200A fused disconnect

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hhsting

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Max I saw capacity wise was 300kcmil cable for 200aa fused disconnect.

I have 2 sets of 3/0 AWG that’s 336kcmil. Does anyone know what is the max wire size capacity for 200A fused disconnect and can it handle 2 sets of 3/0Awg?
 
Depends on manufacturer. Check the mfg catalog !
(Square D shows lug for 1 conductor 6-300)
You needm to watch your wire bending space also (312.16)
 
You need to find terminals for that switch that allow 2-#3/0 conductors. Or maybe a switch that has studs where you can install two crimp on terminals.
 
Interestingly Square D offers a double lug kit for 200 Amp disconnects so you can install two wires instead of one. however, it is not listed.
 
hhsting said:
Max I saw capacity wise was 300kcmil cable for 200aa fused disconnect.

I have 2 sets of 3/0 AWG that’s 336kcmil. Does anyone know what is the max wire size capacity for 200A fused disconnect and can it handle 2 sets of 3/0Awg?
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KCMIL doesn't simply "add" when placing multiple wires in the same lug. In fact, lugs that allow multiple wires are the exception, and not the rule. Product ratings aside, due to the fact that "circle packing in a circle" is the least efficient with 2 circles, you probably wouldn't even be able to fit two 3/0's in that lug.

Terminals are only rated by default for one wire. The onus is on the manufacturer to get it listed and labeled otherwise, if they intend users to connect multiple wires. Typical two wire lugs are "snowman" shaped.
 
Carultch said:
KCMIL doesn't simply "add" when placing multiple wires in the same lug. In fact, lugs that allow multiple wires are the exception, and not the rule. Product ratings aside, due to the fact that "circle packing in a circle" is the least efficient with 2 circles, you probably wouldn't even be able to fit two 3/0's in that lug.

Terminals are only rated by default for one wire. The onus is on the manufacturer to get it listed and labeled otherwise, if they intend users to connect multiple wires. Typical two wire lugs are "snowman" shaped.
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I don’t follow lugs allow multiple wires not listed. So that means it would not comply with 110.3(b) and you can’t use them?
 
Carultch said:
If the product documentation doesn't specify otherwise, it is only rated for 1 wire.
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The reason why their is 2 sets of 3/0 AWG to 200A fused disco because the 2 sets of 3/0 is tapped from wire in trough that has 2 sets of 500 kcmil.

There are other wire tapped besides 2 sets of 3/0 to other disconnects from trough.

If one uses 1 set of 3/0 then would not it cause imbalance in 2 sets of 500kcmil cable in trough?
 
hhsting said:
The reason why their is 2 sets of 3/0 AWG to 200A fused disco because the 2 sets of 3/0 is tapped from wire in trough that has 2 sets of 500 kcmil.

There are other wire tapped besides 2 sets of 3/0 to other disconnects from trough.

If one uses 1 set of 3/0 then would not it cause imbalance in 2 sets of 500kcmil cable in trough?
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Indeed, you do not want to introduce an imbalance by only tapping one of the feeder sets in parallel, as they depend on the symmetry for their theory of operation. The code wording doesn't exactly state this, but the need for symmetry is strongly implied from the general rules for parallel conductors.

To resolve this situation, make your tap with a Polaris block or equivalent, that has 5 terminals. Bring the two sets of 500 kcmil together, initiate the 200A tap with 3/0 Cu, and use the two remaining terminals for the two sets of 500 kcmil that travel to the load. Another solution is to use a 400A disconnect, with 200A fuse reducers, so you have two tap destination terminals by design. Or anything else that allows the two sets in parallel, but this is rare for 200A & less equipment. Usually you are looking at 300A to 600A, where the manufacturer gives you two terminals by design.

If it were anything other than a tap, like a way to mitigate voltage drop on a feeder, you'd be able to use a 3-terminal Polaris block to step 2x 3/0 down to 1x 3/0, to terminate on the disconnect. But tap rules require that your conductors terminate in the overcurrent device, whether it is a breaker or fused disconnect. The tap rules don't allow you to terminate in anything other than an overcurrent device. Only the obscure 100 ft tap rule specifically disallows splices, but I wouldn't recommend relying on a 2-to-1 set reduction being considered "just a splice".
 
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