Bi Wire Conventional System

[Guest RobinIo]

Hi,

I am contacting yourselves to hopefully find an answer to whether this complies with current regs.
On a bi wire conventional system (sounders and zone cabling on same wire) do these have to have a minimum of two zones, like on a standard conventional sounder circuits. My thinking behind this is that if a zone cable gets damaged you are going to want a backup of sounders.
Thanks in advance

Robin

[Tom Sutton]

The BS shows two circuits a radial sounder circuit and ring sounder circuit. The radial sounder circuit has one circuit with one sounder close to the panel and second circuit with the remainder of the sounders. The ring sounder circuit (e.g. addressable loops) has a combination of sounders and detector with one sounder close to the panel and protected by short circuit isolators. 

It appears that if there is a short circuit at least on sounder close to the CIE will be working. How this applies to your situation I do not have the expertise to help therefore I would suggest you contact the manufacturer of the CEI and get their advice, unless there is somebody on the forum who can help.

 

 

[green-foam]

Tom, I believe Robinlo means a system made by / similar to Fike. It does as said, in that it only uses 2 cores and you install "devices" on this cable. The most common device is the detector / sounder. Each device has a range of options that enable it to be a smoke detector, a heat detector,  a combination, as well as being a sounder. They are NOT addressable and are favoured by electricians "as they are simple to install and make a great profit" However  unlike most fire alarms you can easily remove any device and the panel will not indicate that a device has been removed. There are also available just manual call points and strobes, but I have yet to see one fitted. (I am not saying the MCP are never fitted, just I haven't seen one as they are not cheap)

[Tom Sutton]

Green-foam I was only stating what is in the BS and I do not have sufficient expertise to say how Robinlo could comply with the standard,whether two ring circuits or a combination of a ring circuit and a radial circuit would suffice.

[Tom Sutton]

Robinlo I am not a fire alarm engineer but I have looked at BS 5839 pt 1 and I believe you are correct if you are using radial circuits, you have to have a minimum of two zones with the first sounder in the vicinity of the CIE. 

BS 5839 in relation to clause 12.2.2 especially (j) which says “In the event of a single open circuit or short circuit fault on any circuit that serves the fire alarm sounders, at least one single fire alarm sounder, normally located in the vicinity of the CIE, should still sound correctly if a fire alarm condition occurs anywhere within the building.”

My interpretation is, if there are more than two radial circuits, and two of the circuits have the first device, a sounder, located close to the CIE that would comply. Also if there is a dedicated sounder circuit and only one sounder is fitted close to the CIE,  followed by as many radial circuits as you choose, that would comply.

I am sure there are more configurations especially if you use ring circuits you could get away with a single circuit and use short circuit isolators but that is something you would need to discuss with an expert.