Smoke Alarm conflict of regs ?

[bernardgreen]

From the manufacturer

3. INSTALLATION INSTRUCTIONS:
CAUTION!! READ CAREFULLY
WIRING REQUIREMENTS:
• The appropriate power source is 220-240 Volt AC Single Phase supplied from a nonswitchable circuit which is not protected by a ground fault interrupter

From the job's worth supervising the electrical installation

All lighting circuits must be on one or other of the RCBs ( dual RCB ) .

Yet good practise was ( maybe still is ) that smoke alarms were on the lighting circuit so that there was clear indication ( lights not working ) that the MCB / fuse in the supply to the smoke alarms had be tripped / blown.

Still on the bright side there is a battery back up << is there >>

 

[ban-all-sheds]

I don't believe that manufacturers instructions can take precedence over laws, can they?

 

[bernardgreen]

There is logical reason in not using an RCB protected supply. If the smoke is from a burning electrical appliance that has already tripped the RCB then the alarm has been dis-abled by the very event which that it was installed to detect and most importantly alert the occupants of the danger.

 

[ban-all-sheds]

That's true.

Also true is that it's quite possible to install a non-RCD circuit and comply with the regulations.

As for the "monitoring" aspect of using a lighting circuit there are other ways to monitor circuits if you believe that to be a requirement.

And maybe the alarm manufacturers could make their products produce an alert on loss of power. Many (most? all?) do that for low battery, it would hardly be difficult to design then to also start chirruping if the power went off.

 

[bernardgreen]

And maybe the alarm manufacturers could make their products produce an alert on loss of power. Many (most? all?) do that for low battery, it would hardly be difficult to design then to also start chirruping if the power went off.

That was a feature of one of the first alarms (German manufacturer) but it caused problems close to panic when a power cut made all the individual alarms in an apartment block start sounding loud pips. People woke up. Darkness and lots of pips from all the flats and no information what the pips meant led to chaos. ( even Germans do not always read the instructions )

 

[OwainDIYer]

We don't have ground fault interrupters in the UK, we have RCDs, so it sounds like the instructions aren't intended for the UK market or a bad translation in US-English from the Chinese.

If there is an irreconcilable difference between the Mfr's instructions and the Regs then the product cannot be installed, as the Regs require the instructions to be followed but do not allow for the instructions to override the Regs.

If you have a jobsworth supervising the installation then get his instruction to you in writing, signed and dated. Then it's his problem.

 

[ban-all-sheds]

He's not just "supervising" the installation. With a directive like "All lighting circuits must be on one or other of the RCBs ( dual RCB )" he is the one who is required to sign this declaration:

FOR DESIGN
I/We being the person(s) responsible for the design of the electrical installation (as indicated by my/our signatures below), particulars of which are described above, having exercised reasonable skill and care when carrying out the design hereby CERTIFY that the design work for which I/we have been responsible is to the best of my/our knowledge and belief in accordance with BS 7671:2008, amended to................................(date) except for the departures, if any, detailed as follows:

 

[LiamPope]

Mine are on their own RCBO. They are battery backup ones and indicate if the mains power is off. I'd be suprised if any battery backup ones dont indicate mains failure??? They'll at least warn you when the backup batteries start running out, surely?

 

[securespark]

Surely if the smoke alarm wiring is surface mounted - or run in under-floor voids - it does not need RCD (or GFCI!) protection.

 

[seasickstevie]

...If the smoke is from a burning electrical appliance that has already tripped the RCB then the alarm has been dis-abled by the very event which that it was installed to detect and most importantly alert the occupants of the danger.

But surely that's where the back-up batteries come in.

 

[bernardgreen]

But surely that's where the back-up batteries come in.

If the alarms are working on batteries after loss of mains power will the interconnect still work to trigger all alarms ?

I don't know if it does on all makes of alarm.

 

[joinerjohn]

You obviously want to power the smokes from the lighting circuit? Don't. Just run another cable for them , back to the consumer unit and wire them into a separate circuit.