Branches from a radial

[ianb1965]

Hi all.

We had a small outside yard between the house and garage which has now been covered . It will be used as a utility type area so will be arranging for some mains sockets to be installed.

The idea is metal or metal looking conduit attached to the brick wall. If the electrician wires it as a radial (we have a spare way in the CU) coming into the room at the top of the wall and we want individual drops to each of the sockets, will there still be a double length of cable in the drop - one going down to the socket and the other coming back up again and onto the next socket? Or can there be a junction box at the top of each drop with a single cable running down to the socket - like a spur?

From what I’ve Google’d it seems two lengths is the way to go?


Thanks all.

 

[danechip]

Makes no difference, I would double the length and save on the price of junctions and having more connections would be prone to more faults. The minimum cable size must be 4mm obviously. Maybe run 6mm for the first leg from CU for future proof.

 

[JohnW2]

Makes no difference, I would double the length and save on the price of junctions and having more connections would be prone to more faults.

As you say, it makes no difference. I would personally be perfectly happy to use less cable and have the JBs - in fact, that's how my garage sockets are wrired.

The minimum cable size must be 4mm obviously.

Only if it's a 32A circuit. If it were a 20A one, 2.5mm² cable would equally obviously be OK. It's really down to the OP's requirements.

Maybe run 6mm for the first leg from CU for future proof.

I would think that a bit OTT. 6mm² cable would be pretty unusual for even the first bit of any domestic sockets circuit.

Kind Regards, John

 

[danechip]

I'll stay quiet.

 

[danechip]

Perhaps you know an answer to the dimmer issue? been bugging me all morning.

 

[ianb1965]

Thanks guys. Our electrician is a relation but he’s getting on a bit and not in best of health so was hoping I could do some of the donkey work.

 

[conny]

If using JB's I'd be tempted to run 4mm to all the JB's then drop down to individual sockets with 2.5mm

 

[JohnW2]

Perhaps you know an answer to the dimmer issue? been bugging me all morning.

What dimmer issue?

Kind Regards, John

 

[danechip]

This one bud...

https://www.diynot.com/diy/threads/replacing-light-switches-standard-to-dimmer-wiring.568482/

 

[JohnW2]

If using JB's I'd be tempted to run 4mm to all the JB's then drop down to individual sockets with 2.5mm

That's precisely what happens in my garage, and is a very reasonable approach for a 32A circuit.

Kind Regards, John

 

[JohnD]

Hi all.

We had a small outside yard between the house and garage which has now been covered . It will be used as a utility type area so will be arranging for some mains sockets to be installed.

The idea is metal or metal looking conduit attached to the brick wall. If the electrician wires it as a radial (we have a spare way in the CU) coming into the room at the top of the wall and we want individual drops to each of the sockets, will there still be a double length of cable in the drop - one going down to the socket and the other coming back up again and onto the next socket? Or can there be a junction box at the top of each drop with a single cable running down to the socket - like a spur?

From what I’ve Google’d it seems two lengths is the way to go?


Thanks all.

There must be some reason why you don't want to run conduit or mini-trunking along the wall, at socket height, with as many sockets as you desire sprouting from it. No JBs or drops.

What is this reason?

 

[JohnW2]

There must be some reason why you don't want to run conduit or mini-trunking along the wall, at socket height, with as many sockets as you desire sprouting from it. No JBs or drops. .... What is this reason?

I can't speak for the OP, but in the case of my garage, the reason is simple. My (fairly ancient) garage is built out of pre-fabricated panels about 4 feet wide, the joins being achieved with vertical bits of metalwork which protrude 50mm or so into the garage (useful for attaching things to!). However, this means that any horizontal conduit (unless very complicated in shape) would have to be 50mm+ from the wall, and hence non-aligned with the socket backboxes attached to the wall.

Kind Regards, John

 

[ianb1965]

There must be some reason why you don't want to run conduit or mini-trunking along the wall, at socket height, with as many sockets as you desire sprouting from it. No JBs or drops.

What is this reason?

It’s purely cosmetic. Just like the look of vertical drops down rather than horizontal between sockets. Having said that, even if there was a single drop down to bench level there would have to be a junction box or a doubling up of cable as the sockets would be on two adjoining walls but the cable would probably drop down in the corner between the two walls.

 

[conny]

To keep the diameter of the conduit on the smaller side how about using singles rather than T&E?

 

[sparkwright]

Avoid joints and junction boxes. They sound unnecessary and more work.

Consider a ring rather than a radial, as it can be 32 amp using smaller cable (2.5mm2).

Singles will help - if this really is actual round conduit. Do not use singles where there is no conduit (or trunking).