Smoke Detectors - Own Circuit or Lighting?

[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!

 

[andyb]

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.

Why would you be working on the smoke detector at night time?

 

[MTI]

em call out haha? i dont know. its all silly as far as im concerned. we can only do what we are told by engineers/designers and your own governing body. id personally ask for it in writing from elecsa/napit or whoever if thats what they want of you. if we pay them for a service then we should be able to expect all sorts in return and not just to be told what we are allowed to do in general ie what jobs we can and cant certify etc

 

[andyb]

its all silly as far as im concerned. we can only do what we are told by engineers/designers and your own governing body.

Not true, we can make our own mind up.

We have all been told or read that either way is ok, some enginieers say defianetly own circuit but the next will say a local lighting circuit.

You are on site, you know the circumstances and only you know the conditions you are working under.

 

[Steveathome]

Could 12V smoke / Heat detectors be used on an intruder alarm system? They have both mains and back up battery, plus indication of a mains failure. They can also be seperately zoned to indicate location, just like a full time fire alarm.
Could these be used instead of the norm 240V linked smoke heads? Would this satisfy building regs?
Many thanks

 

[hughesy]

If you are using a 17th Edition dual RCD board then surely it could stay as a dedicated circuit as it will go out when it's side of the board trips. People would notice half the house is out and know that the smokes are out also??

what about when the back up battery fails and the smoke alarms start to bleep every so often to warn it needs new batterrys many people who dont know why its bleeping turn them off at the mains seen this too many times so lighting circuit every time for me

 

[Spudnik]

I have just started fitting the 10 year lithium rechargeables.

Punters love the fact they wont have the bleeping every 6 months when they have to change the battery.

 

[lloyd1980]

put them on with the existing lighting mate, if your quote can spare it then get the wireless ones that have built in transmitters in the base which link them all together, cuts the installation time right down, if your lucky could even mean not having to lift floorboards depending how the joists run and if you can fish the cable over

 

[adam.h]

What about heat sensors? I though they where only recomended but we have been told by building control we need to have a heat sensor in the kitchen as the extension is accessed through the kitchen and will contain a bedroom.

Just found this....


Heat Detectors | Blog Sparks Direct

 

[Jimmyb]

I ask at lot of questions about this and looked into it with great detail with just having a few rewire to do, either way is acceptable rcbo or lights but if powered off the lights they cant be on the same rcd as any socket outlets which i would of thought was impossible unless you have 3 rcd's so rcbo for me

 

[Scott F]

I ask at lot of questions about this and looked into it with great detail with just having a few rewire to do, either way is acceptable rcbo or lights but if powered off the lights they cant be on the same rcd as any socket outlets which i would of thought was impossible unless you have 3 rcd's so rcbo for me

Hi Jimmy

why can't the smokes on a lighting circuit be on the same rcd as any sockets ?

Are you confusing up lights with down sockets and down lights with up sockets or have I read you wrong

 

[Jimmyb]

Hi Jimmy

why can't the smokes on a lighting circuit be on the same rcd as any sockets ?

Are you confusing up lights with down sockets and down lights with up sockets or have I read you wrong

it was what i was told by elecsa and also found it on this website http://www.ce2.co.uk/Downloads/21 ConsumerUnitGuideToThe17thEdition.pdf

the reason elecsa gave me was if an faulty appliance started a fire then it may trip the rcd and cause the smoke alarms to be off

 

[andyb]

it was what i was told by elecsa and also found it on this website http://www.ce2.co.uk/Downloads/21%20ConsumerUnitGuideToThe17thEdition.pdf

the reason elecsa gave me was if an faulty appliance started a fire then it may trip the rcd and cause the smoke alarms to be off

This is wrong. Linked smoke & heat detectors with a battery back up form a grade D system for which there is no need to put them on there own rcbo, or an rcd that does not protect sockets.

This requirement is for grade a & b, which have control panels, & e systems which have no back up supplies. These should be on there own dedicated circuit preferably with no rcd protection though if this is necessary there should be no sockets on the rcd protecting the fire alarm.

 

[The Truth]

This is wrong. Linked smoke & heat detectors with a battery back up form a grade D system for which there is no need to put them on there own rcbo, or an rcd that does not protect sockets.

This requirement is for grade a, b & e systems which have no back up supplies. These should be on there own dedicated circuit preferably with no rcd protection though if this is necessary there should be no sockets on the rcd protecting the fire alarm.

agree

anyway i have never yet had to put a smoke detector circuit in an RCBO because the cables are never concealed in the wall?! not even from the DB . bloody wylex experts telling us how to wire houses?! ground floor ring..first floor ring... kitchen ring... Ground breaking 21st century wiring.

before 17th came out the rule specifically stated that no 30mA RCD protetction should cover the circuit. better to have on dedicated mcb. as mentioned a few times here....they beep when there is a problem!

 

[Spudnik]

Surely a dedicated fire panel would have a back up battery similar to an intruder alarm system??

 

[andyb]

You'r right Jason, grade e has no back up supply my post was poorly worded (I edited it to make it hopefully clearer)

The rcd-sockets requirements are from bs 5839-6 and not to my knowlege bs 7671.