Three Phase / transformer/ neutral?

[mike n]

Recently at the educational institution I work at, a new electrical service was installed.The new service is configured as 120/208 4 wire delta.
A 120/240 delta - 120/208 Y transformer was also installed to feed existing 120/240 loads.The transformer was back fed to obtain 120/240. No neutral was brought over,so XO was left not used and isolated.The distribution panel for this 120/240 load does not have a ground reference to any of the phases (0 volts to ground).So whats the deal,is this install correct? safe/unsafe.
thanx in advance

 

[hassaf]

Re: Three Phase / transformer/ neutral?

There seem to be discrepencies of what you're describing. So let me re-word what you've said and you can confirm if it's correct:

The new service is 120/208Y 3ph 4w (not delta). a new step-up transformer was installed to feed existing 240V loads. So the primary is 208V and secondary is 240V.

The primary feeder to the step-up transformer is three conductors w/Gnd and no neutral. And you're question is why we didn't bring a neutral with the primary feeder to the step-up transformer. Please confirm this set-up!

 

[don_resqcapt19]

Re: Three Phase / transformer/ neutral?

There is no need to land a conductor on XO on the 120/208 side. You need a system bonding jumper, a grounding electrode and a grounding electrode conductor on the 120/240 side.
Don

 

[mike n]

Re: Three Phase / transformer/ neutral?

THANX FOR YOUR REPLY,
They back fed the transformer,the 208v went to (the secondary),X1-X2-X3, and 240v is measured at H1-H2-H3 (primary).

 

[pierre]

Re: Three Phase / transformer/ neutral?

Mike
If the secondary side of the transformer is feeding 3 phase loads only, than you need to have a bond between the secondary side of the transformer and the panel/disconnect it is feeding. If there are neutral to phase loads, this installation is not to code, and will be a problem.

0 volts to ground sounds like a problem to me.