Butt splicing different gauge wires?

Maine Sail · Oct 25, 2015

Dan_Y said:
Adhesive-lined heat shrink butt splice connectors seem to come in 3 popular sizes. 10-12, 14-16 & 18-22 AWG. Are butt splices available that splice between these three sizes? For example, 12 to 16 AWG?

Doubling the smaller wire over to fit the connector doesn’t seem a satisfactory solution for a couple of reasons. 1) A 10-12 AWG connector takes from 10,500 to 6,500 circular mil wires respectively. 16 AWG is 2,600 CM, so I would need to triple over the 16 to get enough cir mil for a proper crimp (2 x 2,600 < 6,500 so 3 x 2,600 > 6,500 CM. 2) I’m not sure the heat shrink designed for 10-12 AWG would contract and seal around the 16 AWG wire.

I have seen this situation a few times where the load has become more efficient and draws fewer amps when upgraded (ex. LED lights). In one case I replaced an old 12V LCD TV with a 120 VAC LED TV/DVD that draws only 30W. I used a small, dedicated 120w continuous inverter that uses 16 AWG wire. The old circuit was generously wired with 12 AWG probably due to the length of the run and current draw or voltage drop sensitivity of the old LCD TV. Not being in a bilge space I used a terminal strip, but like to use waterproof crimp butt splices whenever possible.
Thanks for any advice!
Dan

They are called "step down butt splices". Phil sells them just search for FTZ in the SBO store and you'll find them. They are not cheap, very costly to manufacture compared to other terminals, but worth it..

IStream · Oct 25, 2015

Strip the 12 gauge wire extra long so it goes all the way through the butt connector with the tip extending just a bit out of the metal barrel. Then insert your 16 gauge wire into the other end so it's side-by-side with the 12. That'll give you the build you need for a good crimp. The extended tip of the 12 gauge makes it easier to start the feed of the 16 gauge into the metal barrel.

EDIT: Of course, MS's response is the best way but this will work well in a pinch.

shemandr · Oct 26, 2015

I've run into this situation many times. Most recently installing a bow light for which the wiring for the light from the manufacturer is very small in comparison to the wiring from the panel. I ended up cutting wire away in the larger wire but there still was a discrepancy. I did not feel the crimp is trustworthy. Local hardware stores and at least two marine hardware stores do not stock the Step Down connectors. I'm going to do it over again so it's off to Phil's ... I just need to learn the wire gauges first.

Maine Sail · Oct 26, 2015

IStream said:
Strip the 12 gauge wire extra long so it goes all the way through the butt connector with the tip extending just a bit out of the metal barrel. Then insert your 16 gauge wire into the other end so it's side-by-side with the 12. That'll give you the build you need for a good crimp. The extended tip of the 12 gauge makes it easier to start the feed of the 16 gauge into the metal barrel.

EDIT: Of course, MS's response is the best way but this will work well in a pinch.

Every good quality brand of butt-splice I know off has an insert stop in the middle to prevent the wire from inserting too deeply. It also usually prevents pass through..

shemandr · Oct 26, 2015

Question about sizes: For boat applications in the 15 to 30' area, are the most common conductor AWG sizes 14 and 16. What are the most common sizes for bilge pumps, lights, power for instruments. I would like to build up an inventory of terminals and connectors but want to stick to the sizes I'll be most likely to use. I don't like the kits because it seems you get a lot of hardware that will take up space for years while you still have to buy the sizes that you use up.

IStream · Oct 26, 2015

Maine Sail said:
Every good quality brand of butt-splice I know off has an insert stop in the middle to prevent the wire from inserting too deeply. It also usually prevents pass through..

I've found that, depending on the brand, you can often get a 12 gauge wire through the stop of a 10/12 barrel.