Hot neutral on 120/208 secondary?

[Spacious Ideas]

I have discovered a hot neutral in a panel board and at the distribution transformer. A pen tester and two meters confirm around 117v between primary feeder’s EGC and secondary Neutral or EGC. There is no system bonding jumper in transformer OR panel board that I can see. There is only a lug on one side to accept the primary EGC and same on opposite side for secondary EGC (no common terminal block just connected via enclosure).

I know the SBJ needs installed but I want to move forward safely. Also what about circuit breakers and fuses trip/blowing or other problems that may show up after there is SBJ.

Thanks ahead of time for responses.

 

[infinity]

Well the SBJ needs to be installed. As for opening an OCPD wiring a ground fault it's probable that it won't open without the SBJ. Once installed the system should operate normally if everything else is done correctly. I'm guessing that there is no GEC either?

Welcome to the Forum.

 

[Spacious Ideas]

It has been inspected before and had an arc flash study and sticker in 2019. I have been at this facility for 6 months so still new. It has 6-7 different services due to evolution and multiple buildings Many of other electricians have came before me. Manufactured date on xfmr is 2006.

The Hot neutral is odd though and do not k pe if SBJ will fix that. It is 117v also not 67v or some stray voltage number?

 

[hillbilly1]

Once the SBJ is installed, and you turn it back on, you will most likely find a tripped breaker somewhere. An easy way to locate the circuit before hand, is to go through turning off individual breakers one at a time until the voltage goes low, such as 40-50 volts, or less before you put the bond in.

 

[Spacious Ideas]

Once the SBJ is installed, and you turn it back on, you will most likely find a tripped breaker somewhere. An easy way to locate the circuit before hand, is to go through turning off individual breakers one at a time until the voltage goes low, such as 40-50 volts, or less before you put the bond in.

Awesome
Good idea

 

[infinity]

The Hot neutral is odd though and do not k pe if SBJ will fix that. It is 117v also not 67v or some stray voltage number?

Not sure what the bold means but installing the SBJ should solve the problems with the neutral to EGC readings which should be 0. Unless you're reading that 117 volts with one of these the number might not be accurate.

 

[Spacious Ideas]

Thank you
I guess I need grammarly

 

[wwhitney]

To put things another way, if you hook up a light bulb between the primary EGC and the secondary neutral, it shouldn't glow. That 117V you are reading is almost certainly due to capacitive coupling and will only show up when you use a high-impedance meter.

Now if the light bulb does glow, and you do install an SBJ, you can expect something interesting to happen when you repower the system. That would be where post #4 is applicable.

Cheers, Wayne

 

[Spacious Ideas]

To put things another way, if you hook up a light bulb between the primary EGC and the secondary neutral, it shouldn't glow. That 117V you are reading is almost certainly due to capacitive coupling and will only show up when you use a high-impedance meter.

Now if the light bulb does glow, and you do install an SBJ, you can expect something interesting to happen when you repower the system. That would be where post #4 is applicable.

Cheers, Wayne

I appreciate the response. No surprises for me. I will continue safely finding possible ground faults via breaker flipping and reading neutral voltage readings before adding the SBJ.
I will have to admit that my pen tester has been helpful with this. Neutrals should not glow.

 

[Spacious Ideas]

To put things another way, if you hook up a light bulb between the primary EGC and the secondary neutral, it shouldn't glow. That 117V you are reading is almost certainly due to capacitive coupling and will only show up when you use a high-impedance meter.

Now if the light bulb does glow, and you do install an SBJ, you can expect something interesting to happen when you repower the system. That would be where post #4 is applicable.

Cheers, Wayne

Same reading with LoZ meter.

 

[wwhitney]

Same reading with LoZ meter.

Ah, that makes it more interesting. What's the impedance of the LoZ meter? [For my own edification, I would be tempted to try the incandescent light bulb test, along with measuring the voltage drop across the light bulb if it glows. A 60W incandescent bulb is about 240 ohms.]

Anyway, that makes post #4 a good approach.

Cheers, Wayne

 

[wwhitney]

P.S. If you measure the voltage from the secondary line conductors to the primary EGC, are any of them near zero? If so, that will tell you which line conductor has a ground fault that is causing your secondary neutral to be 120V to ground. A ground fault that a properly installed SBJ would have caused to trip a breaker, but which didn't, as before that ground fault occurred, the secondary was ungrounded.

Cheers, Wayne

 

[Spacious Ideas]

Ah, that makes it more interesting. What's the impedance of the LoZ meter? [For my own edification, I would be tempted to try the incandescent light bulb test, along with measuring the voltage drop across the light bulb if it glows. A 60W incandescent bulb is about 240 ohms.]

Anyway, that makes post #4 a good approach.

Cheers, Wayne

I think 3k

 

[Spacious Ideas]

P.S. If you measure the voltage from the secondary line conductors to the primary EGC, are any of them near zero? If so, that will tell you which line conductor has a ground fault that is causing your secondary neutral to be 120V to ground. A ground fault that a properly installed SBJ would have caused to trip a breaker, but which didn't, as before that ground fault occurred, the secondary was ungrounded.

Cheers, Wayne

The A phase reads around 3v to ground. B and C read 205v ish to the same ground.


I have two breakers that when turned off secondary neutral goes back to normal and so do all voltage readings. No voltage to ground at the neutral and pen tester does not light up.
The single pole breaker (120v with neutral) does put some voltage on the neutral but the main culprit seems to be the 2pole with no neutral.
1 x 2pole (no neutral)
1 x 1 pole (with neutral)

This is with the floating neutral

So it sounds like there are two problems then???

1- No SBJ which equals a floating neutral

2- A ground fault on one of two hots from a 2 pole 20 amp breaker and possibly the single pole as well that cause the neutral to have 120v to ground.

This ground fault brings the A phase voltage down to around 3 v and B and C phase are both brought up to around 205v to ground?

So if the inspector and previous electrician did their job correctly and SBJ was installed this ground fault would have most likely tripped its breaker and revealed itself ?

 

[Tulsa Electrician]

Since there is no SBJ, is there a GEC.
Also the secondary EGC as you call it, sized correctly as an SSBJ.

Move forward safely by shutting it down before making any corrections. I take it's an SDS since you are referring to it as a SBJ and not an MBJ.

We do like pics.

 

[Spacious Ideas]

P.S. If you measure the voltage from the secondary line conductors to the primary EGC, are any of them near zero? If so, that will tell you which line conductor has a ground fault that is causing your secondary neutral to be 120V to ground. A ground fault that a properly installed SBJ would have caused to trip a breaker, but which didn't, as before that ground fault occurred, the secondary was ungrounded.

Cheers, Wayne

The A phase reads around 3v to ground. B and C read 205v ish to the same ground.


I have two breakers that when turned off secondary neutral goes back to normal and so do all voltage readings. No voltage to ground at the neutral and pen tester does not light up.
The single pole breaker (120v with neutral) does put some voltage on the neutral but the main culprit seems to be the 2pole with no neutral.
1 x 2pole (no neutral)
1 x 1 pole (with neutral)

This is with the floating neutral

So it sounds like there are two problems then???

1- No SBJ which equals a floating neutral

2- A ground fault on one of two hots from a 2 pole 20 amp breaker and possibly the single pole as well that cause the neutral to have 120v to ground.

This ground fault brings the A phase voltage down to around 3 v and B and C phase are both brought up to around 205v to ground?

So if the inspector and previous electrician did their job correctly and SBJ was installed this ground fault would have most likely tripped its breaker and revealed itself ??

Once the SBJ is installed, and you turn it back on, you will most likely find a tripped breaker somewhere. An easy way to locate the circuit before hand, is to go through turning off individual breakers one at a time until the voltage goes low, such as 40-50 volts, or less before you put the bond in.

Thank you
That fruited

 

[Spacious Ideas]

Since there is no SBJ, is there a GEC.
Also the secondary EGC as you call it, sized correctly as an SSBJ.

Move forward safely by shutting it down before making any corrections. I take it's an SDS since you are referring to it as a SBJ and not an MBJ.

We do like pics.

Yes, it is a separately derived system and do not know if SSBJ is sized correctly but it looks in the ball park but I will have to check.

Missing System bonding jumper (XO to EGC)

 

[wwhitney]

1- No SBJ which equals a floating neutral

2- A ground fault on one of two hots from a 2 pole 20 amp breaker and possibly the single pole as well that cause the neutral to have 120v to ground.

I believe your observations are all consistent with this theory, and proceeding on that basis makes sense. Obviously if you fix 1 before fixing 2, the breakers should trip. Not sure if it makes more sense to try to find the ground fault(s) before adding the SBJ--one of the more experienced electricians here may have an opinion.

Cheers, Wayne

 

[hillbilly1]

I believe your observations are all consistent with this theory, and proceeding on that basis makes sense. Obviously if you fix 1 before fixing 2, the breakers should trip. Not sure if it makes more sense to try to find the ground fault(s) before adding the SBJ--one of the more experienced electricians here may have an opinion.

Cheers, Wayne

I think the op would be ok installing the SBJ at this point, leaving the double pole breaker off, locate the load and troubleshoot that circuit.

 

[LarryFine]

I suggest being ready to kill the power in case an arcing fault or something similar develops.

Or maybe use a high-wattage bulb as a temporary MBJ while you troubleshoot so the breaker doesn't trip.

This is similar to my suggestion of a bulb in series with the breaker while searching for a short.