I have to make some connections inside an electrical box between #10 solid
and stranded #12.
I tried wirenuts, but it doesn't seem particularly secure.
I have only used crimp connectors on standed; can they be used on solid?
If not, then what? Thanks.
The only stranded - solid connection that I trust is solder. You'll
likely get about 37 other different opinions...
You can 'tin' the stranded end so it acts more like solid wire under the
I think you're right, the tinning process isn't making the connection,
just organizing the wires. But then you might be in violation of 2002
NEC 110.3b ( label and listings) since wire nuts say nothing about
tinned wires, just usually copper, copper-clad AL, and AL depending on
Still an interesting question.
The only places the US NEC forbids the use of solder is in connecting
grounding or bonding conductors to electrodes and connecting Equipment
Grounding Conductors to boxes. In both cases the connection may not be
"depending on solder."
250.70 Methods of Grounding and Bonding Conductor Connection to Electrodes.
250.148 Continuity and Attachment of Equipment Grounding Conductors to
In other applications the US NEC specifically permits soldering vis.
[110.14 Electrical Connections.
Because of different characteristics of dissimilar metals, devices such
as pressure terminal or pressure splicing connectors and soldering lugs
shall be identified for the material of the conductor and shall be
properly installed and used. Conductors of dissimilar metals shall not
be intermixed in a terminal or splicing connector where physical contact
occurs between dissimilar conductors (such as copper and aluminum,
copper and copper-clad aluminum, or aluminum and copper-clad aluminum),
unless the device is identified for the purpose and conditions of use.
Materials such as solder, fluxes, inhibitors, and compounds, where
employed, shall be suitable for the use and shall be of a type that will
not adversely affect the conductors, installation, or equipment.
(B) Splices. Conductors shall be spliced or joined with splicing devices
identified for the use or by brazing, welding, or soldering with a
fusible metal or alloy. Soldered splices shall first be spliced or
joined so as to be mechanically and electrically secure without solder
and then be soldered. All splices and joints and the free ends of
conductors shall be covered with an insulation equivalent to that of the
conductors or with an insulating device identified for the purpose.]
copyright 2002 the National Fire Protection Association.
I think this points out that you must NOT rely on the solder. You
must first do the job first then add the solder second.
Which leads me to the question, after you mechanically and
electrically secured your connection, why would you add solder? Where
is this a good practice?
First off you can attach a stranded wire to a solid wire inside a wire nut
just fine. If the wire nut is sized for 2 or 3 connectors I will usually
wrap the stranded around the solid from top to bottom and then kind of flip
the end over the top before twisting on the wire nut.
To test take a scrap of each assemble and see how hard you have to pull to
obtain a failure. If it is easy then you are using too large of a wire nut
or you did some thing wrong.
If you need to pull real hard then the wire nut is doing its job.
I interpret the phrase mechanically and electrically secured to mean you
twist the wires together rather than laying them side by side to solder
them. It might have a different meaning if you were dealing with some
heavy cable or something.
About the time I had mastered getting the toothpaste back in the tube, then
I think somepeople's option against this is, if you get a short, or a
groundfault, the solder could melt and break the circuit. I think
people want faults handled by protective equipment, not the wire
itself. Imagine you overload the circuit and your connections come
I tried soldering on some scraps. I dipped the wires into flux and then
tried to solder them. The solder adhered to the stranded wire as well as
could be, but it skated right off the solid.
I have never soldered anything but stranded before, but don't understand why
the solid is different.
Any advice here?
More heat. If you have the wire hot enough, without oxidizing the copper, the
solder will stick (actually form an alloy).
Soldering is a trick that was well known to old electricians but was lost whwn
they started using wirenuts. BTW an electrician's soldering iron is ~200w,
about an inch in diameter with a 5/8" or larger tip. The idea is that the tip
brings enough heat to the job that it instantly brings the ends of 2 or 3 #12s
to soldering temperature without slowly heating the length of the wire and
melting the insulation. If it takes more than a second or two, you need a
You probably need a hotter soldering iron. I bet you've got a fairly
low-powered unit. Try something around 100W or bigger.
Also, don't use plumbing solder, which is lead-free. Get some 50/50 or 60/40
leaded solder and try that.
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