Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Cable requirements for fire alarm outputs
#1
This is something iv never really given much thought. If I was installing door hold open magnets, or installing a connection from a fire alarm to a door access controller, I would just use FP200 as it makes sense to.

Today I took over a new job. The fire detection, alarm devices, mains supply, all cabled in FP200 as it should be. The door hold open magnets are cabled in twin & earth and the door access controller links are cabled in 6 core intruder cable. It sort of threw me when filling in the take over report. I couldn't find a clear awnser in the regs that would indicate if this is a deviation or not.

Anyone looked into this before?
Nothing is foolproof to a sufficiently talented fool...   24

Reply
#2
The signaling should be fire rated until it reaches the 3rd party system - especially for normally closed circuits like those controlling doors. If the insulation melts, the circuit can't open . Even on normally open cable , the entire cable could melt.
The cable from the psu to the door retainers can be in whatever they like. If the cable melts the power drops off and the doors close. Same for maglocks as long as the section of cable that links it to the fire alarm is fire rated to ensure the voltage can drop off no matter what other part of the cabling melts or shorts.
Reply
#3
26  Cables, wiring and other interconnections 26.1  Commentary The components of most fire detection and fire alarm systems are connected by cables and wiring, but it is possible to connect them by other means, such as radio or fibre optics. Recommendations for radio-linked systems are given in Clause  27. Where fibre optic connections are used, they need to provide at least equivalent integrity and reliability to other cables that are recommended for the same purpose. 

It is essential that all interconnections operate correctly at the time of a fire. This is particularly important in the case of cables that link control equipment to manual call points, automatic fire detectors and fire alarm devices, and that transmit signals to an alarm receiving centre. It is only less important in the case of interconnections between the fire alarm system and other equipment that are so arranged that failure of interconnecting cables during a fire would not lead to a dangerous condition (e.g.  because the failure causes the other equipment to change state to that appropriate to the fire condition).
Reply
#4
BS 7273-4:2015

14.1 In order to prevent inconvenience, maintain accessibility, or to avoid risk to occupants from unnecessary actuation of electrically held-open fire doors (see Annex A), the cables should be sufficiently robust to resist mechanical damage, or should have additional mechanical protection against damage. 
NOTE The critical signal path normally fails safe. Therefore, an open circuit or a short circuit on any wiring of the critical signal path will cause actuation of the release mechanisms. Accordingly, no special recommendations apply to these cables; for example, they need not be fire-resisting, unless, exceptionally, the circuit does not fail-safe.


the bit in red is the critical signal path not the same as BS 5839-1

[img][Image: dhyzfiN.png][/img]
www.fia.uk.com

Technical Manager FIA

All comments and views are mine own and may not reflect the views of FIA
Reply
#5
Maybe the people who wrote that assumed that the whole 24v comes down the cable from the psu into the fire relay, meaning a short on it will close the doors . In practice that isn't what usually happens. 
One cable comes from the psu to the relay , the relay breaks one core of the power , meaning it's far from exceptional that a short on the cable would mean the doors don't drop off .
Reply
#6
all depends on the category of door

It is desirable that, where practicable, a short circuit or open circuit of any circuit between the other control equipment and a release mechanism also results in
actuation of the release mechanism within a reasonable period of time. For reasons of security, this might not be practicable.

10.1 If a short circuit or open circuit of any circuit external to enclosures would prevent actuation of a release mechanism in the event of a fire signal, these faults should result in an audible and visual indication at, or close to, the fire alarm CIE if the system design is not such that the faults themselves result in actuation of the release mechanism.

plus the green break glass is double pole

11.2.3 The switch mechanism of every manual release control (green break glass) should be of the double pole type, and should be connected directly in series with the power supply (including any standby power supply) to the release mechanism.

10.3 If communication between fire alarm CIE and a release mechanism is achieved via an interface device on the loop of an addressable fire detection and fire alarm system, communications with the interface device should be protected against a single cable fault (i.e. both short circuit and open circuit) anywhere on the addressable loop (e.g. by the provision of short circuit isolators on each side of the interface device).
www.fia.uk.com

Technical Manager FIA

All comments and views are mine own and may not reflect the views of FIA
Reply
#7
We're talking about the cabling between the interface and the door psu.
The common protocols use dry contact interfaces, ie a normally closed contact. 
In an ideal world, these are fitted right beside each psu, but that isn't always the case, more so with door retainers. That cable is carrying 2 cores, and breaks (usually) the 24v +ve to the door retainers or the 12v +ve to the maglocks.
A short on the cable will mean the n/c contact opening will have no effect on the doors. 

The green bgu isn't really the concern of the fire alarm engineer since it shouldn't affect the automatic release of the doors by the fire alarm. Shorted cables on a normally closed circuit affects it regardless of the category of door .
Reply
#8
If Shorted cables on a normally closed circuit affects it regardless of the category of door
then you need top use double pole interfaces as where practicable, a short circuit or open circuit of any circuit between the other control equipment and a release mechanism also results in
actuation of the release mechanism within a reasonable period of time. For reasons of security, this might not be practicable.

double pole interfaces are practicable
www.fia.uk.com

Technical Manager FIA

All comments and views are mine own and may not reflect the views of FIA
Reply
#9
Double pole interfaces should still be using fire rated cable for their link to the 3rd party equipment if it's a non monitored (ie open or closed) circuit.
I still ask for fire rated cable even for intruder links that are monitored by resistors from their end.
Reply
#10
fire alarm interface FR cable - cables to door holders - anything as worst case the doors close and thats the ideal situation to have fire doors closed at all times.

Access control systems such as paxton who can have a golbal fire command over the its network = fire alarm interface in FR cable at every door controller as the access control network that sends a global fire is wired in Cat 5
All posts are of my own opinion and knowledge and do not reflect the views of the Company I work for.
Reply


Possibly Related Threads...
Thread Author Replies Views Last Post
  legal period for keeping fire alarm records in logbook alonso 7 1,146 23-07-2019, 05:27 PM
Last Post: Graeme
  residental sites and requirements inc RP KKGMC 1 409 07-06-2019, 06:54 PM
Last Post: AnthonyB
  Fire doors closing not immediate luggsey 3 506 02-05-2019, 02:53 PM
Last Post: luggsey
  Cable Joints Beagle 8 978 27-02-2019, 09:40 AM
Last Post: MD Martin
  Linking a Fire Alarm to a Sprinkler System Dan 5 758 22-02-2019, 10:40 PM
Last Post: Graeme
  Replacement of cabling to fire-resisting rtfm 7 624 15-02-2019, 08:41 PM
Last Post: AnthonyB
  fire relay operating 3 other relays to operate shutdowns and fire pagers alonso 6 1,896 26-11-2018, 11:56 PM
Last Post: sparky999
  Cable colour atherton1930 14 1,726 23-10-2018, 05:16 PM
Last Post: firemonkey
  how dedicated a dedicated fire alarm supply? alonso 21 2,382 19-10-2018, 08:01 PM
Last Post: Trickle Charge
  Maglock reducing height of fire escape doors alonso 0 530 28-09-2018, 09:18 AM
Last Post: alonso

Forum Jump:


Users browsing this thread: 1 Guest(s)