Smoke alarm off lighting circuit

[meady]

Just a quick one, can you install a smoke alarm of the lighting circuit if there is no rcd? The lighting circuit doesent go into a bathroom so I'm asuming I can work on it without adding the rcd

thanks for any advice

 

[Apache]

Well, if your additions are not in the walls <50mm then I suppose you could!

Lets see what the others have to say

 

[Lee321]

Well, if your additions are not in the walls <50mm then I suppose you could!Lets see what the others have to say

+1

new builds normally own circuit

 

[ianmacd]

Would agree with the vet too.

 

[paul b b]

+1new builds normally own circuit

Assesser told me to put them on to a light circuit.

resons, if it on its own circuit you would not know if it tripped out. or if there was a problem you would not bother getting it sorted.

 

[Bez]

Think we discussed this in length a while back.

If you put them on the lighting circuit, they must have a seperate means of isolation.

Will try and dig up the thread unless Patch beats me to it.

 

[Theorysparky]

Part B of the building regs states a requirement for a seperate cct from the distribution board,,,this is for new builds.

old builds,,, lighting cct acceptable

 

[ianmacd]

Think we discussed this in length a while back.If you put them on the lighting circuit, they must have a seperate means of isolation.

Will try and dig up the thread unless Patch beats me to it.

Was it this one?

http://www.talk.electricianforum.co.uk/showthread.php?t=7803

 

[ianmacd]

Part B of the building regs states a requirement for a seperate cct from the distribution board,,,this is for new builds.old builds,,, lighting cct acceptable

Erm does it. This is from AD B

15.5 Recommendations for power supplies for Grade D systems

The following recommendations are applicable.

a) The normal supply for smoke alarms and any heat alarms in a Grade D system should be derived from

the public electricity supply to the dwelling. The mains supply to the smoke alarms and heat alarms

should take the form of either:

i) an independent circuit at the dwelling

 

[Bez]

Was it this one?http://www.talk.electricianforum.co.uk/showthread.php?t=7803

No, wasn't that one

 

[Theorysparky]

Erm does it. This is from AD B15.5 Recommendations for power supplies for Grade D systems

The following recommendations are applicable.

a) The normal supply for smoke alarms and any heat alarms in a Grade D system should be derived from

the public electricity supply to the dwelling. The mains supply to the smoke alarms and heat alarms

should take the form of either:

i) an independent circuit at the dwelling

 

[ianmacd]

have i not just said that ?

Where does it differentiate?

 

[PC Electrics]

I think this is the thread you're thinking of:

http://www.talk.electricianforum.co.uk/showthread.php?t=7776&page=2

The upshot was that smoke alarms can be on their own circuit or combined with a lights circuit. Either way, the smokes must be provided with a means of isolating them from the supply without interupting the lights.

Many ways to skin a cat and all that: I'm putting in the wiring for a loft conversion at the moment. This entails adding smoke alarms (x3). I'm extending the upstairs lights to give lighting for the new rooms and adding the smokes to this circuit. The smokes will take their supply from the 2nd floor landing switch, so to achieve the requirements above, I'm putting in a grid switch with one switch and one key switch for isolating the smokes (and a label on the CU).

If you can take the smokes supply back to the CU then a means of isolating could be to simply remove the supply cable from the MCB (label the cable for easy ID).

 

[PC Electrics]

As for whether you need to add an RCD, well the usual rules about buried cables and special locations apply as normal, so you need to decide if your new work falls under these requirements.