Radial instead of ring?

[jason61c]

I'm sort of thinking that when I start to wire my house i'll just use 4mm T+E radial circuits instead of building a ring. Basically as its safer under fault conditions.

4 radials, 2 upstairs, 2 downstairs
1 for the kitchen


Any negatives? I know it might cost a few quid more to do but not much in reality.

Any other thoughts?

 

[AndyPRK]

Here we go again lol.

Unless its a very large house the number of radials in 4mm sounds excessive.
Takes up more room in the cu. and way over the amount of current required unless your having heaters plugged in everywhere.

A kitchen radial
An upstairs ring
And downstairs ring
Should be sufficient.

 

[jason61c]

Here we go again lol.

Unless its a very large house the number of radials in 4mm sounds excessive.
Takes up more room in the cu. and way over the amount of current required unless your having heaters plugged in everywhere.

A kitchen radial
An upstairs ring
And downstairs ring
Should be sufficient.

House is about 2200sq Ft, a box of about 60ft x 20ft, 2 floors.

I'm more leaning towards the fact its got to be safer if faulty, easier to fault find in the future?

 

[ericmark]

I have only found a few cases of 4mm radials and each one some one had extended them using 2.5mm and result I had to down grade to 20A.

The main thing against the ring is where some one has played and ended up braking the ring but you have exactly the same with 4mm radials so it's simply not a valid argument.

So to stay within the 11.5 volt drop or 5% with 4mm your allowed to use 38 meters of cable with a ring with 2.5mm your allowed 106 meters of cable. Yes I know it seems a lot but once one starts to wire one is surprised at how much is required. I know of a few houses split side to side rather then up and down to reduce cable required and keep within the limits and that's with a ring.

As to kitchen I have seen many times where two 2.5mm cables are run in parallel to a distribution unit (Grid Switch) simply because can't get 4mm in the terminals.

Also Reference Method 100# (above a plasterboard ceiling covered by thermal insulation not exceeding 100 mm in thickness) for 4mm cable is 27 amp you would need to use 6mm cable so with 4mm all cables would need to be Reference Method C* (Clipped direct) and to be frank I would prefer to have cables berried in the wall.

Using 2.5mm radials to each room protected at 20A is an option but so many RCBO's are required it's that which bumps up price not cable.

 

[jason61c]

I have only found a few cases of 4mm radials and each one some one had extended them using 2.5mm and result I had to down grade to 20A.

The main thing against the ring is where some one has played and ended up braking the ring but you have exactly the same with 4mm radials so it's simply not a valid argument.

So to stay within the 11.5 volt drop or 5% with 4mm your allowed to use 38 meters of cable with a ring with 2.5mm your allowed 106 meters of cable. Yes I know it seems a lot but once one starts to wire one is surprised at how much is required. I know of a few houses split side to side rather then up and down to reduce cable required and keep within the limits and that's with a ring.

As to kitchen I have seen many times where two 2.5mm cables are run in parallel to a distribution unit (Grid Switch) simply because can't get 4mm in the terminals.

Also Reference Method 100# (above a plasterboard ceiling covered by thermal insulation not exceeding 100 mm in thickness) for 4mm cable is 27 amp you would need to use 6mm cable so with 4mm all cables would need to be Reference Method C* (Clipped direct) and to be frank I would prefer to have cables berried in the wall.

Using 2.5mm radials to each room protected at 20A is an option but so many RCBO's are required it's that which bumps up price not cable.

If a ring has broken, its hard to locate where, surely with a radial, knowing cable routes etc its massively easier? I see your point about using some 2.5mm for some area's.

As the house its going through a 'zoned' full refurbishment part of the attraction is the ease at which I can do set parts.

 

[AndyPRK]

Once you have split a ring in half at the CU (disconnected one leg), its just as easy to find the fault.

 

[jason61c]

Once you have split a ring in half at the CU (disconnected one leg), its just as easy to find the fault.

True.

However with the way I need to wire the house, in stages would you say its the best way?

 

[AndyPRK]

It's hard for me to understand what your doing, so only you could say. Is it a full rewire ?

But you could fit a 20A MCB and have 2 radials while you work on the house and then convert it to a 32A ring at the last room on that floor.

 

[jason61c]

It's hard for me to understand what your doing, so only you could say. Is it a full rewire ?

But you could fit a 20A MCB and have 2 radials while you work on the house and then convert it to a 32A ring at the last room on that floor.

Its a full rewire, currently surface mounted. My plan was to do it in parts as I work my way through the house.

 

[JohnW2]

4 radials, 2 upstairs, 2 downstairs
1 for the kitchen

As has been observed, that's rather a lot of sockets circuits. A 4mm² radial is usually essentially equivalent to a standard 32A ring final, and it's very common in 'ordinary houses' to have just one ring for upstairs and one for downstairs (plus one for kitchen). If, nevertheless, you wanted to stick with the four upstairs/downstairs circuits, you might consider having 20A (or even 25A, if you can find the MCBs) ones, in which case you could usually use 2.5mm² cable.

You can, of course, argue that the more circuits you have, the easier is fault-finding (the ultimate being one circuit per socket). However, given that fault-finding is a 'once in a blue moon' exercise, I think there is a limit to how much time, effort and money one should sensibly expend on that account.

Kind Regards, John