Addressable systems
If the interfacing is to be carried out at the panel then the requirements are as the non-addressable system above.
If the interfacing is on the addressable loop then an interface that is loop powered energised in it's normal condition is required (Hochiki manufacture such a device). With other interfaces it will be necessary to also wire a simple relay powered from the loop and wire the contacts of both relays in series to the fail-safe BS7273-4 signalling relay.
I would welcome comments from those that are interested in the above summary so that we can 'tweak' it until it is correct and understandable to everyone.
Hello Wiz...
Seems about right to me.... my only question is still regarding the action of the Hochiki I/O - do you know if it changes state on "software failure" and what that means?
Re the "other interfaces" I've also been advised by Apollo in the past not to power relays directly from a loop... but just to be clear, are you suggesting a relay connected to the loop (permanently energised) in turn connected to its own closed contacts (open on power fail) in series with the normally closed on the I/O (the "part 4 relay") so if either one opens the magnet releases?
Dave, my understanding is the 'software fault' monitoring is a standard requirement of the current EN/BS for control panels. What this actually covers, I don't know because I don't design control panels. Obviously, there is some sort software fault monitoring on control panels and this will give a panel 'fault' condition.
So the C&E would be that any fire or fault condition monitored by the the cie would operate the addressable loop output interface. If the panel fault condition also operated on disablements then no further action is required. (although it seems the disablement function giving a fault condition isn't a standard requiremnt of the EN/BS for panels)
However, most addressable panels have a seperate disablement warning (i.e doesn't necessarily create the fault condition) so in this case the C&E would be either a fire/fault/disablement condition on the cie would operate the addressable loop output interface.
To cover the requirement whereby the interface fail-safes on loop power failure we would need an interface that was energised on in the normal condition and fail-safe de-energised on loop power failure. Evidently one of the Hochiki models does this.
Evidently, the Apollo output units don't do this because they have more of a 'flip-flop' style relay which might stay in it's last state even after power disconnection. In this case if we use a simple standard relay kept energised from the loop and wired it's contacts in series with the addressable output unit, either relay changing state (the addressable on fire/fault/disablement data received , and the standard on power failure) will provide the signalling circuit to our 'part 4' system. I note your comments about not powering a standard relay coil from the loop. I could see that back emf etc. might cause problems. I've powered other stuff from the loop with no problems but never relays. I'm going to talk to Apollo about this. It might mean a 'special' relay or relay circuit is going to be required.
Going back to the software fault, it would seem that this doesn't have to include loss of data on the loop. I thought that it might. Buzz previously highlighted that the BS doesn't specifically mention it. So I think he is right. We just need to know when the panel detects a 'software' fault as determined in the panel standards.
This BS recommendations don't seem to provide a perfect fail-safe situation. But does this matter to us? At this time we're more interested in finding out how to make the BS work rather than any potential failings with it.
