Safety service

Off the top of my head, as long as the detectors have built-in backup batteries, then the mains supply to detectors isn't considered a safety circuit (rather just a convenient means of re-charging or an alternative to the safety source).

I might wonder about the interconnecting wiring in the case of a interconnected system though...

   - Andy.

Looking at the definition in Part 2, I cannot see how it would exclude domestic, hard-wired detectors. 
According to Mark Coles, in the recent IET presentation on Amendment two, such systems are not safety services. An important consideration if SPDs are not to be employed.

I know of one domestic installation where the ASDs along with loads of  other equipment needed to be replaced following an over voltage incident.

I think I agree with Andy ... Isn't the interpretation of this partly within BS 5839-6, and the Grade of the system? Clause 110.1.3 and indent (v) to that regulation, effectively says that BS 7671 isn't stand-alone for fire detection and fire alarm systems, and that BS 5839 supplements BS 7671 in this respect.

It's what differentiates a Grade D1 and D2 (and, if considering the interlink cable, F1 and F2) systems from Grades A and C systems?

Clause 16.4 a) of BS EN 5839-6 appears to indicate that normal domestic mains cable is OK. Compare with the requirements for cable types for Grades A and C systems in Clauses 16.2 and 16.3 ?

I am in no doubt that smoke, heat and CO detectors are  Safety Services.

Have a look at the Part 2 definition of a Safety Service.

Then have a look at the list of Safety Services in the Chapter 56 and the Note to Regulation 560.1 where you will find listed "Fire Detection and alarm systems" and separately listed "CO detection and alarm systems".

JP

It would be queer if they were not. For me, I'd want them not only on their own circuit, but also on their own RCBO. However, 2 working days until I get my BBB, so I might be talking piffle. 

443.4.1 insists that overvoltage protection is provided for “safety services” as defined in Part 2, so we have no need to look to any other publication. I hold with JP, and whether intended or not, there is no doubt, having read the definition, that domestic alarms as I described above constitute a “safety system” and therefore over voltage protection is required.

I am in no doubt that smoke, heat and CO detectors are  Safety Services.

The actual detector may be a safety service, but whether the circuit supplying it is a safety circuit might be a different issue.

If it were deemed to be a safety circuit then we'd be wiring domestic smoke detectors in Pyro or FP rather than T&E, have a UPS and/or backup generator for them and be supplied from switchfuse connected upstream of the main switch, and inaccessible or ordinary persons. The fact we don't was, I thought, explained by the safety source being deemed to be the internal battery, rather than the mains.

I thought that Mark Coles's comment about SPDs was in relation to that - we don't treat domestic smoke alarm circuits as safety circuits, but nevertheless it might be a good idea to provide SPD protection for them.

   - Andy.

Interesting, so Grade D1 and D2 systems can't go on an ordinary lighting circuit, as that isn't classed, protected or routed as a circuit for safety services?

I think I'm with that as being the only interpretation for Grade D1 & D2 systems (and wired interlinks for Grade F1 and F2 systems).

Grade A and Grade C are of course a different kettle of fish.

Andy

Nothing to do with the cable type supplying Safety Service. Emergency lighting, unless the supply is from a Central Battery Service or a UPS, is usually  in T&E.

For you argument to work a safety Service would be defined by the cable type supplying it rather than as Defined in Part 2 of BS 7671 and the list in Chapter 56.

And yes to SPDs if you have smoke alarms in your house.

I think Mark was thinking on his feet when he answered the SPD question on the live webinar. I will have the debate with him when we next meet.

JP