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Missing Grounding Means for Multiple Commerical Service

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techgod

Member
While doing work on a 80 year old building that had it's Meter/Mains replaced about 10 years ago I discovered that none of the panels are grounded or bonded.

The OH Service feeds four 100 amp panels and one 400 amp panel through a large gutter. Will one or two ground rods with a 3/0 GEC be sufficient or does each panel need a ground rod with a full size 3/0 GEC; Or is the GEC size based on the size of the tap conductors from the main OH conductors in the gutter to the smaller panels?

Does the Bonding conductor to the water main have to be 3/0 or can it be smaller?

TIA,
Mark
 
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pierre

Senior Member
Location
Westchester County, New York
Re: Missing Grounding Means for Multiple Commerical Service

Mark
You can install a common grounding electrode conductor to the cold water. The size is based on the service entrance conductor and than referencing 250.66. The individual panel disconnects can then tap off of the common grounding electrode conductor. The size of the taps will be based on the size of the conductor that supplies the panels, also from table 250.66
 
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