480 3 phase to 120/208 sub panel

587 Views 13 Replies 6 Participants Last post by gpop, 14 d ago

Magick

Discussion Starter · 21 d ago

i have a 480 3 phase transformer that is feeding a 120/208 sub panel... the nuetral is just capped off and not connected and all circuit nuetrals are tied into the ground bar with the ground that came in from the transformer. is this proper ??? frome the 480 transformer, i have 2 legs/ground/nuetral... but again, the nuetral is just capped off

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backstay

· #2 · 21 d ago

Your sub is not 120/208 if the neutral is not connected.

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Magick

Discussion Starter · #3 · 21 d ago

backstay said:
Your sub is not 120/208 if the neutral is not connected.

when i take readings, each leg is 120 but together is 208... of course im reading from leg to ground since the nuetral isnt connected

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backstay

· #4 · 21 d ago

How can that be if the secondary mid tap(neutral) is not landed? Something you’re explaining is not correct.

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Magick

Discussion Starter · #5 · 21 d ago

Magick said:
when i take readings, each leg is 120 but together is 208

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Magick

Discussion Starter · #6 · 21 d ago

backstay said:
How can that be if the secondary mid tap(neutral) is not landed? Something you’re explaining is not correct.

perhaps the explanation is wrong... but by the looks of it in the pic... does that even look correct ??? if so, then what reading should i be getting ??? so i can try that tomorrow... heres a pic of the transformer label

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backstay

· #7 · 21 d ago

Then the center tap is grounded. Like this Mike Holt diagram. Your neutral needs to landed in the sub.

X0 needs to be landed in the sub and bonded to the ground.

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Magick

Discussion Starter · #8 · 21 d ago

backstay said:
Then the center tap is grounded. Like this Mike Holt diagram. Your neutral needs to landed in the sub.
View attachment 176565

ok... so whoever wired this sub wired it wrong... is that right??? the nuetral should connected, right ? as well, heres a pic showing the nuetral not even connected inside the transformer when coming to the sub

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backstay

· #9 · 21 d ago

Any 120 volt loads are now returning on the ground wire. That is a violation.

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Magick

Discussion Starter · #10 · 21 d ago

backstay said:
Any 120 volt loads are now returning on the ground wire. That is a violation.

exactly... this whole thing threw me off... never seen someone do this.. it threw me way off... i knew this was wrong lol... thanks

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ScooterMcGavin

· #11 · 20 d ago

Where is the green wire landed? Somehow the green wire is connected to the transformer X0. So it’s either landed on X0 directly or there is a bonding jumper in the transformer and it’s landed on the chassis of the transformer.

If X0 is bonded in the transformer and you’re bonded in the panel (which it appears that you are) double bonded which is not code compliant. If you want to bond at the transformer and run the neutral you would need to separate all the grounds and neutrals in the panel.

What’s even stranger to me is why they’re feeding a single phase panel with a three phase transformer? It will never be balanced not using the third leg.

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kb1jb1

· #12 · 20 d ago

ScooterMcGavin said:
Where is the green wire landed? Somehow the green wire is connected to the transformer X0. So it’s either landed on X0 directly or there is a bonding jumper in the transformer and it’s landed on the chassis of the transformer.

If X0 is bonded in the transformer and you’re bonded in the panel (which it appears that you are) double bonded which is not code compliant. If you want to bond at the transformer and run the neutral you would need to separate all the grounds and neutrals in the panel.

What’s even stranger to me is why they’re feeding a single phase panel with a three phase transformer? It will never be balanced not using the third leg.

That is what it looks like to me. Just switch the white wire with the green or you can pretend the green is really white and it is compliant. That is if all secondary bonding and grounding is done in the panel and no XO to case at the transformer. .