Hole in joist (different query) - 2.5mm T&E

[David]

I'm just getting back into the DIY mind set and rooting around in the shed to dig stuff out of my stash.

I'm extending the 13A ring in the 3rd bedroom/office, and need to run two

2.5mm T&E wires through the joists. Ring out, and ring return.

I've put my digital callipers on the T&E and it is perhaps a whisker under

10mm wide.

I assume that a 10mm hole would be just adequate to pass a single wire.

However I do have a 16mm spade wood drill as well.

Would it be acceptable/better to drill a single 16mm hole and run both wires?

Cheers

Dave R

[Steve Walker]

That's what I've done - and in some cases 20mm with two, plus a couple of lighting wires.

Yes they are all together and that affects how much heat they can lose to the air, but it is only for a very short distance and copper conducts heat very well, so local overheating is very unlikely, as it'll travel along and escape elsewhere.

SteveW

[ARW]

Depending on how many joists and how much cable you have to pass through the joists is the deciding factor. I would suggest buying a new 20mm or even a 25mm spade bit.

[John Rumm]

IME its not worth messing about with holes that are "just big enough" and "in theory" - just slap a 20 or 25mm bit hole in the joist and make life nice and easy for threading stuff through and pulling in cable.

[David]

Larger bit now being searched for in stash. :-)

Thanks to all who responded.

Cheers

Dave R