Terminating stranded flex

[rick]

I am terminating some 3 core flex onto an mcb and busbar For a short final length connection.

BS 7671 allows for using flexible cables, it does stipulate that: A flexible cable shall be used for fixed wiring only where the relevant provisions of the Regulations are met. Flexible cables used for fixed wiring shall be of the heavy duty type unless the risk of damage during installation and service, due to impact or other mechanical stresses, is low or has been minimized or protection against mechanical damage is provided.

In this case risk of damage is low - The cable will be clipped direct to rafters, and at least 2m above floor level.

I don't have a ferrule crimp tool, I could twist and solder the stranded ends, or I could spirally wind around a short piece of solid conductor to provide mechanical strength ..... is there a better way ?

Would I be better to ignore bus bar and use WAGO connectors

[Tricky Dicky]

Do not solder the strands and insert into screw terminals owing to metal deformation of the solder it can cause a high resistance connection inducing heat.

Richard

[rick]

In this instance I crimped on a pin to make mcb connection and used a WAGO for N

So is the 'approved method' now compression ferrule or pin ? Sen a youtube vid of spiral wrapping stranded around piece of solid core ... but I have never used that.

[Brian Gaff]

Yes. Solder may look good initially, but can fail in the long term since the solder does flow slowly even when set from what I can tell, and it goes toward the proverbial dry joint status. Brian

[Brian Gaff]

Yes fell foul of this on speaker cables before. Mind you, it very much depends on the wire and solder used. Leaded works much more reliably on ready tinned copper wire. Which brings me to a query, my cooker cable appears to have aluminium wire, solid, in it. It seems to new that these screws, brass I assume,work loose a lot, and on one of the highest current feeds in a home, why did they use it? Brian

[Hoof Hearted]

rick pretended :

Just buy a crimp tool and box of assorted ferrules (from 0.5 to 10mm) from either eBay or Amazon for about £20 all in.

[Animal]

bad idea, solder is too soft to form a long term gas-tight joint under compression.

I wouldn't, having played with that idea long ago. High failure rate

ferrules. Screw connectors are usually able to work well with flex, but I'd not trust MCB connections to.

[rick]

I ended up buying a 6 way ferrule crimp tool - does do a very good job.