Supply side equipment jumpers and main bonding jumpers

[dmanda24]

Looking at illustrations from this website I see that there is a supply side equipment bonding jumper that bonds the neutral to the case at the supply side (meter can) and there is a main bonding jumper that bonds the neutral to the grounding conductor or effectively to the case in the service disconnect.
Doesn't this provide an alternate path for currents on the neutral? what prevents currents from traveling on the frames and raceways between these two bonding jumpers?
I'm a Bit confused, I appreciate all the help

 

[dmanda24]

Illustration with a boning jumper on the supply side and at the main

 

[LarryFine]

Doesn't this provide an alternate path for currents on the neutral? what prevents currents from traveling on the frames and raceways between these two bonding jumpers?

Yes, and nothing. Ahead of the disco, it's allowed.

 

[brian john]

In most but not all residential installations this is addressed by the use of SEC cable or PVC. In Most large commercial installations the duct banks are fiber PVC or other non-conducting material.

And yes the use of metallic raceways can result in some problems. Had jobs with arcing issues from trough that had loose connections (a byproduct of poor installation practices), another issue is the multiple ground paths will effect the GFP operation on ground return GFP's

 

[dmanda24]

Can you eliminate the bonding jumper at the disconnect and run the grounding conductor from the meter or supply side equipment that has a bonding jumper tp eliminate objectionable currents?

 

[don_resqcapt19]

dmanda,

Can you eliminate the bonding jumper at the disconnect and run the grounding conductor from the meter or supply side equipment that has a bonding jumper tp eliminate objectionable currents?

No, that would be a violation of 250.24(B). While you can make the groundind electrode connection at any point on the line side of the disconnect, each service disconnect enclosure requires a bonding jumper.

(B) Main Bonding Jumper For a grounded system, an unspliced main bonding jumper shall be used to connect the equipment grounding conductor(s) and the service-disconnect enclosure to the grounded conductor within the enclosure for each service disconnect in accordance with 250.28.

Don

 

[dmanda24]

ok but can I do the oposite then? take out the equipment bonding jumper at the supply side and run a grounding conductor from the main disconect to the case of the equipment on the supply side?

 

[Dennis Alwon]

ok but can I do the oposite then? take out the equipment bonding jumper at the supply side and run a grounding conductor from the main disconect to the case of the equipment on the supply side?

And where would you connect this conductor in the main disco?

 

[iwire]

ok but can I do the oposite then? take out the equipment bonding jumper at the supply side and run a grounding conductor from the main disconect to the case of the equipment on the supply side?

Very doubtful, the supply side is typically a utility owned / or controlled transformer and they will require it be bonded if it supplies a grounded system.

 

[don_resqcapt19]

take out the equipment bonding jumper at the supply side and run a grounding conductor from the main disconect to the case of the equipment on the supply side?

In many areas there is a permanent physical bond in the meter can and you are only permitted to use the meter specified by the utility.
Have you experienced problems with the parallel current paths? I am not aware of any in our area, and every service has the parallel paths as we require the use of rigid or IMC for service conductors.
Don

 

[dmanda24]

I got a small shock when touching a nipple between the meter and the disconect, I currently have no time and told my friend to hire someone to check it out. It just surprises me that this situation is allowed and there is nothing to prevent it other than using nonmetallic conduit. However I have seen a lot of services where they used metallic raceways. Is there a code that prohibits the use of metallic raceways in this case?

 

[George Stolz]

Is there a code that prohibits the use of metallic raceways in this case?

No, in fact 230.43 offers many metallic options for service entrance conductors.

As Don mentioned, many services are installed and have not had problems.

I got a small shock when touching a nipple between the meter and the disconect...

There should not be a difference in potential among the different enclosures of the service equipment - this seems to indicate the enclosures themselves aren't bonded properly; the flow of neutral current is not really germane to this more serious problem, IMO.