Which Type of RCD?

[Joules]

The article Which RCD Type? from the Institution of Engineering and Technology introduces Selectivity (Discrimination) when installing multiple RCD in series.

The question is, will a householder be protected by a Type AC RCBO in the consumer unit which then supplies a 2 Pole Type A/B RCCB positioned local to a GTI or inverter? The way I see this is that the RCBO is protected from DC currents by the local RCCB which would sense the presence of DC currents and trip before the RCBO became locked up or blinded.

Which highlights the danger of connecting GTI to consumer units protected only by Type AC RCD. There are a lot of them out there and electricians should be especially aware that a blinded RCD would not trip if an electrocution was in progress something that might later result in a fatality.

 

[johnb2713]

There are a lot of them out there and electricians should be especially aware that a blinded RCD would not trip if an electrocution was in progress something that might later result in a fatality.

I wonder what they use in the USA Department of Justice for their equipment?

 

[binky]

I wonder what they use in the USA Department of Justice for their equipment?

slow blow rusty nails...

 

[binky]

The article Which RCD Type? from the Institution of Engineering and Technology introduces Selectivity (Discrimination) when installing multiple RCD in series.

The question is, will a householder be protected by a Type AC RCBO in the consumer unit which then supplies a 2 Pole Type A/B RCCB positioned local to a GTI or inverter? The way I see this is that the RCBO is protected from DC currents by the local RCCB which would sense the presence of DC currents and trip before the RCBO became locked up or blinded.

Which highlights the danger of connecting GTI to consumer units protected only by Type AC RCD. There are a lot of them out there and electricians should be especially aware that a blinded RCD would not trip if an electrocution was in progress something that might later result in a fatality.

Interesting article. To my way of thinking, this is another reason for using RCBOs to minimise any potential DC leakage that a single RCD will see. It also begs the question should we be testing for DC leakage, and how would we achieve that?

 

[johnb2713]

Interesting article. To my way of thinking, this is another reason for using RCBOs to minimise any potential DC leakage that a single RCD will see. It also begs the question should we be testing for DC leakage, and how would we achieve that?

Could you not do it with a clamp meter set to DC, it should remove any AC content?

 

[Joules]

Interesting article. To my way of thinking, this is another reason for using RCBOs to minimise any potential DC leakage that a single RCD will see. It also begs the question should we be testing for DC leakage, and how would we achieve that?

Could you not do it with a clamp meter set to DC, it should remove any AC content?

Approved electricians need to consider the layout of the consumer unit/board they are installing. I think at least a two module wide space just after the main breaker for RCBO is a must. If all the spare slots connected after RCD are used up then these spares can be used for RCBO mitigating the need to install a bigger board. As for the clamp give it a go cos I really don't know. Another issue is that I cannot find single module RCBO Type A Curve B 100mA. The ones available seem to be Curve C so a test for Zs is a must. Nuisance tripping can be the bane of an electricians life especially with customers if they have replaced a board fitted with Type AC RCD with one fitted out with Type A.

 

[Murdoch]

Approved electricians need to consider the layout of the consumer unit/board they are installing. I think at least a two module wide space just after the main breaker for RCBO is a must. If all the spare slots connected after RCD are used up then these spares can be used for RCBO mitigating the need to install a bigger board. As for the clamp give it a go cos I really don't know. Another issue is that I cannot find single module RCBO Type A Curve B 100mA. The ones available seem to be Curve C so a test for Zs is a must. Nuisance tripping can be the bane of an electricians life especially with customers if they have replaced a board fitted with Type AC RCD with one fitted out with Type A.

No decent sparks fit dual rcd boards these days

Rcbo all the way

 

[Joules]

No decent sparks fit dual rcd boards these days

Rcbo all the way

Yes they do, normally splitting the neutral into two parts lighting and power. By splitting the neutral into three parts the spare slots after the main breaker can be used to accommodate the unexpected by relocating from any offending mcb into the neutral zone and using an RCBO as part of a discovery process as to what is really causing nuisance tripping. If you are pricing a job a board filled with RCBO is going to loose you the tender because mcb are cheaper to buy.

 

[Murdoch]

Yes they do, normally splitting the neutral into two parts lighting and power. By splitting the neutral into three parts the spare slots after the main breaker can be used to accommodate the unexpected by relocating from any offending mcb into the neutral zone and using an RCBO as part of a discovery process as to what is really causing nuisance tripping. If you are pricing a job a board filled with RCBO is going to loose you the tender because mcb are cheaper to buy.

Nonsense

Rcbo board or nothing

 

[Joules]

Nonsense

Rcbo board or nothing

Resorting to rhetoric and an all inclusive use of RCBO is simply an excuse for poor design. You see electricians lost the freedom they once had before RCD were introduced. Now consumer units/boards needs careful thought and design if the customer is to enjoy a lower installation cost and avoid nuisance tripping.

In your board design you have no idea what the total leakage current is for the board as a whole. Indeed, you don't care just as long as each RCBO sees less than what is needed not to trip. Across all RCBO the total leakage current could be so high that it impacts the customers electricity bill. RCBO have a role to play but not the one you endorse or BS7671 intended.

 

[Murdoch]

Resorting to rhetoric and an all inclusive use of RCBO is simply an excuse for poor design. You see electricians lost the freedom they once had before RCD were introduced. Now consumer units/boards needs careful thought and design if the customer is to enjoy a lower installation cost and avoid nuisance tripping.

In your board design you have no idea what the total leakage current is for the board as a whole. Indeed, you don't care just as long as each RCBO sees less than what is needed not to trip. Across all RCBO the total leakage current could be so high that it impacts the customers electricity bill. RCBO have a role to play but not the one you endorse or BS7671 intended.

More nonsense.

It can be argued that dual RCD's don't comply with the regs too.

I think you are clutching at straws to try and make your argument.

 

[binky]

Yes they do, normally splitting the neutral into two parts lighting and power. By splitting the neutral into three parts the spare slots after the main breaker can be used to accommodate the unexpected by relocating from any offending mcb into the neutral zone and using an RCBO as part of a discovery process as to what is really causing nuisance tripping. If you are pricing a job a board filled with RCBO is going to loose you the tender because mcb are cheaper to buy.

Not seen a high integrity board for ages.

The regs state the need for minimising the inconvenience caused by a single fault, so after a very long discussion on here we concluded that shared RCDs are therefore not compliant with that requirement, ergo, RCBOs all the way. Personally I find that if you discuss the difference and explain the advantages of RCBOs the customer is happy to pay the extra, and as you can get RCBOs for around £12 a piece the cost difference isn't so large. I would also say that if you are struggling to win work, that perhaps you need to view business a little differently. Around my neck of the woods, £850+ is not unusual for a board change, partly down to lack of electricians, partly some are just greedy! I don't charge that much, have very happy customers and can make a good living.

I spent many years at the 'bargain basement' end of pricing works, which was a mistake for 2 reasons. 1/ customers who only want the cheapest, are usually shit customers. 2/ Why should I work my arse off to keep prices low when I have 5 years legal liability for such a job - see how much any other profession would charge for that level of liability. So, a few years ago, I upped prices, lost no customers other than than those I didn't want anyway, have the time to do a much tidier job, and still get referrals to friends of family of those I have worked for. People are prepared to pay for a decent job, in fact, I would say customer service is probably more important than price, with so many tales of trades failing to show up, show up late, and generally doing rough work, customers actually like service. Turn up on time, do what you say you will properly and tidily. Phone them to let them know if you are running late or can't make an appointment, tidy up after yourself, mind your Ps & Qs, etc etc. Do that and you will find you probably get more work than being cheap. A friend of mine once put it this way, he would rather lose 8/10 quotes, but when he does get a job he's really happy to do the job, and if you check his ratings on Cheackatrade etc etc he's got 5* across the board.

 

[Joules]

More nonsense.

It can be argued that dual RCD's don't comply with the regs too.

I think you are clutching at straws to try and make your argument.

More misleading rhetoric from you spoken with an assured confidence designed to convince and without any presented evidence. Provide us with the evidence to support your argument. Meanwhile this article by Doepke may be a useful read as it refers to BS7671 531.3.2 and 531.3.3 mitigation of unwanted tripping.

Installs that feature split neutrals and dual RCD work by separating out essential services such as lighting, boiler/heating and smoke alarms these are attached to the lighting RCD the rest to the power RCD except GTI which is RCBO in the third neutral split.

 

[Murdoch]

More misleading rhetoric from you spoken with an assured confidence designed to convince and without any presented evidence. Provide us with the evidence to support your argument. Meanwhile this article by Doepke may be a useful read as it refers to BS7671 531.3.2 and 531.3.3 mitigation of unwanted tripping.

Installs that feature split neutrals and dual RCD work by separating out essential services such as lighting, boiler/heating and smoke alarms these are attached to the lighting RCD the rest to the power RCD except GTI which is RCBO in the third neutral split.

That Doepke document is over 4 years old.

Do keep clutching at straws as NOTHING would convince me to install a dual RCD board these days

So in the case of a dual RCD board how would you plan to restrict the leakage across up to 10 circuits to less than 10 mA?

 

[Joules]

Not seen a high integrity board for ages.

The regs state the need for minimising the inconvenience caused by a single fault, so after a very long discussion on here we concluded that shared RCDs are therefore not compliant with that requirement, ergo, RCBOs all the way. Personally I find that if you discuss the difference and explain the advantages of RCBOs the customer is happy to pay the extra, and as you can get RCBOs for around £12 a piece the cost difference isn't so large. I would also say that if you are struggling to win work, that perhaps you need to view business a little differently. Around my neck of the woods, £850+ is not unusual for a board change, partly down to lack of electricians, partly some are just greedy! I don't charge that much, have very happy customers and can make a good living.

I spent many years at the 'bargain basement' end of pricing works, which was a mistake for 2 reasons. 1/ customers who only want the cheapest, are usually shit customers. 2/ Why should I work my arse off to keep prices low when I have 5 years legal liability for such a job - see how much any other profession would charge for that level of liability. So, a few years ago, I upped prices, lost no customers other than than those I didn't want anyway, have the time to do a much tidier job, and still get referrals to friends of family of those I have worked for. People are prepared to pay for a decent job, in fact, I would say customer service is probably more important than price, with so many tales of trades failing to show up, show up late, and generally doing rough work, customers actually like service. Turn up on time, do what you say you will properly and tidily. Phone them to let them know if you are running late or can't make an appointment, tidy up after yourself, mind your Ps & Qs, etc etc. Do that and you will find you probably get more work than being cheap. A friend of mine once put it this way, he would rather lose 8/10 quotes, but when he does get a job he's really happy to do the job, and if you check his ratings on Cheackatrade etc etc he's got 5* across the board.

Pricing is regional and electricians will turn away jobs that they think they may loose money on. The full use of RCBO works but as said it is a design cop-out. Not all customers are earn to burn types that can afford what works for you as the installer. NICEIC rates vary but £350 for a new consumer unit is about right and customers are protected by a six year Platinum Guarantee. The failure to make jobs affordable forces people to go off and do DIY self installs. People will always chase the money being unable to do the decent thing.

 

[SPECIAL LOCATION]

Possibly you need to refer to articles that relate to current wiring regulations BS7671:2018 Amendment 2...
Rather than out of date articles referring to now superseded regulations.

And have a re-read of 531.3.2 (ii).

 

[Murdoch]

Pricing is regional and electricians will turn away jobs that they think they may loose money on. The full use of RCBO works but as said it is a design cop-out. Not all customers are earn to burn types that can afford what works for you as the installer. NICEIC rates vary but £350 for a new consumer unit is about right and customers are protected by a six year Platinum Guarantee. The failure to make jobs affordable forces people to go off and do DIY self installs. People will always chase the money being unable to do the decent thing.

I suspect the NICEIC figures are well out of date

Around here people don't complain for a quality RCBO board with SPD, new tails etc for around £600

Many sparks here charge more.

 

[binky]

Pricing is regional and electricians will turn away jobs that they think they may loose money on. The full use of RCBO works but as said it is a design cop-out. Not all customers are earn to burn types that can afford what works for you as the installer. NICEIC rates vary but £350 for a new consumer unit is about right and customers are protected by a six year Platinum Guarantee. The failure to make jobs affordable forces people to go off and do DIY self installs. People will always chase the money being unable to do the decent thing.

That's way out of date price wise, unless that's a 2 way board or just the labour, especially bearing in mind that you also have to test the place.

As for RCBOs being a design copout, what utter nonsense, it's actually a better design, as it's actually more reliable than a dual board, apart from being fully compliant with regs.

As for affordability, not my problem, why should I offer my skills, experience and knowledge on the cheap? You either value your trade or give and stack shelves for Tesco.

You are of course entitled to your opinions, but I would seriously reconsider those

 

[SPECIAL LOCATION]

Pricing is regional and electricians will turn away jobs that they think they may loose money on. The full use of RCBO works but as said it is a design cop-out. Not all customers are earn to burn types that can afford what works for you as the installer. NICEIC rates vary but £350 for a new consumer unit is about right and customers are protected by a six year Platinum Guarantee. The failure to make jobs affordable forces people to go off and do DIY self installs. People will always chase the money being unable to do the decent thing.

Try another google search..
The sort of thing the average untrained customer may do, and I think you will find suggested costs are a lot more than £350!?

e.g.
A typical find a trades person sort of site.

They imply £450 to £800...
(However for most professional competent electricians I think £450 could be a bit on the low side if you are intending to actually cover your overheads sufficiently?)

 

[Joules]

Try another google search..
The sort of thing the average untrained customer may do, and I think you will find suggested costs are a lot more than £350!?

e.g.
A typical find a trades person sort of site.

They imply £450 to £800...
(However for most professional competent electricians I think £450 could be a bit on the low side if you are intending to actually cover your overheads sufficiently?)

The bottom line is if your quote for an all RCBO board (not that the customer cares, but one can frighten them) is accepted all well and good but you have to consider that leakage currents are a parasitic load that makes the meter tick over. The problem with the regs is that they expect you to do an earth leakage test on all circuits and Zs to determine the required design. Instead, the tests are conducted if at all post installation.

The real problem that has not been addressed by the regulator is that manufacturers' of consumer products are not obliged to provide an RCD Declaration as is required by GTI makers. How is an electrician expected to know that a Type F RCD/RCBO is required rather than a Type A or Type B? Its all down to the experience of the electrician and a lot of guess work.