[ptnoble]

What is the difference between Metallic and Nonmetallic Liquid Tight Flex Conduit? Specifically can either be buried (1" diameter in question)? Is one cheaper or easier to find? Is 1" liquid tight adequate to run 4 #8 THHN wires underground from spa box to hot tub? What should burial depth be? Anything specific to know about the connectors for liquid tight?

THANKS in advance,
ptnoble

[tkrussell]

There is no huge difference between LFMC and LFNMC conduit, the metallic being the first available for many years the non-metallic only being around a few years.

All types of approved raceways are addressed in the NFPA 70: National Electrical Code®

Any conduit you want to bury must be listed and rated for direct burial. This will be stamped on the product and listed in the manufacturers data sheet.

I will tell you, most electricians never use direct burial flexible conduit, mostly use PVC Schedule 40 or 80, or rigid steel.

So, I can't tell you how available it is.The flex we use every day probably is rated for direct burial, but we never noticed or would care to look or use it.

I don't know why, just stubborn and traditional I guess.

1 " conduit will be fine for 4-#8. I can tell you that one wire can be a #10 for the green equipment ground, you don't need #8 for the ground.

If you use direct burial cable, such as UF cable, the trench needs to be 24" deep, any conduit needs to be 18" minimum.

Nothing I can tell you special about LT connectors, other than they need to be rated for the type of conduit they will installed on.

[ptnoble]

Thanks tkrussell, you are a trove of info.

I know that it is not traditional to bury flex conduit but it seems easier than glueing PVC together and then transitioning from PVC to LT to come up to the hot tub. Altogether this should be a short run (10' or so).

[tkrussell]

Thank you for the kind words.

Hey, no problem. I learn something every day in this trade. I need to be openminded. A lot has to do with geography. I have noticed a good deal of terminology difference in a 300 mile span, just as an example.

Just be sure it is rated, follow the trenching rules, and no problem.

[labman]

The metallic should be more resistant to mechanical damage. After my dog chewed through the non metallic feed to my A/C, I replaced it with rigid conduit.