[RE-wrenches] Neutral to ground bond in a wye wound secondary

[William Miller]

Friends:

We came across an interesting situation in a local winery recently:

The service is 480 volts and the inverters are operating at 208 volts.  To 
make the two systems connect, the original installer integrated a 480 Delta 
to 208 Wye transformer, pretty standard procedure.

We found a stray voltage of 18 volts between the neutral and ground as 
measured in the AC combiner panel.  I noticed that there was no bond 
between the neutral and the ground in this panel.  I do not believe this is 
correct.  One reason is the stray voltage seems wrong.  Another, more 
important consideration is that I do not believe there is path for fault 
currents to return to the transformer.  In the case of a phase short to 
chassis, there would be no fault current to open the OCPD.

Is my analysis correct here?

Thanks in advance,

William Miller


Miller Solar
Voice :805-438-5600
email: william at millersolar.com
http://millersolar.com
License No. C-10-773985