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I have several floor joists in my basement that need to be sistered up but unfortunately the 8 gauge wire that powers the AC compressor runs diagonally through all of them. Disconnecting it from the AC unit or at the panel aren't very good options and would require digging into drywall or siding to free up the cable.

My ideal method is to cut the cable, splice in an extra ~10 feet, and reroute it to avoid running though any joists. This would require using two junction boxes in order to add the new section.

What's the preferred method for connecting #8 wires in a j-box? Additionally, would there be any concern in regards to adding 10 more feet of cable or potential loss of capacity with the connections of such large wires? Thank you for any advice.

isherwood
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Matt Whitehead
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2 Answers2

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Properly sized wire nuts will work fine. The typical ones most people use around the house won't handle larger than 10 AWG. Some examples of large-enough Ideal wire nuts are: 342 Gray, 454 Blue, B4 Blue, BT2 Red (just barely), WT54 Blue.

An extra 10' and an extra 2 connections should not have any material effect on the circuit.

manassehkatz-Moving 2 Codidact
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    Just remember those junction boxes will always have to be accessible. – JACK Mar 21 '23 at 12:32
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    Note that the nuts commonly laying around a person's garage are probably not large enough. Look at product specifications. – isherwood Mar 21 '23 at 12:53
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    From a non-pro, when someone experienced says "will work fine", I would add "if you buy some extra wire and nuts and practice a little first". Expect to make a mess of the wires initially. – jay613 Mar 21 '23 at 14:49
  • I would add to at least look at wire sizing tables to see that the circuite is not exceeding the total maximum wire length for the draw from that AC. – gns100 Mar 21 '23 at 15:48
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    @manassehkatz-Moving 2 Codidact, would you use a plastic or metal box? Metal would obviously need to be grounded and creating an 8 gauge pigtail would just add extra work to stuff it all into the box. Full discloser, I'm not a newbie in regards to DIY electrical, I've just never spliced wires quite this big before so I need to ask lots of questions first. :-) – Matt Whitehead Mar 21 '23 at 16:44
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    Definitely metal. – manassehkatz-Moving 2 Codidact Mar 21 '23 at 16:49
  • For splices I like the 3M Scotchlok. It would be Type G with grey color insulating cover for two #8 wires. – Jim Stewart Mar 22 '23 at 01:13
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Use WAGO Lever Nuts. Wire nuts will work fine, but they are a hassle. WAGO Lever Nuts are becoming an industry standard. They are sold in a variety of wire sizes. You can get them on eBay, Amazon, and from some of the Construction Suppliers.

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I used them in all of my electrical work as seen here. It all passed inspection. It's a 3 Phase 30amp 10gauge wired wordshop. If a wire splits, it has a WAGO on it.

Mr.GfCs Welding
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    Note that as far as I'm aware, WAGO does not make lever nuts big enough to fit the #8 that this question is asking about. The largest they can fit is #10, and the two sets you linked to are only big enough for #12. – Miles Budnek Mar 21 '23 at 18:52
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    Yeah, the wago lever "spling connectors" only go up to #10, they have din-rail terminals which will take bigger wire but I'm not sure the OP wants to get into dealing with din rail terminals. – Peter Green Mar 21 '23 at 19:54
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    Do not get them (or other small safety critical items) from eBay or Amazon. Too many counterfeits. – Phyzz Mar 21 '23 at 20:17
  • @Phyzz, I try not to buy anything from Amazon as a general life rule. Other companies need my business way more than they do. – Matt Whitehead Mar 21 '23 at 20:50