UK Cowboy electrician

[pc1966]

fitting an upfront RCCB, rather than relying on a main switch, and I liked that thinking as it afforded protection from loose tails as well as from busbar links in a split load board.

It is always the case that a RCD/RCCB/RCBO provides protection only for the downstream system.

Some folk have argues that in the TT case a non-metallic CU enclosure is safer as loose tails (or lack of entrance grommet), busbar going astray, etc, making contact with the case that are upstream of the incoming RCD do not make the system's CPC live. That may be true, but I suspect that of all the serious CU installation faults you might have a partial contact leading to a fire risk is a bit more likely!

But I still think no single point of failure (at least for things depending on electronics - my own background!) is a good goal for safety-critical systems.
[automerge]1597519566[/automerge]

It was this point which set the discussion off in a bit of a spiral. The member in question had expressed a preference for split load boards 'every time' and I tried to ask why when RCBOs are now available at quite reasonable prices. I could see why a relatively small price difference may be too much for some customers, but felt that others might be happy to pay a little extra to minimise potential disruption.

Folk have different reasons, different customer bases, etc.

• Some say they will only do RCBO boards as they feel it is the best solution - that is technically valid and saves a bit of fault-finding time in the future
• Others do dual-RCD only - most customers will always choose the cheaper option and doing the installation properly is more important than the specifics of what is chosen

Giving folk a choice seems more democratic, but then take a look at how various democracies are more like idiocracies!

 

[magnoliafan89]

I did an EICR for a 30+ Yr old install. 4 circuits and an RCD covering all.
I didnt fail it on this and didnt think anything of it....should I have???

 

[pc1966]

I did an EICR for a 30+ Yr old install. 4 circuits and an RCD covering all.
I didnt fail it on this and didnt think anything of it....should I have???

No, it is not considered a safety risk (generally*) and not in the best-practice guides or similar to do so.

But if you were planning a new system you ought to take in to account the inconvenience of a fault taking out everything, the higher risk of electronic equipment leakage adding up to the 30mA RCD's trip point (which could be as low as 15mA), and you would not go for a single RCD - the whole starting point for this thread!

* = if it were a workshop or commercial site you would need to think of the safety aspect of loss of lighting supply, so if no emergency lighting then it is a concern. Just my 2p

 

[nicebutdim]

It is always the case that a RCD/RCCB/RCBO provides protection only for the downstream system.

Some folk have argues that in the TT case a non-metallic CU enclosure is safer as loose tails (or lack of entrance grommet), busbar going astray, etc, making contact with the case that are upstream of the incoming RCD do not make the system's CPC live. That may be true, but I suspect that of all the serious CU installation faults you might have a partial contact leading to a fire risk is a bit more likely!

But I still think no single point of failure (at least for things depending on electronics - my own background!) is a good goal for safety-critical systems.

Upstream is the term I was looking for.

A few years back I fitted a 100mA S type RCD upstream of the CUs at my parent's house. This was after they'd had a fault which caused them to receive shocks off metallic surfaces, were let down by several electricians and I discovered that they had an old ELCB which had never been connected.

I ended up buying a Wylex REC2S for its enclosure as I couldn't find anything else that was reasonably compact, insulated and suitable for meter tails without drilling and glanding. I press the test button periodically, when I visit, so they can shout at me for switching off the power.

 

[pc1966]

I press the test button periodically, when I visit, so they can shout at me for switching off the power.

Good to hear that somebody tests the RCD!

 

[nicebutdim]

Good to hear that somebody tests the RCD!

I'm very dilligent about ensuring everything is in order for them, but have to admit that I rarely test the pair in my own board. Every time it comes to mind someone is watching the TV and I resolve to do it the next morning, but subsequently forget all about them.

 

[pc1966]

I'm very dilligent about ensuring everything is in order for them, but have to admit that I rarely test the pair in my own board.

Ah, the cobbler's shoes!

 

[nicebutdim]

Ah, the cobbler's shoes!

Not quite - I'm not an electrician.

 

[radiohead]

I did an EICR for a 30+ Yr old install. 4 circuits and an RCD covering all.
I didnt fail it on this and didnt think anything of it....should I have???

IMO the circumstances of the installation would dictate the code. If the board was in a property with stairs and the occupier was elderly or infirm i would consider a code 2 appropriate. Regardless, if that was not the case and I coded it 3 then there would be a carefully worded recommendation that consideration should be given to the risk of a total power failure in the event of a single fault.
It must also be taken into account though that total power failures occur regardless of fault protection on the consumers installation.

 

[davesparks]

I did an EICR for a 30+ Yr old install. 4 circuits and an RCD covering all.
I didnt fail it on this and didnt think anything of it....should I have???

You don't 'fail' and EICR at all, you give an overall assessment of satisfactory or unsatisfactory, that is all.

In that particular scenario I would probably give a C3 if anything for all circuits being on one RCD.

 

[Moley]

Ah, the cobbler's shoes!

You have to kick a rcd to test it?

 

[Simon47]

Think it has sumin to do with discrimination, I would never put the lowest sized breaker next to rcd just common practice to go down in size is that what you do?

I cannot see any reason for putting them in a specific order - these days.
AIUI, with some of the older fuse boards, some of them had a single high current space next to the main switch which could take a higher rated fuse than the rest of the ways. So I guess this created a "rule" that the high power loads go next to the main switch, and this "rule" had been passed down from tradesmen to apprentices ever since - with no-one really thinking about the "why ?"
There is an argument for spacing "heavily loaded" devices. MCBs or RCBOs that are loaded will heat up, and the heat will affect (reduce) the tripping current of adjacent devices. Putting a number of such loaded devices all together (very slightly) increases the risk of nuisance tripping.

£12 nett of VAT - perhaps I should have been clearer on that point. There have now been two options posted in this thread for RCBOs well under your price of £30 - CP Fusebox and BG - both of which are roughly half of that.

I'll add that SBS Trade Sales charge £16 net for compact RCBOs (single module, 2 pole switching) - type AC or A, curve B or C.

i don’t agree with that from what I gather we are having dual rcd consumers as recommended for paat few years

There's a difference between "recommended" and "most cost effective way to meet regs". In practical terms, for most installations you need 2 RCDs minimum to meet specs - and back when dual-RCD boards came in, RCBOs were either non-existence (for some makes/models) or just stupidly expensive. So that really only left the dual-RCD board as an option.
As above, that is no longer the case - and a full RCBO board can cost less now than a dual-RCD board would have cost a few years ago.

NO, you do the fault finding there and then I would never leave a customer with 4 or 5 circuits without power untill next day. Why would you do that???

OK, you're on another job (or on holiday), the other side of the country, and a customer phones up because "half the house" has gone off. They can't reset one of the RCDs even with all the MCBs off - so please explain how you will fault find "there and then" and leave the customer with everything but the faulty circuit working ?

CP Fusebox compact RCBOs are finally available. Their size is of little relevance, but it's worth noting that they also disconnect neutral and bring another DP option to a market that will benefit greatly from competition on price.

Yes, some of the RCBOs have 2 pole switching - as do the SBS ones which are also just under £20 inc VAT. You need to be careful exactly what's on offer - AIUI few of the single module devices have 2 pole sensing for the over-current, so they will switch the neutral, but not trip on neutral current (which shouldn't be a problem for most installs).

If you take that argument far enough then each individual socket, light etc would be on it's own RCBO protected circuit.

No, that would be reductio ad absurdum. But to a point, yes you are correct - it's why we don't (generally) put all the lights on one circuit, all the sockets on one circuit, etc.
A while ago I went to look at a fault in one of our lass's cottage - all the lights had tripped and she couldn't get them back on. There's an argument that at the time it was last re-wired, having all the lights (all 6 of them) on one fuse was acceptable. At some point, the bathroom (in a flat roofed extension) had been converted to a wet room, and as part of that they'd added an RCD to the lights. The fault was easy enough to guess - damp in an outside light.
These days I'd expect to see at least 2 light circuits in all but the smallest of properties - that's just one of those things where standard practices change over time.

 

[nicebutdim]

Yes, some of the RCBOs have 2 pole switching - as do the SBS ones which are also just under £20 inc VAT. You need to be careful exactly what's on offer - AIUI few of the single module devices have 2 pole sensing for the over-current, so they will switch the neutral, but not trip on neutral current (which shouldn't be a problem for most installs).

It wont be an issue for me as I've no reason to buy any, but interesting to learn this and it's something I'll have to read a bit more about.

I'd mentioned their new range of RCBOs after noticing they had finally been released and it seemed appropriate to mention in this thread.

No, that would be reductio ad absurdum. But to a point, yes you are correct - it's why we don't (generally) put all the lights on one circuit, all the sockets on one circuit, etc.
A while ago I went to look at a fault in one of our lass's cottage - all the lights had tripped and she couldn't get them back on. There's an argument that at the time it was last re-wired, having all the lights (all 6 of them) on one fuse was acceptable. At some point, the bathroom (in a flat roofed extension) had been converted to a wet room, and as part of that they'd added an RCD to the lights. The fault was easy enough to guess - damp in an outside light.
These days I'd expect to see at least 2 light circuits in all but the smallest of properties - that's just one of those things where standard practices change over time.

I took that reasoning to unnecessary lengths a couple of years back in my parent's home, by replacing 2 lighting circuits with 5. I'd decided to give the kitchen/utility lights their own circuit as it was fairly practical to do so and also liked the idea of them still having some downstairs lights on the off chance a fault should take out one of the circuits. Later when thinking about the outside lights, I figured potential water ingress was the most likely situation that might take out a lighting circuit, so figured outside lights could have their own way on the board - due to the distance between the front and rear lights, that 1 circuit became 2.

It was overkill, but there was plenty of space to do so and the additional cost wasn't particularly significant. They're old, they're my parents and they couldn't get anyone to fix a fairly significant fault, so when I found myself doing a job I'd rather not be doing, it seemed like a good idea to depart a little from convention and try to make things better for them.

 

[Grant1987]

I cannot see any reason for putting them in a specific order - these days.
AIUI, with some of the older fuse boards, some of them had a single high current space next to the main switch which could take a higher rated fuse than the rest of the ways. So I guess this created a "rule" that the high power loads go next to the main switch, and this "rule" had been passed down from tradesmen to apprentices ever since - with no-one really thinking about the "why ?"
There is an argument for spacing "heavily loaded" devices. MCBs or RCBOs that are loaded will heat up, and the heat will affect (reduce) the tripping current of adjacent devices. Putting a number of such loaded devices all together (very slightly) increases the risk of nuisance tripping.

I'll add that SBS Trade Sales charge £16 net for compact RCBOs (single module, 2 pole switching) - type AC or A, curve B or C.

There's a difference between "recommended" and "most cost effective way to meet regs". In practical terms, for most installations you need 2 RCDs minimum to meet specs - and back when dual-RCD boards came in, RCBOs were either non-existence (for some makes/models) or just stupidly expensive. So that really only left the dual-RCD board as an option.
As above, that is no longer the case - and a full RCBO board can cost less now than a dual-RCD board would have cost a few years ago.

OK, you're on another job (or on holiday), the other side of the country, and a customer phones up because "half the house" has gone off. They can't reset one of the RCDs even with all the MCBs off - so please explain how you will fault find "there and then" and leave the customer with everything but the faulty circuit working ?

Yes, some of the RCBOs have 2 pole switching - as do the SBS ones which are also just under £20 inc VAT. You need to be careful exactly what's on offer - AIUI few of the single module devices have 2 pole sensing for the over-current, so they will switch the neutral, but not trip on neutral current (which shouldn't be a problem for most installs).



No, that would be reductio ad absurdum. But to a point, yes you are correct - it's why we don't (generally) put all the lights on one circuit, all the sockets on one circuit, etc.
A while ago I went to look at a fault in one of our lass's cottage - all the lights had tripped and she couldn't get them back on. There's an argument that at the time it was last re-wired, having all the lights (all 6 of them) on one fuse was acceptable. At some point, the bathroom (in a flat roofed extension) had been converted to a wet room, and as part of that they'd added an RCD to the lights. The fault was easy enough to guess - damp in an outside light.
These days I'd expect to see at least 2 light circuits in all but the smallest of properties - that's just one of those things where standard practices change over time.

I would obviously have no chance if I was away but would call in favours from my fellow sparks. If it’s still tripping with all mcbs off usually means a neutral earth fault so you need to unplug everything which is standard practice but yes many ifs and buts just saying I would do my best To ensure all is back to normal whether it’s me or someone else to get power back on

 

[Duncan Norman]

a thing of beauty is a joy forever - arse about face and copper showing on almost every connection - totally non compliant seems to me theres ever more rules and regulations and the standards slip ever faster year by year .