service grounding concern

[sjspad]

my local poco wants the GEC brought into to the meter socket.usually not a problem for me.In this case i have a service with just a meter socket on the house .The service entrance conds (load side of meter), are piped in under a slab 25 ft to the main.I want to bring a GEC from the main to the meter socket also, but this appears to be a violation to 310-4.My concern is a lost neutral between the meter and the main. There is no ground return.There was no room for a disconnect next to the meter or this would not be an issue.So at this time The GEC is brought into the meter only.the poco will not energize unless GEC is in the socket.should i be so concerned?Any sugesstions

steve

 

[al hildenbrand]

Re: service grounding concern

Steve,

Up in my area, we commonly run metal conduit from the meter socket to the service panel. The PoCo doesn't want us to bring the GEC to the meter socket. The common install has a meter socket outside with conduit running on the exterior of the building until it reaches the location closest to the service center. The local rule of thumb is that we have a max of five feet of pipe allowed from the point we penetrate the exterior until the pipe terminates in the enclosure of the service disco. The GEC is bonded to the neutral in the disco. We bond the GEC to the neutral in the disco. The meter socket neutral in manufactured bonded to the enclosure of the socket.

Here's my point. The metal conduit is a parallel conductor to the insulated neutral inside it in the run of pipe between the service center/disco and the meter socket. This is a good thing because this is the PoCo side of the overcurrent protection of the disco, and these are service conductors.

I'm guessing you've used PVC for your run. The GEC, run with the neutral and hots, electrically, will behave no different than if the conduit were conductive metal.

What you're doing sounds right to me.

Al

 

[sjspad]

Re: service grounding concern

Thanks al for the info.
yes the conduit is pvc under the concrete.do you think it would be ok to run the GEC from the main to the disco thru the building . the service conds are all in place and connected.It sure would make me feel better installing a GEC from the main, back to the meter as well as having A GEC going to my 2 gnd rods connected to the meter socket .This would satisfy the poco and provide a safe grnd path if the neutral failed between the socket and main disco.SO you dont feel the ground loop would be a problem?

 

[al hildenbrand]

Re: service grounding concern

Steve,

Not only is it not a problem, on the service side of the disco, but multiple paths are intended by the NEC.

Now, ignoring the NEC's requirements for the GEC/neutral bond, I could argue about other things, but, strictly speaking NEC only, this is not a problem.

 

[gwz2]

Re: service grounding concern

Al,

Using the DC ohms law to calculate the amount of current on the 5' of rigid metal conduit (RMC) when the grounded conductor ( and the 1.5" RMC is in parallel with a 2/0 copper grounded of a residential 200Amp service between the meter and the main disco ) is carrying a 30 Amp unbalance current, the 2/0 copper and the 1.5" RMC almost equally share that 30A of unbalanced current.

The grounded conductor for that 5' of 2/0 copper and the 5' of 1.5" RMC each carry about 15 amps.

Of course on an AC system, Z must be considered instead of ohms, but the comparison is there.

And on a 200A service, a 30 Amp unbalance of L1 and L3 would not be unreasonable.

 

[sjspad]

Re: service grounding concern

Al
what do you mean about muliple paths are intened by the NEC?what about 310-4?

 

[gwz2]

Re: service grounding concern

Al,

Using the DC ohms law to calculate the amount of current on the 5' of rigid metal conduit (RMC) when the grounded conductor ( and the 1.5" RMC is in parallel with a 2/0 copper grounded of a residential 200Amp service between the meter and the main disco ) is carrying a 30 Amp unbalance current, the 2/0 copper and the 1.5" RMC almost equally share that 30A of unbalanced current.

The grounded conductor for that 5' of 2/0 copper and the 5' of 1.5" RMC each carry about 15 amps.

Of course on an AC system, Z must be considered instead of ohms, but the comparison is there.

And on a 200A service, a 30 Amp unbalance of L1 and L3 would not be unreasonable.

 

[sjspad]

Re: service grounding concern

How can i relocate this topic to a new forum
say grounding and bonding? I did not realize i entered it in the EMF forum

 

[hurk27]

Re: service grounding concern

Glen didn't we have a threed in the old forum that came to the conclusion that if the GEC is brought to the meter then the neutral ran into the main panel would act as the GEC to pervent paralleling of the neutral? and the three service conductors ran to the main panel would be adaquate? I think it was this one:

http://www.mikeholt.com/forum/Forum1/HTML/006012.html

 

[jxofaltrds]

Re: service grounding concern

Steve

Am I missing something? How are you compling with 230.70(A)(1)? Have I been shoveling snow too long?

Mike P.

 

[don_resqcapt19]

Re: service grounding concern

Mike,
Look at 230.6. The raceway from the meter to the service panel is not in the building.
Don

 

[al hildenbrand]

Re: service grounding concern

Steve,

I see the other thread covered the points pretty well. The PoCo side of the disco has to have a minimum of three parallel current paths for the unbalance current to travel in back to the PoCo transformer. In your case one path is the neutral conductor, the second is through the two ground rods - earth - up the pole to the transformer, and the third is to the water service - earth - up the pole to the transformer. If this house is connected to a municipal water system shared with other houses connected to the same transformer, more parallel paths are added. The common water system pipe becomes a conductor in its own right, and is tied back to other electrical services through their GECs, and in turn back to the transformer. Consider:

Glenn,

Thanks for the practical example. Makes ya think, don't it?

Al

 

[hurk27]

Re: service grounding concern

Al I was making refrance to the statement of running a gec to the panel from the meter
Quote by sjspad

It sure would make me feel better installing a GEC from the main, back to the meter

[ February 23, 2003, 09:55 PM: Message edited by: hurk27 ]

 

[sjspad]

Re: service grounding concern

Al
The house has a deep well with plastic pipe feeding the water service to the house.so the water will not be used as part of the GE system.It will just be bonded.The house electric service is by itself.no other homes connected to the same secodary of a pad xformer.Ifeelit will still be best to run aGEC from the main disc to the meter socket even though there is a GEC conn made at the socket already by the 2 ground rods . do you agree

steve

 

[jxofaltrds]

Re: service grounding concern

Don

Thanxs.

Steve

I believe that a ground from the panel to the meter would be a violation of 310.4

My setup is exactly as yours except no bonding at the meter.

Al

Would you please explain your post. I do not understand what you are trying to explain.

Mike P.

 

[al hildenbrand]

Re: service grounding concern

Mike,

Which post?

 

[jxofaltrds]

Re: service grounding concern

Al

"The PoCo side of the disco has to have a minimum of three parallel current paths for the unbalance current to travel in back to the PoCo transformer."

Mike P.

 

[al hildenbrand]

Re: service grounding concern

That's a good point, Mike. I don't have enough information from Steve to really make that statement. I can imagine at least one way that the only connection to ground would be the two ground rods. So, if the two ground rods are the only thing in the grounding electrode system, then there are only two paths back to the PoCo transformer for the unbalance current. One path is the neutral, itself, and the other is thru the rod, thru the earth and up to the transformer.

 

[hurk27]

Re: service grounding concern

Thank's Mike I thought I was reading somthing wrong

 

[hurk27]

Re: service grounding concern

I have never heard of three paths back to the poco's transformer for the neutral? what would you do if all the plumbing in the house is pvc? run another wire to the pole?