Part P regs

[JohnW2]

I was careful not to date BS7671 as there seems to be some confusion as to which version Part P requires.

There can't be any confusion like that, as it doesn't require it at all. This is Part P:

Whilst that is literally true (we have both pointed out to Eric that 'Part P', per se, is just that one sentence), it is not very helpful in addressing the point made my Derek.

As you know, Approved Document P gives 'official' advice on how compliance with Part P can be achieved, and the 'primary' (which we all agree does not mean 'only') way is to work in compliance with BS7671. Eric's comment undoubtedly relates to the fact that, in this context, the current version of Approved Document P still refers explicitly to BS7671:2001.

That being the case, I would imagine that if the matter ever got into a court of law (which we know it almost certainly won't), that court would very probably take note of the 'current' official guidance and uphold a claim that compliance with BS7671:2001 was an adequate demonstration of compliance with part P, even if the work was not compliant with the current edition of BS7671.

Kindest Regards, John.

 

[acmedone]

For instance, if a spur is added and it works (perhaps doing basic checks with a multimeter before energising), what value is parametric testing expected to add?

When you say "it works", I presume you mean that when an appliance is plugged in, it functions? In terms of the work actually done, testing could reveal problems such as incorrect polarity, absent CPC continuity, low insulation resistance, high loop impedance. More generally, it may reveal the existance of any of those problems (together with RCD malfunction etc.) which were not due to the new work but were pre-existing in the circuit prior to adding the spur.

Polarity, continuity and absence of shorts (eg N nicked when screwing the plate to a back box) are easy to confirm with basic tests so lets assume they're correct. (Though I appreciate not all diy-ers check first.) Then as you suggest, parametric testing is probably only useful for finding pre-existing faults. So if a circuit is added and tests to BS7671 are not done on that circuit, essentially the question is - so what? (So long as a faulty circuit is not extended into a controlled zone.)

 

[JohnW2]

Polarity, continuity and absence of shorts (eg N nicked when screwing the plate to a back box) are easy to confirm with basic tests so lets assume they're correct. (Though I appreciate not all diy-ers check first.) Then as you suggest, parametric testing is probably only useful for finding pre-existing faults. So if a circuit is added and tests to BS7671 are not done on that circuit, essentially the question is - so what? (So long as a faulty circuit is not extended into a controlled zone.)

As you presumably understand from the final comments in my previous post, I don't really disagree with you - although, as you imply, I strongly suspect that the average DIYer does not do any tests (and may well not have any facilities and/or knowledge to do any tests), particularly if "it works". However, as we all know, the regs (and hence, by implication, probably the law) do require 'full testing' of any circuit that has been worked on - so there is no option as to what advice has to be given to those who want to stay on the right side of the rules/laws.

What individual DIYers choose to do is, of course, ultimately their decision. Electricians have little choice, since they are generally obliged to document results of their tests, whether or not the truly believe that there would be any significant safety risks if they didn't undertake them all.

Kind Regards, John.

 

[acmedone]

Polarity, continuity and absence of shorts (eg N nicked when screwing the plate to a back box) are easy to confirm with basic tests so lets assume they're correct. (Though I appreciate not all diy-ers check first.) Then as you suggest, parametric testing is probably only useful for finding pre-existing faults. So if a circuit is added and tests to BS7671 are not done on that circuit, essentially the question is - so what? (So long as a faulty circuit is not extended into a controlled zone.)

As you presumably understand from the final comments in my previous post, I don't really disagree with you - although, as you imply, I strongly suspect that the average DIYer does not do any tests (and may well not have any facilities and/or knowledge to do any tests), particularly if "it works". However, as we all know, the regs (and hence, by implication, probably the law) do require 'full testing' of any circuit that has been worked on - so there is no option as to what advice has to be given to those who want to stay on the right side of the rules/laws.

What individual DIYers choose to do is, of course, ultimately their decision. Electricians have little choice, since they are generally obliged to document results of their tests, whether or not the truly believe that there would be any significant safety risks if they didn't undertake them all.

Kind Regards, John.

A well considered answer.

 

[ban-all-sheds]

Polarity, continuity and absence of shorts (eg N nicked when screwing the plate to a back box) are easy to confirm with basic tests so lets assume they're correct. (Though I appreciate not all diy-ers check first.) Then as you suggest, parametric testing is probably only useful for finding pre-existing faults. So if a circuit is added and tests to BS7671 are not done on that circuit, essentially the question is - so what? (So long as a faulty circuit is not extended into a controlled zone.)

A "so what" example is that you might have added a socket where the loop resistance is too high, or the RCD isn't working properly.

The existing faults were not your responsibility, but adding a socket which is not safe was.

 

[acmedone]

Polarity, continuity and absence of shorts (eg N nicked when screwing the plate to a back box) are easy to confirm with basic tests so lets assume they're correct. (Though I appreciate not all diy-ers check first.) Then as you suggest, parametric testing is probably only useful for finding pre-existing faults. So if a circuit is added and tests to BS7671 are not done on that circuit, essentially the question is - so what? (So long as a faulty circuit is not extended into a controlled zone.)

A "so what" example is that you might have added a socket where the loop resistance is too high, or the RCD isn't working properly.

This comes under the second part of my original question.

 

[ban-all-sheds]

That makes no sense whatsoever - Part P applies to all work, no matter where it is, on fixed electrical cables or fixed electrical equipment located on the consumer’s side of the electricity supply meter which operate at low or extra-low voltage and are—
(a) in or attached to a dwelling;
(b) in the common parts of a building serving one or more dwellings, but excluding power supplies to lifts;
(c) in a building that receives its electricity from a source located within or shared with a dwelling; or
(d) in a garden or in or on land associated with a building where the electricity is from a source located within or shared with a dwelling.

 

[JohnW2]

A "so what" example is that you might have added a socket where the loop resistance is too high, or the RCD isn't working properly. The existing faults were not your responsibility, but adding a socket which is not safe was.

An analogy I often think of is taking my car to a service station to have its (very worn and potentially dangerous) brake pads replaced. They replace the pads, maybe do a simple functional test to confirm that the braking system functions as required, and then return the vehicle to me.

It could be that the braking sytem as a whole is in a dangerous state - leaking or worn pipes or hoses, master cylinder about to give up or whatever, but I don't think that I (or any rules) would expect them to do any inspection/testing of the braking system as a whole (unless I had specifically commissioned them to do so) in the course of just replacing the pads.

Kind Regards, John.

 

[acmedone]

However, as we all know, the regs (and hence, by implication, probably the law) do require 'full testing' of any circuit that has been worked on

This almost suggests that if we blindly adhere to rules, a retest should be done even after doing something simple like releasing a faceplate for wallpapering.

 

[ban-all-sheds]

I don't think that I (or any rules) would expect them to do any inspection/testing of the braking system as a whole (unless I had specifically commissioned them to do so) in the course of just replacing the pads.

What if the law said that they had to make provision to ensure that anybody using the brake pads was protected from injury?

 

[acmedone]

That makes no sense whatsoever -

Difficult to know who/what you are replying to. What you say might be relevant to something I said later on but not to the "second part of my original question" which was

If there is a problem not found with simple tools (lets imagine a loop impedance too high for a short to be detected by breakers), how often does it actually happen? How many RCDs come with parametric failures straight from the box (as distinct from obviously broken)? etc

 

[stillp]

I don't think that I (or any rules) would expect them to do any inspection/testing of the braking system as a whole (unless I had specifically commissioned them to do so) in the course of just replacing the pads.
quote]
Bad analogy John! They have a general duty of care, and would at least be expected to point out any visible defects to you and advise to to have them corrected. At least one major fast-fit workshop does have a policy of carrying out an inspection and check after fitting new brake pads, and I would expect the others to, as a matter of course.

 

[JohnW2]

However, as we all know, the regs (and hence, by implication, probably the law) do require 'full testing' of any circuit that has been worked on

This almost suggests that if we blindly adhere to rules, a retest should be done even after doing something simple like releasing a faceplate for wallpapering.

Indeed - one could argue that a literal interpretation of the regs would require that. This may not be all that good an example, since people have been known to do damage (which might not be apparent without 'sophisticated' tests) in the manner you describe, but there clearly is a need to apply some common sense and pragmatism in interpreting the regs. However, adding a socket and not doing any testing probably goes beyond 'interpretation', since the regs clearly require the testing, so one would be deciding to ignore clear regs, rather than just 'interpreting' them.

Kind Regards, John.

 

[JohnW2]

Bad analogy Jihn! They have a general duty of care, and would at least be expected to point out any visible defects to you and advise to to have them corrected.

That I do not doubt, and makes total sense - if they become aware of such defects, they clearly should advise the owner. However, do they have any duty to actually look for any such defects?

If your answer is 'yes', then how far do you think this goes? If they were doing work on the steering system, or the engine, would you say that they had a duty to look for, and report, defects in the braking system? It sounds as if you are suggesting that they have a duty to carry out a full inspection of the vehicle whenever they do anything to it!

Kind Regards, John

 

[JohnW2]

I don't think that I (or any rules) would expect them to do any inspection/testing of the braking system as a whole (unless I had specifically commissioned them to do so) in the course of just replacing the pads.

What if the law said that they had to make provision to ensure that anybody using the brake pads was protected from injury?

As I've just implied in my response to stillp, there's no end to that. Anyone 'using the brakepads' is also reliant for their safety on correct functioning of steering, seatbelts and goodness knows what else. Does the person replacing brakepads really have to inspect and/or test everything else relevant to safety on the vehicle?

Kind Regards, John.