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Topic Title: RING FINAL CIRCUIT Topic Summary: Should they be banned for new work Created On: 09 November 2011 07:33 PM Status: Post and Reply |
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 09 November 2011 10:12 PM
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Rings were something of a kludge when they were introduced, and nothing much has changed since. I'd be quite happy to see them abandoned.
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09 November 2011 10:25 PM
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Dave,
Don't I know it, the theory is one thing but finding the problem socket, broken conductor is something to be experienced. The one thing that cheeses me off, you can spend a day chasing a fault around and the customer then says. 'what exactly have you done today to earn all this money ?'. I then have to explain the first class airfare to the Seychelles is rather expensive you know! 
Legh ------------------------- Why do we need Vernier Calipers when we have container ships? http://www.leghrichardson.co.uk "Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections." |
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09 November 2011 10:28 PM
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So adding to the proposed death of rings we have spur upon spur from rings, over lapping rings, radials run from rings, single rings run from 2 different circuit breakers or fuses, the difficulty of tracing faults etc. etc.
The potential to screw things up by the new breed of semi skilled installlers and DIYers it is not looking good for these UK strange circuits. Putting the advantages of RFCs against the disadvantages in the pans of the scales it could be curtains for RFCs? ------------------------- John Peckham http://www.astutetechnicalservices.co.uk/ |
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09 November 2011 10:37 PM
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Oddly, the testing of radials is a lot less thorough than of rings. Rings get N continuity checked, standard tests on radials don't. L-PE reversals on rings would be spotted, no so on a radial if the standard R1+R2 test is used. But surely that's a feature of the tests rather than the ring itself. If you has to test radials just as thoroughly as rings (say with an additional R1+Rn test at all points), together with perhaps a greater number of circuits to test, would the difference be that great? - Andy. |
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09 November 2011 10:46 PM
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Most of these faults are not actually dangerous when you think of the protective devices that are now installed. None of them comply with the regs , of course Where MCBs and RCDs are used then the danger from most of these faults reduces considerably.... as it were. I remember a conversation I had with some chap about the use of RCDs and how they would cover a multitude of sins.! Spur upon spur - I have never seen a real dangerous problem overlapping rings - only if you load them irregularly with heating appliances. radials run from rings - possibly volt drop but overload is unlikely with present type of loading and no chance under short circuit conditions using MCBs A ring split across two MCBs - that's a definite no no and is dangerous to the uninitiated that must be corrected ! Radials are much easier to negotiate Legh ------------------------- Why do we need Vernier Calipers when we have container ships? http://www.leghrichardson.co.uk "Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections." |
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09 November 2011 10:59 PM
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Although we see no drama in that scenario with "ring mains" - I've seen plenty of them with 2 x 300mm conductors into 630A ACB's on either end of a dual fed switchboard. Exactly - only dangerous in the minds of the inspector, who equates lack of compliance with BS 7671 as dangerous without thinking through the actual risk Regards OMS ------------------------- Failure is always an option |
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09 November 2011 11:04 PM
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I love this thread.
When you work on your own for much of the time, or are the only electrician on site, you gently develop your own views. No, do not ban ring finals. Keep the choice. Every time Dave Parry posts an opinion on one of these discussions I wonder if we are living in a parallel universe. I agree with Dave all the way. Further, we know when a simple radial is the quickest and easiest to install. Or even the most appropriate. It is ok for the UK electrical engineer to be the finest. For Him to be trusted to make a call on how to install without dictate. Even the regs are now quietly indicating UK regs against harmonised ones, if you know what to look for. Testing a RF is peasy. Testing a radial means finding the end of it. Fault finding a RF may be a little more complex, but fault find it we do. Spell-checking a post on the other hand. . . Now that's a toughy
Zs |
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09 November 2011 11:58 PM
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Although we see no drama in that scenario with "ring mains" - I've seen plenty of them with 2 x 300mm conductors into 630A ACB's on either end of a dual fed switchboard. I've done work in a few LV mains switch room cabinets but never worked on a duel fed compressed air switches before so this another starting point of my educational process...... Exactly - only dangerous in the minds of the inspector, who equates lack of compliance with BS 7671 as dangerous without thinking through the actual risk agreed, but we all have our relative starting points .... It's difficult to get a start when you've been on your own for so long Regards OMS Legh Legh ------------------------- Why do we need Vernier Calipers when we have container ships? http://www.leghrichardson.co.uk "Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections." |
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10 November 2011 12:15 AM
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Although we see no drama in that scenario with "ring mains" - I've seen plenty of them with 2 x 300mm conductors into 630A ACB's on either end of a dual fed switchboard. I've done work in a few LV mains switch room cabinets but never worked on a duel fed compressed air switches before so this another starting point of my educational process...... ACB's - air circuit breakers - they use air (rather than liquid) as the arc quenching medium (via splitters and arc chutes) - they are usually motor rather than air driven. These are not necessarily the same as gas quenched (say SF6) or vacuum operated breakers (the latter two usually being HV rather than LV types). It's quite common for resilient LV supplies to arrange primry and secondary distribution as ring mains fed from two breakers (although they may not always be operated as ring closed due to elevated fault levels) Exactly - only dangerous in the minds of the inspector, who equates lack of compliance with BS 7671 as dangerous without thinking through the actual risk agreed, but we all have our relative starting points .... It's difficult to get a start when you've been on your own for so long Perhaps - but thinking through the problem is as important as blindly repeating available guidance in every circumstance don't you think Regards OMS Legh OMS ------------------------- Failure is always an option |
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10 November 2011 12:42 AM
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I've been at it for a few years so its not all blindly regurgitating the fuel that is fed into the machine ... and as for the duel fed ACB switching devices I'll get back to you ...eventually .. as they say, 'seeing is believing'! Legh ------------------------- Why do we need Vernier Calipers when we have container ships? http://www.leghrichardson.co.uk "Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections." |
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10 November 2011 12:55 AM
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Try a google for HTM 06-01 - that should have examples of duel unified supplies within a healthcare environment. Trust me they do exist
Try here Page 39 - Substation ISS switchboard shows a duel fed ring from each half of the duel fed switchboard feeding risk category 4 and 5 services (in this instance into a UPS but that could also be a switchboard) Regards OMS ------------------------- Failure is always an option |
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10 November 2011 01:19 AM
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OMS,
Thanks for the information, some of those diagrams look familiar. I've had enough for tonight good night! Legh ------------------------- Why do we need Vernier Calipers when we have container ships? http://www.leghrichardson.co.uk "Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections." |
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10 November 2011 01:26 AM
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Having a RFC on two fuses was quite common when they were first introduced.
A number of 15A radials were converted to RFCs by simply connecting the ends of the radials together. Then again fuses in neutrals were allowed by the then Regulations. No I wouldn't advocate the banning of RFCs, to my mind they are versatile, cheaper and easier to install or adapt than the alternative. |
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10 November 2011 07:55 AM
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It must be frustrating for suppliers of protective devices outside the UK to see the lost sales that Ring Circuits mean to them.
Why don't they put maximum pressure on the UK in committees to make us "harmonise" like "good" Europeans ? |
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10 November 2011 10:16 AM
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I can see both sides of the argument for and against ring finals, but can also see an argument for retaining them, that no one else has mentioned.
Changes to the regulations are not normally intended to be retrospective, yet many seen to regard thaem as being retrospective. IF ring finals WERE banned for new installs, then it would not be long until "inspectors" start giving code ones to every existing ring final. Remember the relatively new requirement that most socket outlets in most situations should be RCD protected ? There are many reports of installations only a few years old, and correct at the time, being given "code 1" or bet best "code 2" for non RCD sockets. There is a very general view among non electricians, that continuall changes to regulations are a money making scam. If installations done only a few years ago by reputable contractors now need renewing before a house can be sold, no wonder people are cynical. |
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10 November 2011 10:54 AM
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I thought that the IET and the ECA documented a study on ring final circuits and radials a few years ago. The conclusion being RFC were safer due to there being 2 x cpc at each socket. Anyone still got a copy of this? I'll have a dig for it when I'm back in the office
As for testing them, I agree they are a pain. Nothing like a dozen RFC to take the smile off your face 
Regards Jobbo |
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10 November 2011 11:54 AM
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A ring circuit per se, is quite common in industry, to give a greater measure of security for L.V., M.V. and H.V. circuits, e.g. airport perimeter lighting etc.,etc. I imagine that the principle was adopted for the domestic ones from these, in the industrial case though, they are usually for security of supply; and in most cases here, they have time graded directional protection.
The main reason usually given for the introduction to the domestic and commercial scene, was they were more economical to install than radial circuits. All in all, I see nought wrong with them if they are correctly installed and maintained, e.g. using the correct fuse sizes. I suspect that the yanks would be using more of the principle, if they had thought of them first. Lets face it, they're the only real challenge for wiring on the "home" front. 
Regards |
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10 November 2011 02:26 PM
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In my opinion john - RFC's are a perfectly good circuit design for flexibility, convenience, safety and security of supply. Is that not like saying "my connections might be dodgy so I will connect at both ends to double my chances"
Now now we will be in the Euro if you continue down that route! Daydream believer! ------------------------- Regards Martyn. Only a mediocre person is always at their best www.electrical contractors uk.com |
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10 November 2011 03:16 PM
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In my opinion john - RFC's are a perfectly good circuit design for flexibility, convenience, safety and security of supply. Is that not like saying "my connections might be dodgy so I will connect at both ends to double my chances"
Not really Martyn - although we do that for protective conductor currents. It's flexible in terms of where the loads may be connected, it's convenient in terms of a large number of outlets over a given area, it's a pretty safe design and it's secure if you need to operate with partial damage. Doubling the chances is down to poor installation. Now now we will be in the Euro if you continue down that route! Maybe, but Europe is a big trading area - we are better off on the inside ***** out for sure Daydream believer! Maybe - but it's not that hard to get 6 ccores into a semblance of order is it Regards OMS ------------------------- Failure is always an option |
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10 November 2011 07:09 PM
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Every time Dave Parry posts an opinion on one of these discussions I wonder if we are living in a parallel universe
-------------------------------------- Many thanks for that comment ZS, it's nice to know who of us are on the same wavelength! regards, Dave. |
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RING FINAL CIRCUIT
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