Post-Meter mixing

[jerm]

We can't find anything in the Code to forbid this, and our inspectors say they can't either and so they're letting us do it. Wanted to see what you guys (my 'experts') thought about it.

We're moving a multi-family dwelling service (20 meters, 18+2 house) from inside a building to the outside of the building (and adding a 1200a disconnect before everything so we don't have to argue about 6-handle grouping/occupancy vs building).

Anything say we can't put wires (feeders) from multiple meters back into the same raceway, to get back inside to where the old feeders were at? Imagine a trough on top feeding the meter banks and a trough on bottom to send multiple metered feeders back into the building.

If that doesn't make sense, tell me and I'll draw a picture. Of course, it's more complicated that I've written, no one just moves a bank of meters for the pure enjoyment of a job well done.

 

[mdshunk]

Sure, why not. They're all in the same place in a ganged meter socket or a meter center. Have you considered using a meter center instead of the gutter arrangement, by the way? It is sometimes beneficial to have the tenant disconnect right there with the meter, so that your load side conductors are now fused and not unfused service conductors. Gives you a little more flexibility when routing the conduits or cables to the indoors.

 

[jerm]

That's kind of what I figured. Like I said, it's more complicated than I wrote.

The trough on top feeds the meters from the 1200a disconnect (3r). So the meters are all fused/tapped. The meter cans are provided free of charge from the poco, 'real' meter banks are at customer expense. Each meter is gonig to have a small panel (6 circuit) after it, then into the bottom trough. From there the trough goes into the building to feed the old feeders to existing panels in each unit (now sub panels, but it's all in rigid so the ground is there, we'll remove n-g bonds at each panel if they exist!) and the bottom trough also feeds conduits to the roof to the 18 new condenser units and to feed each furnace- we're piping from the roof down through each unit to feed furnaces (the furnace closets are nicely stacked on top of each other.) The best news? The building is, other than us, empty. No occupants to deal with.

The fun part is that the entire building has been condemed; there are "NO TRESSPASSING BY ORDER OF THE FIRE MARSHAL" signs everywhere.

 

[mdshunk]

I'm somewhat surprised that they let you put a fused disco ahead of all these meters. Normally, the PoCo will want to seal such a disconnect, which sort of precludes the use of fuses inside of it. Your load side conductors will essentially be tap conductors and not service conductors, with a length limitation now, the way I see it. This sounds like an unnecessary can of worms just to use a few free meter cans.

 

[jerm]

Additional CT's are going to be in the poco pad-mount transformer with it's own meter, so I'm not sure why they'd want to seal the disco. They have some way of taking the reading from that first meter, putting it in their computer along with all the other 18 meter readings and it charges the house with the leftover. Or something like that.

I haven't seen meter banks with anything other than 2 or 4 circuits, we need 6- 2 for 240 to the old panel, 2 for 240 to the ac units, 2 for 240 to the new furnaces. Maybe someone makes it, but probably have a lead time? :-?

 

[mdshunk]

Additional CT's are going to be in the poco pad-mount transformer with it's own meter, so I'm not sure why they'd want to seal the disco. They have some way of taking the reading from that first meter, putting it in their computer along with all the other 18 meter readings and it charges the house with the leftover. Or something like that.

Man, that's a weird arrangement. Sounds like you've got a plan. Giv'ver hell.

 

[Pierre C Belarge]

I'm somewhat surprised that they let you put a fused disco ahead of all these meters. Normally, the PoCo will want to seal such a disconnect, which sort of precludes the use of fuses inside of it. Your load side conductors will essentially be tap conductors and not service conductors, with a length limitation now, the way I see it. This sounds like an unnecessary can of worms just to use a few free meter cans.

Service conductors are not required to follow the requirements of 240.21(B), feeder taps.

As Marc has posted, once you install the main service disconnect ahead of the meters, the conductors you will "tap" into the feeders from the load side of the service disconnect will be limited to the length of installation.
You may want to think about installing the panels or disconnects outside to shorten the length of your run.

 

[jerm]

The 1200a disconect, the meters, the 6-circuit panels, the top and bottom trough are all 3r outside.

Does that change anything, Pierre? Not sure I completely follow your post.
:-?

 

[mdshunk]

Are you saying that below each of the meters, you will have a 6-circuit panel? If that's the case, then all your conductors that you're bringing indoors in those pipes are just branch circuits. No big deal there.

You're going to have some double-ugly GEC arrangement outdoors there too to make a compliant install.

 

[Pierre C Belarge]

The 1200a disconect, the meters, the 6-circuit panels, the top and bottom trough are all 3r outside.

Does that change anything, Pierre? Not sure I completely follow your post.
:-?

Yes, I believe it would.
That is sort of what I was trying to explain.


Next question:
How come you are not finished yet. :grin:

 

[jerm]

Are you saying that below each of the meters, you will have a 6-circuit panel? If that's the case, then all your conductors that you're bringing indoors in those pipes are just branch circuits. No big deal there.

Si. They are all as you say 'just branch circuits.'

You're going to have some double-ugly GEC arrangement outdoors there too to make a compliant install.

elaborate?

 

[jerm]

How come you are not finished yet. :grin:

LOL! We spent a week in the shop arguing over the "best" way to do this, for us and for the building owner. We finally compromised on this plan and started work on it on Thursday. I'm not working any more weekends!

 

[mdshunk]

You're going to have some double-ugly GEC arrangement outdoors there too to make a compliant install.

elaborate?

I guess I should say "I think". That fused disco through all the meters really screws with my head. I guess your GEC's would land there, then, but now we've got a 4-wire arrangement through all the meters. They giving you isolated neutral meter cans? If not, you putting in the MBJ in the 1200 amp disco and the 6-circuit panels? My head hurts.

 

[jerm]

Ahh. Yes, good point. It screwed with all of our collective heads for at least a week before we even visited the site.

You're right though- the panels after the meters are sub panels, and the meters can't bond n-g I don't think. We'll have to work this out with the AHJ and poco.

 

[Pierre C Belarge]

Ahh. Yes, good point. It screwed with all of our collective heads for at least a week before we even visited the site.

You're right though- the panels after the meters are sub panels, and the meters can't bond n-g I don't think. We'll have to work this out with the AHJ and poco.

Take a look at 250.142(B) Ex No.2

"located immediately adjacent" is the key to this requirement.

 

[jerm]

Ahha. I think you fuond my loophole. Standard meter cans will do just fine then.

 

[Pierre C Belarge]

Ahha. I think you fuond my loophole. Standard meter cans will do just fine then.

To "seal your deal", I would run that by the inspector first...better to be sure than sorry.

Try to draw an accurate illustration for him/her to see just what you are trying to do, it may help.

 

[mdshunk]

Ahha. I think you fuond my loophole. Standard meter cans will do just fine then.

Think about this, now.... I think I have this straight...

You're still going to need 4-wire from the main disco to those 6-circuit boxes, so at least one conductor will be passing straight through the meter can.

If you're not using 5th terminal meter cans, it really doesn't matter if you terminate the EGC or the neutral on that center terminal in the meter can.

If you're using "regular" meter cans, you might as well land the EGC on that center terminal. This way, you won't have to utilize that exception Pierre pointed out, and you will totally eliminate the circulating currents.

By doing the above, and just passing the insulated neutral conductor straight through each meter can, it really cleans things up and makes it easier to get your head around. After all, that center terminal in a regular meter can (not 5th terminal) is just the "ground" for the metal parts of the meter can anyhow.

 

[Pierre C Belarge]

This may be what Marc is trying to discuss - minus the bypass.

 

[mdshunk]

This may be what Marc is trying to discuss - minus the bypass.

Yes, but in that case, the one in Pierre's picture is a 5th terminal meter, so you really didn't have a choice but to land the neutral in the meter can. If it's going to be a regular meter can, might as well land the EGC in the meter can, and just let the netural just pass through, unspliced.