Transitioning from PVC to LFMC in concrete?

[jeremyinAZ]

Installing DC fast chargers throughout Colorado. Original contractor installed 3" Schedule 40 in hand-holes, preparing for the site to be "make-ready." Unfortunately, the 3" conduits are not in the right layout for the new charger. We proposed excavating the area down 24", then adjusting the 3" to the right layout. Very expensive to do- customer suggested we just install 3" LFMC onto the 3", then pour the footing around it, so we don't have to excavate.

I'm finding conflicting articles to support LFMC as an option.
350.6 says I CAN use LFMC encased in concrete. Assuming I can get a LFMC fitting that transitions from LFMC to Schedule 40- can that be buried in concrete?

Any help clarifying if I CAN encase the fitting in concrete- or article showing why I can't- would be greatly appreciated.

 

[don_resqcapt19]

The UL Guide Information for Conduit Fittings (DWTT) says:

A liquid-tight fitting is usable in wet locations and is also rain-tight and concrete-tight.

Stops a bit short of saying you can put the transition fitting in the concrete, but implies that you can.

Note that some LFMC is marked 60°C for wet locations, and if you have LFMC with that marking, the current on your conductors cannot exceed the 60°C ampacity.

 

[wwhitney]

Note that some LFMC is marked 60°C for wet locations

Per UL 360, section 24.4 (Markings), all LFMC is limited to 60C wet. I.e. it says if it is unmarked, it is 60C wet, 60C dry, and the only options for marking all include "60C wet."

, and if you have LFMC with that marking, the current on your conductors cannot exceed the 60°C ampacity.

But if you just have a short section of LFMC within a longer run, then (2020) 310.14(A)(2) Exception could apply? Or do you feel the wording of 350.10(4) prohibits the use of that exception?

Cheers, Wayne

 

[don_resqcapt19]

Per UL 360, section 24.4 (Markings), all LFMC is limited to 60C wet. I.e. it says if it is unmarked, it is 60C wet, 60C dry, and the only options for marking all include "60C wet."

But if you just have a short section of LFMC within a longer run, then (2020) 310.14(A)(2) Exception could apply? Or do you feel the wording of 350.10(4) prohibits the use of that exception?

Cheers, Wayne

I don't see the exception to ampacity adjustment having anything to do with the rule in 350.4.

 

[shortcircuit2]

Per UL 360, section 24.4 (Markings), all LFMC is limited to 60C wet. I.e. it says if it is unmarked, it is 60C wet, 60C dry, and the only options for marking all include "60C wet."

But if you just have a short section of LFMC within a longer run, then (2020) 310.14(A)(2) Exception could apply? Or do you feel the wording of 350.10(4) prohibits the use of that exception?

Cheers, Wayne

Good point. Can the 10% or 10ft rule be used?

 

[wwhitney]

I don't see the exception to ampacity adjustment having anything to do with the rule in 350.4.

Sorry, I'm not following you, or perhaps I misunderstand 310.14(A)(2) Exception. So a couple examples:

1) In a wet location in EMT with no ampacity adjustment or correction applicable, I have 100' of #8 AWG copper with THWN insulation spliced (say in a conduit body) to 5' of #8 AWG copper with TW insulation. The TW portion has an ampacity of 40A (60C), while the THWN portion has an ampacity of 50A (75C) Does 310.14(A)(2) Exception apply and allow for a circuit ampacity of 50A?

2) If yes, then change the TW/EMT portion to THWN/LFMC. Does 350.10(4) now trump 310.14(A)(2) Exception, and limit the circuit ampacity to 40A?

Cheers, Wayne

 

[don_resqcapt19]

Sorry, I'm not following you, or perhaps I misunderstand 310.14(A)(2) Exception. So a couple examples:

1) In a wet location in EMT with no ampacity adjustment or correction applicable, I have 100' of #8 AWG copper with THWN insulation spliced (say in a conduit body) to 5' of #8 AWG copper with TW insulation. The TW portion has an ampacity of 40A (60C), while the THWN portion has an ampacity of 50A (75C) Does 310.14(A)(2) Exception apply and allow for a circuit ampacity of 50A?

2) If yes, then change the TW/EMT portion to THWN/LFMC. Does 350.10(4) now trump 310.14(A)(2) Exception, and limit the circuit ampacity to 40A?

Cheers, Wayne

If the current in the conductor that is installed in the LFMC in the wet location exceeds that shown in the 60°C column of Table 310.16, then you cannot install that conductor in LFMC. (assuming LFMC rated 60°C wet)