7273 and location of detectors

[Wiz]

Further to my earlier posts regarding suitable fire panels for use with BS7273-4 systems.

Two of the 5 manufacturers contacted felt their panels were not suitable due to lack of having a 'disablement' relay.

Two of the five have not yet responded. They could be still looking into the matter because they hadn't yet given BS7273-4 any thought. Or they could be showing their disdain of BS7273-4 because it is only an 'installation standard'.

Ampac have responded and confirmed that their FireFinder range has both a Fault and Disablement relay that they believe could be used for interfacing to a BS7273-4 installation. They are now giving the matter further consideration.

Ampac's techinical guy is also considering ways of using their configuration programme and current Apollo interfaces to provide a loop-powered interface for BS7273-4 systems. He thinks he can make it work!

I hope CT doesn't say this was the manufacturer he knew about!

I'll keep you informed of any further developments.

[Allen Higginson]

Surely data signals are part of the software as such?

The way I see it, is that to comply with BS7273-4 for Cat A systems using a loop-powered interface you would need

i) To have the interface relay loop-powered and normally energised

ii) For it to de-energise to the appropriate fault conditions elsewhere on the system, it would need to receive the appropriate data telling it to de-energise. But that is the problem. What if the data doesn't get through because of any sort of other fault stopping it?
I believe that it would need to work with the loop interface being sent regular 'o.k.' signals but if these should stop for any reason the relay would de-energise.

I read it as the generation of a fault due to software failure as already monitored by panels that have to comply to part 4 (internal watchdog etc. that monitors the software or config).It doesn't mention data.

[David Rooney]

Ampac have responded and confirmed that their FireFinder range has both a Fault and Disablement relay that they believe could be used for interfacing to a BS7273-4 installation. They are now giving the matter further consideration.

I hope CT doesn't say this was the manufacturer he knew about!

I'll keep you informed of any further developments.

Just for info... the Syncro "Alarm Contact" will change state on any disablement if not used elsewhere in c&e ... so presently I still think the only way of complying is not to use loop powered I/Os and run a separate cable between CIE and door PSUs..... less anyone knows different??

[Wiz]

Surely data signals are part of the software as such?

The way I see it, is that to comply with BS7273-4 for Cat A systems using a loop-powered interface you would need

i) To have the interface relay loop-powered and normally energised

ii) For it to de-energise to the appropriate fault conditions elsewhere on the system, it would need to receive the appropriate data telling it to de-energise. But that is the problem. What if the data doesn't get through because of any sort of other fault stopping it?
I believe that it would need to work with the loop interface being sent regular 'o.k.' signals but if these should stop for any reason the relay would de-energise.

I read it as the generation of a fault due to software failure as already monitored by panels that have to comply to part 4 (internal watchdog etc. that monitors the software or config).It doesn't mention data.

Buzz, what you say sounds absolutely right. But do you think that by not mentioning the word data it means they are not worried about loss of data? If so, that would be great for us who are struggling to comply.

[Allen Higginson]

Well,no one seemed too worried about data loss when complying to the "tick boxes" for CIE in complying to part 4 prior to 7273 in reference to the software part,and as it appears that to comply to 7273 means compliance to other standards amongst other things then I take it as it is written - no point complicating what may be already complicated in my opinion!

[David Rooney]

Wouldn't that be a bit of a hole in the standard then.... surely if there is a state when no data can be sent to an I/O to tell it to change state then the doors should release ?

[Allen Higginson]

Theres holes in all of them if you stop and think about them - if it was amended to include loss of data then (and has already been suggested/stated) there would be a major diffoculty for using any manufacturers equipment as it sits presently (they aren't going to make a special issue panel for the UK that is going to cost more than a few tweaks within software or materials).
If it meets the recommendations of Part 4 1988 (although no time limits are given for the generation of faults within this version) then it ticks the boxes for this.

[David Rooney]

So what we really need then is guidance from the NSI committee to know for sure if they mean the loss of ability to transmit data or something different as it has major impact on the implementation of this standard....

[Allen Higginson]

So what we really need then is guidance from the NSI committee to know for sure if they mean the loss of ability to transmit data or something different as it has major impact on the implementation of this standard....

If you have a gander at the standards for CIE (EN54-2 or 5839-4 1988) they list what needs to generate a fault in relation to software controlled systems.All panels that state compliance to these standards meet the requirements for 7273 (imo) because it cross references from other standards.
There may be a case to look at the implications of software failure but I think that relates to a far bigger picture than the operation and integrity of door closers,and brings into question the standards referiing to CIE and the realistic chance of current manufacturers making such UK specific CIE to comply.

[Wiz]

David you are right to be concerned about this matter. I personally feel that all the efforts to make the system as 'fail-safe' as possible are wasted through not requiring some method for monitoring that the data is getting through correctly.
However, Buzz is right if his interpretation of a 'software' fault doesn't include loss of loop data (and I think he is right). I think his belief that this is not included in recommendations because it is impossible to do with existing equipment is also correct.
If BS, in their wisdom, say that we don't have to correct monitor data loss who are we to argue? It saves us another trying to resolve another difficulty.

[Wiz]

Davie, I do not know what you mean by allowed to fail. If the sounder circuit fails, how CAN an acoustically operated device be triggered??? I am clearly missing why people find that a difficult concept to grasp, but I cannot think of how to make it any clearer. No ding a ling, no close doors. Does that help.

Sounder circuits are monitored, whereas sounders are not. People might feel mildly aggrieved (or so we thought, but then we could be wrong) if they were trapped in a burning building (it's that darn burning building again, Wiz, but if you didnt get them we would all be out of business) because TWO staircases were BOTH impassable because a single bell on just one floor was not working and so doors did not close (i.e. no ding a ling).

To be honest I think I must be missing the point.

I don't understand why an analogue addressable loop, which is part of the critical signal path (11.3)  .....

"11.3 If any part of the critical signal path is not exclusive to the release
mechanisms (e.g. part of a loop of an addressable fire detection and
fire alarm system).............."

...can be allowed to fail, therefore not operating its loop sounders....(no ding-a-ling), therfore not providing an acoustic signal (ding-a-ling) to activate the release mechanism on a Cat B door.

But.....

11.4 In the case of acoustic actuation, failure of any single fire alarm sounder should not prevent the actuation of release mechanisms for self-closing fire doors at more than one location at which the doors protect stairways that form means of escape in the event of fire.

So does this mean that there should be two alarm sounders in the vicinity of each acoustically operated door mechanism in order that the door will still release even if one sounder fails ?

And just generally, why is it acceptable for acoustically controlled doors not to close if sounders fail as you seem to intimate ?

"I do not know what you mean by allowed to fail. If the sounder circuit fails, how CAN an acoustically operated device be triggered??? I am clearly missing why people find that a difficult concept to grasp...."

Well this is what i don't grasp... your major concern over these people trapped in a burning building... doors need to shut if the door is classed Cat A (by definition a hardwired/radio system) but can stay open if its a Cat B door (could be hardwired/radio/acoustic)
 

David, my 'take' on understanding this; The actual sounders themselves are not monitored for failure even in BS5839-1.  Furthermore, 'acoustically' operated door holds can't be used anyway in the most 'critical' categories of system. The liklihood of a single sounder failing is pretty small, but in acoustic systems the most critical doors need to be covered by two sounders anyway.
Also, by my understanding, the csp of the 7273-4 installation is a different element than the csp of a BS5839-1 installation.

[David Rooney]

Well according to Table A2 Cat A/B/C can be applied to the following type of doors at least...

4. Forming part of the enclosures of a stairway that forms part of means of escape (other than stairways described in items 2 and 3 and
stairways in dwellings) A, B or C In the case of Category C, only if the critical signal path, and any wiring from non-fire alarm control equipment to the release mechanisms, fails safe.

5. Forming part of the enclosures of a fire-resisting lobby to stairways described in items 2 to 4 inclusive A, B or C In the case of Category C, only if the critical signal path, and any wiring from non-fire alarm control equipment to the release mechanisms, fails safe.

6. Subdividing corridors A, B or C

7. Any fire door in a dwelling, other than in the common parts of an HMO A, B or C

8. Any other positions, including (but not limited to) fire doors to rooms A, B or C


.........and the following type of building

1. Common places of work, not generally occupied by significant numbers of members of the public (e.g. offices, factories and warehouses), where staff are trained in the fire safety provisions in the building A, B or C


..........So to me it seems that Acoustic units could be used on quite critical doors protecting employees and the public alike and as you say, suddenly the release mechanism needs to be in range of two sounders !

I'd lay odds 99% of dorguards installed in the country aren't within earshot of two sounders. Perhaps we should contact them and ask why they don't mention it in their installation instructions ?

Suddenly the cost saving device might not be so appealing.....!

[Allen Higginson]

I think that the Dorgard is a device (liked or loathed) that was designed with current equipment in mind (ie - loop powered sounder bases etc. throughout the loop) and not the applications that they are commonly used in because of the ease in installing in existing sites (sheltered acc. nursing homes etc.) that have 20 - 30 year old Tann Sync Firecheck panels and one bell in each corridor!

[David Rooney]

Exactly that........... So who's going to tell the owners they either need to upgrade their complete fire system and add more sounders if they want to keep the DGs or replace them with hard wired units....?!!

I think if this Standard was written before any acoustic product was on the market then acoustic products wouldn't be acceptable in a modern building......

[Allen Higginson]

I suppose it's not really Dorgards (or whoever) fault or problem as they make it clear of whats required to activate it.The problem aries when the PAT guy is asked about who can they close the doors automatically because the nasty fire alarm company say it's going to cost a bomb to achieve this -
"They're chancing their arm - I can install handy units with no wiring at each door for £XXX pounds,no problem".Customer asks you why you didn't recommend these and no matter what you say they think you are trying to rip them off!
If you have the scenario that one sounder is meant to close two doors and te first door closes before the other you get dB drop off!!!