LFNC vs. LFMC

A

anbm

Senior Member
Location
TX
Occupation
Designer
What are the benefits of using LFNC over LFMC besides some cost saving? Per code, both can be longer than 6 feet if support properly and has ground wire pulled.
 
Some places don't have the ability to hold a 10ft stick of conduit and position it into the exact location. Other biggest help for it is the ability to negate vibration on a run. The other nice thing is the lack of couplings possible with these since they're used often in environments that are more corrosive or atleast subject to weather and therfore it keeps out some extra intrusion that'd make it through even a rain tight or threaded coupling.
 
There is a difference between mfgs of LFNC. Carflex and associated fittings are junk. I used T&B black LFNC and nylon bullet connectors, quality and tough. A lot of what I wired was instrumentation in in underground damp vaults that had non metallic enclosures so the LFNC worked well were with that. Try the T&B you may like it,
For motors, transformers, the LTMC works best
 
anbm said:
What are the benefits of using LFNC over LFMC besides some cost saving? Per code, both can be longer than 6 feet if support properly and has ground wire pulled.
Click to expand...
In an application with a lot of vibration, I have seen the insulation on the conductors wear through and ground out on the inner metal of LFMC.

If it is in an area where there is a lot of activity, LFMC can get crushed and broken, but LFNC might bounce back.

But also in an area where there is a lot of activity, the plastic fittings for LFNC can breaker sooner than the metal fittings for LFMC.

When the end of LFMC gets ruined from getting stepped on, and the spiral metal is no longer interlocked or completely broken, the jacket split open and conductors showing, (see pic, a 90 degree fitting would have been a good choice here) It can often be repaired in place without pulling the conductors out. You can undo the fitting and carefully trim off the damaged portion and put everything back together.

1711709331583.png

In rare occasions where the best choice for bonding is the conduit itself, LFMC will work, but not LFNC.

In corrosive environments, LFMC fittings can corrode.

I prefer LFMC.
 
tom baker said:
There is a difference between mfgs of LFNC. Carflex and associated fittings are junk. I used T&B black LFNC and nylon bullet connectors, quality and tough. A lot of what I wired was instrumentation in in underground damp vaults that had non metallic enclosures so the LFNC worked well were with that. Try the T&B you may like it,
For motors, transformers, the LTMC works best
Click to expand...
Good to know, maybe I'll give it a try. Definitely just seems like LFNC could be much much better, with a different material having more flexibility, lower coefficient of friction, better fittings, etc. Perhaps the product standard needs some updating.
 
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