30mA RCD as main switch

[leep82]

Done a little bit of searching and found that a situation such as the title of this thread would be against current regs, heres my situation. Been to look at a few jobs on a bungalow. The customer wants lights on there garage, ( which already has a supply present), an outside socket, and an extra lighting point in there living room. Currently the installation has no RCD protection whatsoever. Supply is TNCS and feeds a DB with only 5 circuits ( sockets, cooker, lighting, garage and burglar alarm ). Could it be argued that i have improved the state of the installation and note it as a deviation if i fitted a 30mA RCD as the main switch. Its just that cost is a big issue for the customer and i already have in my possesion the RCD so this would be much cheaper than going down the 3 separate RCBO's route for the individual circuits i would be working on.

 

[Octopus]

How to you plan to comply with minimising inconvienience?

 

[trev]

So you know it's against the regs but you're asking if it'll be ok to do anyway as you've got a bit spare off another job?
Think about this a bit more mate, the solution is not that difficult.

 

[Plonker 3]

Cost over convenience. Just think about what you have just said.

 

[Simonslimline]

Edit..... RCBO already mentioned

 

[Plonker 3]

Why don't you want to fit a RCBO?

Corrected that for you.

 

[Darkwood]

Split board fully loaded cheaper than 3 rcb's... if money is such an issue then tell them to first upgrade the DB with the money and save for the additional ... no room for breaking the regs here to try save money it is what it is...

A good explanation and options should have the customer understanding, I would still be putting the Intruder alarm on its own RCBO in the new board anyway as this could be classed as a potential nuisance if sharing an RCD and the SAB takes over at battery drain.

 

[HappyHippyDad]

I suppose you're right in that it 'could be argued', but you'd probably lose the argument Leep :smiley2:

3 RCBO's maybe £45 in total with a bit of looking around.

I would definitely not fit an RCD as a main switch!

I'm not entirely sure without checking but I think the only one of the jobs that definitely needs an RCD adding is the outside socket, thats if theres no channeling in less than 50mm with the other 2 jobs. Not sure though, Murdoch will know.

 

[Badged01]

Done a little bit of searching and found that a situation such as the title of this thread would be against current regs,

Not saying I'd do it but enlighten me as to why its against regs? As I see it, and happy to be corrected .....

1 - RCD's are rated for use as isolators in BS7671.

2 - BS7671 requirement to avoid danger/minimise inconvenience. Im guessing this is a residence where you could expect people to know their house in the event of a failure and avoid falling down the stairs. Unless there are say standard lamp lights on the sockets circuits on when the light circuit goes down, its dark anyway!!. To avoid danger/minimise inconvenience I could interpret BS7671 meaning no single lighting circuit, no single ring/radial socket circuit, no single cooker circuit, no single immersion circuit etc ..... and no single supply to the CCU!!.

Where do you balance risk v practicality v cost?!?!

 

[leep82]

Done a little bit of searching and found that a situation such as the title of this thread would be against current regs,

Not saying I'd do it but enlighten me as to why its against regs ? As I see it, and happy to be corrected .....

1 - RCD's are rated for use as isolators in BS7671.

2 - BS7671 requirement to avoid danger/minimise inconvenience. Im guessing this is a residence where you could expect people to know their house in the event of a failure and avoid falling down the stairs. Unless there are say standard lamp lights on the sockets circuits on when the light circuit goes down, its dark anyway!!. To avoid danger/minimise inconvenience I could interpret BS7671 meaning no single lighting circuit, no single ring/radial socket circuit, no single cooker circuit, no single immersion circuit etc ..... and no single supply to the CCU!!.

Where do you balance risk v practicality v cost?!?!

i dont have my regs at the minute so cant check, lent them to a lad at work doing his 17th edition, so i did a quick search on here to see if had been asked before and found varying answers. And even now you are saying RCD are acceptable as isolators. If its just about inconvenience what would i be achieving by splitting the circuits, bearing in mind there is only 5 for the whole property, and being a bungalow there is certainly no danger of anybody falling down the stairs should the RCD trip. Is it just about inconvenience?

 

[Darkwood]

Not saying I'd do it but enlighten me as to why its against regs? As I see it, and happy to be corrected .....

1 - RCD's are rated for use as isolators in BS7671.

2 - BS7671 requirement to avoid danger/minimise inconvenience. Im guessing this is a residence where you could expect people to know their house in the event of a failure and avoid falling down the stairs. Unless there are say standard lamp lights on the sockets circuits on when the light circuit goes down, its dark anyway!!. To avoid danger/minimise inconvenience I could interpret BS7671 meaning no single lighting circuit, no single ring/radial socket circuit, no single cooker circuit, no single immersion circuit etc ..... and no single supply to the CCU!!.

Where do you balance risk v practicality v cost?!?!

No one is trying to get silly or wrap it in red tape... my one point which I would be to consider subject to nuisance issues is a security alarm if its a SAB set up on a shared RCD, the new amendments are also due out soon and increasing the requirements for RCD protection and reducing the cases where it can be omitted.

A sit down and a chat with the customer to explain what RCD protection is about, noting at present the existing electrics do not need to be upgraded but your own work has to comply with new standards so at the expense of a little extra cost a board change is recommended and has the addition of affording extra protecting if a fault occured.

Ignore the cash strap talk if they were they would not be adding garage lighting + socket and indoor light, its not the most essential of needs when your cash strapped.

 

[Darkwood]

Not saying I'd do it but enlighten me as to why its against regs? As I see it, and happy to be corrected .....

1 - RCD's are rated for use as isolators in BS7671.

2 - BS7671 requirement to avoid danger/minimise inconvenience. Im guessing this is a residence where you could expect people to know their house in the event of a failure and avoid falling down the stairs. Unless there are say standard lamp lights on the sockets circuits on when the light circuit goes down, its dark anyway!!. To avoid danger/minimise inconvenience I could interpret BS7671 meaning no single lighting circuit, no single ring/radial socket circuit, no single cooker circuit, no single immersion circuit etc ..... and no single supply to the CCU!!.

Where do you balance risk v practicality v cost?!?!

Domestic wise nuisance tripping is classed as not a big issue when you move to elderly residence then things like rcbo for boiler become a forethought so a vulnerable person doesn't lose heating if a fault occurs on a non related circuit they can't reset, essential luxury in winter for a frail old dear! ..other than that not a high priority it comes more into play in commercial and industrial where lost power can be costly effecting everything from production to telephone systems.

 

[leep82]

As another example what if you were asked to do some work on an install that already had 30mA RCD as a main switch. A new circuit for example that required RCD protection. As far as your concerned your circuit is in line with current regs although the install on a whole is not. Is this ok ?

 

[Badged01]

..... you are saying RCD are acceptable as isolators.

Trust me Im a plumbers mate, I know they are acceptable and modern ones can even isolate whilst carrying load!

.....what would i be achieving by splitting the circuits, bearing in mind there is only 5 for the whole property ....

Exactly, you could argue you don't have to ......... if the lighting circuit goes down your doomed to darkness however you split it. And with only one cooker circuit you will be very inconvenienced if your cooking your sunday roast and that circuit pops!!

 

[Badged01]

As another example what if you were asked to do some work on an install that already had 30mA RCD as a main switch. A new circuit for example that required RCD protection. As far as your concerned your circuit is in line with current regs although the install on a whole is not. Is this ok ?

Depends if the current RCD protection is being used to meet disconnection times and the new circuit requires an RCD for additional protection? The mind can boggle at the implications of having two RCD's!!

 

[Darkwood]

TT systems have main switch RCD's although the set-up differs a bit it shows that front end RCD protection is not against regulation, in the event of an existing board having a 30mA DP front end rcd then this would satisfy any new circuit that requires it.

 

[NickD]

The customer wants lights on there garage, ( which already has a supply present), an outside socket, and an extra lighting point in there living room..

Subject to no cables getting buried <50mm deep, the only bit on there that screams "requires RCD protection" is the socket. Obviously it is for you to make the definitive assessment on that. External sockets with integral RCD are readily available and not that expensive (although avoid the double ones which are actually only rated to 13A total, unless feeding from a 13A fused FCU...in which case you may as well feed from an RCD FCU and use a standard outdoor socket, which is the obvious alternative). None of that will add to the overall job cost that significantly. And if they were that strapped for cash they wouldn't be getting the work done, it's all discretionary spending what you're listing.

 

[davesparks]

It's not just about the moment that the RCD trips, you've got to think a bit further ahead!

Let's say a N-E fault occurs on the 1st floor lights and the RCD main switch trips, the homeowner try's to reset it and it won't hold. They actually listened when you explained what to do after you had fitted it and go and unplug everything and switch off all MCBs, and they still can't get it to hold on.

They phone you up to get you out to fix it, it's Friday afternoon and you are already in the pub and a couple of pints have gone down lovely, you explain that you can't get there until Monday.

Faced with the whole house off until Monday and the freezer starting to thaw they start phoning round to get another electrician, you've lost a client and maybe dented your reputation when all their friends hear about the trip you installed knocking the whole house out and them having to get someone else to fix it.

Or the same fault takes out just the upstairs lighting circuit as you have installed RCBOs, it's inconvenient but they have bedside lamps and can survive until Monday.

 

[NickD]

PS Unless the living room or the garage contains a bath or a shower ;-)

 

[HappyHippyDad]

Completely agree with Dave above.

Plus Reg 314.2 does make it clear that each circuit should not be affected by the failure of other circuits and 'due account' should be taken of the consequences of the operation of any single protective device.

 

[Brightspark2]

Just a note, the deviations box is to write down any parts that deviate from BS7671 BUT offer the same degree of safety/protection etc as BS7671

 

[Darkwood]

It's not just about the moment that the RCD trips, you've got to think a bit further ahead!

Let's say a N-E fault occurs on the 1st floor lights and the RCD main switch trips, the homeowner try's to reset it and it won't hold. They actually listened when you explained what to do after you had fitted it and go and unplug everything and switch off all MCBs, and they still can't get it to hold on.

They phone you up to get you out to fix it, it's Friday afternoon and you are already in the pub and a couple of pints have gone down lovely, you explain that you can't get there until Monday.

Faced with the whole house off until Monday and the freezer starting to thaw they start phoning round to get another electrician, you've lost a client and maybe dented your reputation when all their friends hear about the trip you installed knocking the whole house out and them having to get someone else to fix it.

Or the same fault takes out just the upstairs lighting circuit as you have installed RCBOs, it's inconvenient but they have bedside lamps and can survive until Monday.

Your a preacher of doom lol... the clause of design to avoid inconvenience and nuisance shouldn't be over applied to domestic unless requested or circumstances require extra precautions (disabled, medical machines frail etc) and if said case above ever happened Im sure they would ring another available spark not like he's the only one out there.

 

[leep82]

Completely agree with Dave above.

Plus Reg 314.2 does make it clear that each circuit should not be affected by the failure of other circuits and 'due account' should be taken of the consequences of the operation of any single protective device.

so where does this leave a split load board that develops the same N-E fault? Any circuits protected by that RCD are still affected?

 

[NickD]

so where does this leave a split load board that develops the same N-E fault? Any circuits protected by that RCD are still affected?

Then you've still got half a house worth of power for light, heating, plugging the freezer into, watching Cats Do The Funniest Things Down Under 3.

 

[leep82]

so where does this leave a split load board that develops the same N-E fault? Any circuits protected by that RCD are still affected?

Then you've still got half a house worth of power for light, heating, plugging the freezer into.

yes of course but it completely contradicts the regulation that somebody has just stated.

 

[Darkwood]

Completely agree with Dave above.

Plus Reg 314.2 does make it clear that each circuit should not be affected by the failure of other circuits and 'due account' should be taken of the consequences of the operation of any single protective device.

You are misinterpreting this reg' if it was the case as suggested then RCD over multiple circuits wouldn't be allowed even in domestic and as this is clearly not the case then you just have to ensure that losing that half a board is not going to be anything more than a minor disruption at most.

A house owner having to get a sparks out in the rare worse case scenario where they cant reset is a minor disruption and inconvenience as its a rare occurance, where as telecom exchange losing its main servers and cutting of half a city is a major disruption whether rare or not ... you forget the regs cover domestic, commercial and industrial and looking at this regulation in the bigger picture will give better guidance on when to apply it.

When you get a sparks who solely works domestic then its easy to forget the regs cover a wider field and can lead to mis-interpreting and over applying of some regs... take it from a spark that installed under the 15th 16th and 17th edition ... although don't bother domestic now and can easily design a domestic to 3 levels of application of that regulation from minimal , moderate to higher risk of 'small' inconvenience and all comply but down to customers preference and pockets.

 

[davesparks]

Your a preacher of doom lol... the clause of design to avoid inconvenience and nuisance shouldn't be over applied to domestic unless requested or circumstances require extra precautions (disabled, medical machines frail etc) and if said case above ever happened Im sure they would ring another available spark not like he's the only one out there.

I wouldn't say I'm a preacher of doom, but I do attend a fair number of domestic callouts and can honestly say the clients are always far less happy when they've lost the whole house or half of the house than when it's just one circuit out!

 

[Badged01]

I wouldn't say I'm a preacher of doom, but I do attend a fair number of domestic callouts and can honestly say the clients are always far less happy when they've lost the whole house or half of the house than when it's just one circuit out!

Very true but I think in answer to the OP's original question which I read as the client not wanting to pay for a fancy split board, all RCBO sexy number, then a single RCD upfront can be interpreted as meeting the regs?

Let the buyer beware .........

 

[Octopus]

What constantly amazes me is the push to allow fixed appliances WITHOUT DP isolation and SP isolation for garden circuits on shared rcd.s

Madness.

 

[Octopus]

And what about the bonding?

 

[leep82]

And what about the bonding?

bonding is fine

 

[uksparks]

3 RCBO's maybe £45 in total with a bit of looking around.

Really? Sounds a bit cheap...

 

[NickD]

Sixteen quid for an RCD FCU from Screwfix sounds cheaper.

 

[Darkwood]

I wouldn't say I'm a preacher of doom, but I do attend a fair number of domestic callouts and can honestly say the clients are always far less happy when they've lost the whole house or half of the house than when it's just one circuit out!

If they were living there when the electrics were fitted then the Electrician has failed to explain the pro and cons regarding the install and the alternative but usually more costly options available. I'm not a fan of arrive-fit and walk sparkies who don't interact much do it pretty much how they want it and just say thats how it is when these nuisance trips occur, that's not professional and reflects on the industry... people skills is as much part of being competent as the electric side.

If they moved in and it was like that already then quote them happy... yes I get the same customer in my field wanting to know why this why that and its annoying ... they get told the cost to improve or fix the situation and that's where the complaining stops about it been a nuisance. I didn't fit the set-up so not my fault but I can improve it.

Had a friend who couldn't find his torch and banged his head trying to reset the lighting breaker ...wanted it sorting as cheap as possible .. fitted a E/M light fed of the breaker on the cellar steps ... he's happy and is making the transition to low energy lamps too to help matters and didn't have to overhaul anything ... each job as you find it, one solution doesn't fit all.

 

[NickD]

Had a friend who couldn't find his torch and banged his head trying to reset the lighting breaker ...wanted it sorting as cheap as possible.

Hard hat.

 

[Darkwood]

Hard hat.

He can't find his 1million candle torch I really aint going to hold out on him having never mind finding his hard hat :6:

 

[Darkwood]

When ever I do a domestic I normally design it to the highest measure regarding protection then inform the customer I can cut cost but at a cost to the way the system works...

I use split boards with additional unprotected ways in these I fit RCBO's for:-

Security alarm.
Freezer
Boiler
Garage

The rest shared between the 2 rcd's

Explaining I can reduce the bill by up to £100 pounds and explaining the the issues in doing so often is good enough for the customer to go for my design, if you loose one freezer full of food it tends not to be worth the claim through insurance be would pay for the whole additional costs on its own, let the customer decide and have a pre-drafted options chart, they tick the extra they want they feel in charge and can't ever complain if they get nuisance tripping as its been explained and is in writing.

 

[davesparks]

A house owner having to get a sparks out in the rare worse case scenario where they cant reset is a minor disruption and inconvenience as its a rare occurance, where as telecom exchange losing its main servers and cutting of half a city is a major disruption whether rare or not ... you forget the regs cover domestic, commercial and industrial and looking at this regulation in the bigger picture will give better guidance on when to apply it.

Yes the regulations apply to all installations of any size, but they apply to each installation on an installation by installation basis. I agree that in the grand scheme of things one house losing power is a minor inconvenience, but by the same token is that one telephone exchange cutting off half of a city not a minor inconvenience compared to half of the country being cut off? And as far as I am concerned my whole house going off is a major inconvenience wheras I couldn't give two hoots about half of some city miles away losing its communications.

Each installation should be considered in its own right as an installation, and from the point of view of the installation all circuits going off at once is more inconvenient than just one going off, I hope we can all agree that this is true?
Your point, if I have understood you correctly, is that the greater inconvenience when considered alongside the likelihood of it happening is not significant enough to be overly concerned about.
I agree to an extent, I certainly wouldn't 'condemn' an installation for having a single RCD as a main switch or two RCDs or whatever but I would not install it like that and wouldn't ever recommend it.

When you get a sparks who solely works domestic then its easy to forget the regs cover a wider field and can lead to mis-interpreting and over applying of some regs.

I think you have struck on the underlying problem there, we have a set of regulations which can be mis-interpreted or over-applied and contain so many grey areas and mistakes.

 

[Darkwood]

Its the problem with the regs ... its design on a wide scale thus can't be written for individual set-ups in most cases and where it does address individual set-up it can take a whole section up so imagine it trying to cover the 3 sectors at a more detailed level ... it would be enormous and even harder to locate regulations ... its a trade off of detail against broad scope.

Agree the interpretation bit is key and what is a minor nuisance to one person could be a major to the next but we also have to keep a balance too hence my post 37.... design to the best without going to the full rcbo boards (no chance of getting these quotes) and then present the options, the customer has all the required info and also weighs up their own needs of the install, communication is key there should be no customer out their unaware about what they are paying for and what they sacrificed in going cheaper, if this is the case the Electrician has failed to involve the customer in the design stage and/or failed to explain the pro's and cons.

Key to getting this regulation been complied to is circumstantial and relies on getting the customer involved at key points and ensure they understand the install they are getting.

As you imply what is classed as inconvenience and a nuisance to one is not necessary the same for the next... but my post regarding the larger picture still applies to a certain extent as it was mainly why the regulation was introduced to allow firms to lay blame where financial costs and major disruption arose from poor design, its rare for a homeowner to run an Electrician through the courts because he lost all his power because the board did what it was supposed to..unless exceptional his case wouldn't stand.

 

[Lucien Nunes]

things like rcbo for boiler become a forethought so a vulnerable person doesn't lose heating if a fault occurs on a non related circuit they can't reset

I'm with DW on this but the above point can be quite important even in a domestic install because heating failure can lead to serious illness or death. If the main heat source is GCH, when the whole installation is dead they can't use either gas or electric heating. If only one circuit fails, one or other heat source will probably remain available. I'm conscious of this point because of my dad, who cannot withstand losing the heating for even a short time in winter. It's the main reason they have a standby generator!