help with voltage & phase mystery

[olc]

Building has two services (two meters each with separate drops from the pole).
One for a regular 1 phase 3 wire panelboard.
One that ultimately serves a 3 phase air conditioner.

See the photo of the disconnect. The middle phase is grounded (and not fused). In from the meter at the top and out to the air conditioner on the bottom left.
I am 90% sure that the third wire connects to the carrier cable at the mast above.
Is it possibly 3 phase delta with a grounded corner? Is this how it would be wired?

I have photos of the masts and the connection at the transformer.

It is 1-1/2 hours away and I did not have a meter with me.


P.S. That phone at the bottom of the photo is actually a dial telephone.

 

[templdl]

Building has two services (two meters each with separate drops from the pole).
One for a regular 1 phase 3 wire panelboard.
One that ultimately serves a 3 phase air conditioner.

See the photo of the disconnect. The middle phase is grounded (and not fused). In from the meter at the top and out to the air conditioner on the bottom left.
I am 90% sure that the third wire connects to the carrier cable at the mast above.
Is it possibly 3 phase delta with a grounded corner? Is this how it would be wired?

I have photos of the masts and the connection at the transformer.

It is 1-1/2 hours away and I did not have a meter with me.


P.S. That phone at the bottom of the photo is actually a dial telephone.




View attachment 12717

What did you say the service entrance was, 3ph3w or 3ph4w, a 240 or 480v delta corner grounded 'B', 240/120v 3ph4w or a 3ph4w 208y/120 or 480y,/277v wye.
But saying that the center pole has a solids link and the outer poles are fused I would like to understand that you may have a 3ph3w 240v corner grounded 'B' phase.

 

[Tony S]

Building has two services (two meters each with separate drops from the pole).
One for a regular 1 phase 3 wire panelboard.
One that ultimately serves a 3 phase air conditioner.

See the photo of the disconnect. The middle phase is grounded (and not fused). In from the meter at the top and out to the air conditioner on the bottom left.
I am 90% sure that the third wire connects to the carrier cable at the mast above.
Is it possibly 3 phase delta with a grounded corner? Is this how it would be wired?

I have photos of the masts and the connection at the transformer.

I think it would be a good idea to post them.

 

[olc]

I think it may be 240V open corner grounded delta?

 

[olc]

Mast on the right is the one in question. The one on the left is the normal service (regular 120/240 1ph).

 

[olc]

The arrows point at the two drops to the building.
I don't know which is which as they run together on the way (out of the picture) so I can't follow which is which.

 

[kwired]

The arrows point at the two drops to the building.
I don't know which is which as they run together on the way (out of the picture) so I can't follow which is which.
View attachment 12725

hard to see enough details and would be nice to know what is at other poles in the area.

It is possible the bottom three individual conductors on the insulator rack are 120/240 single phase - the right side is connected to the transformer on that pole - the left side is hard to tell if it is a separate system or if there are jumpers on back that connect to the right side.

The top "triplex" cable on the insulator rack may possibly be corner grounded delta with source at another pole.

More common around here would just be a open delta system but the "high leg" transformer would be smaller capacity and they would just make one quad plex drop to your facility in question - even if it still fed both a single and three phase service disconnecting means.

I guess I shoulnd't say more common - that is what it will be - corner grounded systems are no longer supplied by any utility in this area, too many non qualified people messing with wiring and such systems just don't go together well, at least with grounded neutral systems you cut voltage to ground to a lower level, though you could find separately derived systems on a premises that are corner grounded in some instances.

 

[olc]

Update - Someone put a meter on it for me. It is 240V between all 3.
So the only question is - is it open delta or not? (I'm not sure open delta even exists)
This may all be moot as I may rip out both services to put in a new as part of the renovation. But it has my interest. I'll ask the utility.

 

[ActionDave]

You will get Voltage to ground to know if it is a corner ground or open. The utility may not know.

 

[don_resqcapt19]

Update - Someone put a meter on it for me. It is 240V between all 3.
So the only question is - is it open delta or not? (I'm not sure open delta even exists)
This may all be moot as I may rip out both services to put in a new as part of the renovation. But it has my interest. I'll ask the utility.

If it is open delta there will be two transformers, and if it is a full delta, there will be 3. You can have a corner grounded system on either.

 

[kwired]

Transformer in your picture is not the source, or at least is only part of the source with the rest on other pole(s). Most POCO put all transformers of same bank on same pole or if they are too large for one pole will put them on structures that are very close to one another.

 

[olc]

Thanks for the replys.