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Splitting a 400amp Service

B

Bendigo

Member
Joined
Oct 21, 2009
Messages
2
Location
Pennsylvania
Who would allow this method of splitting a residental 400 amp service into two (2) parallel 200 amp main disconnects? I understand that two conductors can not be under the same lug unless specifically rated for that use. The contractor hasn't yet provided "proof" that these lugs are rated for two conductors. This is the first time I seen this in a meter enclosure, other installations always utilized double barreled lugs to split the service.your thoughts???

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Last week I failed a similar installation. I can't read it but the lug has the information written on it.
 
have him pull one of the terminations apart, read the lug, see what it says, it looks like (due to "egg shape") it's a 2 conductor lug, still need to verify that though. good call
 
In pic two on the left side of the lug you see two lines of wire gauges stamped. The top is for single conductors and just above the washer you see 3/0. Bet there is a 2 in front of that.
 
codeworks said:
you're joking right. how is pvc going to get energized ?
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No I'm not joking. It's not the PVC, it's bonding between the can and disconnects. See 250.92 2011 NEC. Additionally, any pvc should have a grounding conductor anyway in all but a few rare circumstances.

BS
 
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BSSTG said:
No I'm not joking. It's not the PVC, it's bonding between the can and disconnects. See 250.92 2011 NEC. Additionally, any pvc should have a grounding conductor anyway in all but a few rare circumstances.BS
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(1) Bonding equipment to the grounded service conductor in a manner provided in 250.8 This is done by the grounded (neutral) already being bonded in the meter can and by the main bonding jumper in the service disconnect.

To install a conductor in the PVC would be a parallel path between the meter can and the service enclosure.
 
jwelectric said:
(1) Bonding equipment to the grounded service conductor in a manner provided in 250.8 This is done by the grounded (neutral) already being bonded in the meter can and by the main bonding jumper in the service disconnect.

To install a conductor in the PVC would be a parallel path between the meter can and the service enclosure.
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Only if the can is listed for the purpose. Most are not. Some are. Addtionally, by that reasoning a parallel path would be had with metal conduit. So what's the difference?

BS
 
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BSSTG said:
Only if the can is listed for the purpose. Most are not. Some are. Addtionally, by that reasoning a parallel path would be had with metal conduit. So what's the difference?BS
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I would consider against making such statements. Why, because I happen to see nearly 99% of the meter socket enclosures do have this case to neutral bond. While there are obviously some meter enclosures for tenant side applications that are not I would venture to say the majority are bonded within the meter enclosure. Now this is clearly not the case in CT Cabinets but I digress.

As for the comment about whats the difference if a metal raceway is installed between the meter enclosure and service panel enclosure versus installing a conductor as Mr. Whitt spoke about previously. The answer is...agreed.....there is no difference as both could technically be a violation. However, it appears that use of a metal nipple is widely accepted (not sure why.....but it is).

Remember as you stated...only if the can is listed for that purpose. In that image you can't determine that one way or the other so suggesting it without knowing is a problem as well. How do we know that can is NOT listed for that application?
 
PaulAbernathy said:
Remember as you stated...only if the can is listed for that purpose. In that image you can't determine that one way or the other so suggesting it without knowing is a problem as well. How do we know that can is NOT listed for that application?
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I'm just going by the research I did on this a few years back. I don't know for sure one way or the other. A lot of cans look to be bonded and reality are, but are not listed. Nevertheless, I shudder to think that of all the thousands of installs I've done over the years that were engineered with a separate grounding conductor in metal pipe was causing a problem because of parallel ground paths. A lot of folks just don't trust metal pipe for a ground anyways. I'm one of them. Throw in some flex at the termination end and it may not be compliant anyway even though it's all metal depending of course on the size, ocp and such.

Bottom line is this, if I see a PVC pipe anywhere without a ground in it, it raises a big red flag.

You folks Have a Merry Chritmas! I'm off to the country to corrupt my grandson!

BS
 
There is a big difference in using a metal pipe for a fault current path and using a metal pipe for a parallel path for the neutral conductor.

The neutral is bonded to the meter can and also to the service disconnect enclosure and if a bonding jumper is installed in the raceway with the service conductors then all that has happened is the neutral is paralleled. This would invoke 310.10(H) and all the requirements found there.

As to using a metal raceway for an equipment grounding conductor 250.118 is the section. All the engineers in the world do not override this section no matter how dumb they are.
 
The neutral is grounded in the meter can by the poco and we are required to ground it again in each of the service disconnects but this picture shows it grounded in the gutter too. That makes 4 and the neutral is paralleled by the EGC all the way..
 
BTW, in this context, until NFPA changes the green wire to an Equipment BONDING conductor I will say grounded. I know there is a push to say the only grounding conductor is the one going to the GES.
 
What we call something has little to do with it actually is.

Ground. The earth.

Grounded (Grounding). Connected (connecting) to ground or to a conductive body that extends the ground connection.

Why would you even mention a green conductor as there is no green conductor in the illustration you posted?

In that illustration there is two main bonding jumpers in the service disconnects and two equipment bonding jumpers one to the trough and the other to the riser. These EBJs are to the isolated neutral bar in the trough and do the same thing that the screw in a single phase meter base does. See 366.60 for more information.

At to the metal raceway between the trough and the two disconnects this constitures a parallel path with the neutral and is addressed in 250.6

Should the neutral of either disconnect be lost then the metal pipe will conduct all unbalanced load for that part of the system.
 
I just used "green wire" to imply the EGC which is actually the raceways in the picture but could be a green or bare wire.

If the neutral bar in the gutter is bonded to the raceway and the gutter itself, how is it "isolated"?

I see 6 places plus the meter where there is a solid bond between the EGC and the neutral

(3 busbar jumpers to the can and 3 bonding bushings)

I understand we are not supposed to have circuit current in EGCs, raceways and cabinets but I think NFPA has given up on that in service equipment in the line side of the disconnect since the poco is going to bond the neutral in the meter can.

They even imply this in 250.24(5)

Load-Side Grounding Connections. A grounded conductor shall not be connected to normally non–current-carrying metal parts of equipment, to equipment grounding conductor(s), or be reconnected to ground on the load side of the service disconnecting means except as otherwise permitted in this article.
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Then there is the above picture in the handbook

I have seen it argued both ways. I am not willing to even get into it. Just saying there are different opinions.

BTW even the road warriors will not agree in seminars. I think it was Minick who said no and Pauley who said yes but I could have that backward. I am not sure if I heard Ode say.
 
I think you are missing the point.

The bonding that is required has nothing to do with grounding. All service equipment must be bonded to the neutral conductor.

When we use a PVC pipe between the meter and the service disconnect enclosure there is no requirement to include an Equipment Bonding Jumper in this raceway.

Should we decide to install a conductor in this raceway then that conductor is under 310 rules including 310.10(H).

If we do install an Equipment Bonding Conductor with the service entrance conductors and it is electrically connected on both ends then it is a parallel conductor that we installed and must follow 310.10(H).
 
I am not sure where you are going with 310.10(H) (2011 for you following along)

Are you saying I can't parallel the neutral unless it is a 1/0 or above?

I do see your concern that grounding conductors and raceways become current carrying conductors if the SE neutral (between the disconnect and meter can) opens up but that is a sticky wicket any time it happens.

There are 3 scenarios.

One you do have the meter can and the service disconnect enclosure bonded via a metal raceway and the raceway is carrying the unbalanced load.

The second scenario is the two are not bonded and the unbalanced load is fed down the ground electrode conductor landed in the disconnect enclosure and you are using earth as a return. Your ground rod is a worm chaser.

The worst case is if the GEC lands in the meter can (popular some places) per 250.24(A)(1), the SE neutral opens and the unbalanced load is presented, unimpeded to every GEC and piece of equipment in the building.

Perhaps that is why some think bonding all of the service equipment together is better than worrying about some objectionable current in the SE raceway.

Actually, if you poke around with your clamp you are going to find objectionable current everywhere if look anyway. Everyone's ground system is swapping current with everyone elses. I have a couple amps in my service neutral with the main tripped and every ground wire on a pole is carrying some current, up to almost 3 amps on my street

If we are going to we expand that discussion I suggest we open another thread.
 
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