Smoke Detectors - Own Circuit or Lighting?

[neil2jo]

good point, i never bothered reading it much further, as it read with 'no other electrical equipment connected', which surely includes lighting? So the statement would basically be contradicting itself?

No less if you were to design smokes/heats in a lighting circuit, in a typical 2 storey house, you would have to run your lighting loop through the smokes i.e distribution board, smoke 1, smoke 2, heat 1 then lounge light, hall light etc, or visa versa placing your smokes at the end of your lighting loop. If you done it any other way, then surely your creating a form of 2 radials/lighting loops where your spurring from a room to run a new radial/loop, to create your smoke 'loop/radial circuit'.
In addition a typical 3 bed house might take around 50-75 metres of 1.5mm per level, if you were to add the smoke circuit which should typically cover the kitchen, lounge, hall and landing, you could be adding a further 40 metres approx to the lighting circuit.

Personally I always run a seperate circuit, where possible, this making it easier for testing and reduces nuisense tripping in the smokes, still caused by blown lamps,

 

[Guest123]

The principal itself is no different to a full fire alarm system chaps. That has it's own dedicated supply with battery backup. Granted the alerts to loss of AC power are more noticable but in essence it's the same.

I always have a dedicated circuit for me domestic smokes and advise customers to check fot the green LED power light daily and to keep an ear out intermittent beeps that also indicate loss of power.

 

[irishsailor]

O debate I love it

 

[MTI]

guy from elecsa has told me that if its new build/rewire-own circuit everytime. if just adding/upgrading then as long as you put in some form of isolation ie key switch so that they can be maintained etc without killing lighting then all is well. seems to contradict itself but for the sake of it, i lways run it that extra feed for what its worth. i mean come on, time and money etc but for the sake of it, what-10m of cable at a guess? its just not worth the argument. also advised that if upgrading an installation etc then try and jig circuits about to suit and give a spare way or just prey for one anyway.

 

[Spudnik]

if just adding/upgrading then as long as you put in some form of isolation ie key switch so that they can be maintained etc without killing lighting then all is well. seems to contradict itself but for the sake of it,

Does this also mean that we need to put a keyswitch next to each pendant as well?

 

[electro]

Does this also mean that we need to put a keyswitch next to each pendant as well?

confused where did the key switches come from

and why would you want to key switch each pendant

regards

 

[Spudnik]

MTI was told that if upgrading etc then the smokes can be powered from the lighting circuit, but should also install a means of isolation for maintenance of the smokes without shutting off the lighting circuit.

Therefore, do we need to do the same for the lighting pendants, for when we want to maintain one and not put the whole house in the dark.

 

[MTI]

this could go on for ever haha! its like mp's expenses at the mo lol! i think we can all guess that its the smokes that need isolating from lighting. i know, i know, to work on one pendant, we may/should isolate circuit, obviously killing lights but the idea is to allow us to work/maintain and test smokes and still have the aid of lighting. plus, they are two different kinds of 'installations' on one circuit. its only like banging in a s/f spur for fixed equipment etc

 

[Spudnik]

I know mate im just having a laugh.

Does my head in with all these tiny little details that really dont have to matter in a day to day install.

You are right about the MP's expenses, but we will save that for another time.

 

[electro]

Hi

Should isolation be both live conductors? a key switch is just a switch not an isolator....

whats your view

Regards

 

[Spudnik]

Hi

Should isolation be both live conductors? a key switch is just a switch not an isolator....

whats your view

Regards

Install a DP keyswitch.

 

[MTI]

im not quoting key switch unless we talking dp isolation. suppose we could have problems here..
current down nuetral etc.
if isolation not dp then whats the point? it wouldnt be fully isolated/segregated. what happens if someone 'pinches a nuetral to another circuit or if the nuetral at smoke is half way through circuit? if you split it, you loose other half of lighting. could be tricky if wired in singles as not all nuetrals will foolow phase conductors to points in turn

 

[Des 56]

In the end all smokes have build in double pole isolation
Just clip the unit off the base

Remembering that unswitched sockets can be used for this purpose of double pole isolation
Just pull the plug out and hey presto compliance

 

[sparks1234]

Put a double pole keyswitch in then

 

[MTI]

i agree-nice one

elecsa etc say this because realistically we are still working 'live' if you remove smokey and lead from smokey without isolating. say a non qualified/member of public does this and gets a crack-thats what we are up against although they should be keepin their grubby mits off anyway!