Bonding requirements for long(er) runs of Flex/FMC

[Solar_ice_caps]

Looking at your common Aluminum FMC.

We have attic runs that go between a roof-mounted junction box and a (side of house) wall mounted combiner box (panel).

Run length and circuit size independent, we have to run a green EGC for solar installs.

This run is often between a plastic combiner box and a plastic OR metallic junction box on the roof.

In the former case, I bond both ends of the run with insulated bonding bushings.

To my question:

Sometimes I need to add a box in the middle of the run to bring in another circuit, or because I want better mounting/access in the attic. Suffice to say now I have a FMC run with a metallic box in the middle. The box is connected via either screw-in or squeeze connectors, which is where I'm starting to feel iffy about the bonding. Neither of those connectors have any kind of penetrative bonding feature that I can tell.

Am I required to use bonding bushings in this center jbox? (keep in mind, again, that there is an EGC already in this run, so I am not using the conduit as a system EGC, I'm just wanting to bond the conduit properly and safely.

Thanks as always to this ever-helpful forum.

 

[electrofelon]

The flex runs need to be bonded, but it only needs to be one end.

 

[Solar_ice_caps]

The flex runs need to be bonded, but it only needs to be one end.

Each individual run of flex, you're saying? In this run, with a metallic jbox in between, that's 2 separated runs. Just making sure I understand you correctly.

Also is there a code reference you can point me to? Thanks.

 

[electrofelon]

Each individual run of flex, you're saying? In this run, with a metallic jbox in between, that's 2 separated runs. Just making sure I understand you correctly.

Also is there a code reference you can point me to? Thanks.

Ok I missed there was a metallic J box in the middle. So no additional bonding is necessary, the fittings will bond the flex to the metal box. Of course just make sure the wire EGC is bonded to the box.

see 250.96(A), 250.97 if applicable, and 250.118

 

[Eddie702]

Although I see a lot of J boxes "in the middle" that are not connected to the EGC they should be and it is code required.

 

[Solar_ice_caps]

Of course just make sure the wire EGC is bonded to the box.

see 250.96(A), 250.97 if applicable, and 250.118

This is throwing me off a bit, so even though the box is bonded via the flex at each end, I need to bond it locally to the EGC that is running through it?

 

[Solar_ice_caps]

Although I see a lot of J boxes "in the middle" that are not connected to the EGC they should be and it is code required.

Do you have a code section for that you can point me to?
In this case I'm looking at 250.148 however I'm not making any splices or terminations of the circuit conductors in this box. It is just a pass-through/pull-box.

 

[electrofelon]

This is throwing me off a bit, so even though the box is bonded via the flex at each end, I need to bond it locally to the EGC that is running through it?

Do you have a code section for that you can point me to?

Ok so say you have a metal box in the middle. If there are no splices or devices in that box, then you could pull the conductors through without landing the EGC on that box, per 250.148. In that case however, of course, the box and flex would have to be bonded elsewhere. IT could be by a bonding bushing at the end(s), however note the use of FMC as an EGC is limited, see 250.118(5)

 

[Solar_ice_caps]

Ok so say you have a metal box in the middle. If there are no splices or devices in that box, then you could pull the conductors through without landing the EGC on that box, per 250.148. In that case however, of course, the box and flex would have to be bonded elsewhere. IT could be by a bonding bushing at the end(s), however note the use of FMC as an EGC is limited, see 250.118(5)

So in this case I'm not doing any splices in the boxes and I'm not using this run as an EGC as there is a dedicated EGC wired conductor running through the raceway already, bonded at both sides to the flex.
My concern now is that the run is >6ft so it would not comply with 250.118(5)(d)..... but it's not meant to be the ECG, it's just physical protection for the circuit (attic wire run).

I had a similar run pass inspection with about 25ft of flex being used so it seems like this would be acceptable and not having to bond the run every 6 ft...

 

[electrofelon]

So in this case I'm not doing any splices in the boxes and I'm not using this run as an EGC as there is a dedicated EGC wired conductor running through the raceway already, bonded at both sides to the flex.
My concern now is that the run is >6ft so it would not comply with 250.118(5)(d)..... but it's not meant to be the ECG, it's just physical protection for the circuit (attic wire run).

I had a similar run pass inspection with about 25ft of flex being used so it seems like this would be acceptable and not having to bond the run every 6 ft...

IF the raceway does not comply with 250.118 then you cant use it to bond the metal box in the middle. Isnt it easy to just land the EGC to that box?

 

[Solar_ice_caps]

IF the raceway does not comply with 250.118 then you cant use it to bond the metal box in the middle. Isnt it easy to just land the EGC to that box?

Yes I can do that with no issue, just making sure I understand what is needed. Can I bond the box with a lay-in lug?

So, in another section of the same raceway, where I have another box within 6ft of where the flex is bonded, and it otherwise complies, I would not have to bond that box locally as I am complying with the flex's use as an EGC?

Thanks for your help.

 

[electrofelon]

Yes I can do that with no issue, just making sure I understand what is needed. Can I bond the box with a lay-in lug?

So, in another section of the same raceway, where I have another box within 6ft of where the flex is bonded, and it otherwise complies, I would not have to bond that box locally as I am complying with the flex's use as an EGC?

Thanks for your help.

Sure, no problem with a lay in lug.

Seems to me if the raceway qualifies as an EGC per 250.118, than it can act as an EGC to bond the metal box yes - just dont forget about 250.148 which requires a bond there in some cases.

 

[Solar_ice_caps]

Sure, no problem with a lay in lug.

Seems to me if the raceway qualifies as an EGC per 250.118, than it can act as an EGC to bond the metal box yes - just dont forget about 250.148 which requires a bond there in some cases.

I feel like this ends in what everyone probably already ends with which is, just bond it anyway to be safe.