Service Grounding when installing a meter disconnect

[cdcengineer]

Alright gang, it's been a while since I've haunted this forum. But I've been run around and incurred some serious brain damage on a local project here in Colorado. Here XCEL requires a cold sequence disconnect on services 320A and less if the fault at the meter is in excess of 10kAIC, and the XCEL standards state that the cold sequence disconnect shall be treated as a meter disconnect per NEC. NEC 230.82(3) states that the meter disconnect be labelled "Meter Disconnect Not Service Equipment" (though I'd argue it's service equipment, but not the service disconnect. 250.82(3) allows for a meter disconnect, but requires that it is grounded and bonded per Parts VII and V of Article 250. 250.142 allows for the grounded conductor to be use for equipment grounding on the supply side of service equipment. So far, clear as can be. As we progress thru code review, NEC 250.24 allows the connection to grounding electrode (GEC) at any point from the load end of the service lateral to the service disconnecting means. So it can be done inside the cold sequence disconnect, and I believe we could bond the neutral here. All fairly clear in my mind.

Here's where it gets tricky. This project has the cold sequence disconnect and meter built on a rack per XCEL dwg SC-50. XCEL requires a ground rod be driven at this rack. There is a feeder (not branch circuit) run to a separate building or structure where there is an exterior disconnect labelled service disconnect. It feeds (back to back) a MLO panel. I view that the bond takes place in the cold sequence disconnect, and a 4-wire feeder runs from the meter to the exterior service disconnect. I argue that I am required to have a GEC at the exterior service disconnect and that the bond is not made here (per NEC 250.32(B) (see also Exhibit 250.19).

I don't think it's correct to use the grounded conductor to ground all the way to the service disconnect. What say you all? FYI - it would've been nice if we could've built the service on the building exterior, but that ship has sailed. I could also put the service disconnect on the rack (the rack would house cold seq disco, meter and service disco) - this would be more obvious that the structure is a separate structure and needs a GEC per 250.32.

It's not real clear why the building permit is being held up. I believe 250.24 allows me to bond any place between the lateral and main service disconnect. I don't think this scenario creates a parallel neutral, but maybe I'm too close to it.

Any feedback is greatly appreciated. If I'm lucky, the AHJ for the project will be scanning the forum and we can resolve this ASAP.

Thank so much, and Happy New Year!

 

[augie47]

IMO, since neither the cold sequence switch or the meter are service disconnects if your conductors to the detached building are connected there they are not feeders but are service conductors and a service disconnect and GEC are required at the separate building.
See NEC 230.70 exception 3
(also no EGC would be required)

 

[cdcengineer]

IMO, since neither the cold sequence switch or the meter are service disconnects if your conductors to the detached building are connected there they are not feeders but are service conductors and a service disconnect and GEC are required at the separate building.
See NEC 230.70 exception 3
(also no EGC would be required)

230.70 exception 3?

 

[kwired]

Your description does not say there is a service disconnect at the rack. If there is not then it is still service conductors when you reach the building, and the EGC is not needed, in fact it simply becomes parallel to the neutral if you have bonding jumper at the building.

If you do have service disconnect at the rack, then you do have a feeder and a separate EGC is needed, and no bonding jumper gets installed at the building. You still need a grounding electrode at the building but it connects to the EGC instead of the neutral when supplied by a feeder like this.

 

[don_resqcapt19]

Alright gang, it's been a while since I've haunted this forum. But I've been run around and incurred some serious brain damage on a local project here in Colorado. Here XCEL requires a cold sequence disconnect on services 320A and less if the fault at the meter is in excess of 10kAIC, and the XCEL standards state that the cold sequence disconnect shall be treated as a meter disconnect per NEC. NEC 230.82(3) states that the meter disconnect be labelled "Meter Disconnect Not Service Equipment" (though I'd argue it's service equipment, but not the service disconnect. 250.82(3) allows for a meter disconnect, but requires that it is grounded and bonded per Parts VII and V of Article 250. 250.142 allows for the grounded conductor to be use for equipment grounding on the supply side of service equipment. So far, clear as can be. As we progress thru code review, NEC 250.24 allows the connection to grounding electrode (GEC) at any point from the load end of the service lateral to the service disconnecting means. So it can be done inside the cold sequence disconnect, and I believe we could bond the neutral here. All fairly clear in my mind.

Here's where it gets tricky. This project has the cold sequence disconnect and meter built on a rack per XCEL dwg SC-50. XCEL requires a ground rod be driven at this rack. There is a feeder (not branch circuit) run to a separate building or structure where there is an exterior disconnect labelled service disconnect. It feeds (back to back) a MLO panel. I view that the bond takes place in the cold sequence disconnect, and a 4-wire feeder runs from the meter to the exterior service disconnect. I argue that I am required to have a GEC at the exterior service disconnect and that the bond is not made here (per NEC 250.32(B) (see also Exhibit 250.19).

I don't think it's correct to use the grounded conductor to ground all the way to the service disconnect. What say you all? FYI - it would've been nice if we could've built the service on the building exterior, but that ship has sailed. I could also put the service disconnect on the rack (the rack would house cold seq disco, meter and service disco) - this would be more obvious that the structure is a separate structure and needs a GEC per 250.32.

It's not real clear why the building permit is being held up. I believe 250.24 allows me to bond any place between the lateral and main service disconnect. I don't think this scenario creates a parallel neutral, but maybe I'm too close to it.

Any feedback is greatly appreciated. If I'm lucky, the AHJ for the project will be scanning the forum and we can resolve this ASAP.

Thank so much, and Happy New Year!

Per the definition in Article 100, the service equipment is the service disconnect.

Service Equipment.
The necessary equipment, consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the serving utility and intended to constitute the main control and disconnect of the serving utility. (CMP-10)

The term "service disconnect" is not a defined term in Article 100.

 

[augie47]

230.70 exception 3?

opps 230.40 Exception 3

 

[kwired]

Per the definition in Article 100, the service equipment is the service disconnect.

Service Equipment.
The necessary equipment, consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the serving utility and intended to constitute the main control and disconnect of the serving utility. (CMP-10)[/quote]
The term "service disconnect" is not a defined term in Article 100.
[/QUOTE]
Correct, and that makes everything up to the building supply side of service equipment and the service equipment is located at the building. Four wire feed was not necessary and in fact creates other issues if you try to use all four conductors. POCO can specify an electrode at the rack if they want, doesn't matter. Still need a GES at the building.

 

[cdcengineer]

Per the definition in Article 100, the service equipment is the service disconnect.

Service Equipment.
The necessary equipment, consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the serving utility and intended to constitute the main control and disconnect of the serving utility. (CMP-10)[/quote]
The term "service disconnect" is not a defined term in Article 100.
[/QUOTE]
Don, you are correct the cold sequence is not service equipment per this definition. But I am not required to bond neutral to GEC within the service disconnect? Per NEC 250.24, I can still bond the neutral to the GEC within the cold sequence disconnect can't I? It is not a very conventional install, but if XCEL didn't specifically call the cold sequence disconnect a meter disconnect, than it could be considered the service disconnect. The customer owns the cold sequence disconnect, and we can access it by cutting the seal. My brain hurts. Grounding and bonding has done this to me before...

 

[cdcengineer]

kwired, I was going to try and upload a photo of the one-line, but it seems too big. Am I understanding what you are all pointing out, is that I can bond to the GEC at the cold sequence disconnect at any accessible point (in this case the cold sequence disconnect), but that there cannot be a GEC conductor run from there to the service disconnect? Would I run a supply side bonding jumper sized per 250.66? Looking at Exhibit 250.10 isn't necessarily fully applicable, but similar in my mind.

 

[cdcengineer]

I guess I'm struggling with this, because the cold sequence disconnect is not the service disconnect in "name only". If XCEL did not specify this as a "meter disconnect", I could just as easily call it the service disconnect and this design would sit right (in my opinion).

 

[don_resqcapt19]

kwired, I was going to try and upload a photo of the one-line, but it seems too big. Am I understanding what you are all pointing out, is that I can bond to the GEC at the cold sequence disconnect at any accessible point (in this case the cold sequence disconnect), but that there cannot be a GEC conductor run from there to the service disconnect? Would I run a supply side bonding jumper sized per 250.66? Looking at Exhibit 250.10 isn't necessarily fully applicable, but similar in my mind.

You do not run a supply side bonding jumper to the service equipment. The neutral is used for all bonding and grounding on supply side and within the service equipment. The main bonding jumper in the service equipment provides the fault clearing path from the equipment grounding conductors to the neutral.

Note that supply side bonding jumpers are sized per 250.102(C) and not 250.66.

 

[jaggedben]

I guess I'm struggling with this, because the cold sequence disconnect is not the service disconnect in "name only".

The name is everything in this case. Code requirements like the MBJ and the GEC termination hinge on the location of the service equipment. By allowing a meter disconnect 'on the supply side of the service disconnect', and by requiring the meter disconnect to be labeled 'not service equipment', the code explicitly and effectively exempts the meter disconnect from all requirements that apply to service equipment. The only requirements that apply to the meter disconnect are those detailed in 230.82(3). (Which is why those requirements are spelled out there instead of referring back to other parts of 230.)

If XCEL did not specify this as a "meter disconnect", I could just as easily call it the service disconnect and this design would sit right (in my opinion).

True, but that's not what's being done according to your description.

 

[cdcengineer]

Thx for the responses everyone. Three last points of clarification...

#1 If XCEL hadn't dictated the cold sequence disconnect as "meter disconnect", than the design as described would be correct - with the bond taking place at the cold sequence disconnect, and a GEC set at the structure (no bond) and treated per 250. 32(B)?

# 2 Can someone explain to me... when the GEC connection occurs in the meter housing per Exhibit 250.7 - does the neutral still bond to ground within the service disconnect, or would that occur in the meter housing and EGC would be required between meter and service disconnect?

#3 Can a ground rod be set at the rack per XCELs standards? Would this connect to the neutral here. Then current carrying conductors and neutral are run in pvc to the separate structure where bond would take place, and ground established thru GEC set there?

If it wasn't a separate structure I don't think it would cause me so much dain bramage... thank you all very much for taking the time to respond.

 

[cdcengineer]

Jaggedben, saw your response after I typed my last post. I appreciated your response.

 

[jaggedben]

Thx for the responses everyone. Three last points of clarification...

#1 If XCEL hadn't dictated the cold sequence disconnect as "meter disconnect", than the design as described would be correct - with the bond taking place at the cold sequence disconnect, and a GEC set at the structure (no bond) and treated per 250. 32(B)?

Essentially correct. (NEC doesn't get into *who* says its a meter disconnect and not a service disconnect. Like, if the AHJ agrees then you could determine that yourself, potentially. But since Xcel are the ones insisting in this case, and probably have the authority to do so...)

# 2 Can someone explain to me... when the GEC connection occurs in the meter housing per Exhibit 250.7 - does the neutral still bond to ground within the service disconnect, or would that occur in the meter housing and EGC would be required between meter and service disconnect?

Main Bonding Jumper is always at the service disconnect. GEC connection can be on the supply side. Since you have separate structures, you need an electrode system at the building with the service disconnect. Maybe I'm wrong, but I don't believe the electrode at the meter disconnect is NEC required. But if it isn't, it can be regarded as an auxiliary electrode for NEC purposes. It's pretty much a moot point if following utility provided spec.

#3 Can a ground rod be set at the rack per XCELs standards? Would this connect to the neutral here. Then current carrying conductors and neutral are run in pvc to the separate structure where bond would take place, and ground established thru GEC set there?

Yes. See previous response.

 

[don_resqcapt19]

Thx for the responses everyone. Three last points of clarification...
...
# 2 Can someone explain to me... when the GEC connection occurs in the meter housing per Exhibit 250.7 - does the neutral still bond to ground within the service disconnect, or would that occur in the meter housing and EGC would be required between meter and service disconnect?
...

An equipment grounding conductor or supply side bonding jumper is NEVER required on the line side of the service disconnect. The neutral will be bonded in the service equipment as the main bonding jumper is required to be installed in the service equipment.

This happens all the time in my area as our utility requires two ground rods at the meter location and a GEC from those rods to the neutral in the meter. Typically the water pipe grounding electrode conductor and/or the concrete encased electrode conductor will be connected to the neutral in the service equipment.

 

[shortcircuit2]

Who owns the meter disconnect after installation? XCEL? If it is over 10K SCA it must be fused?

 

[don_resqcapt19]

Who owns the meter disconnect after installation? XCEL? If it is over 10K SCA it must be fused?

Typically it is like the meter can, owned by the building owner and under the exclusive control of the utility.
Many non-fused disconnects are have a SCCR rating over 10 kA with specific load side OCPDs.

 

[tom baker]

kwired, I was going to try and upload a photo of the one-line, but it seems too big. Am I understanding what you are all pointing out, is that I can bond to the GEC at the cold sequence disconnect at any accessible point (in this case the cold sequence disconnect), but that there cannot be a GEC conductor run from there to the service disconnect? Would I run a supply side bonding jumper sized per 250.66? Looking at Exhibit 250.10 isn't necessarily fully applicable, but similar in my mind

 

[tom baker]

You can copy and paste the picture, or Iemail to myself and change the resolution, or use a photo editing program to change resolution. First option is the easiest