flex connectors used as "bushings"

[craff]

We are running 24VAC HVAC control cables at a university for push button and horn. Where the cables enter the wall we installed a flex whip to a cut-in handy box (metal tiger-grip). Does the flex require a flex connector at the end where the cable exits the drywall? I say no because a flex connector isn't listed as a bushing. My coworker thinks otherwise but can't find it in the NEC. We have fire caulked both the flex opening and wall penetration.

 

[petersonra]

I am having a hard time visualizing what you are doing. Maybe a sketch or photo?

 

[kwired]

Are you talking about flexible metal conduit here? I think the bigger question is whether or not the flex needs some kind of bushing on the end to protect cables/conductors from abrasion. If so you may need a connector even if its only purpose is to have a place to install a bushing. There are bushings on the market to slip on the end of a piece of EMT or RMC but I have not seen one for FMC.

 

[craff]

Yes regarding whether or not the end of the flex (FMC) which is outside the drywall needs a flex connector. My observation to my co-worker was that, since a flex connector isn't a listed bushing, then what good does it do? My contention is that there should be no connector, or a connector and a bushing that threads onto the connector. However, cleanly cut FMC without a connector is nice and smooth. And I can't locate anything in the code regarding this. The cables are plenum rated #18 shielded pair and a four conductor of the same cable type.

 

[infinity]

Since a bushing alone won't stay on the FMC IMO you would need an FMC connector with a bushing to comply with 725.3(J).

725.3(J) Bushing. A bushing shall be installed where cables
emerge from raceway used for mechanical support or
protection in accordance with 300.15(C)..

 

[cpinetree]

Adjustable throat liner

Adjustable throat liner

We often use something like this: http://www.aifittings.com/catalog/miscellaneous/adjustable-throat-liners/

Basically an anti short but larger. They should be used with a fitting on the end to make a complete assembly and hold the liner in position, although electric tape may do the job also, for low voltage applications.

 

[hbiss]

We are running 24VAC HVAC control cables at a university for push button and horn. Where the cables enter the wall we installed a flex whip to a cut-in handy box (metal tiger-grip). Does the flex require a flex connector at the end where the cable exits the drywall?

I'm having a hard time visualizing this too. If you are asking if the flex that sleeves the LV cables needs a bushing at the end where the cables come out of it, the answer is yes. We normally use a box connector suitable for the flex that is threaded for a locknut on the other end (not a Tiger Grip). Install it on the end of the flex, remove the locknut and screw on a bushing.


-Hal