120/208 delta high leg - voltage changed

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rustymetal

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120/208 High leg delta service
4 Wire- 208v[red A]/120v[black B]/120v[black C]/Green[service] and green[ground rod] bonded on N busbar. 1950's farm building.

I go to this service and problems.. the main breaker - not powering the C phase bus bar.
But a 240v/30A drain waste sub is back feeding into the C phase via the actual pump. The lights being powered via pump leg are quite a show.

The panel gets changed out.

During the change out I may have switched B/C phase.

After I put the meter back in the high leg is reading 320v to ground, 420v to phase B, 240 to C.

How can this be? When I pulled the meter there is clear a unacceptable level of corrosion... service conduit is not connect... fittings are just missing... The meter box is scheduled to be changed. But what did I do wrong?

How could I even change the voltage? Maybe I missed the grounding bushing? Corrosion at fault? Meter put in upside down?
 
Sounds like you may have left the neutral floating. See if voltages to neutral are the same, or check between neutral and ground.
 
Something is wrong with your voltage readings. I would start by pulling the meter again and measuring the all of the voltages from the utility.
 
LarryFine said:
Sounds like you may have left the neutral floating. See if voltages to neutral are the same, or check between neutral and ground.
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No, the B/C line are 120v to ground and 240v on phases. Only the high leg is testing off.
It's a cheap delta. Farm land.
Maybe corner grounded but again....I don't know how but a wire changed in the meter box.

Or something changed on the pole the exact same hour I had the meter out. I don't think so..

I will post again later today. I am going out with boss and we will check the drop lines.
When I encountered the 320v/420v.. you all know I stopped everything....
Forgot to check readings on lines in meter box..... If its in the wall between meter/panel. but alas confusion and lack of knowledge...
 
rustymetal said:
No, the B/C line are 120v to ground and 240v on phases. Only the high leg is testing off.
It's a cheap delta. Farm land.
Maybe corner grounded but again....I don't know how but a wire changed in the meter box.

Or something changed on the pole the exact same hour I had the meter out. I don't think so..

I will post again later today. I am going out with boss and we will check the drop lines.
When I encountered the 320v/420v.. you all know I stopped everything....
Forgot to check readings on lines in meter box..... If its in the wall between meter/panel. but alas confusion and lack of knowledge...
Click to expand...

Stopping everthing was good idea. Better to learn than burn.
 
rustymetal said:
High leg delta service
...
During the change out I may have switched B/C phase.

After I put the meter back in the high leg is reading 320v to ground, 420v to phase B, 240 to C.
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It sounds like you did switch the B and C phases. That would put the voltages across C-A and C-B at 120 degrees to each other, so that the A-B voltage is then 1.732 x 240V = 416V. The A-N would then be intermediate between A-B and A-C (which is at 240V) so that's why you measured 320V.
In order to do this reversal, you would need access to both ends of the B-C winding separate from the A-C windings. In other words, you made the open delta connection of the two windings.
 
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Those voltages sound like a polarity reversal on the POCO side.
Was there any work done on the bank while you were there?
Did you check voltage BEFORE you started work?
Maybe the whole issue was polarity reversal in the transformer that fed the wrong voltage to start with

I’d doesn’t matter how you switched the secondary wires, the phase voltages should be 240 and the high leg regardless of where it’s landed should be around 208.
 
Think of a delta triangle with angles of 60 degrees. The polarity reversal will make the angle 120 degrees.
 
The high leg should be coming into the meter on “C” phase, the meter will not work correctly if it is not. Then switches over to “B” phase to be code compliant. Still shouldn’t affect the high leg voltages though.
 
Hv&Lv said:
Those voltages sound like a polarity reversal on the POCO side.
Was there any work done on the bank while you were there?
Did you check voltage BEFORE you started work?
Maybe the whole issue was polarity reversal in the transformer that fed the wrong voltage to start with

I’d doesn’t matter how you switched the secondary wires, the phase voltages should be 240 and the high leg regardless of where it’s landed should be around 208.
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I agree, I think it may have been an existing problem.
 
poco transformer polarity reversed. call poco.

with A as the high leg, your possible B/C swap would only change the rotation. if you swapped A/C or A/B you would change rotation and put 208v on 120v circuits.
 
hillbilly1 said:
Batteries are low in your meter, or the poco f’ed up!
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hillbilly1 said:
The high leg should be coming into the meter on “C” phase, the meter will not work correctly if it is not. Then switches over to “B” phase to be code compliant. Still shouldn’t affect the high leg voltages though.
Click to expand...

A few points for some other posts..
--I checked all the voltages before I began. 208v to ground 240-B, 240-C. 4 Wire. Only 1 taped red and 1 taped green. . Grounding rod comes in different raceway.
--In my confusion of seeing 320v I used about 4 different meters. Including solenoid types etc. Meter problems were not issue.
--High leg was on A, I put it back to stop the breaker shuffle.
--No other work was done that we are aware of yet.

Sorry for the late reply friends. It reads 320v @ drop 100% from the transformer.
Also a nice touch, the smart meter displays voltages reading of each leg and displays error on the high leg when it rolls through it.

Poco is scheduled for this issue tomorrow sometime. I will update you all...
 
Polarity errors happen sometimes, even with seasoned linemen.

Transformers can be additive or subtractive depending on size. Mixed sizes like you get sometimes in a delta can be connected backwards if the poco crew is not paying attention.

They will sometimes get the polarity wrong even if the transformers are all the same. Even the experienced linemen get it wrong sometimes. They are taught polarity checking in school but forget sometimes or never got a good grasp of it to start with and blindly follow wiring diagrams without a clear understanding of what is going on.

This should have been caught with a voltage check but maybe they were in a hurry after changing or reconnecting the transformers.
 
mivey said:
Polarity errors happen sometimes, even with seasoned linemen.

Transformers can be additive or subtractive depending on size. Mixed sizes like you get sometimes in a delta can be connected backwards if the poco crew is not paying attention.

They will sometimes get the polarity wrong even if the transformers are all the same. Even the experienced linemen get it wrong sometimes. They are taught polarity checking in school but forget sometimes or never got a good grasp of it to start with and blindly follow wiring diagrams without a clear understanding of what is going on.

This should have been caught with a voltage check but maybe they were in a hurry after changing or reconnecting the transformers.
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I agree.
I get on our guys sometimes for the “left hot, right not” reasoning without paying attention to the data plate.
 
oldsparky52 said:
Was this question answered?
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OP stated no other work was done, but there is no way polarity swap can happen just by switching legs in a meter can or breaker panel. It has to be done either at the primary side or secondary side of the XF on the pole.
 
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