electrical work - distinguishing old work

[sm_jamieson]

When doing domestic electrical installation, you are often working alongside old work. Since there is no requirement to bring old up to new standards (apart from things affecting the whole installation like earthing etc), how do you make clear to an inspector what is the new work, and what is old and may not be up to latest regs ? Case in point:

1. I have some old electrical wiring passing through the kitchen ceiling (only lighting as it happens) which may not pass the de-rating requirements (grouping, near a central heating pipe). It is for circuits I will not be touching, so I need not change them. But new circuits will be alongside which will obviously be up to the 17th edition.
2. I have some holes in joists outside the 0.25 to 0.4 zone. It would be silly not to re-use them, but the building inspector could complain (not strictly electrical here) if they have new circuits installed using them.

One other question: Regarding ambient temperature. I have central heating pipes (high temp, non-condensing setup) in a ceiling, overall ceiling void basically covering the whole house (support under the joists in places). At present not lagged. I could lag it to some extent. How would I calculate the ambient temperature in various parts of the ceiling void in order to work out the de-rating factor ? (Short of building in a probe and closing up the ceiling to test). It is very common to have heating and wiring taking similar routes around a house !

Thanks, Simon.

[Jim K]

can't help thinking you;re over worrying on all this BCO stuff?

if not "new build" a lot of the onerous nonsense is inapplicable/ "common sense" prevails.....

"what exists already exists" (full stop)

if the BCO says you are lying - kindly ask him to prove it!

from the mouth of my BCO "I understand that you have to work with what you've got"

talk to them!?

Cheers Jim K

[js.b1]

1 - MEB etc must be present & correct before any modification made 2 - Existing install should be safe re ESQW 3 - If you extend a circuit without CPC, you need to a) replace the cable back to the CU with FTE or b) run a 4mm 6491X back to the CU 4 - If you extend a circuit without RCD protection you a) protect the extended part by RCD or b) add RCD closer to the CU which is arguably a much better solution (surface mount RCD SFCU or surface mount 20A RCD Clipsal, Crabtree, etc)

The new circuits must comply. Realise in domestic there is more leeway than the regs suggest - in terms of diversity of circuits. You may have 8x 32A 4mm radials in a house, but with a 60A or 80A fuse etc you are only going to saturate

2-3 of them!! This argument is quite valid otherwise you could end up with everything in 10mm FTE by the OSG grouping & insulation & temp regs.

Interesting one... If the holes are pre-existing then fine. If the holes are 8-11-14mm incidentally it does not matter anyway (ie,

1 cable holes). If the holes are LESS than 50mm from edge then you DO have a problem re floorboard nails.

The point about the hole regs is for whacking great big holes and notches in joists. They are quite immaterial for a 10mm hole for a single cable re alarm or light fitting.

You need to ensure SELV are segregated or insulated for the higher voltage present (LV).

You ignore it unless cables are very close due to the void size. Temp is assumed to be 30oC, I bet the void does not get to that :-)

I would however lag the pipe - Armaflex is good, can be cheap online.

[John Whitworth]

Couldn't agree more. I worried myself stupid over many aspects of the garage conversion, but in reality, the BCO came round, and far from making my life difficult, I explained what was worrying me, and he made superb suggestions that not only saved me time and money, but met his standards too.

JW

[js.b1]

Through a kitchen, have you considered sticking a telephone point in? Reason being adding a "BT socket" is notifiable in a kitchen, or RJ45 etc.

I actually think all kitchens could do with a wireless video camera which on detecting fire automatically switches the TV over - "hey, that looks just like our kitchen, bit too much fog machine tho". I suspect a fair number of kitchen fires are people forgetting about food whilst watching TV - or chucking a towel onto a once hot older electric hob without "still hot" lights.

[dennis]

Too right, I had to remove an somewhat confused old lady from her flat on Wednesday as there was smoke pouring from the windows.. turns out she left an individual fruit pie in the microwave for some unknown time. Some people have no concept of a timer on a microwave and what its for. When I went back to work they all said I smelled of toffee.

[sm_jamieson]

buildings regs for a phone socket. You do make me laugh ...;-0 Simon.

[sm_jamieson]

Only on the electricals ! My direct BCO contact has been quite genial and relaxed. Simon.

[Jim K]

so what's he said about sparks that's got you cr/flappin?

Cheers Jim K

[ARWadsworth]

It would be madness not to use the existing holes. I cannot see the BCO objecting but this really is a case of asking him before you start.

Unless the pipes and cables are very close then I would not worry.

Cheers

Adam

[sm_jamieson]

Main Earth Bonding ? Yep.

What is ESQW ?

Yep fair enough. If I was modifying an existing circuit it must be brought up to 17th. I will be introducing only new circuits.

Holes are 25mm, but none less than 50mm from edge.

I guess this would relate to 12v halogen and mains wiring, keep the separate ?

Pipes in notch on top of joist. Cables in hole about 30mm below the pipes. I'll lag as well as I can without moving the pipes.

Cheers, Simon.

[ARWadsworth]

I guess this would relate to 12v halogen and mains wiring, keep the separate ?

Not always. The segregation is there to stop alarm cables and door bell wires running in the same holes as the 230v cables. However if the alarm cable was rated at

230v then you could run them alongside the 230v cables.

Cheers

Adam

[sm_jamieson]

You can easily tell an old hole from a freshly drilled one, I don't think I'd bother asking the BCO about that unless he was here anyway ;-)

Some of the holes were from the old lead water pipes that snaked through the house. It must have been nice installing those. Just bend them by hand when you need to !

Thanks, Simon.

[Matty F]

I have a TV in the kitchen. In fact I have TVs everywhere. Are seven TVs excessive? :)

[sm_jamieson]

I think its a good idea. You are much more likely to do the washing up ! Simon.

[Frank Erskine]

One TV is excessive.

I don't have a telly at all.

[The Natural Philosopher]

I've got 6 TVS and a TV tuner card for the computer.

Nice to have radio 2 on with no bandwidth costs. Even if it is Dale Winton, the saccharine pooftah.

[js.b1]

I know, they were after Broadband (Q?) too at the time.

BT could have long ago required all telephone cabling sold "for connection to their network shall be insulated to 300/500V". Instead BT are more interested in pushing battery powered telephones & =A3140 callout repair fees.

[Steve Walker]

It could relate to a number of things. We have 12V signal cables from individual room timer/stats in every room to operate our central heating

- specifically done so that exposed cable runs (up the side of doorframes, as we didn't want to decorate the whole house) would be safe if the kids damaged them.

It also means we can have one in the bathroom and, despite what others have said in the past, it has worked for nearly seven years now, regardless of the atmosphere in a bathroom.

I've mainly lagged the pipes anyway, as it stops heat escaping into rooms that don't need it with our individual room system, but in a few hard to access places where pipes are too close, I've rated the cables for running through insulation and put pipe insulation on the cables instead!

SteveW

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[<me9]

If it is lighting and the pipe is lagged then it is unlikely to be out of spec. If adjacent to an unlagged pipe I would certainly do something (like lagging the pipe where close).