Unused cables left in ok? Smoke alarms?

[bureaucrazy]

1) Are there any regulations concerning electrical cables that have been installed in a domestic house that are running under the floorboards or buried inside wall chases that are not connected to anything? For example, if you move a socket and run new cable to it as per bs7671 can you just disconnect the old cable at both ends and leave it in the wall or do you have to destroy the plaster removing it? If you can leave it in, must you do anything else to make it "safe", e.g. connect all conductors to earth or choc bloc each end?

2) I wish to install some smoke alarms as per BS5839 pt 6 grade D LD3 so the house can be used for single occupancy with an alarm in the hallway and one upstairs on the landing. Later I may wish to rent rooms out as bedsits and will require a heat alarm in the kitchen and smoke alarms in every room as per LACORS guidance (grade D LD1). Would I be in breach of any regulations if I were to run all the cable for the complete LD1 system but only intall two alarms in the escape route leaving the rest of the wires unused? (The reason for putting the wires in now is that the house is empty and undergoing refurbishment. It will be very difficult to run more cables after the house is finished and there is furniture and people in the way).

Thanks

 

[bureaucrazy]

Connecting Smoke alarms with 2core+E?

I need to connect grade D smoke alarms. The connections are Live neutral and Interconnect. Is it a breach of any regulations to use 2 Twin and earth cables instead of having to buy 3 core + E? I plan to use the live and Neutral of 1 Cable to connect the live and neutral between each alarm and the Black conductor of the second cable for the interconnect. The rest of the conductors all connected to earth. Should I use sleeving or labelling? I know it's not elegant but does it break any rules of BS7671 or BS5839?

 

[patricklondon]

dont wish to offend but there are a few clues in your two pretty identicle posts on this matter that suggest you are not an electrician but a diyer (if fairly competant). if i am right and this is the case then all of the electrical installation needs to be fully tested and certificated and local authority building control notified of the works before commencing and on completion. if a part p registered electrician is not used then labc will send out one of there own at further costs. not doing this can cause mistakes that can be fatal.

 

[patricklondon]

Re: Connecting Smoke alarms with 2core+E?

as above

 

[mechelec]

Any works other than "minor" works will not be connected to the electricity supply by me but will be inspected tested and connected when the new consumer unit is installed by a part P registered electrician. I want to make sure that the wiring standard is acceptable so he doesn't rip it all out.

How have you got an electrician to sign off your work, it is not allowed although I know it does happen,what about the guys who are doing it properly and trying to make an honest living out of it, it makes a farce of the whole part P situation

 

[bureaucrazy]

Re: Connecting Smoke alarms with 2core+E?

I just checked BS7671 and found section 521.8.1:

"Each part of a circuit should be arranged such that the conductors are not distributed over different multicore cables, etc...

This requirement need not be met where a number of multicore cables are installed in parallel.
Where multicore cables are installed in parallel each cable shall contain one conductor of each line."

OK I've worked out what that bit means now. Both cables must have the same connections at each end.

So the question is, with the smoke alarms in question, the LV power 240v will be a circuit powering the smoke alarms. The other cable carries only a 9V interconect signal. Can the Interconnect ELV signal be considered a seperate circuit from the smoke alarm power circuit or is the definition of circuit encompassing all connections between each alarm unit as one circuit?

If they can be called seperate circuits, then I am allowed to use 2 multicore cables. If they called are one circuit, then it is not permitted.

So which is it?

(N.B. The twin and earth cable I'm using has an earthed metal screen and sufficent insulation for LV)

 

[SirKit Breaker]

I dont think there is a difinitive answer. However when rewiring i remove all the cables which i can possibly get at without causing undue damage to the property.

I do this for several reasons

1, i know that all the cables i am installing are new and wont get accidentally cut.
2, if joist are drilled i can reuse the holes.
3, i can reuse chases in walls as required.
4, i know that if a cable does get damaged accidentally no one will get hurt as it isnt energised.

This is what i do.

Disconnect supply from CU, remove CU and fit new one inc bonding. Connect a 4 way extension lead to my homemade set up with Isolator, RCD, socket and light.

Day1

Remove all old cabling.
Install lighting circuits to all floors, test and energise, this makes life a bit easier at this time of year.
1st fix smoke alarms.
1st fix any fused spurs upstairs
Dont need sockets on day one as homemade thingy is OK for kettles/drills/Radio and any fridges or freezers.

Day2

Install sockets upstairs whilst plasterer does his magic downstairs
Install sockets downstairs sockets whilst plasterer does upstairs.
Install any other bits and pieces
Clean and tidy up whilst plasterer does downstairs socket etc.

Day3

second fix and test everything.
Final clean and tidy up and plasterer snagging if required. usually a few deep chases to skim after yesterdays bonding or whatever.
Carpet fitter in if required.
Cleaners in mid afternoon for deep clean
Keys back to homeowner and money or cheque in pocket
Go to pub.

Issue certs and online job registration with elecsa

 

[bureaucrazy]

I'm asking hypothetically, no notifyable work has been undertaken and I'm not trying to deprive anyone from an honest living. If it is notifyable to add smoke alarms into a lighting circuit, then I still need to know whether running paralell multicore cables (BS7671 section 521.8.1) and running extra isolated cables to add alarms to in future will be acceptable to building control. Hopefully some part P experts on this forum can help?

(I just phoned building control and they told me that wiring interconnected smoke alarms into and existing lighting circuit is not notifyable.)

 

[Spudnik]

I have merged the 2 threads as they are fairly similar.

 

[SirKit Breaker]

I'm asking hypothetically, no notifyable work has been undertaken and I'm not trying to deprive anyone from an honest living. If it is notifyable to add smoke alarms into a lighting circuit, then I still need to know whether running paralell multicore cables (BS7671 section 521.8.1) and running extra isolated cables to add alarms to in future will be acceptable to building control. Hopefully some part P experts on this forum can help?

(I just phoned building control and they told me that wiring interconnected smoke alarms into and existing lighting circuit is not notifyable.)

You are right it isnt, but if you are hardwiring them in then you will be making a new circuit and that is. The only other way to interconnect is to use RF bases.

by the way when i install interconnected smoke alarms i use 3 core and earth cable, it really is that simple. If you wish to future proof for more alarms then just run the cable and leave it under the floorboards and at the last point put a junction box on the end of the cable.

 

[Had8Lives]

Although if you are supplying the smoke alarms from an existing circuit it's not notifiable, for something as life saving as Smoke Alarms, I would advise you use 3 Core and Earth cable and have the circuit tested by a qualified electrician.

 

[Spudnik]

Installing smoke detectors is not notifiable but WILL require a 5839 certificate.