Splicing 6 awg stranded copper wire

I understand that the NEC allows splicing wire feeding a branch subpanel , as long as the splice box is left accessible. For 6awg stranded copper , the split bolt type splice is usually used, along with lots of insulating tape. I've built some electric powered vehicles, where the current in the main cables was up to 400 amps, at around 90 volts. To attach terminals to the welding cables used, I always soldered them . Soldering heavy cables takes some experience, but it can be done successfully, and I never had a bad connection.
My question is this : If I splice the 6 awg copper wires with a split bolt, could I also solder the connections to insure a durable splice ? What about leaving out the split bolt, and doing the job entirely by soldering ? I use a propane torch for the soldering, which does heat the copper wire substantially . Would the heat weaken the wire or affect its electrical properties ?

McMaster Carr sells great "splices" that are encapsulated so you leave the tape in the tool box. Stick a wire in each end a sock down the clamp screws.

John Oder

The NEC does not allow soldering for splices and terminations. Split bolt is good enough buy its self.

A large weller gun or two, or the smaller american beauty iron does a bettter
job that a propane torch.

Jim

Crimped and mechanically connected wires can actually be considered a better elec. connection than soldering. I find it hard to believe, but thats what I've been told.

I would like to know what the NEC finds wrong with soldering splices in addition to the nutting!

If I'm gonna splice fat wire using solder, I use copper tube.

I take a short piece of copper tubing that's close to the proper diameter, and cut a slit down the side. Slide a piece of shrink tube up the wire a ways so it doesn't get shrun accidentally. Then I drill a hole in the tube for the solder to go in right in the middle. I make the tube just a bit longer than the stripped wire, just enough for the solder to get in there. Then I loosely crimp the tube around the wire with the hole pointed up. I have an itty bitty butane torch I use for soldering, it's blue and says "pencil torch" on the side. I heat up the tube with the torch, and feed solder in through the hole in the middle. When I see the solder ooze out the ends of the tube around the wire, it's done. Sometimes I touch it up with some solder around the end of the tube if the solder doesn't come out around the whole wire. I wrap the junction with some electrical tape to protect the heat shrink tube, and slide the tube over it all. That way you don't see the tape, and it looks really good. Obviously this isn't to code, but it works VERY WELL.

"The NEC does not allow soldering for splices and terminations. Split bolt is good enough buy its self."

Only "compression" connections are allowed, thereby eliminating "soldered" connections.

One interpretation of the code is a compression connection which is subsequent to compression "soldered", whereby the "solder" is really there only to ensure gas-tightness of the joint, is OK.

The "solder" would, therefore, be incidental to the mechanical and electrical connection provided by the compression, and the compression would be the "real" connection.

This is always subject to challenge by AHJ's, so I wouldn't use it unless I was the AHJ.

Soldering connections

I suspect that soldering a joint does make an electrically better connection , and one that will be a low resistance connection for decades to come. A compression connection will many times become a bit loose after a period of time , especially if the cable is a stranded variety that may compress more over time. Even just moving a solid wire around a box can loosen a screw connection . However, as long as NEC acceptable compression connections are used, at least there is some standardization involved. Soldered connections invite a lot of poor quality work, and no chance of standardization for larger connectors.
"Cold" solder joints are a problem even with low current electronics wiring, and high current wires that also need mechanical strength invite more problems. It's not that it can't be done, but the variability involved would invite disasters.
I agree that copper tubing can help make good splices and terminals, and I did that quite a few times when building the electric vehicles.
As pointed out, a compression splice that is subsequently soldered may be a good solution
for worry warts like me who want to go the code one better.

"However, as long as NEC acceptable compression connections are used, at least there is some standardization involved. Soldered connections invite a lot of poor quality work, and no chance of standardization for larger connectors."

The only "soldered" connection which even rivals a compression connection for low resistance and high reliability is the so-called "Western Union" splice (also, apparently inaccurately, called a "Western Electric" splice).

This splice is actually a compression connection to which a "solder dip" has been added, for gas-tightness.

Western Union/Western Electric splices are OK for communications purposes, but these are not permitted for power purposes.

Almost every electric utility lineman now carries a complete assortment of approved compression connectors, and the tool which is required to effect such connections.

Almost any combination of entering and leaving wire gauge is provided, not just one-to-one.

The linesman in my area carry everything from #8 (the smallest service allowed) to MCM sizes, in every combination, and the special connectors include both mechanical and environmental protection.

It was "no problem" for the linesman to interconnect my #2 AWG Cu THHN service (125 amp) conductors to his #2 Al service drop.

If his drop had been #4, which is perhaps more common in my area for services up to 200 amps, then he had those connectors, too.

kevin johnson said:

The NEC does not allow soldering for splices and terminations. Split bolt is good enough buy its self.

Click to expand...

The last half is true, a split bolt is a good method of terminating cable, but is not intended to be soldered,the 1st part is not.... see NEC 2002 110.14(A) & (B).... that section is unchanged in the 2005 NEC, dont have a 2008 copy handy but it's been only adopted in limited areas.

A good connector is a Polaris connector no need for tape, heat shrink, but not cheap.


If a statement is made that "code or the NEC" does not allow something show me the code section or it aint true, if something is not prohibited in the NEC then it is allowed.

Soldered joints are frowned upon because it takes skill. It's easy to make a bad
soldered joint, if one does not know how to do it. Crimp connections or split
nut connections take less skill so there is less chance for variation.

Jim

What does the heat from the solder do to the wire insulation? Wire, but not terminations are commonly rated at 90 degrees for thhn/thwn. Melting solder will exceed this temp .

The question is for wiring to a sub panel that I assume is in an indoor location. No mention is made otherwise or I would recommend a set screw termination with a heat shrink made and sold for this application.

Splitbolts are made up tight, hammered lightly to get wire to settle into place, and then retightened. They do not loosen if made up correctly. The need for " gas tightness" in this application is over kill at the least and a code violation at the worst. Read illegal. No jail time will be served I'm sure but illegal none the less.Code violations are breaking the law if the code is adopted in your area.

Crimp connections are great. We use them when we need them, but they are not readily availible to all. They can be made up quicker than a split bolt.

One reason I was told solder is no longer allowed on power circuits is some might use acid core solder that could corrode over time. I have seen many many old splices still in service that had no problem whatsoever. I have soldered low voltage connections but never a power connection. There is no need to do so.

Kevin , L.U. 124 IBEW

I went on line and viewed 110.14 and I stand corrected to the point that solder is allowed if mechanically joined first and parts are listed for porpose. It has been 20 some years since I had last needed to discuss soldered connections. But I stand by the fact that it it is not needed in this case. My original intent was that solder alone does not meet the code .

As this is a machinist oriented site , I did not see the need to qoute section and verse to a simple wiring question.

Kevin L.U. 124 IBEW

kevin johnson said:

One reason I was told solder is no longer allowed on power circuits is some might use acid core solder that could corrode over time. I have seen many many old splices still in service that had no problem whatsoever. I have soldered low voltage connections but never a power connection. There is no need to do so.

Kevin , L.U. 124 IBEW

Click to expand...

"Told" it's not allowed? No code section quoted means it's one of those "Electrical Myths". Soldering is "old school" and in almost all cases there are better methods now.
A compression connector installed w/ the proper tooling is superb.

I would guess (yes just a guess, no research) that a less than adequate solder joint sans a mechanical connector could easily lead to overheating the conductor splice. If you have only a fractional connection trying to handle the same amperage as the total connector you'll get warm wires- similar to using a wire which is too small for a circuit. If it's overheated enough.......well you know what happens to solder when it gets hot enough...

"A compression connector installed w/ the proper tooling is superb."

For sure!


The standard for extra low voltage, extra high current connections at my immediately former employer, a large mainframe computer manufacturer, was a T&B compression connection, followed by a solder pot dip, followed by head-shrunk tubing.

We're talking 70 to 140 KVA of (mixed) -5.2, -2 volts, and also + and - 12 volts and some +5 volts.

The majority of the circuitry was -5.2 and -2 volts. The others only in the peripheral circuitry.

Because of the high currents involved (each of the many cascaded PSUs was rated 2,000 watts) welding cable was our preferred conductor.

Of course, the entire product was UL Listed.

A properly done up solder joint is stronger than the copper wire itself.

Try it. Gently twist two pieces of number 12 wire together, solder them. Then
clamp one in a vise, and pull on the other. See where it breaks.

THHN insulation handles moderate heat from soldering well. The propane torch will
wipe it out a bit, but a couple of weller guns will do just fine. The larger weller
gun can do two number six stranded wires by itself. The insulation survives fine.

The concern about corrosion is because some folks like the ZnCl flux, that's bad,
don't use it. Only rosin.

Or is that rozin.....



Jim

Code sections will not back up why or why not something is done. The code gives minimum standards for installation with shall and shall nots, not why it is done. The reason something is done a certain way can not be ascertained by the NEC in most cases. That does not mean it is a myth.

Old school does not mean better or we would still be pulling "rag" wire in black enameled pipe. We could run this through pot dipped splices to Edison lamps. Or we could run knb and tube and eliminate the conduit altogether. Who needs a ground ? Thats a new fangled thing. Now that a myth.

I can say for certain...

I can say for certain, that when I did the 300A SE at my previous residence, I applied solder to already very physically sound bolted connectionsin the ground system, and my AHJ and utility company was perfectly fine with it.

"Gas Tightness" is important when you want to keep moisture out of the joint interface area, and this was my main concern. While the average person wouldn't see a difference in power capacity, the difference in emitted RFI IS noticeable when you're running a ham radio system... that little bit of corrosion between two bolted connections becomes a rectifier, and brings the noise floor WAY up... so ANYTHING you can do to keep that connection clean and bulletproof is good. To further seal the joint, I used a common coax sealing tape that turns into 'goo', and really seals the connection up well... then I wrapped 'em in the really good 3M tape. My utility electrician had similar wrap for his, and he even flooded the connection with Non-ox prior to bolting it in.

Soldering DOES have an effect on insulation, however, if you use enough heat, and get the job done quickly, it will have no substantial effect. Usually, someone burns up a connection simply because they didn't use enough heat, and they didn't work fast enough... alas, that's one of the reasons why the variation-of-quality issue exists. By the way... Aluminum isn't easy to solder... it's coefficient of thermal transfer is extremely high, so if you plan on adding solder to seal up a big connection, use copper for your wiring. You'll likely not get this opportunity with an overhead drop, as aluminum is the prevailing conductor-of-choice for overhead triplex.

Wether soldering is allowed by code, considered illegal, written in the book, assumed allowed until specified forbidden, I'll still direct your attention to the first few paragraphs and sections... somewhere in there, it says something to the effect that The NEC Code is NOT LAW, and cannot be held or adopted as law, it is merely a guide for the purpose of Fire Protection Safety, and that interpretation and application of The Code is at the discretion of the inspector (AHJ).

So... it really doesn't matter what the book says. The AHJ makes the call, and if you sell him/her on your interpretation, you're golden. If not, back to the toolbox!