Rented House 5 year Electrical Check Tomorrow

scousespark said:

I don't know why you have pulled me into this thread. In another thread, Eric posted that he would omit RCD protection after a Risk Assessment. All I said in reply was that would be inappropriate.

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The point is that that is not "all you said in your reply". You made (and then repeated in this thread) a statement which appeared to be clearly saying that "risk assessment is not applicable in a domestic installation" - which I think we are both agreed is simply not true (you agree that "we carry out risk assessments all the time").

We have both questioned the conclusion that eric has suggested his risk assessment would have resulted in for the OP's situation, but that's a different matter.

scousespark said:

You queried whether I meant risk assessments are never appropriate in a domestic installation. The following was my reply posted yesterday morning.

I have not said I don't carry out risk assessments in a domestic environment. I just said the Risk Assessment to omit RCD protection does not apply in this posters case.
I would agree that we carry out risk assessments all the time.

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I confess that I missed that yesterday (I guess because of subsequent posts). My apologies.

Anyway, it seems that we are in agreement and I just wanted to be sure that anyone reading this thread in the future gets the correct message - namely that "risk assessments ARE appropriate in a domestic environment, just as they are anywhere else". Do you agree?

Kind Regards, John

RF Lighting said:

As you only have a 100mA RCD then straight away your installation will be found to be in an unsatisfactory condition.

The height of the CU shouldn’t really be an issue as the inspector can access it to carry out his work. I have never heard of the step back rule mentioned above.

It is most likely that a replacement CU will be required as virtually all domestic circuits now require 30mA RCD protection and a single up front RCD is not compliant either.

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Just out of curiosity, which reg would you quote to warrant an unsatisfactory rating for the ELCB? I assume you would code this as a C2.

scousespark said:

Just out of curiosity, which reg would you quote to warrant an unsatisfactory rating for the ELCB? I assume you would code this as a C2.

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That is also some thing I would like to know, I would say a TT installation without an ELCB must be a fail, and that would be C2, with a TN not so cut and dried, the electrical safety council say the old Wilex fuse box can still be used, so they do seem to be saying lack of ELCB is not an automatic failure, but the Emma Shaw case shows where had there been a RCD even at 300 mA then she would not have died, so one can show that lack of ELCB is "potential dangerous" so one can hardly say an inspector is wrong giving a code C2 for lack of ELCB, even if the cause of death was given as use of semi-skilled inspection and testing, and there were a whole host of other faults.

But where an ELCB exists but is not 30 mA @ 40 mS then it gets rather hard to show "potential dangerous", I would say an ELCB-v would fail as not reliable, too easy to be shorted out, but if we look at the Emma Shaw case she has phone some one for advise, and has said how there are sparks, so one would assume there was a fair current going to earth, so likely it would have tripped a 300 mA ELCB. Over 300 mA the ELCB tends to be settable so can't be used where an ordinary person is in control, and 300 mA is the size stipulated for fire protection, although tradition it seemed 100 mA was the normal size, and the S type so time delay, but even with a 30 mA @ 40 mS in the main you will get full current for 10 mS even 20 mS so you still get a nasty belt, so in the main the 30 mA trips before some one touches live parts due to water, it does not help that much if the body is the first path to earth.

So what are the chances of a 30 mA drain which would not reach 100 mA making some thing live so "potential dangerous"? I would say that was very low, likely as low as a type AC compared with type A, so if going to fail a 100 mA RCD then with inverter drive washing machines and fridge/freezers etc, also one should fail if a type AC RCD fitted. Maybe we should? But in real terms I would say yes code C3 and bring attention to the problem, but not code C2.

The type AC and type A also needs consideration to size of circuit, with all RCBO even with type AC should DC freeze one device, it is only one and all other circuits are still protected, and with a TN supply the risk is very low, however once one combines circuits and you have many circuits on one RCD then the risk is increased, and with a 100 mA RCD on all circuits it is possible the back ground leakage could be 70 mA OK unlikely, but if that was the case, then the 100 mA RCD would offer same protection as an array of 30 mA RCBO's.

So I can't see how one can really fail an installation due to 100 mA rather than 30 mA. So look forward to seeing the reasons why one would fail an installation due to 100 mA instead of 30 mA, yes code C3 in the same way as code C3 for type AC where there are inverter drives, but not code C2.

I'm not sure what code he used for the CU or downlights in the main bathroom, just that they need replacing.
I suppose I will get the tenants copy when it has all been rectified but it would be interesting to see the failure sheet as well.

scousespark said:

Just out of curiosity, which reg would you quote to warrant an unsatisfactory rating for the ELCB? I assume you would code this as a C2.

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You're probably not particularly interested in the opinion of an 'outsider' but, for what it's worth, my personal view would be that in the case of circuits (or cables) for which current regs require 30 mA RCD protection, then protection with an RCD with IΔn>30mA should be treated exactly the same as the absence of any RCD protection at all. However, that does not answer your question, since there appears to be appreciable variation in opinion (amongst those who do undertake EICRs) as to whether that should be C2 or C3.

Amidst that variation in opinion, it seems that at least some people would base their coding decision (between C2 and C3) on their assessment of risk in relation to the particular circuit/situation involved - i.e. they might give a C2 for absence of (adequate) required RCD protection for one circuit but not for another.

As I often point out, this appears to be the one and only case in which BS7671 gives any guidance at all as regards coding - it indicates that the absence of required RCD 'additional protection' (hence, presumably, 30mA) should be give "at least a C3" - but that doesn't really help to answer your question, either.

I presume that there must be quite a lot of installations out there which do not have (required by current regs) RCD protection of at least some circuits.

Kind Regards, John

ericmark said:

So what are the chances of a 30 mA drain which would not reach 100 mA making some thing live so "potential dangerous"? I would say that was very low ...

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In terms of faults (which make something 'live'), you're probably right that the probability would be very low. Indeed, many L-E faults are 'of negligible impedance' and therefore would presumably (in a TN installation) result in ADS even without any RCD at all.

However, when it comes to ('shock') currents flowing through a human being, things are very different. If physiological responses/reflexes did not result in physical disconnection of the source of electricity, then a current of, say, 90 mA (or, potentially, even 40 mA) which was allowed to flow 'indefinitely' through a person (which a 100 mA RCD would allow) would very probably prove fatal. However, if the duration of the 90 mA (or 40 mA) was limited to <40 ms (by a 30 mA RCD), then the victim would stand a good chance of surviving.

ericmark said:

So I can't see how one can really fail an installation due to 100 mA rather than 30 mA. So look forward to seeing the reasons why one would fail an installation due to 100 mA instead of 30 mA ...

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See above, and what I've recently written - namely that I think that, when 30 mA RCD protection is required by current regs, a 100 mA RCD should be regarded in exactly the same way as 'no RCD at all' - but it's then for you/others to decide whether that should be C2 or C3 (perhaps, as I've suggested elsewhere, dependent on the circuit and circumstances involved).

Kind Regards, John

ericmark said:

the electrical safety council say the old Wilex fuse box can still be used, so they do seem to be saying lack of ELCB is not an automatic failure

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The electtrical safety council seem to regard "16th edition" levels of RCD protection as the minimum that can be "satisfactory", so unless the property is a flat well away from the ground at least some RCD protection is likely to be demanded by an inspector following their guidance.

plugwash said:

The electtrical safety council seem to regard "16th edition" levels of RCD protection as the minimum that can be "satisfactory", so unless the property is a flat well away from the ground at least some RCD protection is likely to be demanded by an inspector following their guidance.

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There seem to be far too many organisations (and individuals) who have their own (differing) opinions about all this.

It didn't used to matter too much, since most people were free to ignore the findings of EICRs if they so wished. However, now that the PRS legislation has given teeth to some EICRs (with potentially substantial financial consequences for landlords), it it really has become very unsatisfactory (I'm tempted to say 'unacceptable').

It's not so much a matter of 'moving goalposts' as of a situation in which the same set of goalposts is not visible to everyone!

Kind Regards, John

JohnW2 said:

You're probably not particularly interested in the opinion of an 'outsider' but, for what it's worth, my personal view would be that in the case of circuits (or cables) for which current regs require 30 mA RCD protection, then protection with an RCD with IΔn>30mA should be treated exactly the same as the absence of any RCD protection at all. However, that does not answer your question, since there appears to be appreciable variation in opinion (amongst those who do undertake EICRs) as to whether that should be C2 or C3.

Amidst that variation in opinion, it seems that at least some people would base their coding decision (between C2 and C3) on their assessment of risk in relation to the particular circuit/situation involved - i.e. they might give a C2 for absence of (adequate) required RCD protection for one circuit but not for another.

As I often point out, this appears to be the one and only case in which BS7671 gives any guidance at all as regards coding - it indicates that the absence of required RCD 'additional protection' (hence, presumably, 30mA) should be give "at least a C3" - but that doesn't really help to answer your question, either.

I presume that there must be quite a lot of installations out there which do not have (required by current regs) RCD protection of at least some circuits.

Kind Regards, John

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I don't dismiss your posts. You are obviously knowledgeable.
I am with you with this thread. I would agree that a lack of RCD would be a C3 (if all other tests are satisfied). As BS7671 is not retrospective, coding a lack of RCD as C2 doesn't seem right. As you say, there are millions of properties with no RCD which are satisfactory in every other respect.
To my mind the ELCB is a bit of an outlier and I wondered which reg Rob was looking at.

scousespark said:

I don't dismiss your posts. You are obviously knowledgeable. I am with you with this thread. I would agree that a lack of RCD would be a C3 (if all other tests are satisfied). As BS7671 is not retrospective, coding a lack of RCD as C2 doesn't seem right. As you say, there are millions of properties with no RCD which are satisfactory in every other respect.

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Thanks. I'm glad that we are agreed.

scousespark said:

To my mind the ELCB is a bit of an outlier and I wondered which reg Rob was looking at.

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I don't think it is just Rob. There seem to be a good few people who believe that, at least for some circuits, the absence of 30 mA RCD protection presents a sufficiently great "potential danger" to warrant a C2 - but I don't think that my personal view about that (whatever it may be) is particularly important or relevant.

Kind Regards, John

I was quoting Rob as he has proposed a C2. I'm just querying, not challenging his decision. I think personal views matter, as an EICR is largely based on personal views.

scousespark said:

I was quoting Rob as he has proposed a C2. I'm just querying, not challenging his decision. I think personal views matter, as an EICR is largely based on personal views.

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Yes, I realise that. I was merely agreeing with what you say, that 'personal views matter' (even if, perhaps, they shouldn't - if we {or, at least, landlords} want 'fairness'/'consistency'), by suggesting that there probably others (even here) who might well make the same decision as him.

Kind Regards, John

JohnW2 said:

when 30 mA RCD protection is required by current regs, a 100 mA RCD should be regarded in exactly the same way as 'no RCD at all

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That seems wrong, what we have to remember the leakage through some ones body does not slowly increase as they touch a live part, but it is a set amount depending on the resistance of their body, if an amp is going to flow, it will flow for same time and same rate be the RCD 30 mA at 40 mS or 100 mA at 40 mS. There will be some situations where the leakage slowly builds up, but in the main the RCD trips either because of direct contact in which case 30 mA or 100 mA will trip in same time, unless type S, or due to water which tends to quickly form a carbon track and be over 100 mA so in real terms very little difference between 30 and 100 mA. Both will cause the RCD to trip, it is not like the 200 mA of a shaver socket which is a limited current.

ericmark said:

That seems wrong, what we have to remember the leakage through some ones body does not slowly increase as they touch a live part, but it is a set amount depending on the resistance of their body, if an amp is going to flow, it will flow for same time and same rate be the RCD 30 mA at 40 mS or 100 mA at 40 mS.

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Exactly - and that was the very point I made.

"An amp" is a bit OTT but, as I said, if, per Ohm's Law, the current through the body was, say, 90 mA (implying a body resistance of about 2.5kΩ, which is far from non-credible), then a 30 mA RCD would limit the duration of that 90 mA to <40 ms, thereby quite probably avoiding death', whilst a 100 mA RCD would (at least, could) allow that 90 mA to flow through the victim's body 'indefinitely', thereby quite probably resulting in death.

Kind Regards, John

going back a bit, RCDs can trip a little bit faster or slower depending where in the AC cycle contact occurs. Current will be zero momentarily, then increase as the cycle climbs (or falls) towards the next peak.

So it may be faster than 30ms

I saw this in some tech doc or other, with graphs and timings.

It included survivability charts, varying by duration and current, which I don't remember.

30ma for 30ms is mostly survivable. Increase one and unless you decrease the other, survivability falls.