Soldered joint on ring main-legal?

[mattylad]

And the purpose of the cable wrapped around the joint is?

 

[OilLecky]

I did an apprenticeship and worked for some considerable time as an aircraft electrician and this is what we were trained to do and expected to be able to do at any time.

Soldered joints could be used provided that they were securely mechanicaly joined before the solder operation (but after "tinning"). As someone said earlier, the solder itself will not provide a good mechanical joint. Also, both sides of the joint have to be mechanicaly secured to prevent vibration or movement as the point were the cable conductors change from flexible to solid solder is vulnerable. ( This is obviously not so important in a completely fixed installation but worth bearing in mind.) Wrapping the bared end of one cable core around another and soldering them will not do.

Crimping was introduced to "de-skill" the jointing operation. It enabled the aircaft factories to work faster with workers that had easier skills to learn. This has now spread into all the electrical industries. However to get quality crimp joints you need quality terminals and crimping tools that have ratchets and are regularly calibrated.

To be able to solder correctly first time every time is not something that you can teach yourself. It takes hours of supervised practice.

It is only in the last 20 years or so that the "migration" of solder molecules has reared its ugly head, or been understood. I don't think that the migration invloves the copper but the basic ingredients of the solder itself separate and give a dry joint. This is why intermittant faults on a circuit board are often cured by retouching all the solder joints with the iron. I don't want to go into what happens with multi-layer circuit boards, the use of freeze spray or thermal cameras to look for hot spots but believe me it is a problem.

Now although it may be OK to use a soldered joint that then gets buried and presuming that we are all really good at soldering, after 10 years the solder will start turning to a dry joint. The joint will then gradually get warmer when passing a load until....................?

 

[chapeau]

The joint will then gradually get warmer when passing a load until....................?

The solder melts and repairs itself???

 

[ericmark]

As an apprentice I had a book describing the method of joining cable mainly overhead telephone and the "Western Role" method of wrapping cables before soldering however with lead free solder many of the previous methods are no longer sound and I do have a small stock of proper soft solder.

The fact that one is still allowed lead in solder for comms equipment routers and the like does show it is well known that the new lead free solder is not as good as the old lead solder.

I have seen crimped lugs fail but very few soldered ones however likely they were crimped then soldered anyway. However where the is some movement I have seen failure at the point where solder ends many times.

However a wrapped cable soldered and shrink sleeve especially where resin shrink is used is very unlikely to fail and far more unlikely to fail than cable joined with screw type connectors and also likely better than many crimped connections but of course there should be no strain on the cable.

As with any joint there is always a chance of failure and sometimes our attempts to ensure they don't fail back fires? I have seen many a necked off cable where maintenance has required that the screws are tested for tightness once every 6 months and each time the electrician gets another 1/8 turn on the screw.

I have seen batteries with lead posts complete their life cycle many times without the post being damaged but I have also seen them completely destroyed in very short time and really nothing to do with lead they are made of but more to do with how they are maintained.

I would trust a soldered joint I have done. Except in 1970's where we had a lot of aluminium cable I have not had a problem with soldered cables using lead solder.

 

[mattylad]

I have not had a problem with soldered cables using lead solder.

Be prepared for lots of problems then.
Unless you have a supply of leaded solder the current lead free stuff is carp in comparison.

maybe not now, but in a few years those joints wont be as good.

 

[ericmark]

I have not had a problem with soldered cables using lead solder.

Be prepared for lots of problems then.
Unless you have a supply of leaded solder the current lead free stuff is carp in comparison.

maybe not now, but in a few years those joints wont be as good.

I will agree lead free should be banned it's rubbish. I had big problems in Uni when I pointed out the health and safety issues of using lead free solder. It's lethal stuff or at least the flux it uses is! All well and good saying use extract fans but get real! Why do they think I have a gas powered soldering iron if there is power to use extractor fans?

I refused to use lead free solder until they can make it so it's not so hazardous.

If you don't believe me read the COSHH sheets on the stuff. Should be banned!

 

[IJWS15]

My background is rail vehilces.

Spent a few hours soldering ups onto 1" csa multistrand cables that would carry 10,000 amps.

Dry joints were not a problem, even after many years and if migration was a problem it would occur quicker at these currents.

In that environment the use of screwed termiantions onto wire was banned - they lasted less than 6 months with the vibration. The transition point at the edge of the solder was not a problem in the same environment.

Don't see the issue with soldering in a domestic installation.

 

[plugwash]

As an apprentice I had a book describing the method of joining cable mainly overhead telephone and the "Western Role" method of wrapping cables before soldering however with lead free solder many of the previous methods are no longer sound and I do have a small stock of proper soft solder.

Note: leaded solder is not in itself illegal (and it can still be purchased from all major electronics suppliers), you can't use it on most equipment that you plan to sell (there are a few exceptions) but afaict there is nothing prohibiting it's use in fixed wiring work.

 

[roberta1000]

Personally I generally use solder joints

Not picking on you or trying to catch you out, but can you take me through the method you use.
Or anyone else experienced in soldering cables together.

Not really rocket science! Some appropriate form of mechanical jointing dependent on the location, cable orientation and conductor gauge followed by application of gun and (non-lead-free) multicore solder. 'Twisting' the conductors with due care to avoid breaks and making sure that there are no stripping nicks is all that's needed for a safe joint (IMHO of course). Some minor care needed for shrink sleeving.

Certainly soldering takes more effort than a crimp but on balance I would say that crimps fail (far) more often even using the correct kit. Down to long-term copper malleability I suggest, same as for failures in screw connections.

 

[ban-all-sheds]

And the purpose of the cable wrapped around the joint is?

To stop the weed falling out