For a standard domestic Install, split board with 2x Type AC main switches.
No PV or Car Chargers should this be a C3 or C2?
Thanks in advance
For a standard domestic Install, split board with 2x Type AC main switches.
No PV or Car Chargers should this be a C3 or C2?
Thanks in advance
Yesterday's announcement from the Government: https://www.gov.uk/government/news/government-to-go-further-and-faster-in-becoming-energy-secure
If plug-in PV is being pushed as a way forward, and these are to have a UK standard plug (although BS 1363-1:2023 Clause 5 states that the UK plug shall not be used for connecting generators) then certainly in rented homes, and in flats (rented or otherwise), for the installation to be considered safe, surely:
1. RCDs (RCCBs and RCBOs) for socket-outlet circuits (and upstream distribution circuits if applicable) would have to be at least Type A (because of the way inverters operate, but also for the existing PV inverter standard BS EN 62109-1, this is stated as a requirement for 'pluggable type A' equipment (i.e.. with a standard plug) to be compatible with Type A RCDs; and
2. RCDs (RCCBs and RCBOs) for socket-outlet circuits (and upstream distribution circuits if applicable) would have to be bidirectional (Regulation 530.3.201 introduced in Amendment 3); and
3. RCDs (RCCBs and RCBOs) for socket-outlet circuits would have to disconnect all live conductors (see Regulation 551.7.1)?
That type test doesn't give me any hint at all as to how many out of a population of (say) 10 million installed MCBs would actually open if subjected to an appropriate current. That information must surely be a key component in any argument as to why fuses are qualitatively worse. Similarly, I agree that rewireable fuses probably have a much higher failure rate than MCBs once human factors are considered, but those are not the only form of fuse which exists. To be clear I think MCBs are generally the right choice and they are generally sufficiently reliable for the applications we put them to.
Whilst I'm happy to engage in a MCB vs. fuses debate, my point was that many people rely on protective devices every day without really thinking about their reliability. We assume that they are "sufficiently" reliable and the Wiring Regulations back that up by permitting their use as best practice - that doesn't mean that things are "safe", it just means that sufficiently few people will be injured that no-one in a position of power will worry about it. That "sufficiently few" test varies over time in tune with popular sentiment.
Plug in solar will need to meet the same test - if it is to succeed it will need to injure sufficiently few people that overall the population thinks it is a good idea.
As I alluded to in my post, I suspect there may be more risks from insufficiently secure panels causing impact injuries than from faulty RCDs (it isn't clear to me how a RCD helps in the one finger touches the live pin on the plug, another touches the neutral pin case anyway) but that is not to say that we shouldn't be making the electrical side as safe as possible. For me, the big debate is balancing the generation standards which tend to favour slow disconnection of generators in the face of network disturbance with safety standards in a domestic setting which favour rapid disconnection. If we think that plug in solar will only ever make up a tiny amount of the grid's generation mix then the answer is obvious and we can specify inverter shutdown / disconnection times of the same order of magnitude as RCD trip times but if widespread adoption is expected then the discussion is more complex.
Just for clarity, the RCD part of a unidirectional RCBO may fail in such circumstances but will the mcb characteristic remain available?
Does that always matter, for example is the RCD is used for ADS due to circuit length, or in cases such as socket-outlet circuits where additional protection is necessary to meet the requirements for ADS in BS 7671?
One interesting question is why can't we (I) tell if my recent trip of a circuit with RCBO protection was because of overload, or a nuisance leakage scenario?
Because we don't know, we can't explain, and aren't sure if it should have tripped in another scenario.
Is there any evidence that RCDs have saved lives over the past 40 - 50 years?
It has certainly been stated in expert evidence that RCD could have saved a life if one had been fitted.
And anecdotally if not saved , certainly less badly burnt.
I for example have been disconnected by 30mA RCD, just once ,and was very grateful for it, but still painfully shaken. I have also been saved by the prompt action of a colleague, on something that had no RCDs, but that left my hands with lovely entry and exit wounds that took weeks to heal. Both were very close calls, and once (twice?) in a lifetime events that required many things to have gone wrong so unlikely, and that is for one who gets stuck in more than the average member of the public.
Equally there must be millions of RCDs that are never called upon to trip in anger during their whole operational life (and of those that are, as above a small % wont..)
If we assume my life is worth £1Million (!) then that justifies the cost of fitting about 50K RCDs at say £20 each on new circuits to save me once.
To call someone out to do a replacement, and certainly if that involves a new CU, is probably ten times more expensive, now unless someone gets saved once per 5000 RCDs installed, it is a net loss. We have less than 100 electrocutions per year (*), which is a chance of somewhere between one and two per million, per year, per person.
As such the argument for the additional cost vs benefit on new circuits is reasonably in favour, but the argument for "must retrofit" to existing is probably rather weak.
Mike
** Actually a lot of those electrocutions are touching overhead lines with vehicles and poles, and there is no number of additional domestic RCDs that would help with that so maybe more like less than 1 per million. But there is an additional reduction in fires and so on to offset that a bit.
If we assume my life is worth £1Million (!) then that justifies the cost of fitting about 50K RCDs at say £20 each on new circuits to save me once.
It isn't quite that simple. You really need to do a number needed to treat analysis. The difficulty is that electrocution is (mercifully) rare.
Let us suppose that the death rate from electricity is 1 in a million = 10-6 = 10 x 10-7. We have a new gizmo, which reduces the mortality by half, so 5 x 10-7. Absolute risk reduction is (10 x 10-7) - (5 x 10-7) = 5 x 10-7. NNT = 1/ARR = 2 x 106.
So 2 million new gizmos have to be fitted to save one life.
It has certainly been stated in expert evidence that RCD could have saved a life if one had been fitted.
As I stated earlier.
Considering the time it take to write/publish a BS like BS7671 the lifecycle should start to consider the recommendation of of type B as a minimum for BS7671 Ammendment 5 or 19th edition. Ideal for EV chargers, solar PV (inverters). Caveat could be if it a new design or retrofit
Lets not forget the type F as well for inverter driven loads like washing machines and heat pumps.
I am sure that will be an interesting debate for the JPEL Team for UK Domestic Dwellings
As always there is a grey area
What is recommended/mandated for a New Design
What coding is given on an EICR or In Service inspection and testing. This could be 3,5 or even 10 years after initial install depending on usage. If for homeowner usage it could be 10 to 20 years or untill the sell the property. if the property is PRS (Private Rental Sector) then EIC and EICR are needed from day 1 of the rental agreement. In effect theis makes a 2 tear system. Rented dwellings are more upto date (BS7671) than owner/occupied dwellings.
I am sure you family would rather pay £10 per RCBO in the CU and have you still there and very much alive. The £1Million value is just what bank and insurance companies use to quantify a life. Your family would say your life is worth way more than that and may even be priceless.
It has certainly been stated in expert evidence that RCD could have saved a life if one had been fitted.
A very valid point!
Perhaps more difficult to convince a court that a type A instead of type AC would have made a difference?
Perhaps more difficult to convince a court that a type A instead of type AC would have made a difference?
I can see it would be difficult if the burden of proof was 'beyond reasonable doubt' ... where 'balance of probabilities' applies, it would be easier, especially if the evidence showed an RCD didn't operate when (all things being equal) you would have expected it to do so.
Perhaps more difficult to convince a court that a type A instead of type AC would have made a difference?
I can see it would be difficult if the burden of proof was 'beyond reasonable doubt' ... where 'balance of probabilities' applies, it would be easier, especially if the evidence showed an RCD didn't operate when (all things being equal) you would have expected it to do so.
That 3% - 7% failure rate might scupper a charge of corporate manslaughter, but you would still have the difficulty of causation and foreseeability in a civil case. Only the lawyers would benefit.
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