"Grouping" How would you interpet this 400amp

[amptech]

Re: "Grouping" How would you interpet this 400amp

If the service, the single metering point served by the utility, is located on one building and you are serving 2 or more buildings from this service, how would you "group" the service disconnects? If you do as allenwayne said and back to back a MB loadcenter with the meterbase and then run 3 wire from the load side of the meterbase to a MB loadcenter in a separate building there could not be any other metal conductive paths between the buildings. If there were you would need a 4th wire. If the utility used one transformer to provide 2 separate drops to the 2 buildings each with their own separate service and metering it is a different story.

 

[amptech]

Re: "Grouping" How would you interpet this 400amp

It seems to me it would be difficult to meet all of the requirements of 250.32(D) for a residential property. Conductive paths between buildings would surely be present. I would be hard to convince that 225.32 Exception No.1 could be applied to a homeowner's situation.
Maybe I've been missing something all of these years. If so, enlighten me.

 

[George Stolz]

Re: "Grouping" How would you interpet this 400amp

Originally posted by amptech:
If the service, the single metering point served by the utility, is located on one building and you are serving 2 or more buildings from this service, how would you "group" the service disconnects?

Look at the diagram in 230.1, which displays the different components of a service. Follow the path of the "service."

First, you have the conductors. Let's check for compliance.
</font>

• <font size="2" face="Verdana, Helvetica, sans-serif">230.2, Check.</font>
• <font size="2" face="Verdana, Helvetica, sans-serif">230.3, Check.</font>
• <font size="2" face="Verdana, Helvetica, sans-serif">230.40, Check per Exc. 3.</font>

<font size="2" face="Verdana, Helvetica, sans-serif">Now, each building has a service, supplied by the same service entrance conductors as permitted by 230.40 Exception 3. Each service disconnecting means must comply with Part V. They must be grouped, on each building served. The two buildings are not considered a unit. They are two independent buildings.

As long as these are service conductors, 230 governs the installation.

If you installed a disconnect ahead of the conductors to the garage, everything changes; Article 225 governs the installation.

If the utility used one transformer to provide 2 separate drops to the 2 buildings each with their own separate service and metering it is a different story.

But 230.40 Exception 3 states that we don't need the utility to do this for us. Both structures can be on the same meter, with the same service conductors, with two service disconnecting means.

[ May 14, 2005, 01:16 PM: Message edited by: georgestolz ]

 

[amptech]

Re: "Grouping" How would you interpet this 400amp

So 250.32 doesn't apply since it refers to feeders or branch circuits? The same hazards that 250.32(B)(1) and (2) address are still present, aren't they? If you run a 3 wire supply to the second building and bond the grounded conductor to the required grounding electrode at the building and you have telephone service ran from the first building to the second building, is this a violation of 250.32(B)(2) or not?

 

[George Stolz]

Re: "Grouping" How would you interpet this 400amp

It's no different than having two neighboring houses sharing the same pedestal or transformer. Instead of two sets of service conductors running two different directions, we have one set go to the first building, do an about-face and hit the second.

I don't think the phone company's habit of grounding their systems to POCO lines makes sense, to me. But I don't know how phones work, myself. I'd be good if someone could explain this. I think others have tried to explain it to me in the past, and it didn't stick.

But as far as these things go, 250.32 has no footing in this installation.

 

[charlie]

Re: "Grouping" How would you interpet this 400amp

Amptech, you are trying to make sense of the NESC rules from the NEC. The NEC requirements require the grounded and grounding conductors to be kept separate past the service equipment. The NESC requirements require the grounded conductor to also act as the grounding conductor in front of the service equipment. In 230.40 Exc. 3, service entrance conductors are taken to a dwelling unit outbuilding and additional service equipment is installed for those conductors. Since this is all in front of the service equipment, the bonding requirements match the NESC requirements.

By the way, the communications companies are required by the NESC to bond their shields and messengers to our pole grounds whenever they attach to the poles where they exist.

 

[amptech]

Re: "Grouping" How would you interpet this 400amp

Charlie,
I don't think I'm confusing the 2 codes. Here's the situation I think George is describing(correct me if I'm wrong, George):
320A meterbase mounted on a house. One set of conductors(3-wire) leaves the meterbase and lands in a MB panel in the house. A second set of conductors leaves the meterbase and runs underground say 75' to a second building and lands in another MB panel. Grounding electrode driven at the house and #6 bare copper GEC connects it to the loadcenter. Neutral is bonded to GEC in the house MB panel. Grounding electrode is driven at the second building and #6 bare copper GEC connects it to the loadcenter. Neutral is to GEC in this MB panel. Homeowner/contractor, not phone company, extends phone lines from the house to the second building. Phone service is grounded to the house's GE system. Now we have the forbidden parallel ground path. I would agree that George's installation is compliant until another conductive path, such as a phone line, is installed between the two buildings. Am I wrong? Or is it permissible to have parallel paths if the supply is service conductors but not if the conductors are feeders or branch circuits?

 

[james wuebker]

Re: "Grouping" How would you interpet this 400amp

Amptech, It's hard for me to follow you guys. Meter base at the house. 3 wire to the MB panel for the house. Again from the meter 3 wire feed about 75' to another building with a MB panel. Have you did something like this? It looks like there's not a Main for these only at each MB panel. Where I'm at they wouldn't allow this set up. It would be OK here if you had a 400 amp main off the meter then feed to each MB panel. Then you would need 4 wires to each. Here, how you were talking about I would have to have the MB panel(House) and a 200 amp disconnect that feeds (Building 75' away) grouped together. That means side by side. I don't have to worry about the telephone and other things that I might have to run to the far building. But I see where your coming from a little.
Jim

 

[charlie]

Re: "Grouping" How would you interpet this 400amp

OK, one more try.

230.40 Number of Service-Entrance Conductor Sets Each service drop or lateral shall supply only one set of service-entrance conductors.

Exception No. 3: A single-family dwelling unit and a separate structure shall be permitted to have one set of service-entrance conductors run to each from a single service drop or lateral.

From the 2005 NFPA NEC Handbook

"Exception No. 3 to 230.40 allows a second set of service-entrance conductors supplied by a single service drop or lateral at a single-family dwelling unit to also supply another building on the premises, such as a garage or storage shed."

 

[hurk27]

Re: "Grouping" How would you interpet this 400amp

You forgot to add that the meter is just fat bulge in the service entrance conductors Charlie.

Very fat with the prices of NIPSCO!

 

[amptech]

Re: "Grouping" How would you interpet this 400amp

I concede the point. Per NEC articles you all have cited, this installation would be compliant. I have been part of a misunderstanding in my area on this point.

 

[charlie]

Re: "Grouping" How would you interpet this 400amp

Originally posted by hurk27:
You forgot to add that the meter is just fat bulge in the service entrance conductors Charlie.

Very fat with the prices of NIPSCO!

 

[George Stolz]

Re: "Grouping" How would you interpet this 400amp

Originally posted by james wuebker:
Have you did something like this? It looks like there's not a Main for these only at each MB panel. Where I'm at they wouldn't allow this set up.

What would you cite to fail it?

I didn't know we could do this either, until it was brought up.

 

[hurk27]

Re: "Grouping" How would you interpet this 400amp

George
Most inspectors will try to have a problem with the part of not having a disconnect on the building or structure. This has been brought up in threads when installing a meter on a pole out away from the building. If the service conductors do not enter or pass through a structure , I don't see where a disconnect is required.
"ON" is not "IN"

230.70 General.
Means shall be provided to disconnect all conductors in a building or other structure from the service-entrance conductors.

Now 225.31 does state it a little different. But this installation is not under 225.31

225.31 Disconnecting Means.
Means shall be provided for disconnecting all ungrounded conductors that supply or pass through the building or structure .

Jim

That means side by side. I don't have to worry about the telephone and other things that I might have to run to the far building.

In this installation, parallel metallic path's are not even considered as the requirement for this in the NEC 250.32(A) is only for where branch circuits and feeders feed an out building, Not service entrance conductors. as George has already posted earlier. Also 250.142(A) allows us to use the grounded service conductor (Neutral) to ground equipment at or on the supply side of any service disconnect. This means only three conductors have to be ran.

[ May 15, 2005, 01:58 PM: Message edited by: hurk27 ]

 

[amptech]

Re: "Grouping" How would you interpet this 400amp

I'm not trying to be a smart *** here but why do you suppose adding OCP ahead of the conductors to the second building makes a difference concerning parallel paths to ground?

 

[iwire]

Re: "Grouping" How would you interpet this 400amp

Originally posted by amptech:
I'm not trying to be a smart *** here but why do you suppose adding OCP ahead of the conductors to the second building makes a difference concerning parallel paths to ground?

It doesn't' make a difference to the electricity only a difference in code requirements.

 

[George Stolz]

Re: "Grouping" How would you interpet this 400amp

A line has to be drawn somewhere.

The code is akin to the real world, where there needs to be a clear demarcation point for requirements. For the battle between NEC and NESC in this case, the demarc is the disconnecting means of the service.

 

[physis]

Re: "Grouping" How would you interpet this 400amp

Point of attatchment.

 

[iwire]

Re: "Grouping" How would you interpet this 400amp

Originally posted by physis:
Point of attatchment.

Sorry Sam I will have to side with George on this one.

The service disconnect is the location where the grounding requirements change.

Check out 250.142's "Supply-Side Equipment" and "Load-Side Equipment" terminology.

 

[physis]

Re: "Grouping" How would you interpet this 400amp

I'm sorry Bob. George said NEC-NESC demarcation. I didn't see ground in there.

But then I only looked at George's post.