3ph to single temp

Are the breakers single or double pole? I don't think "eddy currents" are the problem.

InPhase277

single -
well .... if you connect ground to N bus and remove the N it wont trip the breakers but wont test .....
if I turn all 14 breakers on and touch the N to the bar - with NO LOAD - all trip at same time ....
I say eddiy but mean load imblance or some other reason it do this - dont really care what cause is (would be nice to know) but what the cure is!!!
Thank you for your time ....

ok ... its a 480 delta to 208 wye transformer taking X0 from the bar (marked X0) and drop A phase and send B and C phase to 240 panel - thought it wasnt grounded proprerly so re-grounded trans and also a new one to panel - with ground landed to N bus (single phase box) trips breakers .... take off N and keep ground and it dont trip breakers but wont test .... push the test button and it wont trip .....
touch the N back in panel and all breakers at same time trips ..... with no load.
tested voltage and no abnormal readings .....
and yes - GFCI are installed properly.

That is a good pic of transformer!

Ohh yes - this is a outside install
thanks

I'll take a stab at it...and probably be wrong. Is the transformer bonded? Is the panel bonded? If they are both bonded, maybe that is causing the GFI breaker to see an imbalance. (this sounded better in my head)
For troubleshooting purposes, the white wire off the GFI breaker could be hooked to either the ground or the nuetral, and it should test and operate correctly. Was there a voltage difference between ground and nuetral?

primary egc, transformer case, xo bonded ? (if xo is bonded at transformer then you should have isolated neutral bar at panel ?)

You can connect the neutral/ground of a transformer in one of two ways.

#1) As shown in the Mike Holt pic above. In that setup, the case of the transformer is connected to X0, and a separate neutral and ground are run to the 120/208 V panel, and kept separate there. The grounding electrode connects inside the transformer case.

#2) In this setup, X0 does not bond to the case. You need a bonding jumper from the 120/208 V panel back to the transformer case. The neutral and the ground are bonded in the panel. The grounding electrode connects to the ground in the panel.

You can bond ground and neutral at one location or the other, but not both. This may be the source of your trouble.

InPhase277

sorry for delay in respond to this!
I tryed it all ways and it not working .... try bond at Xmer try not .... try run ground for both trans and panel ..... still ....no work
Would guess that remove a phase was cause a imblance in there somewhere and that was cause it .... so need to get a 75kva SINGLE PHASE trans or 3 phase panel .....

Thanks for all your help

GFI's are over rated anyways. :laughing:

I agree -
But must have them on jobsite!

GFI Tripping

You could get a new xfmr and panel if you like, but your going to have the same problem.

fireupyours2 said:

single -
well .... if you connect ground to N bus and remove the N it wont trip the breakers but wont test .....
if I turn all 14 breakers on and touch the N to the bar - with NO LOAD - all trip at same time ....
I say eddiy but mean load imblance or some other reason it do this - dont really care what cause is (would be nice to know) but what the cure is!!!
Thank you for your time ....

Click to expand...

Since this post is over a month old, we can only assume you've solved the problem. If so, what did you find out?

That sticking around after people help you out is out of the question.