Wiring in 17th C Timber Framed house

[Zebra]

Oh yes I don't disagree. But rules is rules, and some of them sometimes lead to daft situations. For example any new cables buried in a wall having to have RCD protection irrespective of whether the rest of the house does. But I'm sure some very clever people sat down for a very long time writing that big book of Regulations, and they had to draw the line somewhere. It would probably be impossible to write a book of regulations which catered for every possible situation.
Ours is not to question why!
I've drilled into cables myself even when they're in the safe zone. But if they said "It can go wherever you like so long as it's got RCD protection" then you'd have a right mess, with people drilling into cables all over the place, and having to have all the plaster dug out to make a repair!
You can do a deviation if you reckon it's safe, but if you're signing it off with a certificate you'd just be liable if anything went wrong! Whereas if you go by the book you're on safe ground!

 

[agbagb]

Well I just drilled into a cable yesterday, luckly a dead one. I'm sure what I do now will be much safer than whatever the old wiring was even if I do need some "deviations" from the standards, fully recorded and referanced on the certificate.
I'll be sticking as close as I can to the standards, but the option of deviations does give some flexibility that could help practicalities and aesthetics. On the vertical run down from the attic to the first floor, chased in to a wall, I'll be putting an 'unnecessary' socket so it will comply. But where I'm running across a ceiling in the small gap between plaster board and floor boards to a rose, it would have to be recorded as a deviation (I think?).

Just another thought. Someone should invent a small embossed plaque that could be fixed to the wall or whatever, with a recognised symbol to indicate a hidded cable and its direction. This would be able to the job of an outlet or switch as the indicator so the normal rules on avoidance can be followed. If it's not been invented, don't tell anyone and I'll get on to the patents office.

 

[Penners]

The now prefered radial instead of rings make things a bit easier. As many sockets as I like off one 2.5mm t&E of a 20amp breaker

Is that really the case? You can now run one radial supply in 2.5mm TW&E from a 20A breaker and put as many sockets on it as you like?

 

[agbagb]

Yes - Final Circuit Arrangements, Regulation 433.1

(With an RCD and 20A overcurrent protective device "note: As a rule of thumb, the floor area served has been limited to 50m2"
and - Cable fixed in position not covered by thermal insulation, it it is ref 523.6.6)

You can have an unfused spur off the radial as well in 2.5, As long as the total likely load is less than 20A it doesn't matter how many tellys, computers, lamps, Hi-fi are potentially pluged in.

If on 4mm2 with 30 or 32A breaker the rule of thumb note is to 75m2. An unfused spur on 2.5mm off this can only go to max, one double socket.

I've been told radials are now prefered over rings as its tricky to test rings for continuity. If a ring is broken in effect you get two radials on 2.5mm2 on a 30 fuse/breaker.

 

[tobydog]

:shock: I thought I had stumbled across a website in a foreign language there was should be a union jack you press to convert it back to English!!

I'm glad you guys know this stuff. Sorry - please carry on.

 

[Penners]

Yes - Final Circuit Arrangements, Regulation 433.1

(With an RCD and 20A overcurrent protective device "note: As a rule of thumb, the floor area served has been limited to 50m2"
and - Cable fixed in position not covered by thermal insulation, it it is ref 523.6.6)

You can have an unfused spur off the radial as well in 2.5, As long as the total likely load is less than 20A it doesn't matter how many tellys, computers, lamps, Hi-fi are potentially pluged in.

If on 4mm2 with 30 or 32A breaker the rule of thumb note is to 75m2. An unfused spur on 2.5mm off this can only go to max, one double socket.

I've been told radials are now prefered over rings as its tricky to test rings for continuity. If a ring is broken in effect you get two radials on 2.5mm2 on a 30 fuse/breaker.

That's very useful to know agbagb. Thank you. (Not that I shall ever do my own electrical installation. Goodness no! )

 

[worms]

The now preferred radial instead of rings...

Does this mean that my 60-year-old wiring is coming back into fashion? :shock:

 

[Penners]

Take it from one who knows - nothing that's over 60 years old ever comes back into fashion.

Just ask my children.

 

[Flyfisher]

I've been told radials are now prefered over rings as its tricky to test rings for continuity. If a ring is broken in effect you get two radials on 2.5mm2 on a 30 fuse/breaker.

That makes sense to me. These days, outside of the kitchen/utility room/workshop, high-wattage appliances are pretty rare so I can quite understand that a 20A supply is just as practical as a 30A one.

As for the number of sockets, I never seem to have enough and have loads of multi-way socket strips around the house. I think my record is something like 22 outlets into a single 13A wall outlet - effectively a radial circuit ion a 13A fuse.

As for ring circuits being tricky to test, I may have once mentioned a faulty socket in a previous house that I needed to change. No problem, just remove the appropriate fuse in the consumer unit and do the deed. Except than none of the fuses would isolate the socket in question. Switching off the entire CU did isolate the socket so it had to be wired to it somehow. So I removed ALL the fuses and switched the CU back on. The socket was still dead so I replaced the fuses one at a time and discovered that the socket was fed by two fuses!

A little further investigation revealed that the socket had been installed by connecting across two rings. Effectively, the entire house was one big ring with a 60A fuse. It's times like that make wiring regulations and 'competent persons' seem like a sensible idea.

 

[Penners]

As for the number of sockets, I never seem to have enough

It's one of the immutable laws of the universe that (a) no matter how many sockets you install, it will never be enough, and (b) no matter how carefully you plan their location, at least one of them will always be behind the chest-of-drawers.

 

[Lime]

It's times like that make wiring regulations and 'competent persons' seem like a sensible idea.

It has always been a sensible idea.
The problem is in its implementation.
Regulations do not make people competent nor do short courses that confer "competence" on those that attend them.
The IEEE regulations have existed for 100 years yet mistakes, bad workmanship and dishonesty is still common.
Many people who have expensive kitchens and bathrooms fitted give no thought to who installs the electrical circuits… and they don’t want to pay for it.
According to many on the IET Wiring and Regulations forum the kitchen and bathroom fitter is THE main culprit for creating dangerous electrical situations.
Since most householders make decisions on price it is hardly surprising that electrical work is often skimped and not tested correctly and that cowboys in all their forms are encouraged.

 

[Zebra]

On the vertical run down from the attic to the first floor, chased in to a wall, I'll be putting an 'unnecessary' socket so it will comply.

Good idea!

But where I'm running across a ceiling in the small gap between plaster board and floor boards to a rose, it would have to be recorded as a deviation (I think?).

Yes, come to think of it, technically it would be. Although there are no zones in ceilings or floors where cables should be run as there are in walls, nevertheless cables buried in a ceiling or floor should be 50mm from the surface of ceiling or floor (to prevent penetration of nails etc). Thanks for reminding me, I shall have to note the same thing as a deviation, because I've done exactly as you have, run a load of cables in a gap between ceiling and floor which is about 30mm deep.

 

[MdB]

Thanks for reminding me, I shall have to note the same thing as a deviation, because I've done exactly as you have, run a load of cables in a gap between ceiling and floor which is about 30mm deep.

Aren't you ok if you have used an RCD/RCBO?

 

[Zebra]

Whether you've used an RCD/RCBO or not, you still have to comply with all the rest of the big book of Regs, or note it down as a deviation if you haven't. RCD/RCBO protection actually isn't required for cables concealed in a ceiling/floor, only for those chased into a wall. Strangely. It may not always make sense, but there it is......

 

[MdB]

Whether you've used an RCD/RCBO or not, you still have to comply with all the rest of the big book of Regs, or note it down as a deviation if you haven't.

That's my point. Doesn't the big book say that the wires in walls have to be buried 50mm OR the circuit has to have an RCD/RCBO? I don't have a copy here to look it up but that was (my possibly wrong) understanding.

RCD/RCBO protection actually isn't required for cables concealed in a ceiling/floor, only for those chased into a wall. Strangely. It may not always make sense, but there it is......

Interesting, I wasn't aware of that.

 

[Zebra]

Whether you've used an RCD/RCBO or not, you still have to comply with all the rest of the big book of Regs, or note it down as a deviation if you haven't.

That's my point. Doesn't the big book say that the wires in walls have to be buried 50mm OR the circuit has to have an RCD/RCBO? I don't have a copy here to look it up but that was (my possibly wrong) understanding.

Yes, I see what you mean. However, there's a difference between ceilings/floors and walls.
Yes, cables in walls have to be buried 50mm OR have RCD/RCBO.
Cables in ceilings/floors have to be 50mm from top or bottom (or have earthed armouring or mechanical protection) irrespective of RCD/RCBO. There is no requirement for RCD/RCBO on cables under a floor or above a ceiling.
So if my gap between ceiling and floor isn't 50mm deep, then the rule I reckoned I was deviating from was the one about the depth, irrespective of whether I have RCD/RCBO protection.

However, upon a closer inspection of the On Site Guide, what it says is that where a cable passses through a joist or ceilings support it must be 50mm from the top or bottom as appropriate, to avoid risk of damage from someone sticking a nail/screw into the joist from above or below. If I'm running cables in the void but not passing them through any joists, perhaps I'm not deviating after all.

 

[MdB]

Thanks - that ties up with what I thought (and what I've done...)

 

[Penners]

I know what an RCD is. What's an RCBO?

 

[LadyArowana]

I know what an RCD is. What's an RCBO?

An ASBO for wayward electricians?

 

[Lime]

An RCD effectivly monitors residual current leaking to earth, an RCBO does that and also act as an ordinary circuit breaker (like a fuse) too.