Bonding RMC Underground Service

Status
Not open for further replies.
E

euclid43

Senior Member
Inspector wants me to bond underground service (GRC) to meter. I thought that having any grounding wire in their meter was prohibited. Furthermore, I am not sure what they expect when they bond with #6 to main service. It's not going to facilitate any shutoff on the supply. I have a bonding bushing on the loadside, which was good in the past.
 
External bond to a pipe clamp.

Just noticed that you said you already have a bonding bushing. What article is he citing you for on the correction?
 
He was hooked on concentric knockout, and he wondered how it would shut off if energized. The only scenario I could think that could conceivably happen is the dirt not settled and breaking the concentric knockouts and then there's nothing bonded; but that only protects for potential touching.
 
euclid43 said:
He was hooked on concentric knockout, and he wondered how it would shut off if energized. The only scenario I could think that could conceivably happen is the dirt not settled and breaking the concentric knockouts and then there's nothing bonded; but that only protects for potential touching.
Click to expand...
Does your bonding bushing have a jumper to the grounded conductor?
 
euclid43 said:
He was hooked on concentric knockout, and he wondered how it would shut off if energized. The only scenario I could think that could conceivably happen is the dirt not settled and breaking the concentric knockouts and then there's nothing bonded; but that only protects for potential touching.
Click to expand...

What do you mean by nothing bonded? The meter enclosure is already factory bonded to the neutral so that wouldn't matter. Do you mean the RMC?
 
euclid43 said:
Yes, it's all about the RMC.
Click to expand...
If the ground settles and separates the concentric knockouts from the meter enclosure, the RMC will still be bonded though the bushing and bonding jumper... unless the jumper has no slack to allow for this possibility.
 
An fitting is required for potential ground movement so the point about the breaking of the concentric KO is moot.
 
I did a service change with the RMC, and underground conductors being the only salvaged parts. I passed my inspection, but the department chief called me and wanted me to bond the RMC. So, I failed, but I want to know what their reasoning is and what they're trying to achieve. Perhaps they will learn something new.
 
Metallic raceways that contain service entrance conductors require bonding beyond that of normal locknuts and bushings. If you had a full size KO then you could have used a bonding locknut, bonding wedge or other device. Since you have concentric KO's then that point is moot and you need the bonding bushing. Even if there were no chance of breaking the KO's you would still need the bonding bushing. You should have also failed for not complying with 300.5(J).
 
euclid43 said:
Inspector wants me to bond underground service (GRC) to meter. I thought that having any grounding wire in their meter was prohibited. Furthermore, I am not sure what they expect when they bond with #6 to main service. It's not going to facilitate any shutoff on the supply. I have a bonding bushing on the loadside, which was good in the past.
Click to expand...
Take a look at 250.92(B). Even if you do not have concentric knockouts it requires more then just standard locknuts to ensure the service raceway is bonded.

(B) Method of Bonding at the Service.


Bonding jumpers meeting the requirements of this article shall be used around impaired connections, such as reducing washers or oversized, concentric, or eccentric knockouts. Standard locknuts or bushings shall not be the only means for the bonding required by this section but shall be permitted to be installed to make a mechanical connection of the raceway(s).


Electrical continuity at service equipment, service raceways, and service conductor enclosures shall be ensured by one of the following methods:


1. Bonding equipment to the grounded service conductor in a manner provided in 250.82.
2. Connections utilizing threaded couplings or threaded hubs on enclosures if made up wrenchtight
3. Threadless couplings and connectors if made up tight for metal raceways and metal-clad cables
4. Other listed devices, such as bonding-type locknuts, bushings, or bushings with bonding jumpers
Click to expand...
 
You say you have a bonding bushing on the load side. Are you referring to the conductors after the meter? Is this the raceway in question or is the inspector questioning the raceway on the line side of the meter?

You are required to bond all raceways containing service conductors. Standard locknuts are not acceptable. You need to use threaded hub or bonding busing. Review 250.93
 
infinity said:
... Even if there were no chance of breaking the KO's you would still need the bonding bushing. You should have also failed for not complying with 300.5(J).
Click to expand...

--shame on me for thinking the ground will settle more after 30 years

After all things considered, I have to state a few things.
  1. I installed a bonding bushing on the panel side of service conductors (supply side)
  2. There's just a locknut on the RMC coming into meter.
  3. Between the two locations is a chase and three areas of concentric knockouts, of which one is bonded.
Now....do I have to bond all the concentric areas of the supply side service conductors raceways? (probably not)

By the way, Xcel Energy doesn't allow ground wire in their meter housing.

Thanks.
 
Last edited:
Each separate section of metallic service raceway would require bonding on one end with something other than standard locknuts.
 
euclid43 said:
--shame on me for thinking the ground will settle more after 30 years

After all things considered, I have to state a few things.
  1. I installed a bonding bushing on the panel side of service conductors (supply side)
  2. There's just a locknut on the RMC coming into meter.
  3. Between the two locations is a chase and three areas of concentric knockouts, of which one is bonded.
Now....do I have to bond all the concentric areas of the supply side service conductors raceways? (probably not)

By the way, Xcel Energy doesn't allow ground wire in their meter housing.

Thanks.
Click to expand...
POCO probably doesn't want grounding electrode conductor run to the meter, bonding jumpers to raceways are likely allowed. If not, you could always use an external bonding clamp (like used to connect GEC to a water pipe) and route bonding conductor to the service disconnect. Bottom line is NEC wants more then just standard locknuts to assure bonding of metallic service raceways.
 
Status
Not open for further replies.
Top