Smoke detectors

[1billy wiz]

what about the isolation??can you feed it straight in or does it need a switch to isolate for maintenance?

 

[Spudnik]

what about the isolation??

Unplug it or remove it from its base.

 

[Sintra]

Just highlighting some differences between 7671 & building regs.


From BS 7671


Fire detection circuits must be supplied independently of other circuits and not protected by an Rcd protecting multiple circuits. 560.7.1



From Building regs.


The smoke alarms have to be interconnected, have a battery backup, and be permanently supplied from a separate way in the ccu, or supplied from a local lighting circuit that is regularly used. Please note this requirement conflicts with 560.7.1

Except for TT systems, the circuit supplying a smoke alarm should not be protected by an RCD. For TT systems the smoke alarm must be supplied from the fixed equipment section of the ccu, not through a 30mA RCD.

 

[1billy wiz]

so unless a tt system it cant be wired of an rcd protected circuit.

 

[JUD]

Just highlighting some differences between 7671 & building regs.


From BS 7671


Fire detection circuits must be supplied independently of other circuits and not protected by an Rcd protecting multiple circuits. 560.7.1



From Building regs.


The smoke alarms have to be interconnected, have a battery backup, and be permanently supplied from a separate way in the ccu, or supplied from a local lighting circuit that is regularly used. Please note this requirement conflicts with 560.7.1

Except for TT systems, the circuit supplying a smoke alarm should not be protected by an RCD. For TT systems the smoke alarm must be supplied from the fixed equipment section of the ccu, not through a 30mA RCD.

560.7.1 Circuits of safety services shall be independent of other circuits.
NOTE: This means that any electrical fault, maintenance or modification work on one system must not affect the correct functioning of the other. This may necessitate seperation by fire-resistant materials or different routes or enclosures.

Where does it mention RCDs???

 

[Sintra]

560.7.1 Circuits of safety services shall be independent of other circuits.
NOTE: This means that any electrical fault, maintenance or modification work on one system must not affect the correct functioning of the other. This may necessitate seperation by fire-resistant materials or different routes or enclosures.

Where does it mention RCDs???

It doesn't specifically mention rcds but if you have an electrical fault on for example a rfc backed up by the same rcd as the fire detection circuit then you can not comply with this reg.


From BS 5389.


The circuit supplying a fire detection circuit should not be protected by an rcd unless this is necessary to comply with the requirements of BS 7671.
Were an rcd is required for electrical safety, a fault on any other circuit or equipment in the building should not be capable of resulting in isolation of the supply to the fire detection system.

 

[JUD]

This is why it states that you put it on a lighting circuit so that if there is an electrical fault it will be known and repaired straight away as there will be no lights.

This only applies to the interlinked smoke alarms (Grade D) that are installed in dwellings. Grade A,B & C systems require their own independent circuit and must be installed using fire resistant cable with mechanical protection.

 

[s1m0n]

Hi
Just come across this thread to this Thread,
and I am interested in the outcome of the conflicting regs.

It seems to me it is nearly impossible to get away from RCD protectionon circuits in the domestic house.

522.6.7 for cables without earthed metallic covering installed in walls or partitions at a depth of less than 50mm and not protected by earthed steel conduit or similar.

522.6.8 for cables without earthed metallic covering installed in walls or partitions with metal parts (not including screws or nails) ant not protected by earthed steel conduit or the like.

Thanks

Simon

 

[Ponty Massive]

Yeah this is confusing me as well. So on a new installation, if you are using a split load dual RCD board, the supply for the smoke alarms MUST come from a lighting circuit (so you know if it's tripped) and not be put on it's only supply.

 

[High Tower]

I always put em on lighting circuit, that way when the lady of the house sets fire to the dinner the alarms don't simply get isolated

 

[davelerave]

good practice would be same circuit-even with radiolink

 

[Ponty Massive]

or would it be better to put them on seperate cct, so if one trips, you still have the other??

 

[1billy wiz]

I REGRET becoming an electrician, it's so fickle & at times my confidence is shot to bit's

 

[davelerave]

I REGRET becoming an electrician, it's so fickle & at times my confidence is shot to bit's

true

you could give a job 100% and someone else would screw it up for you

nothing but headaches and pitfalls - electrical work

 

[RexT]

Hi Guys,

Would it be down to each case on its merits and following the 'risk assessment' that we all do! It always seemed to me that there can be two or three right answers to what appears to be conflicting info.

From the comments made here by competent and working electricians it would seem that there must (or should be) some notice taken of the ideas / solutions / interpretations / opinions.

I guess it all comes down to when the system is examined by others if something goes wrong. I agree with the comment that you can do all you can and it can be messed up by someone else.

Thanks again guys for the interesting viewpoints,

Best wishes,

Rex