Thread: jumper at main

hmmm. i know its wrong but i cant come up with all the reasons.

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• Why would anyone do this? "Phase Jumper"

Three phase panel wired with single phase power.

The problem is the lug is only listed for use with one conductor.

Originally Posted by Jim Port

The problem is the lug is only listed for use with one conductor.

Plus the jumper is too small.

I also see, top left breaker (100 amp), which supplies SOMETHING and there is no neutral, and it looks like there is another similar cable behind it.

If that supplies another panel, that feeder needs to have 4 wires: 2-hot, 1-neutral, and 1-ground.

If that supplies equipment or appliance which is truly only 240 volts (and there is no 120 volt aspect in it), then those should be okay, but at 100 amp ... that is rather large for a single appliance.

Even if the wire were properly sized it would still be wrong for the reason I posted.

that 100 amp feeds a non service panel whose neutrals and grounds are not floated

the main service cables are 1/0 copper with a 200 amp block type fuse. lots of things for an electrician to do here.

Originally Posted by Jim Port

Even if the wire were properly sized it would still be wrong for the reason I posted.

I know, that's why I quoted you and said "Plus ... ".

Originally Posted by Jerome W. Young

that 100 amp feeds a non service panel whose neutrals and grounds are not floated

Not allowed.

Needs to be a 4-wire feeder cable.