Discuss Radials V Ring mains in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

Sparky10

Regular EF Member
Messages
62
Location
London
Hi all,

This may be a common topic and may already have been spoken about 100s of times so forgive me in advance.

I have always wired in ring mains for my sockets up until recently..

I came across an install where all sockets were wired in 2.5 radials protected by 20A RCBO they had wired 3 bedrooms all on separate 2.5 radials (Loft & 1st floor)
i did question why each room was separate and the response i got was "customers request due to computers"

I am hearing more and more people wiring 4mm radials protected by 32A as its "convenient"

whats peoples general thoughts on this?
 

buzzlightyear

please let me back in to the prison cell.
Electrician's Arms
Messages
6,887
Location
star command
I am hearing more and more people wiring 4mm radials protected by 32A as its "convenient"
I can understand if a couple of sockets covered by a 20amp, but a full floor would be a ring .
but it down to the installer what he thinks at the time .
 
OP
Sparky10

Sparky10

Regular EF Member
Messages
62
Location
London
Each room is on a separate radial with around 4 sockets in - very weird arrangement i know
 

Spoon

Forum Mentor
Messages
7,166
Location
Lancashire
Hi all,

This may be a common topic and may already have been spoken about 100s of times so forgive me in advance.

I have always wired in ring mains for my sockets up until recently..

I came across an install where all sockets were wired in 2.5 radials protected by 20A RCBO they had wired 3 bedrooms all on separate 2.5 radials (Loft & 1st floor)
i did question why each room was separate and the response i got was "customers request due to computers"

I am hearing more and more people wiring 4mm radials protected by 32A as its "convenient"

whats peoples general thoughts on this?
Great idea.
20A is plenty for a bedroom and when the kids don't get off the consoles you can switch off the mains to their bedroom.
 
OP
Sparky10

Sparky10

Regular EF Member
Messages
62
Location
London
Haha! i never looked at it that way - No more fortnight for my son if i had this wiring arrangement
 

Strima

Electrician's Arms
Messages
3,525
Location
St Neots
Each type of circuit has its merits, whatever suits the need of the installation and the client.
 

Pete999

Forum Mentor
Messages
21,810
Location
Northampton
Take it you do 4mm Radials?
Not any more Sparky 10, as I have been retired for a few years, but to answer your question, yes I did, but always in conjunction with the restraints and the advice in Appendix 15 BS7671, floor area etc.
I also ran 6mm radials whilst working in Canada @110Volts using MK 110V socket outlets, had nil trouble with connecting them up either. Just saying.
 

Pete999

Forum Mentor
Messages
21,810
Location
Northampton
Not any more Sparky 10, as I have been retired for a few years, but to answer your question, yes I did, but always in conjunction with the restraints and the advice in Appendix 15 BS7671, floor area etc.
I also ran 6mm radials whilst working in Canada @110Volts using MK 110V socket outlets, had nil trouble with connecting them up either. Just saying.
Just to be a Pedant they are not Ring Mains any more they are Ring Final Circuits or RFCs
 

Murdoch

Regular EF Member
Messages
25,126
Location
Woking
Give the customer the choice , the prices and the pros and cons and let them decide
 

buzzlightyear

please let me back in to the prison cell.
Electrician's Arms
Messages
6,887
Location
star command
I also ran 6mm radials whilst working in Canada @110Volts using MK 110V socket outlets, had nil trouble with connecting them up either
that was the old MK sockets put in them days ,try the new ones ,then you will struggle .
 

Baddegg

Still simmering Ken, not boiled yet buddy x
Electrician's Arms
Messages
1,282
Location
Portsmouth
Great idea.
20A is plenty for a bedroom and when the kids don't get off the consoles you can switch off the mains to their bedroom.
Have rewired a house before with that exact request for that reason...
 

GeorgeCooke

Regular EF Member
Messages
486
Location
UK
I also ran 6mm radials whilst working in Canada @110Volts using MK 110V socket outlets, had nil trouble with connecting them up either. Just saying.
I cannot understand how someone can be working on electrics in Canada and not know the voltage is 120v plus or minus 5%. 110v is a myth and outside the permitted tolerance.
 

garyt

EF Member
Messages
6
Location
Essex
I cannot understand how someone can be working on electrics in Canada and not know the voltage is 120v plus or minus 5%. 110v is a myth and outside the permitted tolerance.
Hi check regulations , can use radial 2.5 mm serves 50 square meters 20 amp cb& 4mm at 75 square meters 32 amp cb
 

Simon47

Regular EF Member
Messages
47
Location
Cumbria
If you think about it, if you take an RFC wired in 2.5 and supplied by a 32A MCB and: remove one section of cable, and split the tails across two 20 or 25A MCBs then you have :
  • Increased the total available current from 32A to 40 or 50A
  • Reduced the amount of cable used
So the two radials (assuming a new install or a rewire) will need less cable and provide a higher total load capacity than the same outlets wired as an RFC. You've also (assuming RCBOs) reduced the amount of stuff that goes off when a breaker trips.
However, you've also increased the volt drops. So if the alternative RFC was on (or near) the limits, the two radials would most likely be over the limits for volt drops.
 

Lucien Nunes

Respected Member
Messages
2,822
Location
London / Tallinn
Increased the total available current from 32A to 40 or 50A
However, you have also restricted where the current can be used. With a 32A circuit, regardless of whether it is radial or an RFC, you could spread 32A around half of it, or all of it, and nothing will be overloaded. With two 20A radials, to get even 32A let alone 40A it has to be correctly split between the circuits, which the customer knows nothing about and may not be convenient. E.g. if a room gets flooded and needs drying out, they will plug two heaters and a dehumidifer in there and the 32A circuit would be OK with that, whereas a 20A might trip. I know that's an unusual situation but there are lots of similar scenarios.

This is one of the advantages of the 32A socket outlet circuit that is often overlooked - a larger circuit with more points makes better use of diversity and is less likely to get overloaded if the loads are not in the anticipated places. A typical family home with GCH will run quite happily on a single 32A circuit. Not ideal in the event of a fault etc. but it works fine for loading. Our entire living area used to run fine on one 30A Wylex MCB with lounge, dining room and kitchen including washing machine, tumble dryer, dishwasher, fridge, freezer, microwave etc. Theoretically you can't put just the washer and dryer together on a 20A.

But, importantly, the distinction between 32A circuits and 20A circuits is a different one to the difference between RFC's and radials. The current rating dictates how many circuits are needed, the RFC / radial aspect dictates cable size, testing method etc. A 32A radial provides the same functionality as a 32A RFC.
 

Simon47

Regular EF Member
Messages
47
Location
Cumbria
I agree with all of that. But of course, a 32A radial needs more copper than a 32A RFC.

On overloading radials, at a local church the boiler broke down so they had to use electric heaters - which could barely take the chill off. Of course, someone got over ambitious - and after blowing a fuse (radial on 15A rewirable fuse), told me he'd been careful and plugged them into different sockets :rolleyes: He was also amazed that I was able to find the blown fuse :astonished:
 

l4urence

Regular EF Member
Messages
168
Location
East Sussex
I rarely do final ring circuits now, generally radial in 4mm but watch the cable length.
 

Matthewd29

Regular EF Member
Messages
1,192
Location
Belfast
I always use rings unless for 1 or 2 dedicated sockets. I find there are far more positives to the ring than a 4mm radial circuit.
 

davesparks

Forum Mentor
Messages
12,803
Location
guildford
I cannot understand how someone can be working on electrics in Canada and not know the voltage is 120v plus or minus 5%. 110v is a myth and outside the permitted tolerance.
I can't understand how you can tell from his post that he was working on the 120V public supply and not a 110V supply for special purposes. Considering the kind of installations Pete has told us he worked on either is clearly possible.
 

GeorgeCooke

Regular EF Member
Messages
486
Location
UK
Are there 110v supplies for special purposes? Would be pretty pointless in a country that has a public supply or 120v.
 

Pete999

Forum Mentor
Messages
21,810
Location
Northampton
Hi all,

This may be a common topic and may already have been spoken about 100s of times so forgive me in advance.

I have always wired in ring mains for my sockets up until recently..

I came across an install where all sockets were wired in 2.5 radials protected by 20A RCBO they had wired 3 bedrooms all on separate 2.5 radials (Loft & 1st floor)
i did question why each room was separate and the response i got was "customers request due to computers"

I am hearing more and more people wiring 4mm radials protected by 32A as its "convenient"

whats peoples general thoughts on this?
As long as the 4mm2 Radial complies with 433/1 and Appendix 15 BS7671 I see no problems at all with a Radial wired in 4mm2 protected by either a 30A or 32 A OCPD
 

Simon47

Regular EF Member
Messages
47
Location
Cumbria
I came across an install where all sockets were wired in 2.5 radials protected by 20A RCBO they had wired 3 bedrooms all on separate 2.5 radials (Loft & 1st floor)
i did question why each room was separate and the response i got was "customers request due to computers"
IMO there's a lot to be said for this sort of arrangement - as well as reasons against. It does mean that if one offspring trips the RCD using damaged hair curlers, it doesn't "cause family discord" by tripping off the power to another offspring's gaming rig in the next room, or to dad's servers ;) OK, someone could potentially overload a circuit by plugging in (eg) two fan heaters, kettle's, whatever - but that's just going to trip the overload protection and not damage the wiring, and it's not exactly likely in most homes.
It's going to cost more in RCBOs, but they are coming down nicely in price these days so not likely to be a deal killer as part of the grand scheme.

At our last house I was considering splitting the (single) RFC into two radials - in part because of the difficulty of doing stuff room by room while maintaining the integrity of the ring and not having non-compliant spurs. Haven't determined what to do with the current house yet ...

A an aside, I've seen a new and quite small office wired with what seemed like a ridiculous number of RFCs for the same "because, computers" reason. A couple of jobs (and more years than I care to work out :rolleyes:) ago when I first came across this, I went and measured the earth leakage of a representative sample of our IT kit and found ... nothing significant, definitely no reason to be talking about only using single sockets, high integrity earthing arrangements, and so on.
 
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