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#### carryyourbooks

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I am installing a 3 phase 480/277 primary to 240/120 secondary. I have x1, x2, x3, x4. is the x4 the one to bond to ground?

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#### Switched

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Whatever happened to "The only stupid question is the one you didn't ask"?

Maybe it's been years since he's hooked one up and wants to double check himself before he effs it up.

#### sstlouis03

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Switched said:
Whatever happened to "The only stupid question is the one you didn't ask"? Maybe it's been years since he's hooked one up and wants to double check himself before he effs it up.
I helped out didn't I.

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#### Resiwireman

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If its 120/240 secondary, he would need to ground x2 the center tap, since x1 & x4 are the ungrounded conductors.

#### micromind

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If its 120/240 secondary, he would need to ground x2 the center tap, since x1 & x4 are the ungrounded conductors.
If it's 120/240 3ø, then it's a high-leg ∆ system.

Typically, X3 is the high leg, and X4 is the neutral, but not always.

If possible, power it up with nothing connected to the secondary side and measure voltages. You should have 120 from X4 to X1 as well as X4 to X2, and 208 from X4 to X3.

240 should be present from X1 to X2, X2 to X3, and X3 to X1.

If so, ground X4; it is the neutral.

#### carryyourbooks

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we had it figured out shortly after the OP. thanks to all that offered help. it had been several years since I had a delta xfmr, I had x0 on the brain.

#### Southeast Power

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I am installing a 3 phase 480/277 primary to 240/120 secondary. I have x1, x2, x3, x4. is the x4 the one to bond to ground?
You are going delta/delta.
One of the transformers are center tapped. You might be able to physically see it.
If not, don't take a chance, fire it up and see what voltages you have.
One of them will give you 120/120/208. This will be the center tapped one, all others will be 240 to each other.

#### brian john

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carryyourbooks
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