proper use of bonding wire in LFMC? just grounded locknuts?

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emiller233

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pittsburgh, pa
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Controls-Automation engineer
never dealt with the LFMC that has the bonding wire in it so not sure what proper installation is? is landing it on the fittings grounded locknut at both ends sufficient?
 
emiller233 said:
never dealt with the LFMC that has the bonding wire in it so not sure what proper installation is? is landing it on the fittings grounded locknut at both ends sufficient?
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What do you mean by a bonding wire, is it an EGC? Otherwise there are limits (length, ampacity, and size) as to when LFMC can be used as an EGC. Look at 250.118.
 
we're not planning on using it as an EGC as out cables have the grounds in them. but the customer just sent us this spec asking for the ground in the LFMC. lengths will be roughly 10' max. and most devices are for instrumentation devices, and will be fed back to a wireway to get back to the terminal block enclosures. There are a few 480vac motors and heaters using single conductor SIS pulled thru this LFMC as well.

this is the LFMC that is awaiting the customers approval (3/8" and 1" sizes)
http://flexiblewiringconduits.anacondasealtite.com/Asset/2017 ZHUA.pdf

R-2.3-14
[All cables shall be contained within raceway which shall be Rigid Galvanized Steel (RGS) and liquid
tight metal braided flexible conduit (with grounding wire). Flexible conduit shall not extend more than
three feet without being supported and is only to be used as a final connection to a device and not run
throughout the subassemblies.]
 
ActionDave said:
You don't do anything with it. It's not an equipment ground that runs the length of the flex, it's there to make a strip that shorts each of the turns in the flex together.
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I'll second that. It is only there to improve impedance of the flex itself. NEC still has limits on the use of the flex alone as an EGC.
 
emiller233 said:
we're not planning on using it as an EGC as out cables have the grounds in them. but the customer just sent us this spec asking for the ground in the LFMC. lengths will be roughly 10' max. and most devices are for instrumentation devices, and will be fed back to a wireway to get back to the terminal block enclosures. There are a few 480vac motors and heaters using single conductor SIS pulled thru this LFMC as well.

this is the LFMC that is awaiting the customers approval (3/8" and 1" sizes)
http://flexiblewiringconduits.anacondasealtite.com/Asset/2017 ZHUA.pdf

R-2.3-14
[All cables shall be contained within raceway which shall be Rigid Galvanized Steel (RGS) and liquid
tight metal braided flexible conduit (with grounding wire). Flexible conduit shall not extend more than
three feet without being supported and is only to be used as a final connection to a device and not run
throughout the subassemblies.]
Click to expand...

Sounds like they want you to pull a green in the LTFMC. That's different than the bonding strip that is wound inside the coils of the flex. I don't see anything that says you need a bondindg locknut.
 
ActionDave said:
Sounds like they want you to pull a green in the LTFMC. That's different than the bonding strip that is wound inside the coils of the flex. I don't see anything that says you need a bondindg locknut.
Click to expand...

we could do that, but whats the different between pulling a green wire and using the LFMC as an EGC? some of the instrumentation devices that we'll be wiring into do not have a ground stud in them either...
 
Practically speaking there is no difference other than the restrictions that liquid tite not be used as an egc over 20A or more than six feet, but the Cult of The Green Wire and their fellow brethren, Dirt Worshippers have an enormous influence.
 
emiller233 said:
we could do that, but whats the different between pulling a green wire and using the LFMC as an EGC? some of the instrumentation devices that we'll be wiring into do not have a ground stud in them either...
Click to expand...

No difference in my book but did you check out the code section in post #3? LFMC has limits when used as an EGC.
 
i realized that after i read thru it a 2nd time. customer just told me last night the want RMC as close to the device as possible now...

for fittings, we can just use the normal fittings such as TNB 5231
 
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