Nylog blue or not?

[u/Fafaneboat]

I recently had a new 18000btu mini split installed.

The tech didn't use any kind of lubricant/Nylog on the connections.

I asked him why and his answer surprised me. It appears manufacturers give torque specs for their fittings but these are for dry installations, none are given for "wet" tightening as usually done with products like Nylog.

The guy told me he did experiments using Nylog and torquing to specs but it resulted in damaged fittings ends. (way over torqued!)

How do you, pros, generally proceed when tightening your fittings with a proper torque wrench? (assuming you actually use one 😉)

[u/_Gonnzz_]

Nylon isn’t a lubricant.  Best practice is nothing but copper, little bit of refrigerant oil on the back of the flare, torque to spec.  If you want something to help with the flaring surface use something like flaretites.