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737Pilot 11-05-2008 09:35 PM

stupid electrical question.
 
Ok, just curious. In a breaker box, are the neutral and ground bars basically attached? Thanks.

kbsparky 11-05-2008 09:44 PM

Are they attached? Usually - yes, securely attached to the enclosure.

Are they attached to each other?

If you are dealing with a Service Equipment panel, then yes, they are electrically attached to each other. The neutral conductor is intentionally grounded only at the service equipment. The is to ensure a good return path for ground-fault currents to facilitate the proper operation of your circuit breakers.

If you are dealing with a sub-panel, they must be kept separated. The neutral is a current-carrying conductor, and as such is isolated from the grounds. The ground is attached -- both electrically and mechanically to the enclosure, and is not considered current-carrying for the proper operation of the branch circuits.

220/221 11-05-2008 11:04 PM

Quote:

If you are dealing with a Service Equipment panel, then yes,
I'd like to add that the service is at the first overcurrent protection device.

737Pilot 11-08-2008 09:51 PM

Thanks. I was curious as my house has a breaker panel (of course!) and then my detached garage has a panel in it as well, fed from the house panel. The wires coming from the house to the garage panel are #2 aluminum for the hot and a #4 aluminum for the neutral. No ground is run from the house to the garage. So at the garage there is a grounding wire run to the grounding rod in the ground.

I was looking inside the panel and was curious as it appears that the neutral and grounding bars are basically attached to eachother. So I was wondering, if they are basically attached to eachother, isn't each one acting like a ground AND a neutral bar since the electricity could flow between them? Hope this made sense....just trying to learn! Thanks. :eek:

Yoyizit 11-08-2008 09:54 PM

Quote:

Originally Posted by 737Pilot (Post 182130)
it appears that the neutral and grounding bars are basically attached to eachother. So I was wondering, if they are basically attached to eachother, isn't each one acting like a ground AND a neutral bar since the electricity could flow between them? Hope this made sense....just trying to learn! Thanks. :eek:

http://www.google.com/search?hl=en&q=single+point+grounding&aq=1&oq=%22s ingle+point+ground

jamiedolan 11-09-2008 02:13 AM

Quote:

Originally Posted by 737Pilot (Post 182130)
Thanks. I was curious as my house has a breaker panel (of course!) and then my detached garage has a panel in it as well, fed from the house panel. The wires coming from the house to the garage panel are #2 aluminum for the hot and a #4 aluminum for the neutral. No ground is run from the house to the garage. So at the garage there is a grounding wire run to the grounding rod in the ground.

I was looking inside the panel and was curious as it appears that the neutral and grounding bars are basically attached to eachother. So I was wondering, if they are basically attached to eachother, isn't each one acting like a ground AND a neutral bar since the electricity could flow between them? Hope this made sense....just trying to learn! Thanks. :eek:

You have to look closely, I was looking at boxes earlier tonight, and on some boxes there is a removeable clip that will bond one of the bars to the box or if you remove the clip, the bar will be insulated from everything else and operate seperatly. It is normal for these 2 bars to be connected in the box that is at the service entrance in your home (where ever your main breaker resides outside or in). I think it may be normal for them to be connected / bonded together in a detached garage that has it's own grounding rod as well - but I really do not know for sure - hopefully someone else can give you a firm answer on this.

Jamie

rgsgww 11-09-2008 02:44 AM

In a subpanel the panel is bonded to the ground bus and the neutral is insulated from the panel and ground. The neutral is usually seperated unless at the service.

Yours is most likely a 3 wire system, which is not allowed today, it was back then. This involved using the conduit as a grounding conductor. And you were/are still required to sink ground rods.

InPhase277 11-09-2008 10:09 AM

Quote:

Originally Posted by rgsgww (Post 182202)
In a subpanel the panel is bonded to the ground bus and the neutral is insulated from the panel and ground. The neutral is usually seperated unless at the service.

Yours is most likely a 3 wire system, which is not allowed today, it was back then. This involved using the conduit as a grounding conductor. And you were/are still required to sink ground rods.

Not exactly, but you were close:thumbsup:. At one time, the neutral in a subpanel was allowed to be used as the equipment ground, just like the main panel, as long as there were no metallic paths back to the main. And this was only allowed for detached buildings. Never in the same structure.

Stubbie 11-09-2008 11:57 AM

As Inphase277 has clarified 3 wire feeds to detached buildings are common if no metallic paths other than the feeder existed. For instance a water line to the detached building from the house would require a 4 wire feed. Just recently as of the 2008 code cycle are 4 wire feeds with isolated neutral and ground required for all situations.. There are a lot of jurisdictions still on 2005 or earlier. Pilots installation is perfectly fine under the code cycles prior to adopting 2008 as rgsgww mentioned. In fact you could still install a 3 wire feed if under a code cycle prior to 2008. I just think it would be better to install a 4 wire so you could run water or phone, data lines to the detached garage and it improves human safety.

737Pilot 11-09-2008 02:32 PM

Quote:

Originally Posted by Stubbie (Post 182324)
As Inphase277 has clarified 3 wire feeds to detached buildings are common if no metallic paths other than the feeder existed. For instance a water line to the detached building from the house would require a 4 wire feed. Just recently as of the 2008 code cycle are 4 wire feeds with isolated neutral and ground required for all situations.. There are a lot of jurisdictions still on 2005 or earlier. Pilots installation is perfectly fine under the code cycles prior to adopting 2008 as rgsgww mentioned. In fact you could still install a 3 wire feed if under a code cycle prior to 2008. I just think it would be better to install a 4 wire so you could run water or phone, data lines to the detached garage and it improves human safety.


There is no physical connection between the garage and the house other than the 3 aluminum wires going from the main panel to the garage panel. In other words, no metal pipes for water, etc. Also, so I understand correctly, since there aren't any metal pipes connecting the house to the garage, the 3 wire set up is OK as long as I have a grounding rod (which I do) and the neutral and grounding bars CAN be connected in the subpanel in the garage?

However, there is a phone line run to the garage from the house, but I am curious as to how that is tied into the electric? Thanks.

Gigs 11-09-2008 04:52 PM

Quote:

Originally Posted by 737Pilot (Post 182373)
However, there is a phone line run to the garage from the house, but I am curious as to how that is tied into the electric? Thanks.

Hopefully not at all. Phone doesn't need ground except at the demark, and the telco deals with that so you don't need to.

Edit - Oh I just realized you were asking because of Stubbie's comments. It's because it violates the "no other metallic path" rule. So if you have phone or water or barbed wire or anything metal connecting the structures then you have to use 4 wire.


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