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Splicing three solid 12 gauge wires to a stranded gauge 14 using wire nut

3K views 14 replies 7 participants last post by  WarriorWithWood 
#1 ·
Hello all!

I would like to know your opinion for the following splice:

The connection is for line voltage smart thermostat (240v - 20 Amp) of 20+ year old wiring, the solid wires are very rigid, non flexible and are tightly pre-twisted together in previous installation, what is the best practice to splice a 14 gauge stranded (coming from the the smart thermostat) to these twisted 3 solids of 12 gauge.

Which approach is the best?

1- Twist the strands of the stranded wire (1X - 14 gauge), cut it 1/8 inch longer than the pre-twisted bundle of the solid wires (3X - 12 gauge) and put the wire nut on and twist, tug the wires to test the connection.

2- Wrap the strands of the stranded wire (1X - 14 gauge) around the pre-twisted bundles of solid wires (3X - 12 gauge) then put the wire nut on and twist, tug the wires to test the connection.

3- Cut the old pre-twisted solid bundle (3X - 12 gauge), make new bare wire on all three (leave them straight - no pre-twisting), line them up with the stranded wire being about 1/8 inch taller than the solid wires, then put on the wire nut and twist, tug the wires to test the connection.

Also when removing old wire nuts, sometimes I notice there is some nicks from internal spring of wire nut on the solid wires, what is your opinion? is this acceptable to be reused or it is better to make new bare wire?

P.S: Ideal Tan Twister (341) wire nut is being used.

Thanks
 
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#10 · (Edited)
@WarriorWithWood I am sorry If you have a problem with "DIY" in my name, or if it offends you, there was no rules against it :) I do some DIY amatuer woodworking, that I am proud of.

Just to explain for the technical part:

The thermostat is UL listed for 120/ 240 volts (up to 3800 watt) and It is listed to used with 20 Amp breaker (but not higher) The cable from the Thermostat is 14 gauge stranded (about 5 inch length) and the cables from line is standard 12 gauge (NM-B 12-2) going to the 20 Amp breaker (240 volt).

14 gauge wire of that length can be safely used on 20 amp breaker as listed if and only if the circuit load does not exceed the safety margin of 3800 watt (about 15.8 amp for 240V) at any time. My maximum load verified with clamp meter is 11.2 amp.

Thanks
 
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