Multi-Family gounding

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#1

Originally Posted By: dvalley
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Ok Dennis,


I expect you to be the first to answer..but lets see.

I inspected a two-family house today with two individual 100 amp SE panels. One ground wire was installed at the water main. A single ground wire that was attached at the water main was coming from one of the SE panels. The other SE panel had the ground wire exiting itself and going into the adjacent panel that was grounded at the main.
Aren't these supposed to be two separated ground wires going individually to the main? Or is this acceptable? Can a ground wire be shared with each other?

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David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."

#2

Originally Posted By: tpfleiderer
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David,


Sorry it's not Dennis, but I do have an answer to your question. What you have described is correct as long as the grounding conductor wire is sized properly for the size of the total amps of the two services. The NEC does require the two panels to be bonded together. You see, even though they appear to be two different services (two meterbases, and two panels, etc.) they are considered, to the power company, as one service entering the building, because both panels derive there power from one set of conductor that are connected together at the weather head. So the power company views it as if they have only ran one service to the building (The NEC, in most cases, will only allow one service ran to a building). I hope this has helped.

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Tim

#3

Originally Posted By: Dennis Bozek
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Good answer Tim.


Dave....

Sorry I wasn't the first but I tend to get here later and later every night if at all. Anyway, One wire can extend to the water meter and other panels can be attached to that wire by use of a unreversible connection such as a crimp or even a cad weld. It is also legal to ground both panels as you had stated in your post.

I'm sure you checked this Dave...but on the specific house you speak about in your post....the service should be a minimum of 200 amps...for you are running two 100 amp panels. The meter base should be rated for 200 amps as well and the wire leadiing from the line side of the meter base up to the weatherhead should be ample to run 200 amps. The wires leading from the load side of each meter is then rated for 100 amps. Just some info....for those not aware.

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This information has been edited and reviewed for errors by your favorite resident sparky.

#4

Originally Posted By: dvalley
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Quote:
One wire can extend to the water meter and other panels can be attached to that wire by use of a unreversible connection such as a crimp or even a cad weld.


I read somewhere that ground wires cannot be spliced together. So using unreversible crimps is not considered splicing?

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David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."
#5

Originally Posted By: Dennis Bozek
This post was automatically imported from our archived forum.


Dave…


Yep....it is acceptible but it has to be unreversible and yes it is a splice.

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This information has been edited and reviewed for errors by your favorite resident sparky.