I’m Looking For A Code Section About Service Disconnects

[Seven-Delta-FortyOne]

I hope I make sense.

I was remembering a provision where if there are several actual enclosures that make up the “service disconnect”, the N-G bond does not necessarily have to be in the actual box that contains the main disconnect switch.

Basically, you could have a meter in an enclosure, a main in an enclosure, a distribution panel, all connected with metal conduit, and it’s considered one……I don’t know what.

My specific reason for asking is if such a thing is allowed, then why couldn’t a transfer switch be mounted adjacent to a main panel, 2 metal nipples connecting them, and not have to separate neutrals and grounds?

 

[david luchini]

I believe you're thinking 250.24(A)(1)

 

[electrofelon]

There is nothing allowing what you propose. Now the fine print: There is an exception for meters enclosures after a service disconnect to remain bonded, 250.142 exception. Only possible loophole would be for a dwelling where the first disconnect could be considered the emergency disconnect and not service equipment. I guess you could install the first disconnect on the POCO side of the meter (if allowed by them) and call it a "meter disconnect". Other than those situations, you gotta go plessy V Ferguson, separate but equal after the service disconnect.

 

[don_resqcapt19]

I hope I make sense.

I was remembering a provision where if there are several actual enclosures that make up the “service disconnect”, the N-G bond does not necessarily have to be in the actual box that contains the main disconnect switch.

Basically, you could have a meter in an enclosure, a main in an enclosure, a distribution panel, all connected with metal conduit, and it’s considered one……I don’t know what.

My specific reason for asking is if such a thing is allowed, then why couldn’t a transfer switch be mounted adjacent to a main panel, 2 metal nipples connecting them, and not have to separate neutrals and grounds?

In your example, there is only one enclosure that is the service disconnect. That is the enclosure that contains the main disconnect switch.
David's answer in post #2 is about the location of the connection of the grounding electrode conductor, however I think you are asking about the location of the main bonding jumper. That must be in the service disconnect enclosure per 250.24(C).

 

[augie47]

You might be thinking of 408.3(C)

(C) Used as Service Equipment. Each switchboard, switch‐ gear, or panelboard, if used as service equipment, shall be provided with a main bonding jumper sized in accordance with 250.28(D) or the equivalent placed within the panelboard or one of the sections of the switchboard or switchgear for connecting the grounded service conductor on its supply side to the switchboard, switchgear, or panelboard frame.

 

[Seven-Delta-FortyOne]

I appreciate everyone who responded.

I figured it was probably not the case, I’ve never seen it in the wild.

I thought I had seen something similar, maybe in one of Ray C. Mullins books, a Mike Holt graphic, or perhaps it was just a discussion about what the actual effects of such a configuration would be, but thanks to all for clearing it up.

 

[Seven-Delta-FortyOne]

So I dug into this a little more, and I see what I’ve been confused about.

250.28(d)2 discusses sizing for an MBJ for more than 1 service disconnect, when installed as permitted in 230.71(b)

230.71(b) allows 2-6 service disconnects, which each will have its own MBJ as per 250.28

Informational Note on 230.71(b) states that one of the situations where there would be more than one service disconnect could be a SE-Rated transfer switch.

So it seemed to me that one could have an SE-Rated ATS grouped with the main service panel, and have an MBJ in each.

Where am I going wrong on this?

 

[augie47]

It would all depend on the transfer switch being used as a service disconnect. If the T/S is a service disconnects (or one of the service disconnects)
then, as don mentioned, 250.24(C) requires it have a MBJ.
If the same T/S is on the secondary side of a service disconnect then 250.24(A)(5) prohibits a neutral to ground connection
The fact that the T/S is rated as SUSE does not mean it has to be service disconnect and likely one reason the neutral bar is floating)

 

[Seven-Delta-FortyOne]

But in what situation or configuration could there be a meter/main with a service disconnect, and a transfer switch that is also a service disconnect, as per the informational note?

The feed to the transfer switch is either before the main disco, in which case the TS becomes the service disconnect, or it’s a load side feed, and the main disco remains.

At least with every one I’ve ever done or seen.

 

[electrofelon]

But in what situation or configuration could there be a meter/main with a service disconnect, and a transfer switch that is also a service disconnect, as per the informational note?

There couldn't. Could you post the IN? I am not seeing that in my reference.

 

[augie47]

The service disconnect remains the 1st disconnect and is connected to the service conductors.
Anything connected on the load side of that is not a service disconnect and requires neutral-ground separation.
The fact that a Transfer Switch has overcurrent protection means it CAN be used as a service disconnect (in most cases) but it can also simply be a
T/S with a disconnect and not be service equipment.

 

[Seven-Delta-FortyOne]

There couldn't. Could you post the IN? I am not seeing that in my reference.

 

[wwhitney]

The feed to the transfer switch is either before the main disco, in which case the TS becomes the service disconnect

Yes. And if you further keep the existing main disconnect as is, and supply loads that you want backed up directly from the TS, while keeping other loads supplied directly from the existing main disconnect, then you now have two service disconnects, and each will have its own MBJ.

If you instead refeed the main disconnect from your TS, your TS will be the only service disconnect, and you will need to remove the MBJ in the existing main disconnect, separate grounds and neutrals there, and move any GEC terminations to the TS.

, or it’s a load side feed, and the main disco remains.

In this case, the TS is not a service disconnect, and the only MBJ will be in the existing main disconnect.

Cheers, Wayne

 

[electrofelon]

Informational Note on 230.71(b) states that one of the situations where there would be more than one service disconnect could be a SE-Rated transfer switch.

So it seemed to me that one could have an SE-Rated ATS grouped with the main service panel, and have an MBJ in each.

Where am I going wrong on this?

Right if you have multiple service disconnect enclosures, there is a MBJ in each. When the code refers to multiple service disconnects, it is not referring to or giving permission to put one downstream from another.

 

[Seven-Delta-FortyOne]

Yes. And if you further keep the existing main disconnect as is, and supply loads that you want backed up directly from the TS, while keeping other loads supplied directly from the existing main disconnect, then you now have two service disconnects, and each will have its own MBJ.

If you instead refeed the main disconnect from your TS, your TS will be the only service disconnect, and you will need to remove the MBJ in the existing main disconnect, separate grounds and neutrals there, and move any GEC terminations to the TS.


In this case, the TS is not a service disconnect, and the only MBJ will be in the existing main disconnect.

Cheers, Wayne

OK that makes sense.

That’s how I’ve done every TS ever; Either a load side feed, MBJ remains in main panel, or a line side feed, ATS becomes the new Service Disco, and I move the MBJ from the meter/main to the ATS.

I just couldn’t make sense of the Code article.