Disconnect/metering puzzle...

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mdshunk

mdshunk

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I think I did this emergency job today right, but I'm still not sure. It passed inspection, but I've come to believe that many things pass inspection that don't exactly square with the NEC...

Building was fed from a downtown network secondary into the basement of the building. 208V, single phase. The secondary conductors first hit an existing 400 amp disconnect, which contained the main bonding jumper and the grounding electrode terminations. From there, two 200 amp subfeeds split off to two seperate 200 amp disconnects. No metering involved thus far. The load side of the one 200 amp disconnect is where my work was being done. This 200 amp feeder went to 6 old A base tennant meters and 6 old fuse panels. The thing went down in a blaze of glory.

Here's what I did... I ran 200 amp subfeed cable from the existing 200 amp disconnect to a 6 gang meter socket. I landed the both hots and the neutral on the ganged meter socket line side as usual. I landed the EGC of the subfeed on a distribution block that I mounted in the ganged meter socket (tons of extra room). From the load side of each meter gang, I ran 100 amp subfeed cable to each of 6 panels directly below the meter socket, naturally with neturals and grounds on seperate bars in each tennant panel. The EGC of each load side cable terminated on that distribution block I mounted in the meter can.

What I'm puzzled about is the arrangement I came up with in the ganged meter socket for keeping this neutral and ground seperate, since this socket was after the main disconnect. Is this normal? That is to say, is this how most people do it? I know it's a bit rare to have the metering being done on the load side of a main disconnect when there isn't a factory type meter stack involved. I just want a double check with smart people for the next time I bump into this. I am so famaliar to the inspectors that they hardly check my work, which isn't always what I want.

Thanks.
 
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meter downstream

meter downstream

A few years back when I worked for a smaller firm in the area we did a lot of tenant work in a complex that consisted of 4 platforms floors 1-4 and two towers approx 47 floors each. The large towers belonged to one lese, each tenant on the platforms had an individual tenant meter and if I remember correctly an inspector raised this one time and we ended up having to specify meters with an isolated neutral kit I am not sure how it was actually installed to my knowledge the neutral is isolated thru the meter the ground is connected to the meter case. I do remember tho specifying the isolated neutral kit thru the meter enclosure I am not sure how they wire it but I did find some pictures you can see there is a CT cabinet that feeds into the disc. Means for the space then in the one picture you can see a small neutral wire I believe going from the disc to back to the meter can / CT cabinet and in the CT cabinet you can see the neutral being solid and isolated thru the CT cabinet I hope this helps.

Edit: Pictures blowing out margins of post.
 
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mdshunk said:
...I know it's a bit rare to have the metering being done on the load side of a main disconnect when there isn't a factory type meter stack involved. I just want a double check with smart people for the next time I bump into this. I am so famaliar to the inspectors that they hardly check my work, which isn't always what I want.Thanks.
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Well I can be as smat as posable but I may learn me sumpin hear.

What?s bazaar is the utility service stops at the service disconnect - line side - yet these meters are past the disconnect, therefore the meters can be tampered with by anyone and may be private?!!?

Conversely to this would be the utility owns everything ahead of their meters, in this situation they would own the service disconnect? This situation would be a first for me.

Were does your utility service stop?
 
tryinghard said:
Were does your utility service stop?
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The utility owned conductors stop in the vault under the manhole lid in the sidewalk. All the conductors after that are customer owned. The actual kilowatt-hour meters are utility owned. This arrangement with disconnects ahead of the meters is mostly to satisfy the 6 disconnect rule. This is reasonably typical for downtown type services.
 
mdshunk said:
Here's what I did... I ran 200 amp subfeed cable from the existing 200 amp disconnect to a 6 gang meter socket. I landed the both hots and the neutral on the ganged meter socket line side as usual. I landed the EGC of the subfeed on a distribution block that I mounted in the ganged meter socket (tons of extra room). From the load side of each meter gang, I ran 100 amp subfeed cable to each of 6 panels directly below the meter socket, naturally with neturals and grounds on seperate bars in each tennant panel. The EGC of each load side cable terminated on that distribution block I mounted in the meter can.

What I'm puzzled about is the arrangement I came up with in the ganged meter socket for keeping this neutral and ground seperate, since this socket was after the main disconnect. Is this normal?Thanks.
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Yep this will work because the neutral will be common only at the service disconnect and you?d have to install a ground bus of some sort for the equipment ground conductors.

It?s a safe application and I think your simply reciprocating rarity, IMO your/it?s normal.
 
Marc
It sounds as if you used the neutral conductor to ground the meter base. That is if I followed you correctly the neutral connection at a meter base is generally not floated from can and you stated that you used a power terminal block for the EGC which would be floated typically. Am I following your installation as stated.
 
Bea said:
Marc
It sounds as if you used the neutral conductor to ground the meter base. That is if I followed you correctly the neutral connection at a meter base is generally not floated from can and you stated that you used a power terminal block for the EGC which would be floated typically. Am I following your installation as stated.
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Yes, that is correct. It dawned on me after the fact that it might have been better the other way around; ie used the EGC for the meter can center terminal and floated the neutral on the distribution block. I just had stuck in my head a code section iwire pointed out to me a while back that said it was permissible to have the neutral bond the meter can, so that's why I did it the way I did it. These were 5th terminal meter gangs, but I could have easily ran the 5th terminal pigtails to the distribution block too if I had decided to float the neutral instead of the EGC.
 
Pierre C Belarge said:
Marc
Take a look at 250.142(B)ex No.2, especially the 2nd condition.
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Oooooo.... now that's interesting. That looks like an addition to the '05 code, and we're on the '05 in my area. Yeah, that shouldn't have passed that way. I should have done that the other way around, and hit the gang meter socket's center terminal with the EGC, and hit the power distribution block with the neutrals. I'll know for next time now. Thanks, Pierre!
 
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