Discuss RCD's how to test and when required, and what code? in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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I know how I was taught to test a RCD, 6 tests in all two no go, two under 300 mS and 2 under 40 mS with no load. But thinking about it not so sure on the no load? We are told there are 5 common types with some others not seen much, type S, AC, A, F, and C. OK type S not used much now, but when you seen the RCD is unmarked or type AC then how do you know suitable for the installation?

I watched the John Ward video, and my first impression was Oh dear, have I fitted wrong type, but then I realise I have never used a 4 pole RCD and feed a smooth DC current through the spare ways, and I am not likely to, so only way you can get smooth DC is with some thing that stores or generates DC, battery chargers and solar panels seem to be only way to get smooth DC. Any diode failure will be pulsed DC.

The other thing is the amount of DC, all the AC, A, F, and B RCD's allow a few milliamp of DC, and a solar panel or electric car under fault conditions is likely to allow amps of DC to flow, so unless combined with a DC detection unit, which some are at 6 mA, then it does not really help using type B, and with a 6 mA detection unit type A is good enough.

But how do we test the 6 mA detection unit, and also how do we detect any DC? I don't have a DC clamp-on meter, I know with a standard meter selecting wrong range DC instead of AC can cause some not to read, but to detect 6 mA the wired meter is not really going to help, only option is a clamp on meter.

And if worried about DC should the RCD test be done under load? I know 9 mA is the limit for leakage without a fault with a 30 mA RCD, however my clamp on starts at 100 mA so never tested. Yes on my to get list is a clamp on to measure 1 mA but not got one yet, would be a good idea to test for borrowed neutrals rather than rely on neon screwdriver.

Then the is the question when is a RCD required? In 2008 reg 701.415.2 we got "(ii) All final circuits of the location have additional protection by means of an RCD in accordance with Regulation 701.411.3.3" so although the regulations are not retrospective, where the local supplementary equipotential bonding is not as required before BS7671:2008 then the installation still needs RCD protection to 30 mA.

As to TT supplies, and the old 100 mA S type, clearly with 701.415.2 it still is not permitted, however the EICR has three fail codes C1, C2 and FI and in the main we are looking at C2, this does not say does not comply with current edition of BS7671 as a new installation, it says potentially dangerous, code 4 was dropped as being unhelpful, so we are not looking at the regulations for code C2, yes we may warn about not being able to alter the installation without adding a RCD, but this is not a code C2.

All 230 volt AC is potentially dangerous, so what is really mean by potentially dangerous in code C2? If when BS7671 came out in 1992 it was OK, how can we say today it is not OK, we could go further back, however at one point we had knife switches with exposed contacts, and the regulations were only about fire protection, so clearly there has to be a limit, some seem to think the thirteenth edition is still valid i.e. no earths on lighting circuits, but I think in 1955 we were also using rubber cable so in real terms unlikely any installation before 1966 with fourteenth edition or maybe 1969 when we went metric. However since BS7671 did not exist before 1992 that seems to be a good start point, as nothing complied with BS7671 before that date.
However I don't have a literary of BS7671 editions, so I want some firm point where lack of RCD protection means a code C2, so as well as 701.415.2 we have manufacturers recommendations, yes I know we only need to take them into account, but if a manufacturer says "Type A RCDs RCD's how to test and when required, and what code? Type A - EletriciansForums.netmust be employed where additional protection is required." (Bosch boiler) then I would say we really have no option to issuing a code C2 where it is not complied with.

This is a problem as so many houses even when a RCD is fitted it is only type AC, so following manufacturers recommendations would mean failing or issuing a code C2 even when home is all RCD protected. Since this is only with some boilers clearly the person fitting the boiler should have changed any RCD feeding it to type A and there should be a minor works certificate covering it, what are the chances?

This also means the inspector would need to read all installation instructions for (“consumer’s installation” means the electric lines situated upon the consumer’s side of the supply terminals together with any equipment permanently connected or intended to be permanently connected thereto on that side; ) from "The Electricity Safety, Quality and Continuity Regulations 2002" which is linked to the "The Electrical Safety Standards in the Private Rented Sector (England) Regulations 2020" which has resulted in so many EICR's being done.

I have read the "Pod Point Solo Unit Installation Guide" with "As of the 1st January 2019 either a Type B RCD must be used or a Type A with 6mA DC protection included in the Pod-Point (see detail on packaging to determine what protection is required)," and ask the question with an EICR what is the chance of the packaging being available to read what protection is required?

And with an old 30 mA RCD yes you can remove it and read on the side the BS or BS EN number, but that give minimum requirements not what it is.

If the new law said to treat all homes as new installations under BS 7671 then we would be in a better position, but we have this potentially dangerous label, and I can't with hand on heart say a home without RCD protection on all circuits on a TN supply is potentially dangerous, neither can I say a TT supply with a 100 mA RCD S type is potentially dangerous.

A socket at 200 mm above floor with a wheel chair user is potentially dangerous, as at right height to be hit by wheel chair wheel, but I would not give it a code C2. A consumer unit at ceiling level is potentially dangerous as anyone accessing it could fall, but again not a code C2.

Personally I think all rented accommodation should be RCD protected, but I ordered some type A RCBO's from local whole sale outlet and 3 months latter still not arrived, so 28 days is silly, and rather than force the landlord to evict the tenant as he can't get work done, it is tempting to code C3 so he has time to correct things.

We must highlight errors, that is what we are paid to do, and if we code C3, we have highlighted the errors, even if we know full well the landlord will not do the work unless code C2, we have still done our job if code C3 and any court would have a job saying we had not done our job, as clearly we have, so is it down to us to try forcing the landlord hand? I would say if not sure, then C3.

So an electric car charging point with a type AC 30 mA @ 40 mS RCD what would you code it?
 
It looks like there is an interesting question in there somewhere.
Would you mind most awfully abbreviating it a little?
I know how I was taught to test a RCD, 6 tests in all two no go, two under 300 mS and 2 under 40 mS with no load. But thinking about it not so sure on the no load? We are told there are 5 common types with some others not seen much, type S, AC, A, F, and C. OK type S not used much now, but when you seen the RCD is unmarked or type AC then how do you know suitable for the installation?
Sticking with your first paragraph for now.
The minimum testing requirements changed in Amendment 2.
Type A or Type AC RCDs should be tested with the MFT set on type AC for testing purposes.
Only 1 test at x1 is now required. Additional testing is optional.
Amendment 2 also updated the requirements on choosing RCD types. For a lot of domestic applications Type A will be required.
 
On the point of letting the potential actions or inactions on the part of the landlord influence our decision on whether a defect should be classified as a C2 or a C3, this is not really an option. We are there to give an honest factual report on the condition of the installation, no more and no less.
 
I would say unless we can verify that connected loads have no DC nature, the most common should be FI (resulting in Unsatisfactory) until analysis of loads is done. If the property is vacant then I would argue that same applies; "but there are no loads to analyse" people will cry and yes that is true however we are by nature, going eire on the safe side of things
 
In my opinion, BS 7671 is for guidance & is not a Statutory Document. However, the regs have always been left to the interpretation of the individual Electrician. I think we have all learned something from the latest RCD's & how we test. I recently purchased a Metrel MFT & if I test an A type at the panel I get a warning symbol with no result. Test at a socket outlet and works fine. Use the AC type test as recommended for an A type, all tests fine leaving you thinking did it test the DC side? It also has an EV 6mA test feature along with all the ranges of RCD's. This also has the RCD auto sequence feature now not necessary but I still use it.
 
When I get a chance, I will test my children's homes, and see what they show, it does seem the DC test is a bit hit and miss, the instructions say how it needs zeroing, and it seems my high DC is more down to not zeroing correctly than any fault.

As to imbalance, although high, it is a large house, and it has 14 RCBO's so no problem with tripping.
 
In my opinion, BS 7671 is for guidance & is not a Statutory Document. However, the regs have always been left to the interpretation of the individual Electrician. I think we have all learned something from the latest RCD's & how we test. I recently purchased a Metrel MFT & if I test an A type at the panel I get a warning symbol with no result. Test at a socket outlet and works fine. Use the AC type test as recommended for an A type, all tests fine leaving you thinking did it test the DC side? It also has an EV 6mA test feature along with all the ranges of RCD's. This also has the RCD auto sequence feature now not necessary but I still use it.
When you tested at the panel, was your probe neutral on the rcbo or neutral bar?
To test type A it has to be after the rcbo, ie, the outgoing neutral. That's what I've found anyway.
I also use a metrel btw.
 
When you tested at the panel, was your probe neutral on the rcbo or neutral bar?
To test type A it has to be after the rcbo, ie, the outgoing neutral. That's what I've found anyway.
I also use a metrel btw.
Hi, My probe was on the outgoing neutral of the RCBO. I will be testing again this week so I will play around, many thanks for your reply.
 

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