To bond or not to bond. Neutral to ground.

[Roundeye]

I've really spent a few hours searching and reading this site to find the answer to my specific situation and I'm sure it's here somewhere but I'm tired of searching.:happysad: Looking for some answers...

I purchased my place 15 years ago and back then it only had a double wide trailer and a 200 amp service. No problems.

Since then, I've built a water house which I fed with a 100 amp main.

Then, I built the shop. (with permission from my wife) with a 125 amp main.

Then a new 6000 square foot house with an extension of the 4 wire system at 200 amps from the 200 amp meter that has the bonded ground and neutral. This house is 190 feet away from the shop.

I moved the 200 amp meter base to the shop at the same time I built the house because it was on a broken down pole in the middle of the driveway.

Here I have a 200 amp meter with a ufer to the shop bonded to the neutral at the main panel A.

I have a water house with a 100 main on this panel. 4 wire, with a separate ground and neutral. Sub panel B, not bonded and is 130 feet from the main panel at the shop.

At the house location, Sub panel C, I have another ufer bonded to the gec from the main panel A.

During this last winter, I had a situation where I had 98 volts to ground on either phase but I had 124 VAC to neutral.
At this time, during the summer, I have 124 VAC to ground and neutral.
For the life of me, I can't seem to figure out why this would happen.
NEC states that I don't bond the neutral and ground at Sub panel C in this scenario with multiple buildings but I can't help but wonder, if I did, would this solve my problem?


Let the beatings begin!:slaphead:

Additionally, at the shop, Main panel A, I have a 7KW enphase solar system and that panel is not bonded.

Seriously, any info or feedback would be greatly appreciated.
Thank you,
Bruce

 

[roger]

Bruce, the forum rules do not allow us to assist DIYers so with that said, I must close your thread.

This site is designed for:

• Contractors
• Electricians
• Engineers
• Inspectors
• Instructors
• Other electrically related individuals

* This NEC� Forum is for those in the electrical and related industries. Questions of a "How-To" nature by persons not involved in the electrical industry will be removed without notice.

Roger

 

[roger]

After exchanging PM's the OP is in the electrical industry so I am reopening this thread.

Roger

 

[ActionDave]

During this last winter, I had a situation where I had 98 volts to ground on either phase but I had 124 VAC to neutral.
At this time, during the summer, I have 124 VAC to ground and neutral.
For the life of me, I can't seem to figure out why this would happen.
NEC states that I don't bond the neutral and ground at Sub panel C in this scenario with multiple buildings but I can't help but wonder, if I did, would this solve my problem?


Let the beatings begin!:slaphead:

No beatings happen here.

If I follow what you typed correctly then your panels and feeders are wired correctly. What lead you to test your voltage in the winter and then the summer?

 

[GoldDigger]

...
During this last winter, I had a situation where I had 98 volts to ground on either phase but I had 124 VAC to neutral.
At this time, during the summer, I have 124 VAC to ground and neutral.
For the life of me, I can't seem to figure out why this would happen. ...

Seriously, any info or feedback would be greatly appreciated.
Thank you,
Bruce

Based just on the facts that you provide, by far the simplest explanation is that for some reason (I can't really speculate on what except maybe to cite temperature related expansion) the ground became unconnected. The ground pin of the receptacle was no longer connected via solid metal back to the panel EGC bus.
The 98V you measured from each phase to ground was simply a phantom voltage attributed to capacitive coupling and would have disappeared if you used a low input impedance meter.
At that point it would have been clear that the problem was an open ground.

 

[Roundeye]

No beatings happen here.

If I follow what you typed correctly then your panels and feeders are wired correctly. What lead you to test your voltage in the winter and then the summer?

This is at the house.
During this last winter, my geo-exchange heat pump was faulting on the controls side intermittently. No pattern, no certain time etc. I got on the phone with Climate Master and they had no answers but in our course of troubleshooting, I found I was getting 96 to 98 VAC to ground. On the neutral side, I was getting 124 VAC. Between ground and neutral, I had no volts but had 1.5 to 2.5 Ohms.
This summer so far, I've not had any faults. I have 124 VAC to ground and 124 VAC to neutral. Ohms from ground to neutral today are .2 and .3 :?

 

[Roundeye]

Based just on the facts that you provide, by far the simplest explanation is that for some reason (I can't really speculate on what except maybe to cite temperature related expansion) the ground became unconnected. The ground pin of the receptacle was no longer connected via solid metal back to the panel EGC bus.
The 98V you measured from each phase to ground was simply a phantom voltage attributed to capacitive coupling and would have disappeared if you used a low input impedance meter.
At that point it would have been clear that the problem was an open ground.

I would have to agree but I was measuring this ground from each phase at sub panel C (which is the house).

 

[Smart $]

...The 98V you measured from each phase to ground was simply a phantom voltage attributed to capacitive coupling and would have disappeared if you used a low input impedance meter. ...

I would have to agree but I was measuring this ground from each phase at sub panel C (which is the house).

Consider perhaps the feeder EGC became electrically disconnected at panel A.

 

[kwired]

Put a 1000-1500 watt load on the EGC and see what kind of voltage drop you get. If not too bad of a drop leave it running for maybe 15 - 30 minutes and see if a compromised connection gets worse.

 

[JFletcher]

This is at the house.
During this last winter, my geo-exchange heat pump was faulting on the controls side intermittently. No pattern, no certain time etc. I got on the phone with Climate Master and they had no answers but in our course of troubleshooting, I found I was getting 96 to 98 VAC to ground. On the neutral side, I was getting 124 VAC. Between ground and neutral, I had no volts but had 1.5 to 2.5 Ohms.
This summer so far, I've not had any faults. I have 124 VAC to ground and 124 VAC to neutral. Ohms from ground to neutral today are .2 and .3 :?

As others have said, bad ground. A 120V fault to ground at 2.5 ohms would be 48A, which would be quite bad if it happened on a 50A circuit.

 

[Roundeye]

Consider perhaps the feeder EGC became electrically disconnected at panel A.

And walla! I found that when the solar installer set his new panel, next to the meter panel A, they rerouted the main EGC to house panel C at panel A, leaving it loose in the buss bar!
Thanks for all the help! I was banging my head over this.
Cheers!

 

[cpinetree]

May I suggest, for your solar installer - Let the beatings begin!