Have the rules for ring mains changed over the years?

[7029 dave]

I still like the flexibility of a RFC, as for fault finding them if you know what you are doing it is quite simple.
I have traced a faulty section down between two socket outlets in less than 2hrs, thats from coming through the front door and leaving, temp repair made dropped the mcd down to 20A because had to break the ring convert to radials temporary. Went back when could take the floor boards up in the area of the damaged section JB full of water.

 

[mainline]

It's not simple when you have a 3-story house with one ring and hidden JBs under floors with numerous spurs and cross connections etc.

 

[7029 dave]

It's not simple when you have a 3-story house with one ring and hidden JBs under floors with numerous spurs and cross connections etc.

Well that would get rewired into separate RFC circuits for starters

 

[littlespark]

It's not simple when you have a 3-story house with one ring and hidden JBs under floors with numerous spurs and cross connections etc.

Could be same with a radial and multiple branches. Still have to find the fault and disconnect.
But with an rfc, you might not lose the function of the majority of the circuit until repaired.

I must admit, when I trained ‘86 to ‘90 the journeymen I was with were really old school.
Sockets were always on a ring, unless it was only one on the circuit.
Radials were limited to individual points, such as. Cooker, shower, immersion, heaters, etc
It was very rare to find more than one point on a radial circuit

 

[7029 dave]

Could be same with a radial and multiple branches. Still have to find the fault and disconnect.
But with an rfc, you might not lose the function of the majority of the circuit until repaired.

I must admit, when I trained ‘86 to ‘90 the journeymen I was with were really old school.
Sockets were always on a ring, unless it was only one on the circuit.
Radials were limited to individual points, such as. Cooker, shower, immersion, heaters, etc
It was very rare to find more than one point on a radial circuit

When at college 1980 ish 14 ed/ 15 ed not that the regs stated it I think, but the electrical craft principles book we studied from actually stated max numbers of sockets put on radials. Well it certainly weren't unlimited remember that much.

 

[Dustydazzler]

When at college 1980 ish 14 ed/ 15 ed not that the regs stated it I think, but the electrical craft principles book we studied from actually stated max numbers of sockets put on radials. Well it certainly weren't unlimited remember that much.

Have no idea how true but the old boys on-site were adamant you should only put 4 sockets max on a 20a radial

 

[mainline]

When at college 1980 ish 14 ed/ 15 ed not that the regs stated it I think, but the electrical craft principles book we studied from actually stated max numbers of sockets put on radials. Well it certainly weren't unlimited remember that much.

2.5mm, 20 amp protective device, 50 square metres.

 

[7029 dave]

Have no idea how true but the old boys on-site were adamant you should only put 4 sockets max on a 20a radial

Yeah something like 3 doubles or 6 singles

 

[westward10]

None of these requirements for radials or ring finals have ever been Regulations just informative in the Appendices.

 

[7029 dave]

None of these requirements for radials or ring finals have ever been Regulations just informative in the Appendices.

Yup in my view good working practices, unlimited 20A radials IMO is just ridiculous

 

[nicebutdim]

Yup in my view good working practices, unlimited 20A radials IMO is just ridiculous

It is and it isn't.

If likely to be subjected to loads in excess of protective device rating, it would be poor design and ridiculous on the part of designer.

If that 20A radial serves three bedrooms in a modern home, with lots of points provided for convenience, then there should be no issue as it's highly unlikely that total load at any given time would trouble the 20A breaker.

Edit: What I do find ridiculous is the idea that anyone might refuse to consider a particular option, because of preconceived notions. I've read a number of comments during my time here to the effect of 'I'd never install a ring' and can't help asking myself why?

 

[mainline]

I still like the flexibility of a RFC

What flexibility does an RFC have over a 4 mm radial ?

as for fault finding them if you know what you are doing it is quite simple.

Trying to reinstate an RFC that's 40 years old with multiple faults isn't always simple, even if you unlike us trainee types know what you're doing.

Dropped the mcd down to 20A because had to break the ring convert to radials temporary.

Jb full of water meant you had to break the ring in two places.

Went back when could take the floor boards up in the area of the damaged section JB full of water.

Better off leaving it as a radial

 

[mainline]

Could be same with a radial and multiple branches. Still have to find the fault and disconnect.
But with an rfc, you might not lose the function of the majority of the circuit until repaired.

One of the problems with an RFC is you may not know there is a fault until you have a fire

 

[7029 dave]

One of the problems with an RFC is you may not know there is a fault until you have a fire

If you twist the legs together this will reduce the risk of , and if it drops out of the socket terminal then in won't work a good reason for twisting RFC IMO for the anti Twister's

 

[mainline]

If you twist the legs together this will reduce the risk of , and if it drops out of the socket terminal then in won't work a good reason for twisting RFC IMO for the anti Twister's

The twisting together of solid core weakens them, so could cause more of a hazard.
I don't think a twisted joint is going to be very good at carrying a decent current.

 

[Pretty Mouth]

What flexibility does an RFC have over a 4 mm radial ?

Installation reference methods. 4mm radials can only be installed ref C (or B if using singles in conduit IIRC), whereas 2.5mm rings can be installed 100, 102, A, B, C.

Also, a much longer circuit length is permitted in terms of voltage drop (106m vs 43m), although obviously both ends must be terminated at the CU. This tends to work well for many domestic socket arrangements, although not in all instances.

One of the problems with an RFC is you may not know there is a fault until you have a fire

OTOH, a ring is less prone to arcing should a loose connection occur, so is probably less likely to cause a fire IMO.

Horses for courses, there are advantages and disadvantages to both types of circuits. I personally am happy to work on rings, and install them where appropriate.

 

[mainline]

Installation reference methods. 4mm radials can only be installed ref C (or B if using singles in conduit IIRC), whereas 2.5mm rings can be installed 100, 102, A, B, C.

Also, a much longer circuit length is permitted in terms of voltage drop (106m vs 43m), although obviously both ends must be terminated at the CU. This tends to work well for many domestic socket arrangements, although not in all instances.

Most domestic circuits can be satisfied with radial circuits.

OTOH, a ring is less prone to arcing should a loose connection occur, so is probably less likely to cause a fire IMO.

Also, less likely for AFDDs to work properly?

Horses for courses, there are advantages and disadvantages to both types of circuits. I personally am happy to work on rings, and install them where appropriate.

I have nothing against the use of RFCs, but would prefer not.

 

[timhoward]

Have no idea how true but the old boys on-site were adamant you should only put 4 sockets max on a 20a radial

If they were old enough to know the 14th edition, there were indeed once such rules in the main regs.

 

[Pretty Mouth]

Most domestic circuits can be satisfied with radial circuits.

Probably, but a ring may be a better option in many instances. If you want a 32A socket circuit for, say, a kitchen, where the cables are installed method 102, then you're looking at either a 6mm radial, or a 2.5mm ring.

Also, less likely for AFDDs to work properly?

I don't believe so. As I understand it, they should detect arcs on a ring just as they would on radial. Hager's take on it:

Contrary to common belief, AFDD’s do offer protection against arc faults in ring final circuits and to the equipment being fed from this circuit. A series arc fault in one leg however, is unlikely to be at a dangerous level so will not be detected. This is due to current in this instance flowing around the other leg of the ring. A series arc fault will be detected in equipment and in flexible cables connected to the ring final circuit. Parallel arc faults are detected and disconnected in all parts of the ring circuit and on all connected equipment.

 

[mainline]

Probably, but a ring may be a better option in many instances. If you want a 32A socket circuit for, say, a kitchen, where the cables are installed method 102, then you're looking at either a 6mm radial, or a 2.5mm ring.

True, but unlikely to need a 32amp socket circuit for most kitchens, radial for sockets, radials, for appliances.
Less nuisance tripping easier to test and safer.

I don't believe so. As I understand it, they should detect arcs on a ring just as they would on radial.

Not true, they cannot detect a series fault in a ring final circuit

A series arc fault in one leg however, is unlikely to be at a dangerous level so will not be detected.

Saying that, the arc is unlikely to be at a dangerous level, doesn't instil confidence.