Distro and the 18th Edition Wiring Regs. |
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Jasonstry
Young Croc Joined: 11 September 2007 Location: Cannock. J11 M6 Status: Offline Points: 1367 |
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James, "the distros you linked to are overall 30ma RCD, and individual MCB per way." Yep, as I mentioned, so are mine, which was sort of my point. I also realise that an RCBO is effectively a combination of both but don't see how that helps any in relation to the distro I linked to or mine. Furthers the plot in a way though.
Anyway, I don't have the regs to look at either but I have been looking about (what else is there to do at 10 o'clock on a Sunday evening) and I think that maybe I haven't been able to see the wood for the trees. I believe the reason for RCBOs on outputs is simply that the new requirement is that each socket-outlet up to 32A requires its own, individual, RCD protection just as it requires its own overcurrent protection. From what I have read, part of the reasoning is that RCDs are now relatively cheap. I wasn't looking at 63A but I believe that each socket will need protecting with a 300 mA RCD I am not sure how specific your course was, Jeb, but my understanding has always been that a temporary installation is a new installation so any installation after 1 Jan will have to comply. I would be delighted to be proven wrong. |
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Down with signatures!
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djkeet
Registered User Joined: 26 December 2011 Location: England Status: Offline Points: 462 |
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If this is correct would the majority of Distro's fail a P.a.test come Jan 2019 if they haven't been modified to the new regs?
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Soundbite
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James Tengo
Old Croc Joined: 09 May 2008 Location: Brighton Status: Offline Points: 2155 |
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Certainly our big 72 way distros from SES have 30ma rcd's on the 32a outlets, a current requirement if plugging in a motor controller as a final appliance for instance, but also meaning we can't run an 18 way distro from it with an LED screen hanging off it, so when cascading distros it can present an issue, as it lacks discrimination. Older distros with a single RCD over the incomer would still be valid as each socket is protected by an RCD, albeit a global one, as long as it meets disconnection time and current. |
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chris_k
Young Croc Joined: 14 April 2005 Location: United Kingdom Status: Offline Points: 1258 |
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Or have a documented risk assessment....
""Regulation 411.3.3 has been revised and now applies to socket-outlets with a rated current not exceeding 32 A. There is an exception to omit RCD protection where, other than for a dwelling, a documented risk assessment determines that RCD protection is not necessary."" |
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4D
Old Croc Joined: 13 November 2008 Location: Winchester Status: Offline Points: 4257 |
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Multiple feeds with individual 6A rcbo 's. = Socapex revival....
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DMZ. "The bass was intense. Girls were literally running up to stand next to the subs"
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James Tengo
Old Croc Joined: 09 May 2008 Location: Brighton Status: Offline Points: 2155 |
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Some say it never went away ;-)
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MattStolton
Old Croc Joined: 04 September 2010 Location: Walthamstow Status: Offline Points: 4234 |
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Might be prudent to give James Eade a nudge - he is a contributing editor to BS7671, but also authors BS7909, which is directly relevant to our industry.
He has been threatening a revised BS7909, originally was supposed to be a 2015 revision, hopefully its revision will now harmonise with 18th, and make things clear. However, since BS7909 is just like a special locations section of BS7671, but so big it warranted its own book, is likely to just say BS7671 and use H07. AFDDs have been in place in America and Canada for 15-20 years - However we are unlikely to get them in BS7909 governed areas:
What could be more costly is the electrical efficiency section.That could make electrical installations very pricey. Not just you have to install an outdoor cee form to charge your car, but also run thick enough copper so no heat is generated (i.e. thick enough for no voltage drop!), i.e. no energy loss of transmission within the dwelling. Not sure if it would have repercussion to us/BS7909, but load banking gensets with massive hairdryers may go out of fashion...
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Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
"Sparkius metiretur vestra" - "Meter Your Mains" |
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PatM
Registered User Joined: 22 March 2005 Location: Somerset Status: Offline Points: 198 |
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Heres James Eades's take on it:
https://electrical.theiet.org/wiring-matters/issues/71/implementing-the-18th-edition-in-concerts-theatre-and-events-easy-as/ |
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MattStolton
Old Croc Joined: 04 September 2010 Location: Walthamstow Status: Offline Points: 4234 |
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As ever, risk assessment by a competent person is key.
30mA RCD on anything under 16A is a no brainer, as you go up the supply, 32A/63A, if final circuits, would also need it, but cumulative effects of SMPSU, and spurious but expected earth leakage, makes them problematic. That's why we have adjustable RCDs for larger supply outlets, to maintain flexibility of hire fleet for all scenarios. Goes back to the holistic origins of BS7671/BS7909 - testing, calculations and planning! Measure how much Earth leakage there is from your LED lights or LED TV panels, part of your PAT regime. Then calculate how many you are going to hang off your TES, and how this will cause issue with your upstream RCDs. Then plan your TES to have the correct format of RCD/MCB in the right place to be useful and safe (trip quickly in a genuine fault condition, so cables don't melt), but not a PITA (no nuisance tripping). AFDD are less likely to be relevant in a field, but the mention of a Victorian theatre full of dry wooden structures and TESs coming in starts to make them relevant. Again assessment and planning! |
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Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
"Sparkius metiretur vestra" - "Meter Your Mains" |
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Boxes-R-Blue
Registered User Joined: 11 December 2018 Status: Offline Points: 147 |
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The 18th hasn't changed too much WRT to our industry.
Personal facing final leg has to 30mA/30Ms. We still have min conductor size for Cee-Form (as per like 15 years, 2.5mm for 16A, 6mm for 32A, 16mm for 63A, 35mm for 125A) but we still have requirement for design in a system, so understand 6mm in 16A on long run can put you foul of the regs! Mainland Europe appears to have the jump on us here with DC sensitive RCDs as a requirement and a better map of discriminative RCD mapping. Matt as ever hits the nail on the head with "planning and design" 16A earth leakage is nothing if you knew it was going to happen and you rigged for it!!!!! The "entertainment industry addendum" to the IEE regs is to me a total joke as it just gives more leverage to keyboard warriors with no skills who quote "data" from the WWW, heads up Facebook crew data+context = information!!!
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MattStolton
Old Croc Joined: 04 September 2010 Location: Walthamstow Status: Offline Points: 4234 |
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That isn't me, that is BS7909, as much as BS7671-18th Ed. Both require planning and design by competent/skilled/trained/knowledgeable (delete as per fashion of phrase) persons. It isn't tricky, especially with all the companion guides about to help you break it down into manageable chunks. One of the most awkward ones I do, is deploying power for wedding fairs. So a council assembly hall with 35 odd tables, each table needs a 4 way 13A socket outlet block. Mostly for a laptop and phone charging, odd TV running a .pptx or DVD, odd feature lighting for cabinet of goods. The logistics of cable covers/ramps alone is a nightmare. Venue has a 3 phase 63A, and a 63A SP+N+E off of a separate incomer. So 4 x 63A available. That is only 7.2A per table, which, if used to power a laptop is more than enough. However, when the booth is a hairdresser, with 2.5KW hair dryer, curling tongs, etc, you can see how it gets a bit squidgy. However, by designing in some diversity, and then building a lot of discrimination in, which counters cumulative switch-mode earth leakage, when the tongs were found to be faulty, only her stand tripped. Despite the organiser advising in advance of 8A max, and any electrical appliances must be accompanied by PAT certs, the reality was that most people exhibiting were weekend warriors of weddings, craft jewellers and the like, and so had no clue what they were doing, and a for a lot, it was there first ever "show". So my TES had to be designed to allow for this "naivety" (polite way of saying stupidity and idiocy and complete unawareness of basic electrical safety). It worked, no one died, nothing caught fire, and only the correct breaker tripped, when it should have done. That was in my risk assessment, part of the planning, that this TES would be used by inexperienced users, who probably hadn't done a show like this before. I was right, and, by submitting this to client in advance, justified sticking a shed load more distro (more 32A to 6x16A, each with RCBO on each out) than was probably required - but that makes me more money (not much but every little helps) and the organizer only had to deal with one idiots power tripping. Every table had its own segregated RCBO to it. I didn't necessarily charge for my time in planning and design, which I perhaps should - but by putting my planning and risk assessment down on paper, which was submitted with quote, client could see why I had done what I had done, and its reasoning, so couldn't say no. When it came to build day, an A3 design was taped to each main distro, and another A3 layout of room, so riggers just got appropriate CSA/connector/length cable from crate, ran it A-B, stuck sub distro on. Then repeated for entire build. I wandered round and tested. Done. Hardly any conversation on site of the usual "where does this go", just simple harmonious work flow. No one got sweaty, no one had to work anything out on site (no bodges), we all finished early and got to have coffee/tea and bacon sarnies ahead of schedule. All for the sake of a bit of planning! The UK BS7671 is one of the most robust electrical standards on the planet. Through being very old, but continually revised, it has developed into a practical, affordable, methodical and safe way to implement local distribution of power, at pretty much any scale of final energy consumption. |
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Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
"Sparkius metiretur vestra" - "Meter Your Mains" |
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4D
Old Croc Joined: 13 November 2008 Location: Winchester Status: Offline Points: 4257 |
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Same as...Just provided power to multiple stall holders caterers marquee lighting & heating etc at a Xmas fayre. Sean adapted my distro by adding individual rcbo to every outlet 36 x 6a, 12x16a & 3x32a IIRC the system was rock solid 2 trips went in 4 days and as Mat says with some of these folk especially small caterers their ignorance of matters electrical make them a danger to society.
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DMZ. "The bass was intense. Girls were literally running up to stand next to the subs"
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