Crimping

[coshhassessor]

For interest / clarification purposes, can someone answer the following:

From what is written here, it IS permissible to connect cables with crimps, if they are plastered over (i.e. the connection is non-accessible).

If the connection is to be accessible, can crimps be used? I don't suppose they can beif they are simply left "as is", but what if they are housed inside a suitable enclosure?

M

 

[dingbat]

You're approaching it a tad back to front. It's not a question of how accessible connections are allowed to be made, its how to safely make inaccessible connections.

That is, you are allowed to plaster over crimped connections - you don't have to!!

But all connections should be made in suitable enclosures in any case, whether or not they are visible or concealed.

 

[coshhassessor]

So you CAN use crimps in an accessible location, subject to your point that suitable enclosures are used.

As for being bass-ackwards, maybe that's the background - on instrument repairs there was discussion over whether screwed or crimped joints were better. The arguement revolved around the following:
#1: "But you can't unscrew a crimped joint!"
#2 "That's the point!"

We found that screwed joints were susceptible to "creeping" and hence loosening over time, whereas crimps weren't. Horses for courses, I know, but it made me wonder.

By the way, these instruments drew about 30kw on a good day, from dedicated power supplies, so we were talking moderately substantial current loadings.

M

 

[ban-all-sheds]

By the way, these instruments drew about 30kw on a good day, from dedicated power supplies, so we were talking moderately substantial current loadings.

30kW at 250kV - 120mA
30kW at 30kV - 1A
30kW at 230V - 130A
30kW at 12V - 2,500A
30kW at 5V - 6,000A

 

[coshhassessor]

At 440V, you can do the sums yourself...

The exciting bits had the operating voltages stepped up to 6-10kV, whilst carrying an amp or so of current.

M

 

[megawatt]

I do think the creep issue is overplayed a little.

All of the major components of an electrical installation from the CU to the sockets employ screwed connections and I don't ever recall an occasion where an installation has needed attention due to screwed terminations (which were fitted correctly in the first place) coming loose.

Others may have different views however

 

[coshhassessor]

Megawatt,

as you say, opinions do vary. We tended to crimp on the grounds that not only did it NOT creep, even if it wanted to, but that it was (somewhat) less easy to beggar about with a crimped connection.

Still doesn't answer my original question, though,

M

 

[Sparkysystem]

I phoned several crimp manufacturers and asked which of their products were certified to carry 32 Amps if used in a knockout box in a brick and plaster wall, would connect 2.5mm wire from a BS Twin & Earth cable and whose insulation was rated to 600V. No manufacturers I spoke to were able supply a certified product to that spec. You can see the reasons why I'd want these specs but I guess I'm on the wrong track somehow.

Please could someone suggest what spec of crimp could be used to join 2.5mm live conductors on a final ring cct and which manufacturers supply them?

I would also appreciate suggestions as to why the spec I was originally trying to get seems wrong. Many Thanks.

 

[andy]

but you can use a blue crimp for 2.5mm²? and just because a ring main is on a 32A MCB doesnt mean the cable is rated at 32A. 2.5mm² is rated 27A

 

[plugwash]

and far less than that in the majority of installation methods.

 

[Sparkysystem]

Thanks for the info. Does anyone have a manufactures max design current for a blue crimp in a steel knockout box in a brick and plaster wall?

 

[ban-all-sheds]

What on earth is there in here that could have prompted a post that had to be removed?


//www.diynot.com/forums/viewtopic.php?p=255343#255343

 

[Sparkysystem]

Is the answer to my blue crimp question that manufactures simply don't specify the safe max operating current under the circumstances covered above? If that is the case, I guess I'll continue with using terminal blocks as I'd be just guessing that the blue crimp was OK. Any further light on this one?

 

[Adam_151]

Rapid electronics quote the insulated butt splices they sell upto 32A for the blue (25A for the red, and 48A for the yellow)

http://www.rapidelectronics.co.uk/r...CAT_CODE=30226&STK_PROD_CODE=M31246&XPAGENO=2

 

[Sparkysystem]

Many Thanks for this info. Along with info from related posts across the site (such as using heatshrink, self amalgamating tape and good ratchet crimping pliers), I'm happy I've now got a good solution to using crimps. Happy Christmas to all.