Mains Supply to Intruder Alarm

[Deryck Tintagel]

I'm just about to install an intruder alarm and the easiest option for the mains supply is the lighting circuit to the understairs cupboard where the panel is to be located. Socket ring and radial pass through the cupboard but I prefer the cleaner supply of the lighting circuit and is easier to identify.

At the moment the light has the following cables to the batten holder (ceiling rose type):

Supply in from CU
Supply loop out to next light
Switch leg
Supply to bell transformer
Single red to live - presumably for the two-way lighting on the stairs.

Obviously, with all these cables it is a bit of a squeeze to fit another so I have thought that I would do the following

Remove supply in from CU and supply loop out and single red live feed to a 10A junction box.
Connect new feed to understairs cupboard light to junction box
Connect feed to bell transformer to junction box
Connect new feed to intruder alarm via fused connection to the batten lampholder

Any comment would be appreciated.

 

[breezer]

you can not spur off a lighting circuit

 

[il78]

Your easiest option is to connect into the ring and put a fuse spur (5A) in.......as you have said the supply is in the cupboard.

 

[BR]

The ideal thing to do here would be to have a seperate radial circuit specially for the alarm from the CU. Is this not feasible?

 

[breezer]

the above suggestion would also mean that should anything else go wrong you alarm will still have a supply (assuming the rcd does not trip)

 

[Deryck Tintagel]

It's an old installation in the house - not actually mine but a friend's. The CU is an old style updated with MCBs (No RCD) and has only 4 ways - one socket ring, one lighting circuit, one radial to the outbuilding, and one cooker circuit. Added to this it is an old Victorian house with the meter and CU in the lounge behind a window seat.

Ideally I would say put a new CU in the understairs cupboard but cand you have meter tails about 6m long?

Question. Why not use the lighting circuit for the alarm? I have seen it done although I haven't (as yet) done it myself.

 

[masona]

Question. Why not use the lighting circuit for the alarm? I have seen it done although I haven't (as yet) done it myself.

My alarm was fitted approx 20 years ago by professional and they spur off the lighting circuit protected with a 5A fused spur.I think you'll find most people do it this way because it the easiest route.

So,is this okay what they have done ?

 

[breezer]

no it isn't you still can't spur off a lighting circuit.

What you forget is they may be a "professional" alrm company, but that does not make them electricians. I worked for an alrm Co. for a short while, the boss said it is ok if you spur off a socket to the alarm fcu in 1.5 t & e because the alrm does not draw much current. he was a good business man a good sales man (he brought in most of the work) he was a useless electrician.

The alarm industry is very cut throat, so if some one can be shown how to connect a spur given the materials to do it, off they go. they do this because it is cheaper than getting in an electrician and better than asking the customer to get an electrician, as they think xyz company didn't say that i will go with them.

The engineers just fit spurs "parrot fashion" they have no real idea of what they are doing

 

[il78]

Maybe I'm missing something......why cant you spur of the lighting for the alarm....

 

[BR]

******************* 16th edition

 

[ban-all-sheds]

Yeah - you can spur off lighting for a fan, so it can't be the principle.....

 

[masona]

no it isn't you still can't spur off a lighting circuit.

Okay fair enough,any idea what the real reason behind it ?

 

[breezer]

presumably in case some one puts something on the spur eg electric fire / socket

 

[ban-all-sheds]

So why doesn't that concern apply to a spur supplying an extractor fan?

ARRGGHHH!!! I'm doing it again!!

I will not look for logic in the wiring regulations
I will not look for logic in the wiring regulations
I will not look for logic in the wiring regulations
I will not look for logic in the wiring regulations
I will not look for logic in the wiring regulations
I will not look for logic in the wiring regulations
I will not look for logic in the wiring regulations
I will not look for logic in the wiring regulations
I will not look for logic in the wiring regulations
I will not look for logic in the wiring regulations
I will not look for logic in the wiring regulations
I will not look for logic in the wiring regulations

 

[il78]

presumably in case some one puts something on the spur eg electric fire / socket

Does not come into it, the circuit (spur) has been designed to do its job at the time.

Example: Would you change a socket face to put on a cooker point on.....