Terminal blocks in sockets

[EFLImpudence]

Properly crimped with a decent tool, there is no issue with solid core cable.

People don't have decent crimp tools.

I cannot make out what's what in your picture - but it doesn't look too good.

 

[crystal ball]

I was certainly brought up to believe that solid conductors should tonot be crimped and, as discussed here before, at least one set of Standards/'rules' (those applicable to NASA) says that, but I'm not personally aware of any rules/regulations applicable to UK electrical installations which actually 'forbid' it.

Personally speaking, I'm not totally comfortable with the practice - but that's just me!

Kind Regards, John
Edit: typo corrected

Certainly MOD spec in the 70s forbade solid crimping

 

[RF Lighting]

I’ve been crimping solid cores for 20+ years and never had an issue.

 

[JohnW2]

I’ve been crimping solid cores for 20+ years and never had an issue.

Yes, of course, in the hands of someone experienced, with appropriate tools, it seems to very rarely 'result in an issue'. However, as always, 'very rarely' is not necessarily the same as 'never' ...

Provided that the joints were in places where they would not be subjected to stresses, you could probably have been just 'twisting the conductors together' (with pliers) for 20+ years without 'ever having had an issue', but ..... !

Kind Regards, John

 

[Minatoar]

I have recently used used these and they were a doddle to do.
https://www.screwfix.com/p/ideal-spliceline-in-line-wire-connectors-pack-of-10/42201
Perhaps someone with more experience than me can confirm they are suitable?

 

[aptsys]

People don't have decent crimp tools.

I cannot make out what's what in your picture - but it doesn't look too good.

It's essentially a perfect crimp, some of the artefacts are due to the shear cut through the crimp terminal, but you can see there is exact deformation of the copper to fill the shape of the crimp.

 

[JohnW2]

It's essentially a perfect crimp, some of the artefacts are due to the shear cut through the crimp terminal, but you can see there is exact deformation of the copper to fill the shape of the crimp.

I don't think it's the extent to which the copper fills the shape of the crimp that is necessarily the issue - it's the quality (in both short- and long-term) of the contact between conductor and crimp that matters. As you have said, copper is very soft and, unless a stable 'cold weld' is created, it can 'creep' when it is under some pressure - potentially leading to a situation comparable with a screw terminal which has been tightened only very 'loosely'.

I think we are all agreed that a properly executed crimped joint on a solid conductor will 'nearly always' be fine - but that leaves the question of what 'nearly always' actually means.

Kind Regards, John

 

[aptsys]

I don't think it's the extent to which the copper fills the shape of the crimp that is necessarily the issue - it's the quality (in both short- and long-term) of the contact between conductor and crimp that matters. As you have said, copper is very soft and, unless a stable 'cold weld' is created, it can 'creep' when it is under some pressure - potentially leading to a situation comparable with a screw terminal which has been tightened only very 'loosely'.

I think we are all agreed that a properly executed crimped joint on a solid conductor will 'nearly always' be fine - but that leaves the question of what 'nearly always' actually means.

Kind Regards, John

Where is the copper going though if it's filled the crimp? How is the situation different for stranded conductors?

 

[JohnW2]

Where is the copper going though if it's filled the crimp?

Along the length of the conductor. If one applies appreciable pressure to the sides of a conductor, some copper will 'ooze' out beyond the ends of the region of compression. A similar phenomenon can occur with 'creep', at much lower pressures. Try it with Plasticine if you have any doubts

How is the situation different for stranded conductors?

That's something I'm not so sure about - but it is one version of 'traditional wisdom'.

NASA's concerns presumably relate primarily to very high levels of vibration and, in that context, something seems to have convinced them that crimping stranded, but not solid, conductors is OK.

Kind Regards, John

 

[rsgaz]

Where's your grommets, Gaz!

They're very thin, but present! The scale of the drawing went a bit tits up, that's the thickest line Paint can draw freehand on that size image!

Apologies, I did forget to draw the wallpaper and the great dollops of plaster splodged all inside the box, with the plasterer's skilled knack of getting most of it on the faceplate lugs!!

 

[JohnW2]

NASA's concerns presumably relate primarily to very high levels of vibration and, in that context, something seems to have convinced them that crimping stranded, but not solid, conductors is OK.

In case anyone here missed, or has forgotten, the past discussions, the NASA's "Workmanship Standard for Crimping ...." can be found here . I would draw particular intention to 7.2.26 on page 24 (of 101), which says ...

7.2.26 The following requirements apply for crimped connections.
a. Crimped contacts shall be used with stranded wire only.
b. Solid wire shall not be used with crimped contacts.
c. Solid, tinned wire shall not be used in crimped contacts

They clearly want to make their point since, having written (a), they did not really need to underline it with (b) and (c)!

More details about crimping practices are given section 12 (pages 51-54) and Appendices A8-A10 (pages 96-100). Nowhere does there seem to be any explanation of their prohibition of crimping of solid conductors.

Kind Regards, John

 

[aptsys]

Not sure NASA is any particular standard for excellence

 

[JohnW2]

Not sure NASA is any particular standard for excellence

Possibly, and I wasn't really intending to cite them as being divine or omniscient - merely indicating that they were one organisation which, for whatever reason, forbade crimping of solid conductors.

We've been told that, at least in the past, the MOD also had such a prohibition - but you might also question whether they should be regarded as a 'standard for excellence'!

Kind Regards, John

 

[ban-all-sheds]

I would not question their status as a standard for excellence in the environments within which they operate.

I would question the relevance of their environments and their external influences to the environment inside my accessory back boxes and floor/ceiling voids.

 

[ban-all-sheds]

Or is there another, better, perhaps safer method which falls short of replacing an entire run of cable? This is a house with solid floors.


Soldering, then covering the joint with heat shrink or self amalgamating tape.

No he didn't.

And soldering is OK only if it is used to assist with electrical contact. The joint must be mechanically sound without solder.