BS 7273 pt 4 .... lots of questions...

[David Rooney]

I ran out of bike mags and started reading this BS the other night. You all need to swat up because I foresee many questions.

First off....for a system to be fail safe, either Category A,Bor C one of the conditions it has to meet is this.....

..... 5.1.1 a    open or short circuit of wiring that forms part of the critical signal path (within 120s of occurrence)

The critical signal path being...

"all interconnections and communications between fire alarm CIE and the input terminals on, or within (a) devices provided to open, release or unlock a door or shutter or between CIE and other control equipment by which such devices are controlled."


So if i read this right, where we would normally stick an addressable I/O unit on a loop (analogue system obviously) by the door to interrupt the power supply to the locking mechanism..... this is now no longer allowed (under the terms of being "fail safe" as an open or short circuit in the loop cable will not cause the I/O unit to change state.....

Or is it just me.......!!!

[Galeon]

Dave ,
Yes that's how it comes across to me , although the cat a door is the real pig. They have just not thought about the logistics of how this is going to work , I will moan to my dear old Scottish mate about this when I see him.
I have just had a good go at the old salamander  door units and found them to be spot on.
We will have to say good bye to the old bell relay , it served us well.

[David Rooney]

So presumably if there is a "green breakglass" we could say sod it and agree with the customer a variation?

[Allen Higginson]

On an adressable system could you have an I/O around the location of the CIE monitoring an internal fault contact This input would then be used to permanently energize the I/O controlling the door closer,so you would have it connected to the normally open contact.
It does mean that the door would close on any fault condition though.

[Galeon]

As I read it on the Cat A door  assuming say the retainers are 24vd/c :

Feed the transformer rectifier via the incoming 240 v supply (that covers your mains failure in relation to the fire panel)
Then wire relays permanently energised , n/c on common fault and fire respectively

The issues you now have with I/O Units is that subject to the make they wont change state if the loop goes off line ie mains & battery failure ie does the i/o n/c stays closed all the time.

It appears to  me we are heading back to the 1970's when relay logic ruled.

What we need to confirm within the industry has the loop interfaces have caught up with this yet , perhaps you boys might have info on various I/O units so we can check it out.

It appears me that there will be no I/O in the field , but you will have  to control it at source .

[David Rooney]

Insider information from a source I can only describe as "the third man" tells me that Apollo are looking into addressable I/Os that will change state if they lose comms with the control panel.

........another question, Notifier tell me their panels can be fully programmed down to "head removal level"

.... kentec at present do not have plans to implement the additional controls, but when they do implement this we will add another output attribute as a "door control" and then it will activate under the BS7273-4 specific events.

Does anyone know any other open protocol panels that can be programmed to this level??

Hochiki get over the problem using their Powered Output Module that could permanently energise a relay, dropping out in the event of loss of power on the loop....

[Galeon]

Got a little kit fro c tec rated @ 250m/a built on a double gang plate with rectifier , manual close button on the front , circuit monitored to mags as well , looks the part might be useful to you guys , have a mooch at it.