Whipsawed between the utility and the electrical inspector and the GFI requirement

[Ingenieur]

BINGO

This is also a perfect example of what I have been saying. You say "delta" , you never said ungrounded. Do you know if the left the wye ungrounded? If so, any reason you can't use an ungrounded wye?

they requested a delta
they got an ungrounded wye
the utility did not call it a delta

 

[electrofelon]

they requested a delta
they got an ungrounded wye
the utility did not call it a delta

Right, but they did apparently assume a floating wye would be equivalent and meet the clients needs. I agree they should inform the client of this though just in case it matters. Perhaps something like:

Utility : "please note we provide ungrounded 480 services, commonly called "delta" with a wye secondary. Please advise if this meets your needs."

 

[augie47]

IMO, Jaref's post (#3) is likely the most pertinent to the situation.
That said, in the past few years with our POCO's wanting to reduce transformer inventories, they have commonly supplied industrial delta systems with a wye pad and not bonded the XO in their transformer in any manner.

 

[jim dungar]

Yes, the utility transformer's secondary is wye.

I would bet, that if inventory is the issue, what you got was a Yg-Yg winding configuration.

Yg-Yg is not the same as a Y-Y. All of the letters are extremely important.

 

[electrofelon]

I would bet, that if inventory is the issue, what you got was a Yg-Yg winding configuration.

Yg-Yg is not the same as a Y-Y. All of the letters are extremely important.

Good point. Transformers normally meant for a MGN system would typically not be "unbondable". Maybe this utility doesn't have an mgn system.....I could see the utility taking the liberty of giving someone an ungrounded wye when they requested an ungrounded delta, but giving they a grnd wye when they requested delta with no communication seems like a pretty big leap!

 

[jim dungar]

...but giving they a grnd wye when they requested delta with no communication seems like a pretty big leap!

My customer found out when putting their 'utility acknowledged' pulsing NGR on-line caused several VFD's internal caps to fail explosively.

 

[electrofelon]

My customer found out when putting their 'utility acknowledged' pulsing NGR on-line caused several VFD's internal caps to fail explosively.

:rant:

 

[texie]

I would bet, that if inventory is the issue, what you got was a Yg-Yg winding configuration.

Yg-Yg is not the same as a Y-Y. All of the letters are extremely important.

Id make that bet as well. In this day and age I can't imagine any POCO agreeing to supply a new service with anything but a grounded Y unless there were some very special circumstances and had the Pope's blessing. As such Yg is the norm for most I'm familiar
with today.

 

[Ingenieur]

Right, but they did apparently assume a floating wye would be equivalent and meet the clients needs. I agree they should inform the client of this though just in case it matters. Perhaps something like:

Utility : "please note we provide ungrounded 480 services, commonly called "delta" with a wye secondary. Please advise if this meets your needs."

lol
pure speculation
we provide ungrounded wyes we call deltas
an ungrounded service is not commonly called a delta
although is usually IS a delta config
a delta is a delta, not a wye, entirely different configuration

if that's the case he doesn't need the full size neut only a egc between frames
after all the utility says it is a delta...correct?

 

[electrofelon]

lol
pure speculation
we provide ungrounded wyes we call deltas
an ungrounded service is not commonly called a delta
although is usually IS a delta config
a delta is a delta, not a wye, entirely different configuration

if that's the case he doesn't need the full size neut only a egc between frames
after all the utility says it is a delta...correct?

Whatever you say iggy

 

[electrofelon]

OP: please keep us posted on what you find out and what happens. Also, here is a past thread on ungrounded wyes:

http://forums.mikeholt.com/showthread.php?t=163092

 

[Ingenieur]

as was mentioned imo an ngr is the way to go
let's you know you have a fault and still operate
limits fault current
limits frame potential
can be bought as a package with protectinn

does the nec require a full sized neut with say a 25 A ngr?