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Topic Title: smokes of lighting circuit with shared rcd
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Created On: 18 April 2014 02:39 PM
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 18 April 2014 02:39 PM
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ccfc0587

Posts: 80
Joined: 28 February 2011

Hello
Got to install some radio linked aico smoke and heat alarms on a rewire these are each wired to the nearest lighting point with perm L and neutral. Been told that you cant wire of lighting circuit shared with rcd which protects sockets and also leds in circuit can cause problems with interference giving false alarms. Comsumer unit is dual rcd board circuits shared over the two rcd in usual way so these alrams are due to be fitted to downstairs lighting circuit which shares rcd with up stairs sockets . Do you see this being a problem doesn't say anything on aico installation guide or web site just to wire to closest light fitting and avoid noisy circuits or spikes which I presume to be florries and dimmers. Obviously tehse will be wired from loop in fed at fittings not the switch side.
Ta
neil
 18 April 2014 02:53 PM
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JZN

Posts: 573
Joined: 16 November 2006

There a lot of rubbish talked about what you can and can't do with smoke alarms. What you propose to do is fine. There's nothing in the wiring regs or Aico's instructions to stop you doing this. There'd be almost no point in Aico making RF units if you couldn't use different RCD protected circuits for the alarm system.

Regards
John
 18 April 2014 03:03 PM
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ccfc0587

Posts: 80
Joined: 28 February 2011

Thanks JZN
Been told that the rcd part was in bs5839-6:2013 but cant find anything to say so and as you said most cu's are split dual rcd with one light circuit and one socket circuit sharing a rcd cant see how you would fit the radio linked ones with out changing config of board to high integrity with rcbo or installing small cu just for lighting and smokes.

Edited: 18 April 2014 at 03:12 PM by ccfc0587
 18 April 2014 03:42 PM
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slittle

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Joined: 22 November 2007

I'm with John on this one.

Much safer in my opinion to install the smokes on a lighting circuit than on their own protective device. Makes it pretty unlikely anyone is going to turn them off that way.

Stu
 18 April 2014 03:51 PM
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ccfc0587

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stu
Thanks I agree but what about using a lighting circuit that shares a rcd with a socket circuit apparently shouldn't be done cant find anywhere that says so was going to ring aico but realised what day it was ill try on Tuesday but cant see it being a problem.
Ta
 18 April 2014 04:19 PM
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JZN

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From memory, BS5839 says that you should not use an RCD for the power supply to the alarm except where BS7671 says you must. So in other words electrical safety overrides BS5839. I think where RCD is required then you must have a dedicated RCBO circuit protecting the power supply to the alarm system.

However, even the above only applies to systems with an addressable panel such as you find in commercial installations. Most dwellings don't have or need this.

John
 18 April 2014 04:40 PM
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ccfc0587

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Cheers john ill crack on then
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