joining cables

[brman]

What's all this about adding a fuse?

If the protection at the origin of the circuit is rated for the smaller cable, no need to stick an additional fuse in where the cable sizes change.

For example, you might choose to do a long lighting run in 2.5mm² to minimise voltage drop and then do the final few metres to fittings in 1mm² or 1.5mm² to make termination easy. If it's all on a 6A breaker, no problem.

Good question! I was taught that you had to add a protective device whenever the csa was reduced. This is I think application of 434.2. However it does look you are correct according to the exception in 434.2.2 which treats a change in csa the same as a change in installation method etc. i.e. select the PD for the circuit based on its minimum capability.

 

[malcolmsanford]

No not quite Br there is nothing wrong with say having a 10mm cable with a 45amp PD and the last 2 metres in 4/6mm say, providing you can achieve all the criteria of the regulation

 

[brman]

No not quite Br there is nothing wrong with say having a 10mm cable with a 45amp PD and the last 2 metres in 4/6mm say, providing you can achieve all the criteria of the regulation

sorry, i am not sure I follow you. 4mm would not be protected by the 45A PD so how is that allowed?
From my re-read of the regs I thought that would only be allowed if the PD is smaller than the current rating of the 4mm.

Do I need to read the regs again?

 

[malcolmsanford]

Yes remember we have 2 conditions concerning protection over current and fault protection

Have a look at 433.3.1 and section (i) particularly about and a device need not be provided

 

[brman]

Yes remember we have 2 conditions concerning protection over current and fault protection

Have a look at 433.3.1 and section (i) particularly about and a device need not be provided

You are right, I referenced the regs on fault protection when I was talking about current capacity and overload protection. But doesn't 433.3.1 affectively say the same thing? i.e. a supply side PD must be capable of protecting the cable under fault (434.2) and overload (433.3.1).

I know there are always exceptions (eg 433.3.1 (ii)) but in general it still appears to be saying the PD must be selected for the minimum capacity of the circuit.

If I have still got it wrong you might have to spell it out for me....

 

[PC Electrics]

Presuming there is a legitimate reason for joining 2.5 to 1.5 I think a wago would be better than a crimp in this instance. Similarly for joining metric to imperial:
https://www.wagobox.com/shop/pushwire/

 

[LineProducts]

If you do decide to follow pcelectrics advice remember that:

Best deal on Wagos etc at for electricians by electricians

 

[Octopus]

Best deal on Wagos etc at for electricians by electricians

Not the most helpful post as the debate goes on about joining 2 cables of different sizes.

All your post is likely to do, is say its OK.

 

[Guest111]

I think blue crimps are rated from 1.5 to 2.5 if u look on the packet

not if using proper crimps with an approved crimp tool(ratchet type) which was brought in to ensure a correct crimp regardless of the strength of the individual,as ratchet does not release until crimped to a predetermind level,in fact crimp tool manufacturers(biccon)recommend you only use the crimp made by the crimp tool manufacturer as there can be differences in size between makers,I have seen this when using cheap crimps and sometimes they will pull out,ex father in law used to work at biccon in r&d so thats how I know so much about them.

 

[lauriehurman]

IMHO a Wago is great if it's enclosed and accessible. The beauty of a crimp is that you can shrinkwrap it and hide it.
526.3 (vi) allows maintenance free but none of the Wagos I have have "MF" embossed on them. Do they conform to BS5733? They also all have a "test" hole which means they are not to IP4X (and so need an enclosure).

Laurie