When should an RCD be fitted or not?

[Risteard]

As I write this I have a nagging feeling that these sorts of problems are going to be addressed, possibly, in AMD1? What are the proposals in the DPC?

Three codes for Periodic Inspection and Testing (proposed to be recorded on an "Electrical Installation Condition Report"). I believe the proposal is for three codes (C1, C2 and C3) but would need to check DPC for exact nature of the proposed codings.

 

[ericmark]

BAS has again touched on a very valid point. If I was to have buried cables less than 50mm in my house without RCD protection would it still comply with BS7671:2008? As the installation is intended to be under the supervision of a skilled or instructed person then we don't need an RCD. So our houses don't need to comply with the same rules as houses for Joe public.

 

[ban-all-sheds]

And for that reason I would have no qualms about signing an EIC for work in my house where I had not provided RCD protection re 522.6.7.

But I think a good case can be made for the same situation with Joe Public.

Skilled person. A person with technical knowledge or sufficient experience to enable him/her to avoid dangers which electricity may create.

Instructed person. A person adequately advised or supervised by skilled persons to enable him/her to avoid dangers which electricity may create.

("advised" is important here.)

Now, clearly it would be nonsensical for the knowledge or experience needed to avoid dangers to be context free. This site is full of regulars who are genuinely and unarguably sufficiently knowledgeable and experienced to avoid dangers which low voltage electricity may create, but are nowhere near knowledgeable or experienced enough to work on HV systems, or even carry out live jointing of LV cables. Or if they only work on dry land don't know about things which can bite you on boats.

So as we have to consider context, what is the context of the danger which 522.6.7 seeks to ameliorate? Hard to see, given that it refers to 522.6.6(v), that it is anything other than the danger of penetrating cables because you're ignorant of the existence of the so-called safe zones, such ignorance being the reason that so many people have traditionally questioned the safety of those zones.

So if you make people aware of the existence of the zones, are they then not sufficiently advised to enable them to avoid dangers from penetrating cables buried in the zones, and therefore in the context of 522.6.7 are they not Instructed persons?

 

[Risteard]

BAS has again touched on a very valid point. If I was to have buried cables less than 50mm in my house without RCD protection would it still comply with BS7671:2008? As the installation is intended to be under the supervision of a skilled or instructed person then we don't need an RCD. So our houses don't need to comply with the same rules as houses for Joe public.

No, because it is made perfectly clear that no domestic premises can ever be considered to be under the supervision of skilled or instructed persons. That cannot be applied to a domestic installation ever.

 

[ban-all-sheds]

No, because it is made perfectly clear that no domestic premises can ever be considered to be under the supervision of skilled or instructed persons.

Where?

And how can that be made perfectly clear when some domestic premises really are under the supervision of a skilled or instructed person?

That cannot be applied to a domestic installation ever.

Read my post above again, and consider the context of ONLY 522.6.7.

 

[STI]

As I write this I have a nagging feeling that these sorts of problems are going to be addressed, possibly, in AMD1? What are the proposals in the DPC?

Three codes for Periodic Inspection and Testing (proposed to be recorded on an "Electrical Installation Condition Report"). I believe the proposal is for three codes (C1, C2 and C3) but would need to check DPC for exact nature of the proposed codings.

Your correct and a C1 or C2 on the new system get the overall report outcome as an unsatisfactory. Which is why i question the need for C1 and C2 they both (will) have the same end result.

 

[STI]

I feel most electricians will know how to inspect and test and how to write a technical report on what they have found.

All the time we see electricians here who can barely string two words together and remain coherent.

In some cases near opposite meanings as with "Decimate" which comes from the Latin and days of Roman's meaning to kill one in ten. Hence "Deci" meaning ten. However many now consider it to mean to get rid of nearly everything.

But those people are wrong.

Words like "need" and "dangerous" seem to mean different things to different people and really they need qualifying i.e. "Danger of electrocution" which of course is very different to "Danger of getting a shock".

Unless you go with the (utterly and disgustingly appalling) decision of the Oxford dictionary, of all institutions, to dumb themselves down to the level of the semi-literate idiots who think that "electrocution" means a non-fatal electric shock.

And so if the item is safe unless there is some one armed with tools I would say it's satisfactory.

And there's another oft-misunderstood word. How many people, when told that their performance or creations were "satisfactory" feel that they have been criticised? (As an aside, "adequate" is another such word).

Code 2 Would benefit from improvement but not dangerous. Satisfactory classification

May or may not be satisfactory (inspector's judgement required) I believe would be more appropriate.

The only problem then is it becomes subjective again. My definitions are trying to position it so that if it requires improvement to the extent it would cause an unsatisfactory classification it should actually be thought of as dangerous and therefore a code 1

But "satisfactory" is subjective.

2 people might take the same second hand car for a test drive, over the same roads etc, and one might consider it a satisfactory vehicle, the other not - it depends on what their minimum acceptable standards are for performance, comfort, NVH etc.

Or I might stop for fish, chips & mushy peas on the way home, and regard it as a satisfactory meal. If I got the exact same food in a Michelin starred restaurant I would judge it to be far from satisfactory.

Agreed so perhaps a simple pass or fail . Along with the notes. So to say i dont like your fish chips mushy peas is not good enough. I dont like your fish chips mushy peas because the chips have not been deep fried enoughand arent cooked therefore i am very likely to get food poisoning a fail.

Your fish and chips mushy peas were cooked but could benefit from being cooked for a further 2 mins and put on a plate rather than in a newspaper not a fail

Code 1 DANGEROUS Fail
Code 2 not dangerous but would benefit from improvement not a fail
Code 3 Needs further investigation could still be either a pass or fail.

 

[Risteard]

Where?

And how can that be made perfectly clear when some domestic premises really are under the supervision of a skilled or instructed person?

411.3.3 (a)

Ordinary persons can come into a domestic premises at any time. Are they suitably supervised by a Skilled person to make them an Instructed person upon entry? No, they are not.

 

[ban-all-sheds]

411.3.3 (a)

1) That dos not make it clear that perfectly clear that no domestic premises can ever be considered to be under the supervision of skilled or instructed persons.

2) 411.3.3 (a) is not 522.6.7.

Ordinary persons can come into a domestic premises at any time. Are they suitably supervised by a Skilled person to make them an Instructed person upon entry? No, they are not.

Would you expect the installation in a hospital, or a restaurant, or a theatre, or a shop, or an office or... or... or... to be under the supervision of skilled or instructed persons?

 

[Risteard]

And then 3.6.1 (b) of the On-Site Guide (which is obviously not strictly speaking part of the Regulations but a way of complying with them in simple installations).

 

[ban-all-sheds]

That's twice you've tried that...

3.6.1 (b) of the On-Site Guide is referring to 411.3.3

411.3.3 is not 522.6.7.

Ordinary persons can come into a domestic premises at any time. Are they suitably supervised by a Skilled person to make them an Instructed person upon entry? No, they are not.

Would you expect the installation in a hospital, or a restaurant, or a theatre, or a shop, or an office or... or... or... to be under the supervision of skilled or instructed persons?

 

[Spark123]

Would you expect the installation in a hospital, or a restaurant, or a theatre, or a shop, or an office or... or... or... to be under the supervision of skilled or instructed persons?

Hospital Yes
Restaurant No
Theatre Possibly depending on circumstances
Shop No
Office No