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#133106 - 05/08/02 05:11 AM Ring circuits revisited
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
You may all remember some months ago we had quite a discussion about the ring circuits used in British homes. Well, I've just run across an example of why I don't like them.

I added some lights and did a main panel replacement at a house, and as a matter of course I checked continuity on the ring before reconnecting to the new breakers. Hot and ground were fine, but there was no continuity on the neutral.

I traced it to a broken neutral between two countertop outlets in the kitchen.

The point is, that this could have been in this condition for years, with the possibility of overload on a cable if someone had connected heavy loads all on one side of the break (quite possible from the location of the fault).

Rings used in HV area distribution are fine: They are under control of trained engineers and have current monitors around them so that any fault will show up immediately.

Domestic rings are another matter entirely, as there could be a break on the hot and a break on the neutral yet all outlets will still be energized.

Just my opinion, but I finding this sort of fault just comfirms my belief that we should abandon them.

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#133107 - 05/10/02 05:53 PM Re: Ring circuits revisited
motor-T Offline
Member

Registered: 11/10/01
Posts: 293
Loc: Girard, Ohio, USA
Pauluk:
I have only learned about 'Your' ring circuit recently, and was rather intrigued to say the least.
My question is what is the point of using two breakers from the same leg to feed a common circuit. Its just my opinion but I think they are dangerous. If you are not aware of them and shut off only one of the breakers the thing is still hot. Right ?
-Mark-

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#133108 - 05/10/02 07:06 PM Re: Ring circuits revisited
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Mark,

No, you're a little off track there. We don't feed a ring from two separate breakers.

The two "live" (hot) wires from the ends of the ring are connected to ONE fuse or C/B at the panel, rated at 30 or 32A.

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#133109 - 05/11/02 04:47 AM Re: Ring circuits revisited
motor-T Offline
Member

Registered: 11/10/01
Posts: 293
Loc: Girard, Ohio, USA
Pauluk:
Ok I understand better now, but what is the reasoning behind such a circuit ? Why would you run two hots and two neutrals to the same circuit?
Is it just for reduncancy ? On a 30 amp breaker, I am now assuming two no. 10 AWG. I guess I fail to see the benefit to such a circcuit.
Thanks in advance for the reply
-Mark-

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#133110 - 05/11/02 08:04 AM Re: Ring circuits revisited
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
No, the conductors used on our rings are considerably smaller than your #10. Standard size is now 2.5 sq. mm, which is just a little larger than 14 AWG. So proper overcurrent protection for the cables relies upon the integrity of the ring.

I posted a fairly lengthy description of the syustem here, which went into quite a discussion.

All further questions from that welcomed, of course!

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#133111 - 05/11/02 09:13 AM Re: Ring circuits revisited
motor-T Offline
Member

Registered: 11/10/01
Posts: 293
Loc: Girard, Ohio, USA
Paul of the UK:
Ok I read your explanation and it makes sense except for the part of the smaller gauged wires being used for the ' Ring ".
You said it became popular during the War, My question is why ? a Ring type circuit, and what scares me is the undersized wires.
As you said you found one with an open Neutral which means now the remaining neutral carries twice as much current.
I dont understand the logic behind it . I guess
Again thanx for any replies
-Mark-

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#133112 - 05/12/02 07:49 AM Re: Ring circuits revisited
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
"Why a ring?" is a question to which I've never been able to find a definitive answer myself.

As I said in the other thread, I've seen various claims and counter-claims about whether the ring circuit involved the use of less material. (It wasn't actually introduced until about 1949, but shortages and rationing in the the U.K. continued for quite a few years after WWII -- Some items were rationed until about 1953.)

The undersized cable for a 30A OCPD is one of the things I don't like about the system. The theory that so long as the ring stays intact then the wiring is protected sounds fine. But as my recent example shows, in practice a break can go undetected for a long time because no outlets stop working. In the worst case, the break would show itself only when the cables start a fire.

There's also the point that unknowledgable DIYers can easily break the ring during alterations without realizing it.

Another point: Our "code" allows a single outlet to be wired as a radial spur off the ring. According to the IEE, there's no chance of overloading the spur cable because of the fuse (13A max.) in the appliance plug. The one problem there is that a "twin socket" (duplex receptacle) can be counted as a single outlet for this purpose, so it is theoretically possible to overload the spur by connecting two heavy appliances to that duplex outlet. Unlikely maybe, but possible.

If somebody extends a spur cable to another receptacle elsewhere, then the chance of overloading that spur cable becomes much greater. In fact, in the original specifications, a spur was allowed to feed two separate single receptacles.

I may be in a minority here, but I'd like to see rings abandoned from our IEE Regs. altogether.

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#133113 - 05/12/02 12:52 PM Re: Ring circuits revisited
motor-T Offline
Member

Registered: 11/10/01
Posts: 293
Loc: Girard, Ohio, USA
Paul of the UK:
Thanks for the reply. The undersized conductors was my concern too. I suppose before they (IEE) says they are illegal there will have to be a rash of disasters, which seems to be the only way Beaurocrats get any impulse to move. The old saying holds true, the trouble with electricity is, it almost always works.

Thanks again.

-Mark-

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#133114 - 05/12/02 05:32 PM Re: Ring circuits revisited
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
hmmmmm,
If i for some reason stumbled across a ring configuration here, i'd be inclined to part it somewhere in the middle, and feed both branches on individual 15A OCPD's....
I don't suppose the same could be benificial for a broken ring there??

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#133115 - 05/13/02 04:17 PM Re: Ring circuits revisited
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Good thinking there, Batman!

Yes, I have split a ring into two radial circuits quite often. The cable used for a ring (2.5 sq. mm) can also normally be used on a radial circuit (U.S. style) with an OCPD of 20A. (The exception would be if the cable has to be highly derated due to ambient temperature or cable grouping, which isn't normally a problem in residential work.)

The main thing to watch is where a radial created out of a ring feeds a kitchen/utility area, keeping in mind that most homes here have the washer, dishwasher, dryer, etc. on the ring. In those cases I would want to add dedicated circuits for the major appliances (I prefer to do that anyway).

The IEE Regs. on rings have changed very little over the years, but specified radial arrangements seem to alter with almost every new edition.

The current arrangements are here.

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