Help with Regs

[hightower]

Generic title as since I'm going through the book I might have more than one question (which I have so far).

So, first question. Can somebody explain

559.5.1:

At each fixed lighting point one of the following shall be used for the termination of the wiring system:

(i)...
(ii)...
(iii)...
(iv)...
(v) A suitable socket outlet to BS 1363-2, BS 546 or BS EN 60309-2

And why you might install a BS 1363-2 at a lighting point - I think BS 546 is the 2amp socket that will be installed in a pub window or something, but when would you use a BS 1363-2?

Thanks,

 

[Leesparkykent]

Some times high bay lighting gets done like this.

 

[Richard Burns]

It is a simple, cheap and convenient means of isolating a part of a circuit (and fusing it down as well), generally more useful on large lighting circuits with limited accessibility.

 

[happysteve]

Perhaps where the fixed lighting circuit doesn't change, but the lights might. Think: exhibitions in galleries, where each different art installation might want different lanterns.

 

[i=p/u]

we used comando sockets in a morrisons store for some of the lighting.

also have used a light switch to control a socket led strip

 

[hightower]

433.3.1 (i)

"A device for protection against overload need not be provided: for a conductor situated on the load side of the point where a reduction occurs in the value of current carrying capacity, where the conductor is effectively protected against overload by a protective device installed on the supply side of that point"

Just trying to grasp how IET word things still, is this the regulation that permits me to wire the first half of a lighting circuit in 2.5mm and the second half of the circuit in 1.5mm so long as the protective device (for example the MCB at the CU) is rated for the 1.5mm cable (so let's say a 6A MCB).

Am I getting the hang of this, or have a just made up a load of bull? Not wiring anything like this, just trying to translate to a scenario where it would be used.

 

[telectrix]

433.3.1 (i)

"A device for protection against overload need not be provided: for a conductor situated on the load side of the point where a reduction occurs in the value of current carrying capacity, where the conductor is effectively protected against overload by a protective device installed on the supply side of that point"

Just trying to grasp how IET word things still, is this the regulation that permits me to wire the first half of a lighting circuit in 2.5mm and the second half of the circuit in 1.5mm so long as the protective device (for example the MCB at the CU) is rated for the 1.5mm cable (so let's say a 6A MCB).

Am I getting the hang of this, or have a just made up a load of bull? Not wiring anything like this, just trying to translate to a scenario where it would be used.

you are correct.

 

[hightower]

Thanks Tel. Another one, 542.2.6:

"A metallic pipe for gases or flammable liquids shall not be used as an earth electrode. The metallic pipe of a water utility supply shall not be used as an earth electrode. Other metallic water supply pipework shall not be used as an earth electrode unless precautions are taken against its removal and it has been considered for such a use."

I'm thinking of a house I came across a while back that had an outhouse with water pipes in it, which were fed from the house (so privately owned I would assume). It also had an electrical supply provided by the house but without an earth supplied - instead, the earth was wired up to the metal water pipe in the outhouse. Does this regulation mean that the water pipe was perfectly viable as an earth electrode? I'd guess it's not considered great practice, but so long as it all tests okay it should be good to use?

The electrician I was with opted to put a separate earth rod in, which I guess would be the desired way to do it, but was it strictly necessary?

 

[telectrix]

the problem here would be if that water pipe was removed or replaced with plastic.

 

[Bobster]

A family farm of mine is using the old bore hole piping as an earth rod.

1/2mile of buried pipe will be better than a normal earth rod.

 

[hightower]

the problem here would be if that water pipe was removed or replaced with plastic.

I read that as "yep, by the rule of the BYB it's permissible" (although possibly leaving yourself open to repercussions) but you also lead on to my next question:

"unless precautions are taken against its removal"

So what would be an appropriate precaution in the eyes of the BYB? A sign? Something documented in the (what will inevitably be lost by the tennant) electrical certs?

 

[telectrix]

since when would a wet-pants read an electrical cert? your mate did the right thing by banging in a rod. with a bit of luck it might give an acceptable RA.

 

[Bobster]

Another reason, most people don't own the service pipes coming into their house, so they have no control over alterations.

It may well be a plastic joint added out on the road that reduces a perfectly good Ra to something not suitable.

 

[hightower]

since when would a wet-pants read an electrical cert? your mate did the right thing by banging in a rod. with a bit of luck it might give an acceptable RA.

I understand this Tel, and agree with his actions. Just trying to fathom the point of the regulation if most would say to stick a rod in instead - is this a regulation designed for a VERY specific use?

 

[telectrix]

more a case of ensuring electrical safety if existing "unsatisfactory" means of earthing is removed.

 

[hightower]

Another reason, most people don't own the service pipes coming into their house, so they have no control over alterations.

It may well be a plastic joint added out on the road that reduces a perfectly good Ra to something not suitable.

But in the scenario I posted the pipes to the outbuilding aren't from the supply directly, although I see what you are saying: if these 'private pipes' connect to the supply pipe the Ra would be measured from the full lot (private + supply). Then if the supply put plastic in somewhere (which doesn't directly affect the private pipes) the Ra is going to be reduced, and even though the private pipes are not affected directly (as in have been dug up), the Ra could be unsuitable because it was relying on the conductance of the supply pipe?

 

[Bobster]

Bingo.

 

[telectrix]

But in the scenario I posted the pipes to the outbuilding aren't from the supply directly, although I see what you are saying: if these 'private pipes' connect to the supply pipe the Ra would be measured from the full lot (private + supply). Then if the supply put plastic in somewhere (which doesn't directly affect the private pipes) the Ra is going to be reduced, and even though the private pipes are not affected directly (as in have been dug up), the Ra could be unsuitable because it was relying on the conductance of the supply pipe?

the Ra would increase.

 

[hightower]

the Ra would increase.

Yeah sorry

 

[davesparks]

I understand this Tel, and agree with his actions. Just trying to fathom the point of the regulation if most would say to stick a rod in instead - is this a regulation designed for a VERY specific use?

Don't forget the regulations cover all installations, not just domestic. So an industrial site with a lot of underground pipework and an in-house engineering team looking after things could use all that buried metal.

 

[hightower]

Thanks dave, was thinking on the way home whether this was aimed for sites with skilled people on site constantly and where they would have and keep paperwork showing the earth paths