Domestic heat/smoke alarm mains powered from different lighting circuits?

[Let me think]

Hi folks,

Friend is currently renovating his house, including a loft conversion. He had originally hoped to go with Grade F1 (tamper proof batteries) radio interlinked alarms. However architect has stipulated all alarms must be Grade D (mains powered with battery back-up), but can be still be radio interlinked.

All walls and celling's are up, plastered and painted. So looking to minimise damage where possible when installing.

It's going to be pain to run a separate circuit from CU for alarms and to have them hardwired interlinked, but if needs to be done that way then so be it. Same would also apply if running separate mains alarm feed cable connecting into lighting circuit MCB at CU.

So was wondering what your views would be on doing the following (not ideal in my mind, but a possible workaround).

• Downstairs alarms mains feed of downstairs lighting circuit (can 'easily' access - minimal damage).
• Upstairs alarms mains feed of upstairs lighting circuit (can 'easily' access - minimal damage).
• All alarms radio interlinked (could hardwire interlink downstairs, hardwire interlink upstairs with radio interlink between upstairs and downstairs).

Look forward to your input.

 

[richy3333]

Is your friends house in England or Scotland? If Scotland which council?

 

[Let me think]

Is your friends house in England or Scotland? If Scotland which council?

Located in Scotland, Argyll & Bute.

Have tried to argue the case that Scottish government website, indicates that F1 grade would be fine, but architect said no, must be Grade D.

 

[Julie.]

No rules stipulating that they have to be on the same circuit.

Also the Scottish government standard allows for radio Interconnected systems.

Just check that the alarms, type, location, and quantity complies with the tolerable standard as issued by the Scottish government.

Btw there is no regulation in the Scottish standard that prohibits the use of fixed battery alarms Interconnected via radio.

Did the architect misunderstand what was being suggested?

 

[James]

The only risk that I see you might have to be careful to avoid the possibility of shared or borrowed neutral .

Hard wire interlinking is often done with a live feed from one to the other, if they are on separate circuits then some current will pass down wrong neutrual.

 

[Let me think]

No rules stipulating that they have to be on the same circuit.

Also the Scottish government standard allows for radio Interconnected systems.

Just check that the alarms, type, location, and quantity complies with the tolerable standard as issued by the Scottish government.

Btw there is no regulation in the Scottish standard that prohibits the use of fixed battery alarms Interconnected via radio.

Did the architect misunderstand what was being suggested?

Thanks for input. Separate circuits will save a lot of work.

All I know is that my friend has been back and forward with the architect over this, and architect is refusing to budge on this, so to keep the peace will be going with Grade D alarms as stipulated by the architect, hence OP.
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The only risk that I see you might have to be careful to avoid the possibility of shared or borrowed neutral .

Hard wire interlinking is often done with a live feed from one to the other, if they are on separate circuits then some current will pass down wrong neutrual.

Interlink between downstairs and upstairs circuits would be radio not hardwired, so no risk of borrowed neutrals. Thanks.

 

[richy3333]

D2, LD2 which means mains powered as per BS5839-6. As suggested you could radio link them.

Btw there is no regulation in the Scottish standard that prohibits the use of fixed battery alarms Interconnected via radio.

But BS5839-6 Table 1 does prohibit this?

 

[Let me think]

D2, LD2 which means mains powered as per BS5839-6. As suggested you could radio link them.


But BS5839-6 Table 1 does prohibit this?

Would appear BS and Scottish government are not 100% in sync.

Guess Scottish government position is that having smoke alarm(s) whether it's mains or battery powered is better than not having any at all.

On a separate note, if I bought every BS standard that I would touch upon, then storage of these alone (forest of paper) would results in an increased fire risk

 

[Julie.]

D2, LD2 which means mains powered as per BS5839-6. As suggested you could radio link them.


But BS5839-6 Table 1 does prohibit this?

Not on existing properties - F2 would be acceptable - but NOT in Scotland, here F1 is the minimum, it depends on how upgraded the property is, but if it's a loft conversion then the loft portion may be regarded as materially altered so D2 there.

 

[Let me think]

Not on existing properties - F2 would be acceptable - but NOT in Scotland, here F1 is the minimum, it depends on how upgraded the property is, but if it's a loft conversion then the loft portion may be regarded as materially altered so D2 there.

Ahhh...that may explain why architect stipulated grade D. Thanks.