New Combiner and I need to Lengthen/Splice my PV wire

[MrM1]

I'm adding another string to each array. Which means I will out grow my 2 Midnite Solar 3 sting combiners. I'm upgrading to a Watts247 8/2 combiner

Problem is, all PV wires (strings) go into conduit and into the attic and into the MS combiners. But with the the addition, the existing PV wires will be about 2 ft to short-term. They were all cut to length.

How do I lengthen these wires? MC4 connectors could work but not ideal because I want to stay in conduit. Or at least add a junction box. I also don't think wire nuts is a good option. What would you do? Copper Split bolts? 2 screw busbars? Something else?

 

[MrM1]

And a Butt Splice? That just doesn't Feel Right!! ?

 

[MrM1]

What about terminal blocks?

 

[MrM1]

What about the Dinkle Din rail blocks in a box

 

[MrM1]

What about Wago connectors for lengthening PV wires

 

[Hedges]

And a Butt Splice? That just doesn't Feel Right!! ?

This could be the best. Like a pair of MC connectors (which are crimped) but without the MC. Insulate properly. In a box or conduit body where allowed.

Do you have a junction box where you could mount suitable terminals (blocks) instead?

I've used split bolts in a conduit tee. That was 6 awg neutral + ground, taped, but no disaster if the tape got damaged.
Likely too bulky for PV wires.

 

[OzSolar]

What about Wago connectors for lengthening PV wires

In a junction box, right? As long as you stay within the wire size rating of the Wago's they would be my first choice since I've got them on my truck, it's quick and I've personally seen them last for many years in this exact application without any problems. Note that they have two models, one goes down to #10 wire and the other down to #12.

 

[MrM1]

Do you have a junction box where you could mount suitable terminals (blocks) instead?

Plan to use a plastic junction box

 

[MrM1]

My set up will be with #10 PV wire and 117vdc VOC & 28.35 amps ISC

 

[Hedges]

Plastic? Outside not inside.

28.35A is within the ampacity (and allowed max current) of 10 awg. But 28.35A Isc x 1.56, as required by NEC, is not.
It works from the perspective of not exceeding insulation temperature given what PV panel can actually deliver, but does not comply with code.

 

[toms]

Open barrel splice and adhesive lined uv proof heatshrink.

Not sure what your objection to crimped splice is, the wire in the MC4 is dry crimped in a similar manner, except there are two crimps, a male female friction join, and an o ring seal and mating surface. Great for inexpensive installation, not so good for lifetime reliability.

 

[MrM1]

Plastic? Outside not inside.

28.35A is within the ampacity (and allowed max current) of 10 awg. But 28.35A Isc x 1.56, as required by NEC, is not.
It works from the perspective of not exceeding insulation temperature given what PV panel can actually deliver, but does not comply with code.

My bad . And correct, that is the paralleled stings total. Each string is 9.35 amps. That's on #10. It use #8 coming out of the combiner.

My splice will be just a single string at the 9.25a

 

[MrM1]

Not sure what your objection to crimped splice is, the wire in the MC4 is dry crimped in a similar manner, except there are two crimps, a male female friction join, and an o ring seal and mating surface. Great for inexpensive installation, not so good for lifetime reliability.

Not opposed. Just don't have space for the full mc 4 connector. I might do the butt splice and shrink idea

 

[MrM1]

Plastic? Outside not inside.

Just curious, besides code, what is the issue with PVC and plastic conduit for DC inside. My understanding was it was code to protect fire fights from chainsawing through it as they came through your roof, walls, etc.

 

[MrM1]

@Hedges
Is MC (metal clad) flexible cable acceptable for DC PV inside? Or will it only work if stranded. Or at all?

 

[Hedges]

Protection from tools and rodents might be the reason, or part of it.
Maybe PVC is an issue due to arcing or overheating of wires. Maybe DC, not shut off by breakers in case of a short, poses greater risk.

Yes, MC is named by code as acceptable. Others have said BX cable would be OK too, though not explicitly named. BX was steel flexible spiral jacket around solid wire so solid seems fine. I think stranded is just what's needed for flexible connections, and for that fine stranded would be wanted.

My set up will be with #10 PV wire and 117vdc VOC & 28.35 amps ISC

Must badge. And correct, that is the paralleled stings total. Each string is 9.35 amps. That's on #10. It use #8 coming out of the combiner.

My splice will be just a single string at the 9.25a

10 awg is fine for 9.35A Isc, 12 awg would have been too.
8 awg is fine for 28.35A (28.05A you may have meant for 3 parallel strings)

I would guess your panels specify 20A fuse, possibly larger.

Sounds like 3 pairs of splices in 10 awg, wires extend to a combiner with 6, 20A fuses or breaker poles.

 

[MrM1]

Yes 20 amp fuses and yes 3 pairs.

 

[MrM1]

FOR BUTT SPLICING ...

This could be the best. Like a pair of MC connectors (which are crimped) but without the MC. Insulate properly. In a box or conduit body where allowed.

@Hedges
Are you saying take the Male and Female sextions ( ? ) of an MC4 connector WITHOUT the water tight plastic screw and lock part (just the metal part), Crimp each end, and then stick the 2 together and again crimp that? The heat shrink or 3m electrical tape?

Or put both wires under the larger MC4 and crimp on both ends?

Also, can solid and stranded wire be crimped together ?

Can Sold wire be used in an MC4 connector?

Do you have a junction box where you could mount suitable terminals (blocks) instead?

Yes all connections will be inside the attic and in a old large gutted metal Air Conditioner disconnect box.

 

[Hedges]

No, just saying that an MC4 connection, in addition to the mated connection and gaskets and all, contains two crimps.
If you skipped the crimps and just did a butt splice, that isn't any new type of interface, it would have been present in MC4.
So butt splice with suitable sealant should be good.

MC4 metal parts without housing would not be secured together. If taped etc., might pull apart if someone tried hard enough.

I don't know if heat shrink with hot melt inside is proper protection for exposed things people can touch, however.

I'm not sure if crimp on solid wire is proper. Never seen it. See what UL listed connections are described in instructions.
I would have PV cables joined probably exposed, then feed PV cable into a box where it connects to conventional wire for conduit. I used wire nuts initially, now using Ideal set-screw nuts.

 

[MrM1]

I might just buy Midnite solar small DC busbars. I know those