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I am trying to hook up terminals to a 10AWG PV wire to power a water pump with a battery. I got 12-10 connectors, the yellow colored ones which I understand are sized for 10AWG wire. I stripped some of the wire and the stranded wire bundle fits nicely in the yellow connector's wire barrel. The problem is that the PV wire insulation does not fit in the connector's insulation, and the connectors box says:

The stripped conductor must be inserted into the wire barrel until the insulation is against the wire barrel but not inside it. The insulation of the wire must be inside the insulation of the product.

What am I doing wrong here? Did I get the wrong sized connectors, and if so, what am I looking for to add terminals on this PV wire? I need to make another hardware store trip today and want to learn what the issue is before I go so I can get the right parts.

Here's some photos of the issue. First is the wire and some connectors I got, showing size labels. Next couple photos are the connectors up against the wire insulation to show that the insulation of the connector cannot fit around the insulation of the wire.

10AWG PV wire and 12-10 yellow connector

Trying to fit ring connector on wire, the wire and insulation does not fit in the connector insulation

Trying to fit butt connector on wire, the wire and insulation does not fit in the connector insulation

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    the wire insulation looks thicker than usual
    – jsotola
    Jun 17, 2021 at 22:18
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    the yellow sleeve may become pliable if heated, similarly to heatshrink tubing ... carve a tapered dowel from a chopstick and try using it with a source of heat to stretch the yellow insulation
    – jsotola
    Jun 17, 2021 at 22:28
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    That's an idea. I also just spoke with someone who has made these connectors on PV wire before. They said they shave the insulation down on the PV wire a little, where the connector insulation will cover it, and in the end it'll have as much or more insulation. I will try that.
    – cr0
    Jun 17, 2021 at 22:36
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    Probably because it is for long term outdoor use, it uses weather/water tight connectors, instead of run of the mill connectors.
    – crip659
    Jun 17, 2021 at 22:40
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    I would use those connectors, but use some heat-shrink tubing over the join.
    – MikeB
    Jun 18, 2021 at 9:02

2 Answers 2

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PV wires use fatter insulation

As you have found out the hard way, PV wire uses much thicker insulation than ordinary THHN building wires, so it won't fit into ordinary insulated-type crimp terminals. I'd use an uninsulated terminal or splice with a separate adhesive-lined, heavy-wall heat shrink sleeve for this as a result of that fact. You'll have to double check your shrink dimensions though, so that you stay within the 2:1 shrink ratio you can expect out of such a product.

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    There is 3:1 shrink tube available, this may seem the right project to pay premium for this
    – Pelle
    Jun 18, 2021 at 7:40
  • @Pelle -- I don't believe 3:1 is available in the UL listed stuff (which is always the heavywall/adhesive-lined type)
    – ThreePhaseEel
    Jun 18, 2021 at 11:27
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    UL does not apply to me, I'm in the EU :-)
    – Pelle
    Jun 18, 2021 at 11:33
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    .... and the EU hardly has any regulations at all. (dying of laughter emoticon needed)
    – jay613
    Jun 18, 2021 at 14:08
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    @jay613 If you don't build houses with wood frames, and you don't have an electrical distribution system which maximizes risks instead of minimizing them, you don't need the sticking plaster of endless regulations, formal safety inspections, etc.
    – alephzero
    Jun 18, 2021 at 19:29
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I resolved this issue and am posting what I found. Comments and answer so far were in the right direction, thanks.

The first bit of feedback I got was the shave down the insulation on the PV wire, to fit it in the regular 10ga connector's insulation. That does work nicely, but doesn't seem like a proper fix.

It turns out regular 10ga connectors don't fit cleanly over PV wire, because PV wire goes with waterproof connectors to withstand long-term outdoor use. The 10AWG PV wire fit in regular or waterproof 10ga connector wire barrels for crimping without a problem, but the connector insulation (which extends a little past the connector wire barrel) wouldn't fit over the PV wire insulation. Waterproof 10ga connectors fit over the PV wire insulation just fine. Here's photos showing regular (yellow) vs waterproof (yellow-clear) 10ga connectors, note the difference in insulation jacket diameter:

Regular vs waterproof 10ga connector, side view

Regular vs waterproof 10ga connector, top view

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    This is interesting. Why would the crimp part of an open terminal connection need to be waterproof? I guess this prevents moisture from seeping inside the wire insulation? Maybe? What else?
    – jay613
    Jun 18, 2021 at 14:08
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    In some cases the terminal block may have weather protection but the wire itself does not. Also, the Al/Cu connection is probably more subject to corrosion, so sealing that is beneficial.
    – isherwood
    Jun 18, 2021 at 14:24

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