4mm twin and earth

[jg321]

Hi all,

As a follow-up from:

https://www.diynot.com/diy/threads/home-wiring-a-mess-help.485966/

where I stated that I'd get some 4mm T&E to practice with, it's arrived, so I thought I'd give an update.

It certainly is more flexible that I imagined, not much larger overall than 2.5mm (presumably helped by the 1.5mm CPC), and seems to just as comfortably fit through a 20mm grommet. However, the less than positive things I've noticed:

1. The Hager double socket I was using to terminate it into could only fit the 2x 4mm cores, so no additional branches from existing sockets.

2. I could only find a 35mm double backbox, and even with the extra space it was a bit more of a challenge to manoeuvre the socket into place - although a large part of this was probably that the backbox was just loose in my hand - I'll try again with it fixed into place.

3. As a DIYer, I've found single sockets and 25mm backboxes to be a bit of a pain with 2x 2.5mm - so I can't even imagine 2x 4mm! I do have spare single sockets and boxes, so I'll fix some of these up in the shed as above, to see how things go.

4. I've also noticed that it's generally a lot less available, although that's probably less of an issue for professionals as I assume most wholesalers have it.

Overall I'm glad I experimented, but given the lower demand on socket circuits these days (kitchens excepted!), in my (inexperienced) opinion, 20A (or whatever is appropriate) 2.5mm radials, or 32A 2.5mm rings seem to be a good option.

Appreciate that most of you will find all this a bit "yawn" - but for the overly-interested DIYer such as myself, I hope this has been slightly useful.

Cheers,

Jon

 

[EFLImpudence]

1. That's a surprise, certainly there is no problem with other makes. Hager gives the capacity as 5 x 2.5mm² so, I suppose 12mm² is a bit tight but should be possible. Are all the strands staight and cut neatly? Certainly won't be loose.

2. I have never had a problem with 25mm. You can, of course sink 25mm. ones a bit deeper.

3. Do you strip the sheath back to where it enters the box?

4. It is because not many use it but as you say - if you have some ...

- Yes, I only have 16A radials, so you probably never want a ring anyway.

 

[ericmark]

7/0.036 which was normally used for rings, was around 4 mm² and even 7/0.029 was 2.9 mm² and has a thicker insulation than modern PVC cables and they went into the sockets OK, as EFLImpudence says if you mount the back box a little deeper it does give a little more room. the old cable had wooden back boxes so not sure how deep they were.

 

[SUNRAY]

7/0.036 which was normally used for rings, was around 4 mm² and even 7/0.029 was 2.9 mm² and has a thicker insulation than modern PVC cables and they went into the sockets OK, as EFLImpudence says if you mount the back box a little deeper it does give a little more room. the old cable had wooden back boxes so not sure how deep they were.

7/0.029 at 2.9 mm² [rated at 20A] was normally used for radials of 15A and rings at 30/32A, 7/0.036 at 4 mm² was used for 25A radials or possibly 30A but it is actually rated <30A. I wonder if that's why 29A fuses were available.
Cards of fuse wire we used to get from Woolworths were: 5A, 15A, 25A, 35A which work well with imperial sizes but a large seemingly random selection were available elsewhere.
As an aside, 'in the old days' 4000A/inch² was used as a guide figure which comes out to 18.5 and 28.5 for the 2 cables. 0.036 was never a popular size in the smaller cables AFIA, In fact I don't think I have ever been aware of it's use other that my school, most skipped 7/0.036 and used 35A 7/0.044 for 30A cooker circuits.