BONDING

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ronnie

Member
I HAVE INSPECTOR SAYING I NEED A BONDING JUMPER BETWEEN MY METER CAN AND MAIN PANEL. I HAVE A 120/240 VOLT SINGLE PHASE SERVICE WITH PVC NIPPLE BETWEEN THE PANEL AND METER. THE GROUNDED(NEUTRAL
Code:
) LUG IN THE METER CAN IS CONNECTED TO THE METER CAN.
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: BONDING

250.142(A)(1) allows you to use the grounded conductor for grounding the meter enclosure.

A bonding jumper between the meter and panel will be a parallel neutral conductor.

Oh, you can hit the Caps Lock key. ;)
 

russ

Senior Member
Location
Burbank IL
Re: BONDING

I think you have it right the first time.
250.6(B) allows it the way you have it.

I'm in an area that only uses heavy wall conduit between the meter and the main disconnect by our code. I see this as a problem because the service entrance conduit always has current on it. I think either the meters should be change or our code should be change to require non metalic conduit between the two.
 

bennie

Esteemed Member
Re: BONDING

I agree Russ: A fault in the meter can will probably burn clear after the structure is ignited.

I am for a tupperware meter can.
 

charlie

Senior Member
Location
Indianapolis
Re: BONDING

Bennie, Tupperware has already been in the electrical trade when they introduced the Triliant (Square D) equipment. I don't think we want unprotected conductors (no overcurrent protection) in a plastic meter fitting. :D
 

hillbilly

Senior Member
Re: BONDING

Just a thought... Did you bond the neutral (grounded conductor) to the breaker panel enclosure?
steve
 

russ

Senior Member
Location
Burbank IL
Re: BONDING

If the grounded conductor is bonded to the meter 250.92(A) is met.

If the grounded conductor is bonded to the panel at the Main disconnect 250.92(A) is met.

Why do we need a wire or conduit that is parallel to the grounded conductor.

Are you saying if you use 3 wire service entrance cable it's not code, because there is no separate ground conductor.

:eek:
Just had to edit my post because I left the 92 out of 250.92(A). It reads what I ment now.

[ March 04, 2004, 01:27 PM: Message edited by: russ ]
 

stew

Senior Member
Re: BONDING

Johnsonl seems to have made a good point. If the nipple were rigid then a grounding loknut on one side or the other would be a means. Beacause yyou have pvc then the inspector must be citing the requirement in 250.92 and It seems to me he is correct as johnsonl says no?
 

stew

Senior Member
Re: BONDING

I should have looked at 250.6(B) before I opened my pie hole also because in the context that russ speaks of where the neutral is bonded in the meter can(which most are) then what you have done is exactrly what 250.6B adresses"alterations to stop objectionable current" Now I think rus is more right and the 250.92 is overidden by 250.6A. At least they somewhat contradict each other in a way.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
Re: BONDING

Back to the original question, why would an inspector (asuming he has some electrical background) want a parallel path here or anywhere. Doesn't he understand the neutral is the grounded conductor, which is the fault clearing path at this location.

Now the kicker, if the service neutral is smaller than 1/0, this inspector is instructing (not just suggesting) you to violate 310.4. ;)

Look at this diagram, specifically the number of conductors between main and meter

1014151446_2.gif


Roger
 

johnsonl

Member
Re: BONDING

I'll try this again...

If we look at article 100 (Definitions), we are able to see where bonding and grounding is different.

For example, if the grounded conductor becomes loose, then the metal enclosure is both ungrounded and unbonded. Now consider the bond, the bond provides electrically conductive path to the adjacent metallic box, where that box is grounded, therefore the ground fault path is maintained even though one side became loose because all the enclosures are bonded together.

Bonding forms an electrically conductive path that ensures electrical continuity and the capacity to conduct safely any current likely to be imposed on or to the enclosures.
 

bennie

Esteemed Member
Re: BONDING

In my opinion; The meter can and panels should be grounded with the MGN conductor. This insures the lowest impedance fault path to either blow the primary cutouts, or burn clear in the shortest time.
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: BONDING

You can try as many times as you want but it would still be incorrect to run a bonding wire between the meter and the panel.

This bonding wire would end up exactly as Roger said A Parallel Neutral Conductor That is all it would do.

When running metal raceway the bonding is to bond the raceway to the enclosure in case of a fault in the raceway.

The meter is bonded already.

Would you expect a separate bonding wire to the meter when using SE instead of raceway?
 

johnsonl

Member
Re: BONDING

This is for iwire......

If your contention is that adding the bonding jumper would produce a Parallel Neutral Conductor, then it would be wrong to ever use metal conduit, for metal conduit is conductive, so would this then not be an parallel path imposed onto the system.

hmmmmmmm
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
Re: BONDING

Johnson,
Now consider the bond, the bond provides electrically conductive path to the adjacent metallic box
see those green dots on the neutral bars connecting to green dots on the enclosures in the "main" and "meter", that is your bonding jumpers.

The articles posted by Iwire and Russ cover this issue. (and of course 310.4) :D

Roger

[ March 04, 2004, 03:45 PM: Message edited by: roger ]
 

iwire

Moderator
Staff member
Location
Massachusetts
Re: BONDING

Originally posted by johnsonl:
This is for iwire......

If your contention is that adding the bonding jumper would produce a Parallel Neutral Conductor, then it would be wrong to ever use metal conduit,
Well I don't do that either. :)

The last service I did I I used 4" RMC for every thing but the nipple between the 400 amp meter socket and the 400 amp fused switch which where mounted side by side.

For that nipple I used two 4" PVC connectors joined by a piece of schedule 80 PVC.

I may be allowed to run the metal nipple between the two enclosures but I do not think it is a wise idea to intentionally carry neutral current through the enclosures and raceway.

As to running a bond wire when using a PVC raceway that would be a direct violation of 310.4.
 

johnsonl

Member
Re: BONDING

If the meter can is not bonded to the service disconnect by means of a bonding jumper, a potential problem to the grounding system has occured.

If at each enclosure (Metercan and Service Disconnect)the grounded conductor is bonded to the enclosures (using the little green screws), what happens to the grounding and bond of the system if the grounded conductor becomes loose (expansion and contraction due to the heating and cooling of the conductor), and unless the tightness of the connection is checked and maintained on a regular basis, then the grounding and bonding of the system (Service) has been compromised.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
Re: BONDING

Johnson, using your reasoning, what would happen if the larger condutor (properly sized as the neutral) of the parallel path you propose to install comes loose from one of the bars leaving only the smaller conductor?

"What if's" are not part of the code, however parallel paths and bonding rules are and I would still have to wonder why an inspector would mandate a code violation.

How would you maintain a connection?

If the connection is properly torqued at the original installation and you retorque a conductor connection, you have probably done more to damage this connection than all the heating and cooling that will normally occure.


Roger

[ March 05, 2004, 03:34 PM: Message edited by: roger ]
 
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