348.60 (D)

[jes25]

I'm working on some content for our apprentices with Mike Holt's material and I'm not clear on something. 348.60(D) talks about bonding jumpers for FMC and points us to 250.102. Specifically, 250.102 (D) (2) where, it says we can run a bonding jumper on the OUTSIDE of a raceway up to 6 feet. The NEC handbook even shows a graphic with a bond wire on the outside of a piece of flex going to a motor next to this section. Mike Holt also has similar graphics.

What I don't understand is how this wire on the outside of the flex is being classified as a bonding jumper instead of an EGC. 348.60 (B) says an EGC is required for flexible installations and right below in 348.60 (C) says a to install the EGC per 250.134 which doesn't allow any EGC on the outside of a raceway.

What I'm saying is, the way I read this a bonding wire on the outside of a piece of flex doesn't meet the requirement for a EGC. Agree?

Which begs the question, why install that wire on the outside of the flex.

Can anyone clear this up?

 

[mikeames]

EGC and Bonding are two different things so different requirements. Don't view them as being the same. They serve different purposes.

 

[jes25]

EGC and Bonding are two different things.

That's my point

 

[wwhitney]

Say you have two enclosures connected by a piece of FMC, a run of EMT, and then another piece of FMC. And say the requirements of 250.118(5) for the FMC to be an EGC are not met. So you run a wire type EGC through the raceway from enclosure to enclosure.

What about the EMT in the middle of the run? The FMC is not considered an EGC, so if it is only bonded via the FMC, that would not be adequate. So on one end or the other, you run an equipment bonding conductor on the outside of the FMC to connect the EMT to the enclosure. Now the EMT is properly bonded.

Cheers, Wayne

 

[jes25]

Mike, could you explain to me a situation where someone would install a Equipment Bonding Jumper per 348.60 (D) on the outside of a piece of FMC?

 

[mikeames]

HA HA I was just going to post this as an example

bonding jumper/liquid tight fmc

Just wanted to hear from others on this issue. There is liquid tight flex metal conduit ran on both ends of rigid metal conduit. The flex goes to the box. There is a ground pulled inside the conduit, However i believed it was required to run a 'bonding jumper (ground wire)' on the outside of...

forums.mikeholt.com

 

[jes25]

Say you have two enclosures connected by a piece of FMC, a run of EMT, and then another piece of FMC. And say the requirements of 250.118(5) for the FMC to be an EGC are not met. So you run a wire type EGC through the raceway from enclosure to enclosure.

What about the EMT in the middle of the run? The FMC is not considered an EGC, so if it is only bonded via the FMC, that would not be adequate. So on one end or the other, you run an equipment bonding conductor on the outside of the FMC to connect the EMT to the enclosure. Now the EMT is properly bonded.

Cheers, Wayne

OK, yes. That would be the application. The graphics I'm seeing show a wire on the outside of the flex from motor to disconnect which make me think they are installing the EGC, (when FMC itself is not an EGC) on the outside of the conduit.

 

[infinity]

OK, yes. That would be the application. The graphics I'm seeing show a wire on the outside of the flex from motor to disconnect which make me think they are installing the EGC, (when FMC itself is not an EGC) on the outside of the conduit.

Do these graphics actually have an EGC in the raceway or is the bonding jumper being used to make a metal raceway that qualifies as an EGC continuous from the raceway to the equipment?

 

[jes25]

Do these graphics actually have an EGC in the raceway or is the bonding jumper being used to make a metal raceway that qualifies as an EGC continuous from the raceway to the equipment?

In both cases it goes from motor controller to motor so I don't see this as bonding around a non-EGC raceway. I see it AS the EGC.

I suppose there could be an additional EGC inside the raceways that I don't see.......

 

[jes25]

The Mike Holt Graphic is 348-7 from understanding the NEC book 2023 edition. The handbook graphic is next to 250.102

 

[wwhitney]

So, I guess it pays to read the definitions:

"Bonding Jumper, Equipment. The connection between two or more portions of the equipment grounding conductor."

By connecting two or more portions of the EGC, I would say the EBC is itself also an EGC. Nothing says the two terms are mutually exclusive.

300.3(B)(2) gives various options for certain situations for running an EGC outside of the raceway cable. One of them is for an EBC installed in accordance with 250.102(E) (2017 NEC). That section limits the EBC to 6' in length.

The upshot is yes, if you have enclosure - EMT - FMC that is not an EGC - enclosure, and the FMC is short enough, you can install an EBC on the outside of your FMC, and use the EMT plus the EBC as the EGC.

Cheers, Wayne

 

[jes25]

So, I guess it pays to read the definitions:

"Bonding Jumper, Equipment. The connection between two or more portions of the equipment grounding conductor."

By connecting two or more portions of the EGC, I would say the EBC is itself also an EGC. Nothing says the two terms are mutually exclusive.

300.3(B)(2) gives various options for certain situations for running an EGC outside of the raceway cable. One of them is for an EBC installed in accordance with 250.102(E) (2017 NEC). That section limits the EBC to 6' in length.

The upshot is yes, if you have enclosure - EMT - FMC that is not an EGC - enclosure, and the FMC is short enough, you can install an EBC on the outside of your FMC, and use the EMT plus the EBC as the EGC.

Cheers, Wayne

You know, I read that definition before posting and somehow missed the part that it bonds together EGC's.

And thanks Wayne! That is the explanation I needed. Now to explain this to Level 1 students.........

 

[infinity]

The upshot is yes, if you have enclosure - EMT - FMC that is not an EGC - enclosure, and the FMC is short enough, you can install an EBC on the outside of your FMC, and use the EMT plus the EBC as the EGC.

This is what I'm thinking is the actually question represented by the graphic. The bonding jumper is continuing the fault path between the solid raceway and the equipment. There is no wire type EGC within the raceway or the bonding jumper wouldn't be required.

 

[LarryFine]

I imagine the main reason for running it on the outside is it's much easier to terminate.

 

[infinity]

I imagine the main reason for running it on the outside is it's much easier to terminate.

Also it may only need to be a few feet long instead of the wire type EGC being the entire circuit length. These guys pulled a long feed to the transformer primary without a wire type EGC. When they were told that they needed to bond around the FMC they ran it on the outside.