I know the electrical code does not allow junction boxes inside walls. So if I have a run of 12/2 that's not quite long enough, how do I splice it? Or can I?

 

All splices have to be inside a junction box, and all junction boxes must be accessible. So you have a dilema here.

 

Can't I solder the conductors instead of using a junction box?

 

Options:[list=1][*]Replace the cable (end to end) with a longer one that will reach.[*]Install an accessible junction box for the splice with a blank cover plate.[*]Install an accessible junction box with a receptacle in it (you can always use an extra).[/list=1]Hidden or inaccessible junction boxes, or splices outside junction boxes (soldered or otherwise) are not options. In general, you should not be soldering connections (they are not prohibited, but code prohibits a splice that depends on the solder for the connection).

 

Thanks. The suggestion to just add a junction box with a receptacle is surely a good one. But why is the Code so restrictive? Seems to me a properly twisted and soldered connection would be a lot stronger than one using a wire nut.

 

Any connection between two conductors can be a source of failure.

 

Agreed. However, I still contend a properly twisted and soldered connection is less prone to fail than a wire nut connection.

 

True, but since the days of quality wire nuts soldering has become inefficient and restrictive to future work.

 

Twisted and soldered would probably be fine as long as the twisting was enough to keep the wires together without the solder. The problem is that it's hard to make a good solder joint, and hard to recognize a poor one. A properly installed wire nut connection is easy to make, makes an excellent connection, and is less error prone.

 

FWIW - my older home (1955) has soldered connections - all within junction boxes.

I am surprised by the number of wires that are stuffed in each junction box, but it is original.

 

The code allows twisted and soldered connections, it just requires that they still be in a junction box. IMHO the justifications for this requirement are:

Assumption: No matter what the connection technique, the probability of a splice failing (either open or short) is much, much higher than that of an unspliced cable failing.

If you grant this assumption, the I can think of three reasons why a junction box is required:

(1) Locating splices - if a splice fails, it is much easier to locate the failure if you only have to look inside accessible junction boxes.
(2) Strain relief - the junction box clamps provide strain relief for the cables, reducing the probability of a splice failing.
(3) Safety - any arcing or overheating caused by a failed splice is contained within the junction box, which is much safer than arcing or overheating at some random point inside your wall.

I have learned over the last couple of years on this forum that most every article of the NEC has a lot of good, sound engineering behind it.

 

...and most often by a few fatalities.