Voltage on hose bib...

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How about we get back to basics?

Here is what I would do.

  • I would shut the panel down

  • I would carefully lift any GEC connections and isolate them from the neutral

  • While the panel was off I would measure voltage on the line side of the main

  • L1 to N

  • L2 to N

  • L1 to L2

  • Note the readings

  • Now leaving L2 and any two pole loads off I would load L1 as much as possible and take the readings

  • L1 to N

  • L2 to N

  • L1 to L2

  • Note the readings

  • Now leaving L1 and any two pole loads off I would load L2 as much as possible and take the readings

  • L1 to N

  • L2 to N

  • L1 to L2

  • Note the readings

Now if the both the N to L1 and N to L2 voltages remained fairly steady I would have to rule out a neutral problem.

However if both L to N voltages where changing I would continue on my pursuit of a neutral issue somewhere between the panel and the secondary side of the transformers.

This is not complicated, it is simple straight forward trouble shooting we do all the time.
 
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Thanks for everyone's insight, The only way I didn't take test the situation was with the GEC's isolated from the system, which I will test next visit out. I'll keep you posted. :)
 
iwire said:
The change in load on the primary side of the trans would be almost nil.

I think 60 amps of added load at the house would be about 1 amp on the primary given a 13.8KV primary.

So while possible it seems unlikely in my opinion.
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If primary is line to neutral and voltage is 7200 the 60 amp secondary increases the primary by 2 amps. If primary voltage is 2400 then 60 amp secondary current increases primary by 6 amps.

The lower the primary voltage the more likely this could happen.

It should take 288 ohms of resistance to lower 7200 volts by 25. That resistance will not only be a bad connection but will also factor in resistance of earth paths that current flows through. The earth paths are much more unpredictable and the bad connection could be well over 288 ohms. Yet the effect on the transformer secondary is virtually unnoticeable other than possible neutral to earth voltages.

OP does need to rule out secondary neutral problem first by heavily loading it on just one side and checking voltage. If that isn't the problem he needs to get POCO to check their distribution system.
 
kwired said:
If primary is line to neutral and voltage is 7200 the 60 amp secondary increases the primary by 2 amps.
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1 amp, 2 amps, OK, lets thread this needle some more. :D

I have always gone with the obvious first and work back toward the less obvious.

OP does need to rule out secondary neutral problem first by heavily loading it on just one side and checking voltage.
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Without a doubt.
 
iwire said:
1 amp, 2 amps, OK, lets thread this needle some more. :D

I have always gone with the obvious first and work back toward the less obvious.




Without a doubt.
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Only stickboy knows what he did. From his description sounds like he tried to eliminate the possibility of a secondary neutral problem, we are just asking him to double check in case he did miss something. If he is indeed right then we still don't know exactly what the problem is but do have some predetermined direction to go with it.

Based on what he has said so far I still think there is a problem somewhere on the primary side of the transformer.
 
If the problem is on the primary side of the transformer, the voltage should not go away when the main is off unless this building is the only thing fed from the secondary of that transformer.
 
While everything has been covered, remember a primary neutral (MGN) could have been lost down the road and the bad section can be feeding more then one transformer increasing the load on the bad portion of the MGN, I know it's a reach but possible?

But as Don said, the voltage would have not gone away or at least not dropped by much.
 
kwired said:
Only stickboy knows what he did. From his description sounds like he tried to eliminate the possibility of a secondary neutral problem, we are just asking him to double check in case he did miss something. If he is indeed right then we still don't know exactly what the problem is but do have some predetermined direction to go with it.

Based on what he has said so far I still think there is a problem somewhere on the primary side of the transformer.
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The one thing I didn't do was lift the GEC's from the equation, which I wish i did at the time, but i did load up each leg best I could and checked for odd voltage readings...

My boss was going back this afternoon to do final evaluation of situation, I told him to isolate the GEC'S from the panel and re test the voltage with the panel heavily loaded... see if anything changes.
 
I'm going with bad primary neutral on this one too. I don't think I'd lift the GEC unless I knew for sure that it was the only service in the area.

What I would check is if the hose bib is the only ground with voltage or whether the neutral/ground bonding point and/or the neutral in the meter socket is also giving a reading or not to various reference points outside of the house, up to 50 feet away, in various directions. Until you can show that it's not only the hose bib, the POCO guys are just going to try and throw it back in your lap.

This issue can be a dog to get the POCO to react to since most of the first tier troubleshooters don't have the knowledge to confirm it. It sometimes helps to call them out enough times that they finally send a higher tier troubleshooter. It's easier if you have an overhead line and can find a splice on it as a likely culprit, but with underground primaries there's nothing to point to. I've heard there was a cable used by many POCOs with a bare concentric neutral that corrodes away after a number of years - maybe mention that?
 
Final outcome, bad primary neutral, I did suggest this to my boss early on, anyways... POCO is on it, they ran a temporary neutral from the street, out of my hands at least, the only thing I didnt like was the way they treated the situation, and basically blew us off and left it "our" problem.
 
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