NEC on soldering wiring

This certainly is not a dumb question. The NEC makes the answer rather complicated, though. Here is what I came up with using my professional Acrobat search utility.

Solder appears 37 times in the 2005 NEC. In some cases solder is not permitted, in others it is required. The word solder does not appear in Article 334 that covers NM cable.

Article 110 probably covers NM cable where wire nuts are identified for application over soldered connections with this:

110.14(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. Wire connectors or splicing means installed on conductors for direct burial shall be listed for such use.

However, for grounding conductors solder is not permitted to be the only means of connection because of this:

250.8 Connection of Grounding and Bonding Equipment. Grounding conductors and bonding jumpers shall be connected by exothermic welding, listed pressure connectors, listed clamps, or other listed means. Connection devices or fittings that depend solely on solder shall not be used. Sheet metal screws shall not be used to connect grounding conductors or connection devices to enclosures.

Not specifically, but 110.3(b) requires you to use the wirenuts in accordance with the manufacturer's directions. If they don't tell you to solder the wires first, you would be using the wirenuts in a manner that they were not tested and listed for. You are then technically in violation of the NEC.

Bob Weiss N2IXK

It can at least be argued that the US NEC forbids the use of solder under wire nuts in section "110.3 Examination, Identification, Installation, and Use of Equipment. (B) Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling."

Solder is specifically permitted for making splices though. "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. Wire connectors or splicing means installed on conductors for direct burial shall be listed for such use."

There are some uses of solder that are specifically prohibited. "250.8 Connection of Grounding and Bonding Equipment. Grounding conductors and bonding jumpers shall be connected by exothermic welding, listed pressure connectors, listed clamps, or other listed means. Connection devices or fittings that depend solely on solder shall not be used. Sheet metal screws shall not be used to connect grounding conductors to enclosures." This section is often misinterpreted as forbidding the use of solder on grounding and bonding connections. What it actually is intended to forbid is the tack soldering of such conductors to surfaces without the use of a solder terminal.

"250.70 Methods of Grounding and Bonding Conductor Connection to Electrodes. The grounding or bonding conductor shall be connected to the grounding electrode by exothermic welding, listed lugs, listed pressure connectors, listed clamps, or other listed means. Connections depending on solder shall not be used." This section is meant to forbid the use of solder for terminating the Grounding Electrode Conductor to a Grounding Electrode.

Well, as others have shown, there are all sorts of details.

Sometimes solder is okay, but sometimes it can actually make the situation worse. Solder is generally softer than copper so with mechanical fittings it 'squeezes' out of the connection and loosens the connection over time.

Best answer is always, use listed devices/components and install in accordance with the manufacturer's instructions. Generally, that means do

*not* solder wires used in wire-nuts. Over in alt.engineering.electrical there are also a lot of dicussions about this and the other often-asked question, "Should you twist the wires together before installing the wire-nut?"

daestrom

Well that was stupid, this *IS* alt.engineering.electrical. Look in the archives here and see the various opinions.

daestrom

"Mechanically and electrically secure" is commonly done by twisting the wires in a pigtail splice.

I agreee with the intrepretations of Bob and Tom.

bud--

Real electricians made the splice look like this before they soldered it back in the K&T days

Looks like what we used to call a 'telephone splice'. Something the phone man used, not for 'real electricians' :-)

daestrom

That is a Western Union splice but it was also what an electrician used for K&T back in the olden days

You must be too young to know any "real electricians"

This splice was taught in trade school when I was an apprentice. Never used it since it was a holdover from knob and tube days.

I recall the name, "WireMan's Splice." But we are all singing from the same page of music. This particular splice was strong enough to be used to repair or initially join conductors suspected between to telegraph/telephone poles. As such is predated electrical power wiring.

I wish I was 'young' again. No, but 'real electricians' don't mess around with wire measured in AWG :-)

You can't make a splice like that in the kinds of wire some 'real electrician's use, the wire doesn't bend that easily :-)

daestrom

On Sat, 09 Sep 2006 02:38:52 GMT Bob Weiss wrote: | Michael Moroney wrote: |> Dumb question: |> |> Does the NEC specifically allow, forbid or is silent on the subject of |> soldering home electrical wiring (type NM solid copper) together before |> using wire nuts? | | | Not specifically, but 110.3(b) requires you to use the wirenuts in | accordance with the manufacturer's directions. If they don't tell you to | solder the wires first, you would be using the wirenuts in a manner that | they were not tested and listed for. You are then technically in | violation of the NEC.

I disagree. If the directions tell you to use solder, then you must do so. If the directions tell you not to use solder, then you must not do so. But if the directions do not say one way or the other, you can make no assumptions about any requirement. I believe that it is then not specified one way or the other, and thus either choice complies with the directions, and thus the standard. Of course it is your responsibility to be sure you do not overlook any directions.

| Tom Horne, Electrician wrote: | |> "110.14 (B) |> Soldered splices shall first be spliced or |> joined so as to be mechanically and electrically secure without solder |> and then be soldered. | | "Mechanically and electrically secure" is commonly done by twisting the | wires in a pigtail splice.

Just how much electrical contact exists between two solid copper wires twisted together? Depending on the compressibility of the copper, it could be rather small. It certainly is small where one wire contacts another at an angle. Twisting would have a linear, twisted, line of content for the length of the twist. But how much length is needed to provide sufficient contact to avoid hazardous temperature rise? And how well would it stay this way under the effects of slight corrosion in the long term?

I've personally see a couple cases where twisted wires under a wire nut overheated. Fortunately, the damage was limited to the wirenut and some of the wire insulation.

But the twisted wire is then soldered. It was a common practice when splicing in a box before wirenuts. My understanding is the twisted wire sets were pointed down and then a solder pot was raised under them. I have seen one of this type of joint fail, and one knob and tube tap fail where the tap wire was twisted around the running wire. In both cases the original soldered joint was bad ("cold" solder connection).

bud--

On Thu, 21 Sep 2006 01:28:26 -0500 Bud-- wrote: | snipped-for-privacy@ipal.net wrote: | |> On Sat, 09 Sep 2006 10:48:45 -0500 Bud-- wrote: |> |> | Tom Horne, Electrician wrote: |> | |> |> "110.14 (B) |> |> Soldered splices shall first be spliced or |> |> joined so as to be mechanically and electrically secure without solder |> |> and then be soldered. |> | |> | "Mechanically and electrically secure" is commonly done by twisting the |> | wires in a pigtail splice. |> |> Just how much electrical contact exists between two solid copper wires |> twisted together? Depending on the compressibility of the copper, it |> could be rather small. It certainly is small where one wire contacts |> another at an angle. Twisting would have a linear, twisted, line of |> content for the length of the twist. But how much length is needed to |> provide sufficient contact to avoid hazardous temperature rise? And |> how well would it stay this way under the effects of slight corrosion |> in the long term? |> | | But the twisted wire is then soldered. It was a common practice when | splicing in a box before wirenuts. My understanding is the twisted wire | sets were pointed down and then a solder pot was raised under them. I | have seen one of this type of joint fail, and one knob and tube tap fail | where the tap wire was twisted around the running wire. In both cases | the original soldered joint was bad ("cold" solder connection).

That's one of the worst ways to solder it. OTOH, I have in fact tried to solder large solid gauge copper wire, and it's a bitch. An electric solder gun is nearly useless. And a torch is very messy.

And still, a solder joint can have bi-metal issues. If only there was practical way to do small scale tiny CadWelds.

I had a wire nut connect fail OPEN. It was in a house that had been vacant for about a year. When the power came back on the connection "worked" for a few months and then one day it was OPEN.

Try resistance soldering tools. A sort of clamp/plier whose each jaw is insulated from the other. Squeeze the already twisted wires and click the switch. Several amps flows from one jaw through the work to the other jaw, heating it up nice and quick. Use them a lot when making all the connections inside a motor (a lot of different coil groups to make up and interconnect). Of course, we're soldering 'magnet wire' that is insulated with enamel and some high-temp stuff. May get too hot and melt simple plastic insulation.

daestrom

| Try resistance soldering tools. A sort of clamp/plier whose each jaw is | insulated from the other. Squeeze the already twisted wires and click the | switch. Several amps flows from one jaw through the work to the other jaw, | heating it up nice and quick. Use them a lot when making all the | connections inside a motor (a lot of different coil groups to make up and | interconnect). Of course, we're soldering 'magnet wire' that is insulated | with enamel and some high-temp stuff. May get too hot and melt simple | plastic insulation.

An interesting concept. Just how many amps does it take to make a 10 AWG copper wire heat up to the point it can be soldered? That would be a huge number, I would think. But perhaps the heat is from the smaller cross section of the wire to wire contact. If that is so, that would suggest to me that twisted and capped is actually not good enough.

Just how hot will such a twisted and capped connection get with the 125% level of current flow? For solid wire? For stranded wire?

I would much rather have some more solid kind of way to connect wires, such as a terminal block.