Mains linked smokes as part of a two wire system???

[paul21]

Hi

I am looking for peoples advice and views on the following installation. In brief we were asked to add a loft conversion flat to an exiasting alarm which was a two wire system but only 2 zone, 1 for common ways and one for all 4 flats, spread over 4 floors. We advised our client who said that it should have been zoned per floor and should be an 8 zone panel. The installers agreed to rectify the work and we have now revisited to find they have indeed installed an 8 zone rafiki panel however rather than cabling to each flat they have changed the detector to an EI141 mains linked smoke, added a radiolink base and then in a separate enclosure adjacent to the panel, have installe another radiolink base along with a Rafiki MCP set to end of line, this has been repeated for each flat and has therefore been zoned correctly, ingenious but does it comply. As the smokes come under part 6 I cant see how. Your views??

[kurnal]

Have you asked them for design and commissioning certificates?

I guess it all comes down to the fire safety design of the building. It does not sound like a purpose built block of flats with one hour standard of fire resistance to floors and walls protecting the staircase, and with automatic ventilation to the staircase. So it may not be safe for say the occuper on the top floor to stay put in their flat in the event of a fire in a flat on the lower floors. If this is the case then a part 1 alarm system to at least category of system type L3 would have been the most likely best fit, with heat detectors within the individual flats for the purpose of staircase protection together with a self contained part 6 system serving each flat so that nobody else is disturbed when they burn the toast. Sometimes the design and layout may even justify L2.

If a part 1  L3 was needed then what you have is non compliant. If a part 1 L4 was needed then what you have is probably compliant but will result in numerous unwanted evacuations that will probably lead to vandalism of the panel and people ignoring the alarm. If one of the domestic alarms operates does it operate the main panel sounders immediately and does it have to be reset? If so do occupiers know how to do this?

You will of course be aware that the above comments are based soley on the information in your posting and that nobody could give a definitive answer without seeing the building and the alarm installation.

[AnthonyB]

Replies from various fire alarm engineers regarding BS5839 compliance, etc:

"Offhand, it won't comply with 27.2 :

4) at the point at which the power supply(ies) to any radio-linked component can maintain the
component in normal operation for no more than seven days, and, in addition, in the case of fire alarm
devices, 30 min in the alarm condition, a fault warning should be given at the control and indicating
equipment;

If the mains linked smoke lost the mains supply and battery backup, I doubt you would get a fault at the panel."

"No head removal notification either. You can can pull those things down and just leave the base and no-one would now.

I wouldn't think that would comply when using a panel capable of monitoring head removal.

Plus the mains could fail inside the flat rendering that detector to run from its battery and again no indication at the panel.

All very ropey and unnecessary if you ask me.

All in all though a good example of trying anything to avoid a re-wire. Sparky job was it?"

"I suppose for the part 6 element it may only have to be local to the flat but I can't get my head around the whole bringing it back to an enclosure/radio base thing."

It doesn't comply if the coverage is needed for life safety due to structural deviations from code. If it was code compliant and didn't need a system at all it doesn't really matter, but would give a false sense of security due to it's various areas of  fault that would not be readily apparent.