Smoke detectors

[Innominata]

Hi Guys,
I have just completed a PIR for a house that has had a recent upgrade.The general condition is very good.The only thing that I am not sure about is the fact that the hall smoke detector is supplied from the nearby hall light,and the landing smoke detector is supplied from the landing light.The two alarms do not appear to be interconnected.Is this arrangement ok or should it be given a PIR code.
Many thanks

 

[Brian Boyd]

I`d make note of it on pir and cover yourself as best you can.

 

[RexT]

Hi,

I am sure that the smoke alarms should be interconnected and battery back up(?). I agree that this should be recorded on the PIR as you have discovered it.

Are they going to rectify the connection?

Best wishes

Rex

 

[BVES]

You did check they were ot linked by radio link?

 

[Spudnik]

That what i was thinking.

If they are, it takes a few seconds from when the test button is pressed on one, for the other(S) to sound.

 

[Sav]

Hi,
I had a similar problem, I gave it a code 4 (recommendation) and also gave the customer a quote to fit the radiolink bases to the detectors. They are about £35.00 each radiolink. The smoke detectors were from B & Q, so did not have the capability of being radiolinked.
In the end I used the Aico smoke alarm units (optical multisensors, with battery backup and can be radiolinked).
Quick and easy and the customer was pleased.

Best regards,
Sav

 

[RexT]

Hi Innominata,

I must admit the radio link option sounds good and quite reasonable priced. When you did the PIR did you notice if there was three core and earth run between the smoke alarms? I f so I guess it might have been cheaper to replace the fitted smoke alarms if the cabling checked out ok.

Interesting stuff and this forum is great for some sound advice.

Hope this helps.

Best wishes

Rex

 

[Innominata]

Thanks Guys I will check the radio link

 

[1billy wiz]

can someone be kind enough to explain radio link pls.

to my understanding a fire alarm can be off a lighting circuit if it can be isolated by a spur right??& it cant be on a 30ma circuit neither right??

does radio link mean you only need to supply power to one alarm???

sorry people but fire alarms & extractor spurs in bathrooms stump me!!

 

[mnmwill]

A radio link gives a wireless link between the smoke alarms, saves trying to route 3 core from one to the other.

 

[JUD]

can someone be kind enough to explain radio link pls.

to my understanding a fire alarm can be off a lighting circuit if it can be isolated by a spur right??& it cant be on a 30ma circuit neither right??

does radio link mean you only need to supply power to one alarm???

sorry people but fire alarms & extractor spurs in bathrooms stump me!!

In bold:

This isn't entirely true.

Where the use of an RCD can't be avoided it is arguably preferable for the supply for the fire alarm system to be taken from a regularly used lighting circuit as operation of the RCD/RCBO will soon be known (for other than Grade D systems, BS 5839-6 recommends avoiding the use of RCDs on fire system circuits. This will usually require clipping cables direct to the surface or enclosing in steel conduit or the like).

This is from the IEE Electricians Guide to Fire Detection and Alarm Systems

 

[All Sorts]

I gave it a code 4

slight interjection if I may.. is there an online doc available anywhere that lists all possible codes and their descriptions?

Thanks in anticipation

 

[Sav]

Hi Allsorts,
If you go onto the Electrical Safety Council website Electrical Safety Council (ESC) | Committed to reducing deaths and injuries of electrical accidents at home and at work , you can download the Periodic Inspection Reporting document which has all the codes in there.

Alternatively, try the Elecsa website as well.
Hope this helps,

Sav

 

[1billy wiz]

In bold:

This isn't entirely true.

Where the use of an RCD can't be avoided it is arguably preferable for the supply for the fire alarm system to be taken from a regularly used lighting circuit as operation of the RCD/RCBO will soon be known (for other than Grade D systems, BS 5839-6 recommends avoiding the use of RCDs on fire system circuits. This will usually require clipping cables direct to the surface or enclosing in steel conduit or the like).

This is from the IEE Electricians Guide to Fire Detection and Alarm Systems

so if the lighting circuit is on a rcbo becuse the bathroom lights need protecting by 30ma i need to either do a spur of the sockets for the bath lights & change over cb for the lights or run a radial right?

 

[JUD]

so if the lighting circuit is on a rcbo becuse the bathroom lights need protecting by 30ma i need to either do a spur of the sockets for the bath lights & change over cb for the lights or run a radial right?

I don't think you've understood it correctly.

Basically what it is saying is that if you must use an RCD then it is better to run the smoke alarms off a regularly used RCD protected lighting circuit because if the RCD trips you will know about it straight away as none of the lights on that circuit will work.

NOTE: This only applies to Grade D systems which are installed in dwellings.

 

[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

 

[nickblake]

well ill be honest i always install them on their own circuit and use the EI ones where you need to remove the head to access the battery then if they do switch them off it bleeps and drives them mad so they switch them back on , but i must agree with connecting them to the lighting circuit as we used too ,and one thing i always do when i do a PIR is to test them with some canned smoke just to confirm they work or have not had the batteries taken out , and if they have no batteries they get some put in !!!