The root cause is often not solvable, eg due to normal leakage. And the root cause is often the RCD, which is tripping due to above spec but normal and safe heating element leakage. If an RCD trips on leakage that isnt a danger, its the RCD thats the problem. The idea that there must be zero leakage to ensure safety is simply not the case.
Why on earth would you want some people to pay some other people to upgrade their electrics to gain trivial safety advantage, sometimes at much higher cost than they could do it themselves, plus pay for a lot of inefficient bureaucracy overhead? It doesnt make any sense to me. When I rewire, I expect to pay for it myself, and can see little sense in us all paying for each others work plus a load of extra unnecessary paperwork expense as well.
See your points but in the past umpteen years I've had next to no problems from tripping, saved from a nasty couple of shocks and have had a few sudden power cuts which weren't RCD related and haven't fallen over when they did happen, and there was no light around at that time from streetlight s etc!...
I agree to some extent, but your assertion that they are any less liable to nuisance trip than RCDs is skating on thin ice. The causes for their nuisance tripping were very different, but present nevertheless. It's likely that an installation which suffers nuisance trips in one case would not in another (and most installations in either case don't). Most of the causes of nuisance trips with ELCB's were outside your house and your control, which was a problem. Correct installation was a rather skilled job, and that could present problems with today's electricians.
I don't know the level at which I require to pitch in here; and don't understand your reasoning. I assume that you are familiar with the passive, RCD testing sequence to C & G 2391; (which is also part of the P.I.R. test); and includes the mA ramp test function. The actual RCD tripping current in mA; and the operating time in ms can be accurately measured. Further, insulation tests can be carried on the fixed circuit wiring at 500 Volts DC, to determine the insulation level in Megohms, 2 Megohm is acceptable to the IEE regulations, (but if less than 5 Megohm requires further investigation}. In addition, an appliance tester can be used to determine the leakage currents for class I and class II equipment. All of these tests will go a long way to isolate an RCD tripping problem.
This is a nanny state after all; and I was thinking more of the elderly and infirm; who have the legacy and potential hazards of previous regulations; now changed in light of experience. I certainly don't consider this to be a trivial safety advantage.
Yes agreed, reference OSG, pages 21 and 22. I wouldn't advocate the installation of RCBO's in a new and average sized, domestic dwelling: - they are more expensive, although they would be less troublesome in the event of a fault, since the required circuits can be split up. As you are aware, there is justification for the use of these RCBO's for additions to existing; or larger installations, where they are more cost effective. Jaymack
All this can, at significant cost, find deteriorated equipment causing trips, but that doesnt address the point I've been making. The point is that the initial design is at fault and is the cause of a large number of trips that are entirely not necessary for safety. 'Protecting' rings and houses with a 30mA RCD is simply flawed science. When all that was looked at was 'touch the mains and it wont hurt you', it looked like a wonder product. But as time has passed, we can now see that it causes more problems than it solves, including deaths.
To a rather limited extent, but installing flawed systems then running round trying to patch them up individually isnt in any sense competent engineering.
And it doesnt address the numerous pointless trips that occur on grounds of poor design rather than any genuine safety problem, nor the wasted money that results from electrician callouts and food spoilage, nor the accidents and deaths that result. A proper solution would be far better, and I presented it in the form of whole house ELCB plus more selective RCD cover.
I dont think this answers the question tbh. If we wanted to upgrade our national wiring stock, why do it the inefficient costly way? That question still stands afaics.
If you look at the govt statistics on the top 10 killers, you'll see rcd work is not a real prioroty for national spending. The number of deaths from RCDs is small compared to the real problems. But ignorance is popular, ditto inappropriate solutions to the wrong problems. Part P is a great example.
This is precisely the problem with all this nanny nonsense. The goals are wrong, the methods are wrong, the science wrong, and the cost unnecessarily high as well as pointless. It also isnt what the democratic population wants to do. Ask people in the street how many want to pay for a chance to have their rcd removed, and you'll quickly see it has nothing to do with serving the people, it has more to do with command economy and interest groups. Its so wrong it would take a politics lesson :)
The Robin SmartPat tester has an earth clip for attachment to the body of the Class II appliance, for the detection of any earth leakage current. What is your method?
earth under strictly controlled conditions for safety reasons; and connect a high resolution ammeter in series with the appliance earth and the system earth, a recording ammeter would be preferable here but these are expensive, (but please do tell your method).
I have 5 RCBO's in my CU, and ended up with a 4 or 5 of them in the previous two CU's I fitted too. Yes, they are more expensive, but I regard them as the right way to do the job.
I know they both have issues, but I think both evidence and experience points to the resulting nuisance trips being of a whole different order of magnitude.
First to review what they do:
ELCB monitors earth cpc voltage, and trips only if enough cpc current flows to raise the cpc voltage to risk levels. Thus ELCB is insensitive to all minor appliance leakage, and even to fairly large leakage, such as running a 1kW heater L-E instead of L-N. The leakage required to trip one is fairly heavy duty, only something that is guaranteed to be a fault will cause this.
This automatically wipes out the numerous nuisance trips that occur with RCDs, due to minor and non-risky leakage, from in most cases healthy normally functioning items. Cooker element leakage, immersion heater leakage, filter capacitance, none of these are real life safety risks as no-one is dying from them.
I cant really agree. There are 2 problem areas with ELCBs.
If your sense rod is placed close to the neighbours cpc earth, and they have a _gross_ electrical malfunction, ie a live cpc, your ELCB can trip. Since your neighbours will be fried to death within a day by such high cpc to earth potentials, it is a rare and self solving problem.
Close lightning strikes can cause voltage gradient in the ground that can be sufficient to trip an ELCB. My experience of them is that they very rarely do this. One trip a decade is heaven compared to todays RCDs.
is preventable with guidelines in the instructions supplied with the ELCB to keep the earths well away from neighbouring earths. And when this is not done, and the installation is substandard, even then only rarely will any problem result. And if it does, it will soon clear itself.
Is solvable more easily, though even if unsolved it is a huge improvement compared to the high incidence of RCD nuisance trips. Technology has moved on since ELCBs were fitted en masse, and todays electronic circuitry is able to not trip on a momentary spike, and able to trip on a half wave rectified leakage fault. Both these issues are due to the technology used historically in ELCBs, not due to the idea of using an ELCB itself. Not sure how clearly I've put that. IOW early RCDs suffer the same poorer discrimination that historic ELCBs suffer, and new electronic ELCBs would be immune from both nuisance lightning trips, and able to trip reliably on rectified leakage faults.
Whacking in a new sense rod somewhere else is not the toughest job either, for those even rarer cases where 2 properties' rods are electrically connected via a leaking underground pipe, and the neighbours house has both no ELCB or RCD and a system fault taking the cpc to a risk voltage. This is easier cheeper and quicker than sorting out RCD nuisance trip problems, as well as far less likely to occur. These days far fewer neighbouring TT installs have no ELCB or RCD than was the case several decades ago. If they have either, the neighbour trip problem cant occur, and just about every house has now.
Re expertise required to install an ELCB, the only expertise is to locate the sense rod away from the cpc rod or neighbours rod, just in case neighbour has an unprotected faulty install. Included bit of paper (in box with ELCB) with diagram shows how to wire one up, its not complicated in the least. Any future domestic install of ELCBs would be covered by part p, theres already no shortage of experience with wiring elcbs, they are in mass use already, and installers are already required to do a safe competent job. Its possible there might be a little mileage in making the sense wire a different insulation colour to everything else. We've already got bare, red, black, blue, brown, green, g/y striped, and pink (degraded red) so perhaps grey, yellow, black/white striped, etc.
Theres another angle on this too. When ELCBs were installed, they brought the concept of nuisance trips into a system that had never seen such a thing before. Thus their potential nuisance value was regarded as a real weakpoint, a compromise. The issue was always noted in literature, even though the problem was very small.
When RCDs came along, they came into a society with a different mentality, where engineering cockups were seen as just normal, and this ballsed-up-ness aspect of them thus attracted little attention. They also came with the promise of a new era of greatly improved electrical safety, which was seen to justify any nuisance trip problem. So their nuisance trips were just shrugged at, part of the small price to pay for a dramatic improvement in safety. Sadly they have not delivered on this promise, actually causing more deaths than they prevent, and greatly increasing nuisance trips compared to the earlier days of ELCBs.
Lets look at it from yet another angle... how many posters do we see here saying their ELCB has tripped, how do they fix it. And how many with similar RCD questions!
But when you are quoting for work in the absence of the customer's specification, the pencil requires being sharp; the cost difference may lose the job. The standard is for RCD's. Joe Bloggs wouldn't be interested in the justification for RCBO's and would think he was being conned. Jaymack
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