Conductor insulation type vs Raceway type

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greenb181

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Hello and Happy Holidays to all !

Question:
What is the determining factor (or Code article) that governs the selection of a conductor insulation type that can be installed in a raceway system that is environment-tight?

Example:
A listed-for-purpose waterproof raceway is installed in a wet location. The only wire on-hand is THHN (dry or damp locations). Assuming integrity of the raceway, is it legal (and safe) to use this conductor as long as it is contained within the raceway system? What limitations or exceptions apply to a situation like this? Please mention any articles or sources that I should study to better understand this issue.

Thank you in advance for your help.

Bob
 
Re: Conductor insulation type vs Raceway type

I haven't been able to find a code article that specifically addresses your situation. It might be up to the AHJ as to whether or not to consider the environment-tight conduit a damp or wet location. :confused:
 
Re: Conductor insulation type vs Raceway type

I believe 310.8(C) requires the conductors to be listed for wet locations or be of the types specified in that section even if the wiring method provides a weathertight or raintight assembly.
 
Re: Conductor insulation type vs Raceway type

Underground is considered a wet locarion. See Location, Wet in the definitions. Must use a wet location conductor.
Byron
 
Re: Conductor insulation type vs Raceway type

Hello-

My view point is that if its a wet or damp location than the wire has to be rated as such.NEC Art: 310-8 (B)and(c). Also look under "locations" in definitions. Is there a connector or coupling that is U.L. weatherproof?
 
Re: Conductor insulation type vs Raceway type

Happy Holidays!

The NEC defines the appropriate types of conductor insulation by Location.

310.8 Locations.
(A) Dry Locations.
(B) Dry and Damp Locations.
(C) Wet Locations.
(D) Locations Exposed to Direct Sunlight.

So it is not the raceway but the "location" or "area" or "environment".
 
Re: Conductor insulation type vs Raceway type

I think some of us have asked before - "has anyone seen any THHN in the last 15-20 years that was not also THWN rated ?"
 
Re: Conductor insulation type vs Raceway type

In my opinion, there is no such animal as a watertight raceway, hence the requirement in article 225 for raceways to be "arranged to drain".
 
Re: Conductor insulation type vs Raceway type

Ryan I agree with you about the raceways being wet inside.

I wish the NEC was clearer on this though.

Liquidtight Flexible Metal Conduit (LFMC). A raceway of circular cross section having an outer liquidtight, nonmetallic, sunlight-resistant jacket over an inner flexible metal core with associated couplings, connectors, and fittings for the installation of electric conductors.
Click to expand...
So they tell us directly that LFMC is liquid tight. If I use it outside can I use dry conductors in it?

Yes, No?

Now look at a FMC requirement

348.12 Uses Not Permitted.
FMC shall not be used in the following:

(1)In wet locations unless the conductors are approved for the specific conditions and the installation is such that liquid is not likely to enter raceways or enclosures to which the conduit is connected
Click to expand...
So if the NEC has to directly tell us that the conductors in FMC must be listed for the use if installed in wet locations doesn't that suggest that there is no general rule for conductors located outside in "tight" raceways?

Also there was apparently the need for 300.5(D)(5) again that suggests that there is no general NEC rule that wet type conductors are needed in 'tight' raceways.

IMO there should be a section that simply says outdoor raceways are wet locations. :)
 
Re: Conductor insulation type vs Raceway type

Dave Happy Holidays to you also. :)

We could also ask why all the problem with rain tight EMT fittings when the conductors should be wet location type at the same time the raceways must be arranged to drain?

Not trying to give anyone a hard time, I just feel like the NEC is conflicting itself at least a few time on this subject.

As Don has mentioned before, Why is a EMT coupling required to be rain tight when a RMC is not?

Why do I need rain tight EMT fittings at all when I can change over to FMC out in the rain?

I know I am getting off track. :roll:

Bob
 
Re: Conductor insulation type vs Raceway type

This does merit a proposal, IMO, because it hits close to home for me. I thought for a long time that a conduit that starts in a dry location and terminates in a dry location was considered dry.

Strangely, everything gets wet!
 
Re: Conductor insulation type vs Raceway type

Open up a conduit that has run underground after a few years, even in PVC and you will see a lot of condensation, even if there is no leakage into the conduit.
 
Re: Conductor insulation type vs Raceway type

Well, I will defer to those with more experience in the field, and the code reference to the definition. I'll go with wet location. :p
 
Re: Conductor insulation type vs Raceway type

Just like real estate, location,location,location! :D

I believe NEMA uses "location" as well as UL.

Maybe this is the standard and we are just now noticing it?
 
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