Extending Flex using Butt Crimps

[jkayes]

I have two roof vent actuators in my conservatory and need to extend their leads to the switch. The actuators currently have 1 meter of 3 core, 0.75mm flex (no earth) brown, black, grey (made in Italy) which I need to extend by about 3 meters to a 10A retractable switch. They are double-insulated and rated at 55W (loaded).

I cannot open the actuators to replace the flex without invalidating their guarantees. Also, I cannot find 3 core (no earth) flex in the UK.

Can I extend the leads by crimping to 0.75mm 4 core flex using red butt-crimps? I think these are usually used for T&E cables between 1mm and 1.5mm and my flex is 0.75mm multi-core. However, I could overlap each end so that the diameter was increased to 1.5mm. Note also that the joints will be concealed in a conduit of the main beam (wood) and there is not much room for anything else.

Also, is there a convention for colour of the heatshrink I should use?

Thanks for any advice

 

[FrankE]

From your description there doesn't seem to be strain relief issues so crimping would be advised.
Is the conduit plastic?

Crimps are for CSAs of whatever they say on the tin. Red are normally 0.25 to 1.6 so there is no need to fold over the end. Too many electricians are mistaken re: crimp sizes (thinking red is only for 1.5, blue is only for 2.5 and yellow is only for 6 because they haven;t bothered reading the data sheets.
I don;t think many electricians would even use heatshrink (except perhaps in steel conduit).
If you do use heatshrink (it isn;t relly necessary) , tape over with Brown, black, blue for O/C,N or C/O/N respectively. and tape over cores back to the controls with the same tape to follow the colour coding through.

What controls, may I ask out of interest, are you using for opening and closing the actuators?

 

[jkayes]

Hi FrankE. Thanks for your reply.

The "condut" is actually a channel rebate in the base of the wooden main beam. It is covered by a wooden moulding.

I am using a single MK K4900 10 Amp retractive switch module (from the Grid Plus range) to control both vents and have a fused switch upstream with a 5 Amp fuse.

Question re 4-core; what is good practice re the unused earth (green/yellow)? Should I leave it the same length as the other cores but unstripped or cut it back to the outer insulation?

Thanks again

 

[FrankE]

Most sparks would use 3 core (2c&E) and tape the green and yellow with black, oversleeve it at a push.
If you are using 3c&E terminate the E into a butt crimp. personally I don;t like seeing things chopped off.
Maintain the colour coding throughout.

Re: the crimp sizes
http://documents.rs-components.com/EITC/UK/electronics/GLO_0101 UK LowRes1.pdf
page 24
Check the particular brand though.

 

[londonboy]

Use 4 core, its much better practice.

 

[Spark123]

Most sparks would use 3 core (2c&E) and tape the green and yellow with black, oversleeve it at a push.

NOT ON YOUR LIFE!! Never ever ever use a CPC for anything other than a Protective conductor.

I'd do it by mounting an outlet box adjacent to the actuator and using 3c+e, terminate the earth into the box and connect it to the protective conductor of the circuit supplying the appliance.
You can even use terminal blocks if the outlet box is to remain accessible.

 

[holmslaw]

..

 

[Spark123]

Black oversleeving did seem a bit of an odd choice too given all line conductors in a single phase should be brown or oversleeved brown at terminations. However not as big a sin as using the earth core for a line conductor which is outright dangerous and anyone who does so is a cowboy, not a sparks.

Red, blue and yellow crimps can take a range of different cable sizes, they are not just 1.5mm for red, 2.5mm blue and 4mm/6mm yellow.

 

[holmslaw]

..

 

[jkayes]

Spark123 - your solution makes most sense as it allows the actuaror to be replaced easily if need be. However, I went to a lot of trouble to get the rafters and main beam routed so the flex could be concealed and I don't want to ruin the look with outlet boxes. Just means I'll have to remove a decorative cover from the main beam if I need to change the actuator.

I'll go with 4-core flex and join with red crimps unless you think this is wrong. I bought a fancy CK ratchet crimper too.

Re the CPC, should I just leave it loose both ends or fit a crimp as FrankE suggested?

 

[FrankE]

Most sparks would use 3 core (2c&E) and tape the green and yellow with black, oversleeve it at a push.

NOT ON YOUR LIFE!! Never ever ever use a CPC for anything other than a Protective conductor.

I'd do it by mounting an outlet box adjacent to the actuator and using 3c+e, terminate the earth into the box and connect it to the protective conductor of the circuit supplying the appliance.
You can even use terminal blocks if the outlet box is to remain accessible.

That wasn't recommendation,heavens! It was an observation of what most saprkies would do, usually because they are too tight to buy a new drumof 3c&E flex. I use sparkie in the derogatory sense, they make sparks all over the shop.

 

[FrankE]

Most sparks would use 3 core (2c&E) and tape the green and yellow with black,

They most definitely would not do that.

And whats all this bollerx about crimps that can take different size cables? Standard ratchet crimping tools are designed for the size of cable and the crimp. IE when set to 6mm they will correctly crimp a 6mm cable into a 6mm lug, they will not make a satisfactory crimp on cable of a smaller csa. s

I hope you are not a sparks and you should not be giving advice to people.

You are a dangerous bodger with minimal electrical knowledge.

They would, they shouldn't
Sparks! Ugh. No sparks here, sorry, sparks are a sign of poor electrical work.
Had your crimp tool calibrated recently BTW? Had the pull out force of crimp terminations verified?

 

[FrankE]

Could you install a 3c&E flat or FP in the rebate to a discreet J/B near the actuators and neatly clip the flexes to the J/B. You shouldn't use flex for fixed wiring which is what the run you describe is.
The actuators are 24V O/C/N or 230V O/C/N?

 

[ericmark]

When working for GEC Large Steam Turbines we had separate crimp pliers for each size of crimp and they were calibrated and for 1mm we used different crimp pliers to 1.5mm even though the crimps were the same.
Orange 1mm and Red 1.5mm the same applied to 4mm and 6mm the crimps were same but pliers were different.

I got into a lot of trouble for using my own crimp pliers as they were not calibrated also for using my own meter as not calibrated. I was a different world where the motor and pump were lined up to within 0.001 inch. No allowing for layrub coupling taking up any out of true. But 5 years later on next shut down still had same coupling on all motors so seemed it did work.

 

[Spark123]

So how do you crimp say 2 x 1.5's into a 6mm crimp.? The data sheet he referred to says they are suitable for cable down to 2.7mm

One wire, one crimp, if we need to join more than that we use terminal rail and the appropriate size crimp on each conductor.

What sort of crimper do you use? A hammer and cold chisel?

I use a proper set of ratchet crimping pliers