# Grounding & Bonding: Multi-Family Dwelling



## VELOCI3 (Aug 15, 2019)

If I read your bio correctly it doesn’t say if you are an electrician. Sizing a multi family dwelling you will need to consider the NEC cycle accepted by the AHJ, local building codes, POCO codes. 


Sent from my iPad using Tapatalk


----------



## Dennis Alwon (May 9, 2009)

VELOCI3 said:


> If I read your bio correctly it doesn’t say if you are an electrician. Sizing a multi family dwelling you will need to consider the NEC cycle accepted by the AHJ, local building codes, POCO codes.
> 
> 
> Sent from my iPad using Tapatalk



It does now


----------



## Dennis Alwon (May 9, 2009)

Since there is a service disconnect before the meters (unusual) then IMO the 100 amp panels are all subpanels.


----------



## VELOCI3 (Aug 15, 2019)

In NY we have a lot of multi family buildings where 1 to 5 service disconnects feed 40-50 sets of meters in banks. Some buildings we have switchgear with CT’s for each unit and in lieu of separate meters the system uses utility monitoring software like QuadLogic. 

All locations have main service disconnects before the meter banks. Each meter has load side over current devices ahead of the individual unit panels. Grounding is terminated in the service gear then extended to the banks.


Note: the 6th and max allowable service disco is for owner/building loads. 

Sent from my iPad using Tapatalk


----------



## HertzHound (Jan 22, 2019)

There are times we have done similar in strip malls. They are being cheap with not having a single main disconnect. So they’ll get a piece of gear with six main breakers. Then from that they’ll get a 4” to a trough, then tapped enclosed circuit breakers and tenant meters. Keep repeating off of one of the six main breakers. Grounding is a nightmare going through the meters. Especially if some of the tenants have CT cabinets. From what I’ve seen the inspectors don’t say anything about paralleling the neutral with the equipment ground?


----------



## Cow (Jan 16, 2008)

Is the 200 amp disconnect considered a service disconnect or is it a power co. disconnect? Over here the power co's don't have disco's in front of their meters but I've heard other areas may do that.

I would have to run this past our inspector, if that 200 amp was considered our service disconnect. At that point, you'd need 4 wires leaving the disconnect. You may run into downstream neutral-ground bond issues in the metering equipment. Plus you most likely only have 3 wire feeders to each apt, etc.

It can really turn into a can of worms on this one, sounds like.


----------



## joe-nwt (Mar 28, 2019)

Cow said:


> Is the 200 amp disconnect considered a service disconnect or is it a power co. disconnect? Over here the power co's don't have disco's in front of their meters but I've heard other areas may do that.
> 
> I would have to run this past our inspector, if that 200 amp was considered our service disconnect. At that point, you'd need 4 wires leaving the disconnect. *You may run into downstream neutral-ground bond issues in the metering equipment. *Plus you most likely only have 3 wire feeders to each apt, etc.
> 
> It can really turn into a can of worms on this one, sounds like.


I think you can get isolated neutral kits for many of the meter bases out there.


----------



## Dennis Alwon (May 9, 2009)

joe-nwt said:


> I think you can get isolated neutral kits for many of the meter bases out there.


Not sure about kits but you would have to use a special meter for this that isolates the ground and neutral


----------



## Dennis Alwon (May 9, 2009)

IMO, the main 200 amp breaker is for the service disconnect.. If it were not then having 7 panels would not be compliant as it would break the 6 disco rule.


----------



## funkking (May 27, 2020)

Here's a pic of the meters and panels.


----------



## VELOCI3 (Aug 15, 2019)

funkking said:


> Here's a pic of the meters and panels.
> View attachment 151776
> View attachment 151777


That’s what you call 5 pounds of sh#t in a 1 pound bag. The new meter sockets will be physically larger. I would check the POCO blue pages for accepted ganged meter banks with common bus feeds. That will save space and eliminate that trough on top. 


Sent from my iPad using Tapatalk


----------



## joe-nwt (Mar 28, 2019)

Dennis Alwon said:


> Not sure about kits but you would have to use a special meter for this that isolates the ground and neutral


5-Jaw. Use them all the time around here for a 120/208 service derived from 3Ø .


----------



## varmit (Apr 19, 2009)

It would appear that the BX sheath is the EGC. So that would save a lot of work on that aspect. In the present configuration, each panel should be considered a sub panel.

I would think that the major challenge for this job would be space to mount the new services as everything will be much larger in physical size. You would need a plan that would allow a lot of prework to be accomplished before tearing out the old, so the tenants power is not off for too long. If there is space, you could install a new service with all of the metering in one enclosure. Power up the new service, while keeping the old service on, and then replace each panel one at a time. 

Depending on available space, the panels may need to be column width (more $) or stagger the panels high and low to fit. 

Depending on your local AHJ, you may be required to do code upgrades in the apartments- GFIs, more outlets, etc.


----------



## Dennis Alwon (May 9, 2009)

varmit said:


> It would appear that the BX sheath is the EGC.


Not always.. Unless the BX (AC cable) has the small steel wire in it then the sheathing is not permitted as an equipment grounding conductor.


----------



## varmit (Apr 19, 2009)

As for the service grounding, If you installed a single enclosure containing all of the meters, the service grounding would be there. Install the GEC to the water line- if metal, and to two ground rods. Then you would install, with the hots and neutral, a ground wire (EGC) to the sub panel for each unit.

Hopefully, the building owner understands that this is NOT a cheap and easy job.


----------



## Cow (Jan 16, 2008)

varmit said:


> Hopefully, the building owner understands that this is NOT a cheap and easy job.


Going off what Varmit said, in situations like this where you can tell there is going to be a lot of money spent, I would rough price the materials and labor and then ballpark the cost to the customer before you work a formal quote up. If they don't blink, then you know you can spend some time working on an actual quote.

I can't count how many times I've investigated, sourced, priced and found the best way to accomplish a project but when I send the quote over......radio silence.

No sense spending any more time in the office than you have too, working on a quote, when you don't have a chance of getting the job anyways.


----------



## funkking (May 27, 2020)

I was really just thinking about replacing the panels and keeping the existing trough and meter cans. Each apartment only has 4-5 circuits, so I can get away with using a small 10-12 space box for each. If you look in the picture, someone fairly recently replaced the panels for units #3 and #5. This is the route I was thinking of taking too.

I'm going to try and get the inspector to review this job with me prior to giving my customer a quote. There's no sense in quoting a plan that the inspector won't sign off on. But here's what I'm kind of thinking....

Using 3-4 guys...

1. Open the main disconnect, killing power to everything downstream.
2. Have the POCO pull all the meters.
3. Unwire and demo old fuse boxes, but keep meter cans in place.
4. Replace wiring from line side of meter to the bugs in the trough.
5. Replace wiring from the load side of the meter to the new panel.
6. Set new panel and hook up the existing cables.
7. Install 2 ground rods and bond to the main disconnect.
8. Run ground wires from the disconnect to the first panel, and then jump from panel to panel, keeping grounds and neutrals separated in the panels. (I know the BX can serve as the EGC, but I just have a feeling the inspector is going to want to see a separate ground pulled in to each panel)
9. Have inspector review and sign off.
10. Have POCO reinstall the meters.
11. Close disconnect and away we go...

Thoughts?











varmit said:


> It would appear that the BX sheath is the EGC. So that would save a lot of work on that aspect. In the present configuration, each panel should be considered a sub panel.
> 
> I would think that the major challenge for this job would be space to mount the new services as everything will be much larger in physical size. You would need a plan that would allow a lot of prework to be accomplished before tearing out the old, so the tenants power is not off for too long. If there is space, you could install a new service with all of the metering in one enclosure. Power up the new service, while keeping the old service on, and then replace each panel one at a time.
> 
> ...


----------



## Cow (Jan 16, 2008)

I think leaving the old meterbases is not the way to go about it. They are as old as the panels and count on spring pressure to retain the meter blades. I think it would be doing your customer a disservice to not replace them at the same time.

For one, you would be counting on being able to break the lugs loose in the meters to replace the wiring down to your new panels, without breaking anything in the meterbase in the process.

Two, you are not going to be able to isolate grounds/neutrals properly in those meterbases.

Three, when one of those meterbases goes bad in the future, they will most likely not be able to replace it with a modern meterbase because of space constraints.

Now is the time to change the meterbases, in my opinion.


----------



## funkking (May 27, 2020)

You make a good point about the meter bases. Changing them probably is the way to go.



Cow said:


> I think leaving the old meterbases is not the way to go about it. They are as old as the panels and count on spring pressure to retain the meter blades. I think it would be doing your customer a disservice to not replace them at the same time.
> 
> For one, you would be counting on being able to break the lugs loose in the meters to replace the wiring down to your new panels, without breaking anything in the meterbase in the process.
> 
> ...


----------



## varmit (Apr 19, 2009)

Dennis Alwon said:


> Not always.. Unless the BX (AC cable) has the small steel wire in it then the sheathing is not permitted as an equipment grounding conductor.


Just for info, I checked some of my old code books, 1965 and 1975. At that time armored cable was either MC or AC (BX). MC covering was considered a ground path. All type AC was required to have the "bonding strip" under the cable sheath. But, this is today and many things have changed.


----------



## Dennis Alwon (May 9, 2009)

varmit said:


> Just for info, I checked some of my old code books, 1965 and 1975. At that time armored cable was either MC or AC (BX). MC covering was considered a ground path. All type AC was required to have the "bonding strip" under the cable sheath. But, this is today and many things have changed.



I don't understand what you are trying to say. AC cable was made without the steel strip but I am not sure what years that was. The reason they put the strip under the sheathing was to give the cable less resistance so that in the event of a ground fault the cable could carry the current to trip the breaker.

AC cable without the strip has been known to glow during some ground faults


----------



## VELOCI3 (Aug 15, 2019)

Dennis Alwon said:


> I don't understand what you are trying to say. AC cable was made without the steel strip but I am not sure what years that was. The reason they put the strip under the sheathing was to give the cable less resistance so that in the event of a ground fault the cable could carry the current to trip the breaker.
> 
> AC cable without the strip has been known to glow during some ground faults













Sent from my iPad using Tapatalk


----------



## Dennis Alwon (May 9, 2009)

VELOCI3 said:


> Sent from my iPad using Tapatalk



Yes that article was written by Paul Abernathy, I believe. That is where I got the info date of before 1959 for AC cable without the strip


----------



## Doc13067 (Dec 2, 2021)

Definitely cannot use BX sheathing as EGC. I don’t know why anyone thinks that. Hey guys, new member here, I found the thread because I am currently in almost the exact same situation! So what was the main, the disco or each panel? Are you able to use main lug panels after the meters or does there need to be one switch to shut down each unit (if the unit has 3 branch circuits)? I’m going nuts thinking about all this. Also in my case we have a GEC going from the water pipe to the disco before the meter. Does that mean the disco is the main? I’d love to hear how your situation wound up. Thanks!


----------



## Dennis Alwon (May 9, 2009)

@Doc13067 The newer AC cable (BX ) sheathing is allowed to be used as an egc because it has a metallic strip of wire tying all the metal sheathing together.


----------



## Doc13067 (Dec 2, 2021)

Ah I see, 320.108. Ok got it. But the wiring described in the situation is not that, right? I ran into that years ago which lead me to discover it was not an acceptable EGC.


----------



## Majewski (Jan 8, 2016)

Dennis Alwon said:


> Since there is a service disconnect before the meters (unusual) then IMO the 100 amp panels are all subpanels.


Have fun divvying up THAT bill


----------



## Doc13067 (Dec 2, 2021)

Majewski said:


> Have fun divvying up THAT bill


Lol. We’ll there are 5 meters


----------



## Majewski (Jan 8, 2016)

Doc13067 said:


> Lol. We’ll there are 5 meters


yeah and 5 apartments of ppl who dont want to pay the wrong % and will argue til death


----------

