Which Type of RCD?

[binky]

The bottom line is if your quote for an all RCBO board (not that the customer cares, but you 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.

What's vampire amps got to do with the board? Simple fact is dual RCD boards do not comply with regs, and no one is frightening customers, just pointing out the obvious advantages of a more reliable installation. Ever accuse me of trying to frighten customers again and you will regret it, that is entirely the opposite of how I work, I'm semi retired, don't need the money and totally detest dishonest tradesmen

 

[Joules]

What's vampire amps got to do with the board? Simple fact is dual RCD boards do not comply with regs, and no one is frightening customers, just pointing out the obvious advantages of a more reliable installation. Ever accuse me of trying to frighten customers again and you will regret it, that is entirely the opposite of how I work, I'm semi retired, don't need the money and totally detest dishonest tradesmen

Edited 'you' and replaced it with 'one' the pronoun was never meant to be personal to anyone.

 

[Joules]

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

According to Michael Peace’s IET article ‘Earth Leakage’ there are no earth leakage testers available that measure DC leakage. So no calibrated standard to validate any reading obtained.

 

[binky]

According to Michael Peace’s IET article ‘Earth Leakage’ there are no earth leakage testers available that measure DC leakage. So no calibrated standard to validate any reading obtained.

And that's a problem, now how about discussing your other points. NB, I am not trying to belittle you, just point out you may have an error of thinking, based on my own experience of 17 years of running my own business, which at times has barely made me a living, and at others made me over £70k a year, and turned over roughly £750k.

For those who are willing to listen, the members of this forum have been there, done it, and got multiple T shirts

 

[SPECIAL LOCATION]

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.

Have you actually read 531.3.2 (ii) in the CURRENT regulations? or are you still working to amendment 1, or earlier?

Also current regs 531.3.3 (starting on page 156), gives a reasonable description of the different types of RCD...
and some guidance regarding their usage.

I am a trying to find the regulation that you think requires an earth leakage test on all circuits?
and/or which are the model forms where you document this earth leakage current?

This thread has a significant amount of incorrect / outdated information... (mostley from a single contributor).
which in my opinion suggests poor practice and incorrect materials being recommended in order to gain business from an uneducated customer!!!

Which is a significant conflict with the guidance of 134.1.1 (Good workmanship, Skilled or instructed persons & Proper materials).

Dual RCD / Split-Load / High integrity CU's are about as up-to-date as writing a cheque when you pay for your weekly food shopping at Tesco!!

I am trying to remember when I last fitted a dual RCD CU -Vs- writing a cheque?
OR when a customer last paid me by cheque??

Bank transfer, or Card payment, or Google/Apple pay etc. are the norm,
or occasionally cash on jobs less than £75!

What used to be sold as "dual RCD"/"high integrity" Cu's, are so Old-Hat.....
I didn't think anyone other than "DIY", "Bob-The-Builder", "Kevin-The-Kitchen-Fitter", "Barry-The-Bathroom-Fitter", OR "Larry-Loft-Converter", actually bought or fitted them?

If you have any half decent suppliers, the cost difference for full RCBO -vs- 'not very high integrity' is so small it is a no-brainer, to install a better value solution for your customers.

[ But even though I have been doing this job, working for myself for well over 20+ years. Passed all relevant C&G exams, as & when BS761 has been updated/amended. It is possible I may have missed "the bleedin obvious"....

So if you can please tell me the regs that suggest Dual RCD are a good solution..
And how & where you document these earth leakage values you mention?????

Or is it all 'Smoke & Mirrors' plus 'Tosh & Waffle', trying to back-up a very poor design solution using a single or dual RCD to protect multiple circuits!?

I cannot believe anyone who has had to do fault finding on a split load board with no-RCBO final circuits, would ever consider a non-full-RCBO CU to be an economical solution!

 

[johnb2713]

It makes me wonder how I've managed the last 35 years in my house with just a single RCD, the number of nuisance trips in that time I can count on the fingers of one hand. Why are some of you guys really pushing the must have message for RCBO's v dual/single RCD boards, I really dont get it, you appear to be resolving a theoretical issue that in reality doesnt exist.

 

[kerching]

It makes me wonder how I've managed the last 35 years in my house with just a single RCD, the number of nuisance trips in that time I can count on the fingers of one hand. Why are some of you guys really pushing the must have message for RCBO's v dual/single RCD boards, I really dont get it, you appear to be resolving a theoretical issue that in reality doesnt exist.

I don't recall reg numbers but

Circuits shall be installed/arranged to minimise inconvenience and aid testing
A fault on one circuit should not influence another

Just saying
( and my house is all RCBO double pole and have had one 'trip' since fitting it 6 yeas ago, when wife dropped a knife in the ouster during crumpet extraction)

 

[Murdoch]

It makes me wonder how I've managed the last 35 years in my house with just a single RCD, the number of nuisance trips in that time I can count on the fingers of one hand. Why are some of you guys really pushing the must have message for RCBO's v dual/single RCD boards, I really dont get it, you appear to be resolving a theoretical issue that in reality doesnt exist.

Out in the real world I've lost track of the number of customers I have who HAVE HAD nuisance tripping on up front or dual RCD boards, meaning they loose all or half their circuits on a regular basis.

A RCBO board means that they only loose the single circuit with the fault. Which is far better for most people AND cheaper to investigate and resolve for the spark. Sure they are more expensive to install but a far better place to start

 

[johnb2713]

Out in the real world I've lost track of the number of customers I have who HAVE HAD nuisance tripping on up front or dual RCD boards, meaning they loose all or half their circuits on a regular basis.

A RCBO board means that they only loose the single circuit with the fault. Which is far better for most people AND cheaper to investigate and resolve for the spark. Sure they are more expensive to install but a far better place to start

I can see that when changing a board or a new install that RCBO's are the way to go but I dont see the portrayed image that single / dual RCD is the work of the devil and warrants a board replacement immediately.

 

[johnb2713]

Circuits shall be installed/arranged to minimise inconvenience and aid testing

Surely thats just as easy on any board single / dual / rcbo?

A fault on one circuit should not influence another

Its a pretty weak advantage here really, it doesnt warrant ripping out an RCD board to replace it with RCBO's IMHO. New install / board being replaced I understand but if it aint broke, dont fix it.

 

[Murdoch]

I can see that when changing a board or a new install that RCBO's are the way to go but I dont see the portrayed image that single / dual RCD is the work of the devil and warrants a board replacement immediately.

who said ANYTHING about swapping out single or dual rcd boards?

 

[SPECIAL LOCATION]

I dont see the portrayed image that single / dual RCD is the work of the devil and warrants a board replacement immediately.

No one has suggested that.. nor suggested ripping out old wylex boards with 3036..

 

[SPECIAL LOCATION]

I don't recall reg numbers but

Circuits shall be installed/arranged to minimise inconvenience and aid testing
A fault on one circuit should not influence another

Just saying
( and my house is all RCBO double pole and have had one 'trip' since fitting it 6 yeas ago, when wife dropped a knife in the ouster during crumpet extraction)

531.3.2 (ii) specifically mentions the use of RCBO's in residential premises , as a recommended method to minimise unwanted tripping.

 

[johnb2713]

No one has suggested that.. nor suggested ripping out old wylex boards with 3036..

Maybe not in this thread but in other threads and general comments, eg 'frightening people into going RCBO' the general attitude seems to be set against RCD's at any cost and install RCBO's.

 

[Murdoch]

Maybe not in this thread but in other threads and general comments, eg 'frightening people into going RCBO' the general attitude seems to be set against RCD's at any cost and install RCBO's.

Where ?

 

[Sharpend]

Maybe not in this thread but in other threads and general comments, eg 'frightening people into going RCBO' the general attitude seems to be set against RCD's at any cost and install RCBO's.

An RCBO board is the better model, in that it fits better with the Regs and reduces on going costs for fault finding etc, however the regs being the regs are very wishy washy and despite suggesting reducing nuisance tripping they don’t rule out RCD’s in favour of RCBO’s.
Thus, some customers will do cheap as chips budget as will some electricians and opt for the dual RCD boards.
A ‘good’ electrician would always opt for a complete RCBO (DP) board.

 

[Murdoch]

Just to add to the above RCBO's offer far better flexibility meaning

you can have

RCBO's
MCB's
AFDD's

Or even swap between them as required

Which begs the question why would you fit a dual RCD board?

 

[Joules]

Have you actually read 531.3.2 (ii) in the CURRENT regulations? or are you still working to amendment 1, or earlier?

Also current regs 531.3.3 (starting on page 156), gives a reasonable description of the different types of RCD...
and some guidance regarding their usage.

I am a trying to find the regulation that you think requires an earth leakage test on all circuits?
and/or which are the model forms where you document this earth leakage current?

This thread has a significant amount of incorrect / outdated information... (mostley from a single contributor).
which in my opinion suggests poor practice and incorrect materials being recommended in order to gain business from an uneducated customer!!!

Which is a significant conflict with the guidance of 134.1.1 (Good workmanship, Skilled or instructed persons & Proper materials).

Dual RCD / Split-Load / High integrity CU's are about as up-to-date as writing a cheque when you pay for your weekly food shopping at Tesco!!

I am trying to remember when I last fitted a dual RCD CU -Vs- writing a cheque?
OR when a customer last paid me by cheque??

Bank transfer, or Card payment, or Google/Apple pay etc. are the norm,
or occasionally cash on jobs less than £75!

What used to be sold as "dual RCD"/"high integrity" Cu's, are so Old-Hat.....
I didn't think anyone other than "DIY", "Bob-The-Builder", "Kevin-The-Kitchen-Fitter", "Barry-The-Bathroom-Fitter", OR "Larry-Loft-Converter", actually bought or fitted them?

If you have any half decent suppliers, the cost difference for full RCBO -vs- 'not very high integrity' is so small it is a no-brainer, to install a better value solution for your customers.

[ But even though I have been doing this job, working for myself for well over 20+ years. Passed all relevant C&G exams, as & when BS761 has been updated/amended. It is possible I may have missed "the bleedin obvious"....

So if you can please tell me the regs that suggest Dual RCD are a good solution..
And how & where you document these earth leakage values you mention?????

Or is it all 'Smoke & Mirrors' plus 'Tosh & Waffle', trying to back-up a very poor design solution using a single or dual RCD to protect multiple circuits!?

I cannot believe anyone who has had to do fault finding on a split load board with no-RCBO final circuits, would ever consider a non-full-RCBO CU to be an economical solution!

Appreciate what you said and please feel free to correct me. RCD were introduced by the 17th Edition Regs. The case for installing RCBO was made under 314.1 so at that time you could say that this was the only way to go.

But things moved on, in the 18th Edition Regs under 513.3.2 two options are provided. Under Option 1, RCBO are to be fitted a carryover from 314.1.

Under Option 2, a split neutral board with RCD and MCB might be entertained if the PE current is kept below 30% of the rated trip current, for 30mA that would be 9mA. This is open to interpretation: is the 9mA the sum of leakage experienced by all RCD or is it per RCD group? Mine is the latter view. The difficulty is that one needs to measure leakage accurately but as there are no instruments available to measure DC components Option 2 is flawed favouring designs under Option 1.

All I said originally is that a board designed under Option 2 should have some spare slots just after the main breaker to accommodate occasions when a load breaks the 9mA rule and has to be replaced by an RCBO. An Option 2 board is going to be far more affordable than an Option 1 board but the electrician will have to jump through hoops to get there. The value is that if the leakage on a circuit goes out of range and causes tripping it provides and earlier warning of something going wrong than an Option 1 RCBO might do.

All the replies here have been from Option 1 installers.

 

[binky]

It makes me wonder how I've managed the last 35 years in my house with just a single RCD, the number of nuisance trips in that time I can count on the fingers of one hand. Why are some of you guys really pushing the must have message for RCBO's v dual/single RCD boards, I really dont get it, you appear to be resolving a theoretical issue that in reality doesnt exist.

Ever increasing amounts of appliances with electronic controls that leak a little down the earths means tripping is quite common for stupid little reasons, like a bit of damp in a wall. My range cooker has 2 ovens, one of which only gets used at Xmas, so damp in the oven used to trip the shared RCD every time. Now it's on it's own RCBO, it never happens and I don't get an irrate wife on Xmas morning. We also need to consider safety for older people, (many of whom also have old half knackered appliances that also cause issues) if you loose half the ccts, chances are you loose a lighting cct, which can be dangerous for old people trying to access the board - no one wants a customer falling down the stairs. We also get lots of call outs, and questions on here about RCD tripping, which is rarely a faulty cct, but a faulty appliance. Other regular callouts involve fridges and freezers, which seem to have an inate ability to trip a shared RCD whilst the customer is on holiday. So, apart from fully complying with regs, any initial extra cost of parts is far outweighed long term by fitting RCBOs. It also means we don't get called back by irrate customers accusing us of doing a shit job when their daughters knackered hairdrier trips the RCD mid winter and they have no heating or hot water coz the boiler is on the same RCD. If there is a real problem, then it also reduces the urgency of the callout, which helps with work organisation.

Incidentally, a 35 year old RCD may well be not working properly anymore

 

[Joules]

An RCBO board is the better model, in that it fits better with the Regs and reduces on going costs for fault finding etc, however the regs being the regs are very wishy washy and despite suggesting reducing nuisance tripping they don’t rule out RCD’s in favour of RCBO’s.
Thus, some customers will do cheap as chips budget as will some electricians and opt for the dual RCD boards.
A ‘good’ electrician would always opt for a complete RCBO (DP) board.

I agree but what is to done if the customer cannot afford it?