Main panel neutral and grounding

[PoorUB]

In a main breaker panel, is the neutral buss supposed to be bonded to to the ground bus?

Is the box itself supposed to be bonded to the ground bus?

Seems to me the neutral bus is not supposed to be directly bonded to the box itself, but to the ground bus, then to the box.

The reason I ask is a buddy was asking. He told me he checked voltage from the main to the breaker box and got like 10 volts. I was under the impression he should see 120 volts, just like measuring to neutral. He wasn't sure the box was grounded. The house is about 15 years old and he did mention that the neutal and ground wires were sharing the same bus bar. It seems to me his box is not grounded.

Any sparkies want to clear this up?

 

[PCustoms]

Need more details but in general a main panel has ground and neutral bonded, and it is technically the neutral buss that gets bonded to the ground/panel.

 

[mike93lx]

As long as it is the first means of disconnect the neutral and ground are bonded.

Are there any grounds going to a water line, rods or a ufer?

 

[loganb]

As said above...it's the first means of disconnect off the service where the bonding of neutral to ground occurs. If there is a disconnect at the meter before it goes to the "main" panel at the structure...that generally means it's bonded at that disconnect and must remain separate at all panels after that

 

[dave*99]

In a main breaker panel, is the neutral buss supposed to be bonded to to the ground bus?

Is the box itself supposed to be bonded to the ground bus?

Seems to me the neutral bus is not supposed to be directly bonded to the box itself, but to the ground bus, then to the box.

The reason I ask is a buddy was asking. He told me he checked voltage from the main to the breaker box and got like 10 volts. I was under the impression he should see 120 volts, just like measuring to neutral. He wasn't sure the box was grounded. The house is about 15 years old and he did mention that the neutal and ground wires were sharing the same bus bar. It seems to me his box is not grounded.

Any sparkies want to clear this up?

If the neutral and ground wires are sharing the same bus in the main, that's normal.

It seems you are saying there is possibly an elevated voltage on the steel box itself. Is that correct?
Measure voltage from the steel box to the ground/neutral bus and confirm it to be zero.

Once confirmed, you should see 120V from each of the 2 service legs to ANY of the following:
Neutral
Ground
Box.

And ZERO between any two of the following: neutral, ground and box

 

[sparky 1971]

In a main breaker panel, is the neutral buss supposed to be bonded to to the ground bus?

Is the box itself supposed to be bonded to the ground bus?

Seems to me the neutral bus is not supposed to be directly bonded to the box itself, but to the ground bus, then to the box.

The reason I ask is a buddy was asking. He told me he checked voltage from the main to the breaker box and got like 10 volts. I was under the impression he should see 120 volts, just like measuring to neutral. He wasn't sure the box was grounded. The house is about 15 years old and he did mention that the neutal and ground wires were sharing the same bus bar. It seems to me his box is not grounded.

Any sparkies want to clear this up?

The neutral comes from the factory isolated. There is a bonding screw or jumper that needs to be installed which will bond it to the panel. Additional ground bars will be bonded through the mounting screws.

There should be 120 from hot to panel. Since the grounds and neutrals are landed on the same bar, it's a fairly safe bet to say this is the main panel. The bonding screw might not be installed. Sometimes they are stuck in the hole but not run in from the factory. Have him put a screwdriver on the green screw and see if he can tighten it up. At 15 years old, I doubt it has a bonding strap, but if there isn't a green screw, have him check for a phony little metal tab that would land on the neutral and then bend around to a screw in the panel. One time I had a bonding screw that wouldn't get tight, I used a ground bar and a piece of #4 copper from it to the neutral to git 'r done. He also might just need to scrape some paint away. Have him try measuring voltage from a hot to a cover screw hole.

Everyone stating the the first means of disconnect needs to have the neutral and ground bonded are almost right. It's the first point of over current protection, and that is USUALLY also the first means of disconnect, but not always. And, even if it is the first point of overcurrent protection and the first means of disconnect, something mechanical (usually a bonding screw) has to be installed to bond the panel itself to the neutral. All the ground wires in the world landed on the neutral bar isn't going to cause a meter to see 120 volts from hot to the metal of the panel.

 

[mike93lx]

It's the first point of over current protection,

Interesting. I've never seen this distinction mentioned.

Thanks

 

[sparky 1971]

Interesting. I've never seen this distinction mentioned.

Thanks

The only places I can think of where it matters is POCO supplied disconnects, especially REC's. They have pole top disconnects and sometimes they set transformer with customer access to the load side terminals and there will be a non fused disconnect built in to that. I vaguely remember a long time ago it seems like we installed a non fused disconnect for a multi meter service ahead of the meters. Each tenant space then had a meter with a main breaker outside and each of those was then bonded.

 

[PoorUB]

It seems you are saying there is possibly an elevated voltage on the steel box itself. Is that correct?
Measure voltage from the steel box to the ground/neutral bus and confirm it to be zero.

I am assuming it is some weird stray voltage that his VOM is picking up.

Line to the box was 10 and 14 volts depending on which leg he measured from.

Once he bonds the box to the ground I am fairly certain it will go away.

 

[PoorUB]

The neutral comes from the factory isolated. There is a bonding screw or jumper that needs to be installed which will bond it to the panel. Additional ground bars will be bonded through the mounting screws.

I assume the boding strap or screw was never attached or run in.

I also assume the voltage he is reading from line to the box is just stray voltage that his VOM is reading. Once the ground is bonded it will go away.

 

[wyliesdiesels]

The box is floating so there is no path to neutral.

 

[MBfreak]

Floating metal box? Can that really be code compliant.
I admit that I know absolytely nothing about US domestic electricity and rules and regulations for same.
Bot tons more of electrical circuits.
Som kind of box internal insulation fault can energize the metal box and offer a surprise to whoever touches the box.

Ola

 

[dave*99]

Floating metal box? Can that really be code compliant.
I admit that I know absolytely nothing about US domestic electricity and rules and regulations for same.
Bot tons more of electrical circuits.
Som kind of box internal insulation fault can energize the metal box and offer a surprise to whoever touches the box.

Ola

It's not compliant. There is likely a missing bond (screw) between the box and the neutral/ground buss.

 

[PoorUB]

The neutral comes from the factory isolated. There is a bonding screw or jumper that needs to be installed which will bond it to the panel. Additional ground bars will be bonded through the mounting screws.

There should be 120 from hot to panel. Since the grounds and neutrals are landed on the same bar, it's a fairly safe bet to say this is the main panel. The bonding screw might not be installed. Sometimes they are stuck in the hole but not run in from the factory. Have him put a screwdriver on the green screw and see if he can tighten it up. At 15 years old, I doubt it has a bonding strap, but if there isn't a green screw, have him check for a phony little metal tab that would land on the neutral and then bend around to a screw in the panel. One time I had a bonding screw that wouldn't get tight, I used a ground bar and a piece of #4 copper from it to the neutral to git 'r done. He also might just need to scrape some paint away. Have him try measuring voltage from a hot to a cover screw hole.

Everyone stating the the first means of disconnect needs to have the neutral and ground bonded are almost right. It's the first point of over current protection, and that is USUALLY also the first means of disconnect, but not always. And, even if it is the first point of overcurrent protection and the first means of disconnect, something mechanical (usually a bonding screw) has to be installed to bond the panel itself to the neutral. All the ground wires in the world landed on the neutral bar isn't going to cause a meter to see 120 volts from hot to the metal of the panel.

The plot thickens.
His meter sits in his yard. There is a breaker panel at the meter with two breakers, one for house and one for his shop. It also has a couple breakers for outlets mounted at the meter. Would this be considered his main panel and the house and shop panels sub panels?

If so and considering the house is 15 years old, pus the ground and neutral wires in the panel are sharing bus bars. I was thinking the box needs to be grounded, no question. Back in 2006 was it approved to share neutral and ground on the same bus? Then bond that mixed bus to the box?

Would it be reasonable for him to update the wiring and separate the neutral and ground wires and then bond the panel to the ground buss?

My understanding in a sub panel you have a ground buss and a neutral bus and they are not bonded in the sub panel. but they are in the main panel.

 

[mike93lx]

Yes, the house panel is a sub and should not be bonded. Neutrals and grounds needs to be separated.

 

[mm08822]

Pics of all panels opened will probably be the easiest way to determine cause and remedy.

 

[sparky 1971]

The code changed in 2008. A 2006 house could very well have a three wire feeder which would require the neutral in the house panel to be bonded. Since there are neutrals and grounds on the same bar, I suspect this is the case. Photos would help, but are there three or four wires feeding the panel? If four, the neutral should be isolated and separate ground bars put in. If three, everything can be lumped together, but some sort of mechanical bond needs to happen.

 

[sparky 1971]

Yes, the house panel is a sub and should not be bonded. Neutrals and grounds needs to be separated.

That happened with the 2008 code. Before that, a three wire feeder to a separate structure was permissible.

 

[PoorUB]

but are there three or four wires feeding the panel?

Three wire.

But the box should be bonded to the neutral/ground bus, correct?

 

[sparky 1971]

Correct. But only because it's three wires.

 

[wyliesdiesels]

Floating metal box? Can that really be code compliant.
I admit that I know absolytely nothing about US domestic electricity and rules and regulations for same.
Bot tons more of electrical circuits.
Som kind of box internal insulation fault can energize the metal box and offer a surprise to whoever touches the box.

Ola

nope its not compliant. the bonding is missing...

 

[wyliesdiesels]

That happened with the 2008 code. Before that, a three wire feeder to a separate structure was permissible.

as long as there were no parallel metallic pathways

 

[wyliesdiesels]

The neutral comes from the factory isolated. There is a bonding screw or jumper that needs to be installed which will bond it to the panel. Additional ground bars will be bonded through the mounting screws.

Ive seen meter mains with neutral bars that are bolted to the enclosure. no bonding screw or strap needed

 

[sparky 1971]

as long as there were no parallel metallic pathways

Yes but since it's a pedestal service, I doubt that's the case in this instance.

 

[sparky 1971]

Ive seen meter mains with neutral bars that are bolted to the enclosure. no bonding screw or strap needed

I was too general. I should have specified panels. I've never seen a meter main that wasn't bonded.

 

[PoorUB]

Well, all is good again. I had a discussion with my buddy and it seems the neutral/ground bus was bonded to the box. He just doesn't know you need a bare metal surface for your probe to measure voltage!

He went back and looked at both panels and found the bonding screw/jumper and checked voltage from the mains to a bare spot, (screw hole) and he gets the same reading as measuring to the neutral bar.

I told him to stop F'ing with stuff that isn't broke!

This whole thing started when he decided to tighten terminal screws and then he started measuring voltages.

 

[PCustoms]

He just doesn't know you need a bare metal surface for your probe to measure voltage!

I told him to stop F'ing with stuff that isn't broke!

This whole thing started when he decided to tighten terminal screws and then he started measuring voltages.

Sounds like he absolutely needs to stay away from electrical work.

 

[PoorUB]

Sounds like he absolutely needs to stay away from electrical work.

He is retired, and OCD. A dangerous combination!

I give him credit, he calls me when he is in over his head, not that I know it all, but I know where to ask.

 

[sparky 1971]

Sounds like he absolutely needs to stay away from electrical work.

There are a lot of people on here that should stay away from giving advice about electrical work too.

 

[sparky 1971]

Well, all is good again. I had a discussion with my buddy and it seems the neutral/ground bus was bonded to the box. He just doesn't know you need a bare metal surface for your probe to measure voltage!

He went back and looked at both panels and found the bonding screw/jumper and checked voltage from the mains to a bare spot, (screw hole) and he gets the same reading as measuring to the neutral bar.

I told him to stop F'ing with stuff that isn't broke!

This whole thing started when he decided to tighten terminal screws and then he started measuring voltages.

There should be 120 from hot to panel. Since the grounds and neutrals are landed on the same bar, it's a fairly safe bet to say this is the main panel. The bonding screw might not be installed. Sometimes they are stuck in the hole but not run in from the factory. Have him put a screwdriver on the green screw and see if he can tighten it up. At 15 years old, I doubt it has a bonding strap, but if there isn't a green screw, have him check for a phony little metal tab that would land on the neutral and then bend around to a screw in the panel. One time I had a bonding screw that wouldn't get tight, I used a ground bar and a piece of #4 copper from it to the neutral to git 'r done. He also might just need to scrape some paint away. Have him try measuring voltage from a hot to a cover screw hole.

I always try to start with the simple things. It doesn't always work out, but I don't want to be the guy that sets off the parts bomb when I've overlooked the obvious.

 

[PoorUB]

I always try to start with the simple things. It doesn't always work out, but I don't want to be the guy that sets off the parts bomb when I've overlooked the obvious.

Same here, but he is hundreds of miles away, otherwise I would have been looking over his shoulder. He is usually smarter than this!

 

[Norcal]

That happened with the 2008 code. Before that, a three wire feeder to a separate structure was permissible.

It happened when the 2008 NEC was adopted which could be years later.

 

[sparky 1971]

It happened when the 2008 NEC was adopted which could be years later.

Yep. Like I said, the 2008 code. I should have stated before the 2008 code went into effect, A three wire feeder was acceptable. I think everyone got my point though.

 

[wyliesdiesels]

Well, all is good again. I had a discussion with my buddy and it seems the neutral/ground bus was bonded to the box. He just doesn't know you need a bare metal surface for your probe to measure voltage!

He went back and looked at both panels and found the bonding screw/jumper and checked voltage from the mains to a bare spot, (screw hole) and he gets the same reading as measuring to the neutral bar.

I told him to stop F'ing with stuff that isn't broke!

This whole thing started when he decided to tighten terminal screws and then he started measuring voltages.

Thats a good way to screw up terminations

 

[PoorUB]

Thats a good way to screw up terminations

As opposed to leaving them loose? He told me he found a few connections where the wire was all but falling out.

 

[dave*99]

Nobody wants to have a screw loose.

It the terminal screws were torqued properly at install, they are best left alone.

It’s ok to put a driver on one and confirm it is tight but giving them a twist to be sure they are damn tight can crush a conductor beyond the intended design. If you repeat that process enough times the conductor can shear off.