ground wire

[papa smurf]

Could you please explain why we now install a main breaker outside at the meter with the ground and neutral tied together going to a grounded electrode. Then we run a 4 conductor wire to the sub panel inside and seperate the ground and neutral. Dont fully understand this and i need to know. Thanks

 

[M. D.]

Could start here??
http://www.mikeholt.com/mojonewsarchive/GB-HTML/HTML/ObjectionableCurrent~20020610.htm

 

[Smart $]

Could you please explain...

I wish I could.

Perhaps it would help if you told us how you did it before (and when now vs. before occurred)? :grin:

The things that came to forefront of my thoughts was that it has to do with going to a newer NEC code, a local amendment thereof, or a POCO requirement.

 

[raider1]

I would recomend getting Mike Holt's Grounding verses Bonding book. Another good book and the purpose of grounding and bonding would be Soares book on grounding.

Chris

 

[M. D.]

Here is a picture

 

[Smart $]

I would recomend getting Mike Holt's Grounding verses Bonding book. Another good book and the purpose of grounding and bonding would be Soares book on grounding.

Chris

I'm assuming he knows how to do grounding. He's wondering why the main breaker (service disconnect) is outside rather than the main panel breaker inside. The grounding changes accordingly.

 

[M. D.]

another link you might want to read

http://ecmweb.com/news/electric_key_making_proper/

Consequences of improper neutral-to-case connections. There are several consequences of improper neutral-to-case connections that range in severity from problems with equipment to the death of an employee.

Fire hazard. Improper wiring that results in the flow of neutral current on grounding and bonding paths can cause enough excess heat to cause a fire. Fire occurs when the temperature rises high enough to ignite adjacent combustible material in an area that contains sufficient oxygen.

Electrocution. Death from an electric shock can occur when the touch voltage is above 30V rms, and as little as 30 mA flows though the body. These conditions can easily exist when improper neutral-to-case connections are made and the neutral is opened

 

[raider1]

I'm assuming he knows how to do grounding. He's wondering why the main breaker (service disconnect) is outside rather than the main panel breaker inside. The grounding changes accordingly.

I agree that the grounding changes accordingly to the location of the service disconnect.

I understood he was asking about why we run a 4 wire feeder from an outside service disconnect to the panel rather than a 3 wire and use the panel as the service. I could be wrong though.

Chris

 

[LarryFine]

Could you please explain why we now install a main breaker outside at the meter with the ground and neutral tied together going to a grounded electrode. Then we run a 4 conductor wire to the sub panel inside and seperate the ground and neutral.

To put it simply, the service ends at the main disconnect, whether it's in the same enclosure as the BC breakers or not. That's where the bonding and electrode connections are made.

When a main disconnect is located (or added) ahead of the breaker panel, it basically renders that panel a sub-panel, and all of the separate-neutral-and-EGC rules apply.

 

[220/221]

My take.

3w feed with fauted grounded conductor allows for potential backfeed issues thru bonded eqipment and piping.

4 wire feed with faulted neutral limits those potential issues. If you lose a neutral the power is not going to find a path via the ground/bond system.

 

[John Valdes]

Are you guys installing meter mains instead of the just the meter base. Many people are now using meter mains which makes all subsequent panels, sub panels. Is that what you are asking papa smurf?
Sub panels require a 4 wire feeder to comply with 2008.

 

[papa smurf]

Thanks that helps. It's a tough one but thanks.