THHN/THWN Versus XHHW-2/X

More than likely the electrician has a ready supply of the much more common THHN, but if you want to pay for advantages that you may not use, then go for the XHHW. Here's an article that describes the electrical/mechanical differences, call a local distributor for the cost differential.

Thanks for the reply. I trust members here for good advice.

Ram, I clicked on article, it says page not found.

https://solutions.borderstates.com/thhn-vs-xhhw-what-is-the-difference/

Unless there was a specific reason or mfg recommendation to use anything but THHN I wouldn't consider using anything else.

I think I've run THHN a lot closer to 100% of the time than 99%.

..in emt more often than not. above and below grade inside or out.

In my (old) NEC, THHN is described as suitable for dry or damp, but not wet, locations. THWN is usable in wet locations, and chances are that your contractor's THHN is also stamped THWN; if so, it should be okay.

Thanks everyone for the replies. I want to use the best quality material, if I can get it at or near the same price.

I don't believe in stepping over a dollar to pick up a dime.

For chiller application, go for the XHHW which is suitable to -40C.

Insulation issues could occur if THHN is too close to the refrigerant lines, or they can be damaged if there is a refrigerant leak, making the repair much more expensive.

I wonder what the likely hood of that happening would be? May I also recommend explosion proofs boxes and covers?

..You need to leave something for the insurance adjusters after all.

I'm not saying it couldn't happen.. I'm just not the type who buys extended warranties etc. How many tens of thousands has that saved me over the years I'll never know?

Since this is an evaporative ("swamp") cooler, and not a refrigerated chiller, that likelihood is about zilch. Hence the OT.

I don't usually see XHHW for smaller conductors, THHN should last a long time.

Some suggestions for a long term installation:

#10 stranded Cu, if you are willing to invest in more expensive wire

a piece of rigid, depending on how you are penetrating the roof

a real box on the roof (not white metal)

duct seal to prevent condensation from coming back down the conduit

a service receptacle on roof

Good ideas.

1. #10 not really needed as load is usually less then 15 amps. With the exception being 220v line.

2. A real box ( I often use Hubble Electrical Products # 5324-0 )

3. Duct seal ( other than Teflon paste or silicone, I use Design Polymerics DP 1010 Duct Sealant )

4. Service receptacle ( # 5324-0, Hubbell # 3512-8, Halex Co. 28231 )

Generally a single gang box is mounted atop EMT then 12 ga is ran through liquid Tite to Cooler. The service receptacle would be the J-box. In this application.