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Discussion Starter · #1 ·
Hi all,

I have been searching local distributors for the following items and they just do not seem to exist:

1. 400A, 230V (or higher), 4-wire fused disconnect switch
2. 400A, 230V (or higher), 4-wire transfer switch
3. 400A, 230V (or higher), 4-wire splitter trough

I can find ALL of these pieces of equipment for 3-wire systems but not for 4-wire.

4-wire equipment seems to max out at 200A.

Just for a bit of background, this is equipment that is upstream from some distribution boards. The transfer switch is for a backup power source. The winding configuration is a high-leg delta (delta center-tapped) at 230V phase to phase.

If anyone knows of a supplier that carries any of these products it would be greatly appreciated!

Thanks,
Mike
 

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Hi all,

I have been searching local distributors for the following items and they just do not seem to exist:

1. 400A, 230V (or higher), 4-wire fused disconnect switch
2. 400A, 230V (or higher), 4-wire transfer switch
3. 400A, 230V (or higher), 4-wire splitter trough

I can find ALL of these pieces of equipment for 3-wire systems but not for 4-wire.

4-wire equipment seems to max out at 200A.

Just for a bit of background, this is equipment that is upstream from some distribution boards. The transfer switch is for a backup power source. The winding configuration is a high-leg delta (delta center-tapped) at 230V phase to phase.

If anyone knows of a supplier that carries any of these products it would be greatly appreciated!

Thanks,
Mike
What do you mean by 4 wire?

3 hots and a neutral? or four hots?
 

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Discussion Starter · #3 ·
3 phases and a neutral which is the center tap on the transformer, not necessarily a grounded tap

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Discussion Starter · #4 ·
Sorry...that was unclear. There are three hot leads and a neutral but I'm not sure if the neutral is grounded at the transformer

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Discussion Starter · #6 ·
Well apparently there's a difference between a 3 wire disconnect and a 4 wire disconnect. I'd be concerned about floating voltage on the neutral as well.

Do you have any experience with high leg delta configuration at high amperage? This my first kick at this type of system

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I've never seen a 4-pole disconnect. There are plenty of 4-pole transfer switches, though -- that's what you need to use if the generator is a separately derived system.
 

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Discussion Starter · #9 ·
Secondary power source is actually just a feed from another utility company, but its 4-wire delta so I'm assuming the transfer switch needs to be 4 wire

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Typically the neutral gets carried through the disconnect -- you only have to switch the phase conductors.

As for your transfer switch, I would assume if it's a separate utility feed that it's a separately derived system, so yes -- you should use a 4-pole in that application.

When in doubt, it's better to have a 4-pole transfer switch than a 3-pole -- you can always just not switch the neutral. Doesn't work very well the other way, though.
 

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Discussion Starter · #13 ·
In the description it says "no neutral".. So can the neutral still be fed through the switch? Just need to be sure

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I don't see why not -- but if you're unsure you may want to make a quick phone call to the distributor just to be safe.
 

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Discussion Starter · #16 ·
So on a normal three phase system the three hot leads would be fed through the disconnect and the fourth conductor would be ground right?

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No, if it's a disconnect to a load that requires 3 phases and a neutral, you should be pulling 4 wires plus an equipment ground. The neutral and ground would be fed through the switch (which should also have its housing bonded to the equipment ground that goes through it).
 
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