bonding bushing / concentric KO

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OK Matt, then 2 questions.

Why did you use RMC, to use it as an EGC?

If you ran RMC as an EGC, then why pull an additional EGC?

FWIW, looks like cake to go back and install a bond bushing.(for free)
 
chris kennedy said:
OK Matt, then 2 questions.

Why did you use RMC, to use it as an EGC?

If you ran RMC as an EGC, then why pull an additional EGC?

FWIW, looks like cake to go back and install a bond bushing.(for free)
Click to expand...

The panel is a qo612l100rb I found no good info on the concentrics.

I used RMC because 4' below the panel, it goes into the ground into a ditch. I never use pipe as an EGC, Always run a seperate EGC.

It will be an easy fix, But wanted to know who was in the wrong before I drove 70 miles on way one company time.

~Matt
 
If all metal raceways require bonding when concentric KO?s are present why does 250.97 exist. I don?t see any requirement that requires bonding around concentric KO?s on circuits under 250 volts. Is the raceway protecting the GEC non-metallic? If its metallic It would require additional bonding.
 
curt swartz said:
If all metal raceways require bonding when concentric KO’s are present why does 250.97 exist. I don’t see any requirement that requires bonding around concentric KO’s on circuits under 250 volts. Is the raceway protecting the GEC non-metallic? If its metallic It would require additional bonding.
Click to expand...

Would you be kind enough to post 250.97?

The conduit protecting the GEC is PVC.

~Matt
 
curt swartz said:
If all metal raceways require bonding when concentric KO’s are present why does 250.97 exist. I don’t see any requirement that requires bonding around concentric KO’s on circuits under 250 volts. Is the raceway protecting the GEC non-metallic? If its metallic It would require additional bonding.
Click to expand...

Curt you may have hit the nail on the head. I bet the inspector wants a bonding bushing on the GEC-- if the conduit is metallic--

It would need to be bonded on both ends to prevent a choke.

Okay-- that was wrong as noted above.
 
here it is
250.97 Bonding for Over 250 Volts.
For circuits of over 250 volts to ground, the electrical continuity of metal raceways and cables with metal sheaths that contain any conductor other than service conductors shall be ensured by one or more of the methods specified for services in 250.92(B), except for (B)(1).
Exception: Where oversized, concentric, or eccentric knockouts are not encountered, or where a box or enclosure with concentric or eccentric knockouts is listed to provide a reliable bonding connection, the following methods shall be permitted:
(1) Threadless couplings and connectors for cables with metal sheaths
(2) Two locknuts, on rigid metal conduit or intermediate metal conduit, one inside and one outside of boxes and cabinets
(3) Fittings with shoulders that seat firmly against the box or cabinet, such as electrical metallic tubing connectors, flexible metal conduit connectors, and cable connectors, with one locknut on the inside of boxes and cabinets
(4) Listed fittings
Click to expand...
 
250.97 Bonding for Over 250 Volts.
For circuits of over 250 volts to ground, the electrical continuity of metal raceways and cables with metal sheaths that contain any conductor other than service conductors shall be ensured by one or more of the methods specified for services in 250.92(B), except for (B)(1).
Exception: Where oversized, concentric, or eccentric knockouts are not encountered, or where a box or enclosure with concentric or eccentric knockouts is listed to provide a reliable bonding connection, the following methods shall be permitted:
(1) Threadless couplings and connectors for cables with metal sheaths
(2) Two locknuts, on rigid metal conduit or intermediate metal conduit, one inside and one outside of boxes and cabinets
(3) Fittings with shoulders that seat firmly against the box or cabinet, such as electrical metallic tubing connectors, flexible metal conduit connectors, and cable connectors, with one locknut on the inside of boxes and cabinets
(4) Listed fittings
 
curt swartz said:
If all metal raceways require bonding when concentric KO’s are present why does 250.97 exist. I don’t see any requirement that requires bonding around concentric KO’s on circuits under 250 volts. Is the raceway protecting the GEC non-metallic? If its metallic It would require additional bonding.
Click to expand...

Under 250 volts no bonding bushing is required and the inspector is incorrect. Standard locknut's on a metallic raceway are suitable for bonding. For what it's worth that center one is a tangential KO not a concentric or eccentric.
 
You pulled a ground and it's 120/240 so no bond bushing is required.



Don't make me look it up.

Edit. Crap....what they said.

One of my guys got called on the same thing and instead of sticking to his guns, he installed it to get the green tag. I always take the opportunity to educate an inspector like this whenever possible so he doesn't continue to make stuff up.
 
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infinity said:
Under 250 volts no bonding bushing is required and the inspector is incorrect. Standard locknut's on a metallic raceway are suitable for bonding. For what it's worth that center one is a tangential KO not a concentric or eccentric.
Click to expand...

It lookes like this:

sqdko.jpg





~Matt
 
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TOOL_5150 said:
It lookes like this:

sqdko.jpg


So there is no direct contact if you use a 3/4 pipe, but if you use a 1" pipe there is... Why are they made like that?


~Matt
Click to expand...

I don't know but you can see from the photo that a tangential KO is different than an eccentric or a concentric KO.
 
infinity said:
I don't know but you can see from the photo that a tangential KO is different than an eccentric or a concentric KO.
Click to expand...

No matter what size pipe you install, at least part of the locknut and the should of the fitting are going to land against part of the box that has no KO part to it.

If you install a 1" pipe in factory concentric KOs that go up to 2" or more, then the lock nut & fitting are on the KOs alone.

TOOL_5150 said:
I am still a little unclear between tangential and eccentric. Anyone got some pics?

~Matt
Click to expand...

Different terms for the same thing.
 
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480sparky said:
No matter what size pipe you install, at least part of the locknut and the should of the fitting are going to land against part of the box that has no KO part to it.

If you install a 1" pipe in factory concentric KOs that go up to 2" or more, then the lock nut & fitting are on the KOs alone.



Different terms for the same thing.
Click to expand...



Ok, but in my pic, the smallest KO, a 3/4 will have the locknuts rest on the other part of the KO ring, not the chassis. If I were to break out the 3/4 and 1" and install a 1" pipe, then it would be against the chassis.

~Matt
 
infinity said:
Here's a photo of an eccentric KO in the back of the box:

521711234e30_sc1.jpg
Click to expand...



Ok so eccentrics are more round, however look closely at my pic - the smallest KO doesnt have ANY part up against the chassis.

TO ADD: in the pictured eccentric, at least a part of the 1/2 and 3/4 will be touching the box


~Matt
 
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