Evenin chaps'
wherever possible I always wire smokes onto thier own dedicated circuit.
[ I have only once put them onto a lighting circuit when it was nigh on impossible to get a cable run down the the fuse box without wreking the decoration and the customer didn't want to pay a lot. ]
Here's my reasons.....
first the bedtime reading bit: You 'can' do either...
reg 563-01-01 pg 131 16th ed, and reg 560.7.1 pg 153 17th ed
refer to circuits suppling saftey services, (which include fire detection),
stating they should be on thier own dedicated circuit.
On-Site-Guide 7.4.1 Pg 56 says smoke alarms in single dwelling can be wired as above OR from a local regularly used lighting circuit.
Whichever method you chose...
you need a means to isolate the smoke alarms for maintenace work.
i.e. when you change the battery on a lot of alarms you need to unplug the mains connector to open the battery compartment.
(not good for customer to do this on a live circuit!)
where are you going to put your isolator switch?
probably need a fused spur off light circuit because
not much good turning off lights MCB as you may not be able to see what you are doing?
What is the real risk of a dedicated smoke circuit tripping itself off?
As you are not putting any extra load on or switching stuff on or off..
why would the smoke circuit trip out??
unless you manually isolate it I guess it will just stay on!
Whereas a lighting circuit is more probable to trip cuz a bulbs blows!!
There is more probability that you would have the light circuit turned off for repairs/alterations/additions...
whilst you do this your smoke alarms are not powered!!
There is a greater risk that DIY bob changes a light fitting and may leave a wire off/lose/reversed...
jeapardising the continual supply to the smokes.
How can you easily check the supply is on to the smokes?
I put a FCU with neon indicator next to the CU!
smokes from MCB through FCU (only need 3A anyway not 6A protection)
Then supply to downstairs then to upstairs (and on to loft if applicable).
Quick glance at the neon on the FCU you know the smokes have power.
Also FCU provides nice easy Double Pole isolation for customer (or spark) to use when changing batteries!
When you are teaching customers about the MCBs & RCD operation.. you just tell them to keep an eye on smokes.
any person who is genuinley concerned about the saftey of thier family will check it and keep an eye on it & change batteries...
Customer who dont care wont give a fig or do anything no matter what circuit you wire it from!! :|
Well thats my four penny worth!
me fingers are worn down
& now Im going to have a cup of tea...
SL