Emergency outdoor disconnect for dwelling

[barkett519]

Hi all,


I was talking with my boss the other day...we were having a heated discussion, im hoping you guys can shed some light for me? It was regarding the new 2020 requirement for an emergency disconnect outside of a dwelling. I told him I am 90% sure you have to bond the egc, gec and the neutral in the disconnect outside and run a 4 wire ser cable into the house and separate the grounds and neutrals. He says a 3 wire cable is acceptable run to the inside and the egc and neutral do not have to be bonded in the outside disconnect, they can still be bonded in the main panel( providing the main panel has a main breaker of course) can someone please explain? I've read the code and from what I understand neutrals and grounds have to be bonded at the first service disconnect. Isn't that the outdoor emergency disconnect?

 

[hillbilly1]

It’s kinda strange, but I think it’s because it’s not considered the “service disconnect” even though it does disconnect the service. Doesn’t make sense to me, but people that make a whole lot more money than me thinks so at the CMP. LOL!

 

[mkgrady]

I believe if we label the outside disconnect “emergency disconnect” we don’t need the fourth conductor, and if we label it “service disconnect” you do.

 

[don_resqcapt19]

It is just a word game in the NEC, but an intentional one. If you are changing out the service equipment that is in the building, you install an "emergecny disconenct" and all of the bonding remains inside at the location of the service equipment and you do not treat the load side of the "emergency disconnect" as a feeder. If you call the same exact outside equipment a "service disconnect/emergency disconnect", then the load side is a feeder and the bonding is outside.

 

[rnatalie]

Amusingly, I have a big honking disconnect on my house (built in 2008). There was some discussion between me, the electrician in charge, and the building inspector about whether it's the disconnect or not. We finally decided to go that way. Of course, it would suck as the intended emergency disconnect because as soon as you throw it, this 80KW generator fires up.

 

[don_resqcapt19]

Amusingly, I have a big honking disconnect on my house (built in 2008). There was some discussion between me, the electrician in charge, and the building inspector about whether it's the disconnect or not. We finally decided to go that way. Of course, it would suck as the intended emergency disconnect because as soon as you throw it, this 80KW generator fires up.

Stand by power is an issue with the EM disconnect rule as found in the 2020 code. I expect that it will be modified in the 2023 to require a directory of the location of any other power sources. That directory would be required to be placed at the emergency disconnect.

There were a number of PIs on this issue and CMP 10 acted favorably on at least one of those PIs in their panel meeting this week. However that is not the final action on the issue, so we have to wait for publishing of the First Draft report.

 

[xformer]

I believe the wording in the code book is at the first "Disconnecting Means". This wording would apply to the Emergency and then to the Service. IMHO.

Hi all,


I was talking with my boss the other day...we were having a heated discussion, im hoping you guys can shed some light for me? It was regarding the new 2020 requirement for an emergency disconnect outside of a dwelling. I told him I am 90% sure you have to bond the egc, gec and the neutral in the disconnect outside and run a 4 wire ser cable into the house and separate the grounds and neutrals. He says a 3 wire cable is acceptable run to the inside and the egc and neutral do not have to be bonded in the outside disconnect, they can still be bonded in the main panel( providing the main panel has a main breaker of course) can someone please explain? I've read the code and from what I understand neutrals and grounds have to be bonded at the first service disconnect. Isn't that the outdoor emergency disconnect?

 

[don_resqcapt19]

I believe the wording in the code book is at the first "Disconnecting Means". This wording would apply to the Emergency and then to the Service. IMHO.

The code language is at the "service disconnect" and not at the "first disconnect" .

The very reason that CMP 10 permitted the making "EMERGENCY DISCONNECT, NOT SERVICE EQUIPMENT" was to permit the installation of the emergency disconnect without triggering all of the rules that apply to service equipment. This is to make the replacement of the existing service equipment, which triggers the installation of an emergency disconnect, easier, by permitting the grounding and bonding to remain at the location of the new service equipment inside the structure.

 

[xformer]

The code language is at the "service disconnect" and not at the "first disconnect" .

The very reason that CMP 10 permitted the making "EMERGENCY DISCONNECT, NOT SERVICE EQUIPMENT" was to permit the installation of the emergency disconnect without triggering all of the rules that apply to service equipment. This is to make the replacement of the existing service equipment, which triggers the installation of an emergency disconnect, easier, by permitting the grounding and bonding to remain at the location of the new service equipment inside the structure.

I will go put my dunce cap back on and sit in corner for a bit. I stand corrected.

 

[Fred B]

The code language is at the "service disconnect" and not at the "first disconnect" .

The very reason that CMP 10 permitted the making "EMERGENCY DISCONNECT, NOT SERVICE EQUIPMENT" was to permit the installation of the emergency disconnect without triggering all of the rules that apply to service equipment. This is to make the replacement of the existing service equipment, which triggers the installation of an emergency disconnect, easier, by permitting the grounding and bonding to remain at the location of the new service equipment inside the structure.

This has always puzzled me. What should the "ED,NSE" look like wiring wise so that you don't create N-G parallel paths from being bonded at both ends? I've yet to see a good wireing diagram to show this sort of connection. Also local EI's don't seem to agree on this either.

 

[don_resqcapt19]

This has always puzzled me. What should the "ED,NSE" look like wiring wise so that you don't create N-G parallel paths from being bonded at both ends? I've yet to see a good wireing diagram to show this sort of connection. Also local EI's don't seem to agree on this either.

Parallel paths for neutral current on the line side of the service disconnect are not prohibited. Our local code only permits rigid steel conduit for service conductors, so the conduit between the meter can and the service disconnect is always a parallel path for the grounded conductor current.

The emergency disconnect enclosure will be bonded to the neutral, but that, by itself, does not create a parallel path. The parallel path would only be created by a metallic wiring method between the emergency disconnect and the service disconnect. This is the exactly the same as a utility meter...the enclosure is bonded to the neutral and there will be a parallel path is you use metallic wiring methods.

 

[mkgrady]

This has always puzzled me. What should the "ED,NSE" look like wiring wise so that you don't create N-G parallel paths from being bonded at both ends? I've yet to see a good wireing diagram to show this sort of connection. Also local EI's don't seem to agree on this either.

If there is no metal conduit then there is no parallel path. If there is metal conduit you have the same parallel path as ever. Only three conductors are going from the outside ED to the inside Service Disconnect. It basically gets wired like the ED isn’t there.

 

[Fred B]

Parallel paths for neutral current on the line side of the service disconnect are not prohibited. Our local code only permits rigid steel conduit for service conductors, so the conduit between the meter can and the service disconnect is always a parallel path for the grounded conductor current.

The emergency disconnect enclosure will be bonded to the neutral, but that, by itself, does not create a parallel path. The parallel path would only be created by a metallic wiring method between the emergency disconnect and the service disconnect. This is the exactly the same as a utility meter...the enclosure is bonded to the neutral and there will be a parallel path is you use metallic wiring methods.

So let's see if have this right, in the E D you bond neutral ground and enclosure, no ground wire running between the E D and the main service panel, ground neutral bonded again at the main service panel that also has grounding electrode connections. Basically the same as just a meter connection without an extra E D?
Would a seperate grounding electrode also be required at the E D? I'm thing of a disconnect that is remotely located away from (pole mounted) the main house panel.