Isolated ground meter sockets

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jtester

Senior Member
Location
Las Cruces N.M.
I am stumped by this problem. I have a 277/480 volt service with a 1200 amp GFI protected main breaker feeding a medium sized medical office building. The 8 tenant meters and disconnects are downstream of the main disconnect. Our utility insists on a meter socket with a neutral bonded to the can. Our inspector has identified it as a problem, a violation of 250.142 Ex2 because of the GFI protection on the main. I?ve been looking for 277/480 volt meter sockets rated at 200 and 320 amps with isolated neutrals, with no luck. I am not even sure our utility will allow it, but if they are unavailable, it won?t matter.
Has anyone run into this, or have an idea of a solution?
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
If the utility insists on the neutrals being bonded at the meters I think your only choice will be to ditch the 1200 amp metering switchboard and buy two 600 amp metering switchboards eliminating the need for GFP mains.

You would end up with two service disconnect switches which of course is allowed by the NEC.

Edit: If this is not a metering switchboard the same idea applies to separate meter sockets and disconnects.
 
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augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
No. But I know I have inspected some with isolated neutral. You might talk to a Millbank rep or possibly use a K0147 listed on Pg 29
 
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