bonding

[rmonroe]

We have an area in our manufacturing plant that we are experiencing some strange volt readings. From the hot side to neutral we get 120 volts. From hot to ground we get 144 volts and from neutral to ground we are getting 24 volts. The transformer that supplies this panel in up in ceiling above a sea of equipment.

Is this a bond issue at this step down transformer?

Thanks

rmonroe

 

[bennie]

Re: bonding

Is this a recent development? What are the readings at the primary distribution panel?

[ March 16, 2004, 04:01 PM: Message edited by: bennie ]

 

[tom baker]

Re: bonding

What are you using for ground reference? How is that reference bonded to the transformer?
Open the secondary disconnect (turn it off) and have a qualified person check secondary voltage of the transformer.
And of course what comes out of the tranformer is dependant on what voltage goes in, check the primary as bennie suggested.

 

[rmonroe]

Re: bonding

I've been with the company for just a few months. From my understanding this condition has been with them for a long time. I checked the panel and I'm getting the same reading off the bus bars. This panel is feed by a single phase 35 KVA Dry type transformer. The neutral is not bonded to ground.

Thanks

rmonroe

 

[rmonroe]

Re: bonding

The primary is 480 Volt wye. The ground referance is building ground. The transformer frame is the only item bonded to ground.

 

[dereckbc]

Re: bonding

Originally posted by rmonroe:
The primary is 480 Volt wye. The ground referance is building ground. The transformer frame is the only item bonded to ground.

Seems to me you need to read 250.30. The Xo of the transformer needs bonded to building steel, then a MBJ to the transformer frame ground. Your Xo is floating.