by installing a lug for 3 conductors.

Have you considered looking for a different manufacturer that might allow for 3 conductors?

 

[hardworkingstiff]

You didn't say whether it is a NEMA 1, 3R, etc. safety switch.

Square D has a field-installable lug kit for there general duty safety switches which allows for (4) 1/0-250 conductors in their NEMA 1 switch.
Part# GD4060LK.

I didn't check the Heavy Duty series.

 

[buddhakii]

are you sure each lug is only rated for 1 wire? If its rated for more it should be a number in (). i.e. (2) 250c.u.

 

[infinity]

will need to run a (2) wire system and that is with 350 MCM CU. and that runs into a problem of conduit fill. 2 1/2" PVC conduit only allows (4) 350 MCM and that doesn't account for the ground. Any suggestions would be appreciated.
Tx Gaylen

Are these compact conductors? Table C10 says only (3) 350's will fit in a 2.5" Sch 40 PVC. Sounds like changing the lugs is the only real sensible option. I would note that this is done all of the time.