One wire too short for combiner box..splice THHN?

[merc4]

I spliced in about 4 or 5 feet of #10 thhn on just one line, in order for it to reach the combiner. The other 3 were long enough. Now I'm having second thoughts. It is a good waterproof splice. Any thoughts? The PV wire has so much more insulation, it's makin' me nervous!

[inetdog]

I spliced in about 4 or 5 feet of #10 thhn on just one line, in order for it to reach the combiner. The other 3 were long enough. Now I'm having second thoughts. It is a good waterproof splice. Any thoughts? The PV wire has so much more insulation, it's makin' me nervous!

Without getting into the safety aspect (and assuming that you are using a commercial splice kit with a voltage rating and not just taping it up yourself), there will be a problem with the NEC. A splice in either PV wire or ordinary THHN that is running through conduit has to be enclosed in a junction box which allows access to the splice for inspection and maintenance.
THHN cannot be run exposed in the first place, especially on a rooftop in the sun, although PV wire can.

Overall, a bad idea.
You would be better off buying a new, longer, piece of PV wire to replace the short one.

[bcroe]

I spliced in about 4 or 5 feet of #10 thhn on just one line, in order for it to reach the combiner. The other 3 were long enough. Now I'm having second thoughts. It is a good waterproof splice. Any thoughts? The PV wire has so much more insulation, it's makin' me nervous!

Instead of a splice, I would just put MC4 M/F connectors on the wires. I picked up any
scraps of PV wire after construction, and turned them into "extension cords" this way.
Bruce Roe

[merc4]

thanks guys, extension ordered! Peace of mind prevails!