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Do I need a new consumer unit for 3 new smoke alarms?

Stephen Baldry

Hi. I have just had a garage conversion, and in order to get final sign off by building regs, need 3 wired and radio linked smoke alarms. 

Building regs are happy that the wired alarms use the existing downstairs lighting circuit, but I have been given inconsistent advice from the sparks that I have had quotes from. 

The existing consumer unit has a 100 Ma trip protection. Some tell me that I will need 30 Ma trip to comply, others not. Obviously that makes the cost of just 3 smoke alarms quite a bit more expensive, so I wanted to get a view from this forum. 

The alarms would be wired to the local circuit, and in the ceiling bottom and top of stairs, as well as the new room

Help would be really appreciated thanks

Steve

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  • 0

    Bit more info may help - I presume the existing CU is a make or model for which RCBOs are not available, and/or is jammed full ? New circuits do not have to be RCD protected, but it severely restricts the type of cable and or where it is permissible to route it. Conventional Flat twin and earth without RCD or RCBO protection at 30mA is likely to not meet current standards almost anywhere But a cable with an earthed foil or armour may be used in many cases.

    In different situations, either quote you have been told may be right. also note that a new CU is not the only way to add 30mA RCD protection to a circuit. though it may be the neatest.

    mike

  • 0 in reply to mapj1

    Hi Mike. Yes , the CU is full and regs are happy for us to use existing downstairs lighting circuit.  The wires would come off existing electrical wires in the ceiling and not in a bathroom. So, I'm struggling a bit to understand why this electrician is insisting on it but can see that the regulations can be interpreted different ways. I want to make sure we comply with regulations but can't really afford the additional substantial cost, in the context of a simple 3 smoke alarm fittings

    Cheers, Steve

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  • 0 in reply to mapj1

    Hi Mike. Yes , the CU is full and regs are happy for us to use existing downstairs lighting circuit.  The wires would come off existing electrical wires in the ceiling and not in a bathroom. So, I'm struggling a bit to understand why this electrician is insisting on it but can see that the regulations can be interpreted different ways. I want to make sure we comply with regulations but can't really afford the additional substantial cost, in the context of a simple 3 smoke alarm fittings

    Cheers, Steve

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