(L)FMC as conduit/raceway and NEC 2020

[cdsolar]

At my DC panel, between my PV disconnect and between components on the panel, (charge controller, battery, DC loads, all with appropriate breakers), all runs less than 6 feet, I want to use (L)FMC (Liquid Tight)Flexible Metal Conduit, to meet the NEC 2020 requirement that all inside DC circuits must be in metal raceway/conduit. 690.31.

There is an amperage limit in 348.60 (referring to 250.118) of 20A for FMC, and 60A for LFMC. BUT, I think that is ONLY for when the (L)FMC is used as an equipment grounding conductor (EGC). If I am not using the (L)FMC as an EGC, or am running a separate wire for EGC, am I good to go with running my max 40A charge controller wiring in FMC, or even my AWG 2 battery cables in FMC?

Is my interpretation correct? Thanks.

 

[zanydroid]

At my DC panel, between my PV disconnect and between components on the panel, (charge controller, battery, DC loads, all with appropriate breakers), all runs less than 6 feet, I want to use (L)FMC (Liquid Tight)Flexible Metal Conduit, to meet the NEC 2020 requirement that all inside DC circuits must be in metal raceway/conduit. 690.31.

I would personally go with FMC since there are fewer potential gotchas with it (EG allowed insulation temp ratings). Note that there is a minimum conduit size OR physical protection requirement in some installation locations for PV circuits.

There is an amperage limit in 348.60 (referring to 250.118) of 20A for FMC, and 60A for LFMC.

I believe the EGC OCPD restrictions are based on size of the FMC/LFMC not the type.

BUT, I think that is ONLY for when the (L)FMC is used as an equipment grounding conductor (EGC). If I am not using the (L)FMC as an EGC, or am running a separate wire for EGC, am I good to go with running my max 40A charge controller wiring in FMC, or even my AWG 2 battery cables in FMC?

Yes. With the caveat that I don’t understand your sentence structure here. It sounds like you’re clarifying but there’s an outside possibility this English could also mean no EGC is in the system

If I am not using the (L)FMC as an EGC, or am running a separate wire for EGC

 

[cdsolar]

EGC will be there. The question is if I use the FMC as the EGC, I am current limited, whereas if I use a separate wire for EGC, it does not appear that I am limited.

 

[zanydroid]

Right, so don't use the FMC as the EGC since code doesn't believe it will be able to clear the higher currents. It's also not the most robust EGC out there given the fittings / quality of the conduit anyway. Whether you use the twist or clamp style, it's not as robust as as clamping onto EMT. If you look at the other details there are a lot of other restrictions like maximum combined length of FMC.

There might be some other clauses limiting to 20A, I wasn't aware that it was trade size based until I looked up your reference.