Fire alarms

[Luke1]

Ive had a search about and even bought a book ( which was turd ) about wiring fire alarms and how they work.

Can any one reccoemd and good sites for info or a decent book that explains it clearly.

Cheers.

 

[breezer]

they are wired in paralel and make noises what else do you wantto know

 

[Luke1]

well how, when they go off, does the panel know which sensor has gone off on an addressed system?
There just loop in / loop out so i dont understand how the panel knows what is what. If you get what i mean.

 

[breezer]

sure do.

with non addressable detectors they have a light that latches on when it activates, so if its a false alarm you look for the one with the light lit.

You may notice in your travles that you will see some rooms with a led outside on a blanking plate, this is usually connectd to the detector so you know its this one that has gone off, and ideally you feel the door first to find out is it hot, if it is you dont open it (there is a fire the other side)

addressable detectors on the other hand are easier.(in theory)
you open the box of the brand new detector and say "hello mr detector, you are detector number 1" the detector then replies and says "ok"

there, you have now addressed the detector


ok, so you dont actually speak to them, but you do change its switches to set its address, or connect it to a programmer and address it.
(depends on what brand)

addressable detectors send messages to the panel doewn the cable, i.e "its a lovely day, and no smoke here" or "Oh sh** there is a fire here" or even "I am a bit dusty, i need a clean" (it really does)

well thats what the signals mean, its not what they really send, but that is what the panel interprets them as.

The problem with addressable detectors is this


1 - 2 -3 -4 - 5- 6- 7

new install, all detectors in a line

now more are added

1 - 2 -3 -4 - 5- 6- 7
......... I
........ 22-23-47 (ignore the dots)

you then get a fault on detector number 23

where the hell is number 23 if they only have 10 detectors?

23 happens to be next in line to 22, which in turn is "looped" from 5 but you cant see that

ideally a drawing for all detecor addresses should be on site,

now you could say take them all out and look at the addresses, one problem, you are in a warehouse that is 30 feet tall and you cant really see them let alone reach them.

then you can have sounders that if they are just say a bell, will pulse to indicate FIRE in the building, and then it changes to continious to say its in your area evacuate.

you can also get talking sounders clicky (its a genuine talking sounder)

then you have to consider deaf people, so you install strobe lights

then it goes into bringing lifts to the ground floor, closing doors, etc etc

 

[RF Lighting]

I love those vimpex fire cryers

We kitted out a 7 storey office block with 60 of them. Bloody clever how they all synchronise with each other


Each sounder can play different messages depending on what signal they receive from the controller.

 

[breezer]

if they didnt sync, you would only hear a crowd of one lady talking, it done via a conductor, he stans where they call all see him...........

 

[bernardgreen]

addressable detectors on the other hand are easier.(in theory)
you open the box of the brand new detector and say "hello mr detector, you are detector number 1" the detector then replies and says "ok"

Suppose it is a female detector ?

But you do realise that now some boffin is working on in-corporating voice recognition into fire alarm sensors to remove the cost of those switches.

 

[Steve]

addressable detectors send messages to the panel doewn the cable, i.e "its a lovely day, and no smoke here" or "Oh sh** there is a fire here" or even "I am a bit dusty, i need a clean" (it really does)

you can also get talking sounders clicky (its a genuine talking sounder)

Amazing what they can do isn't it

One question breezer, I've seen our fire alarm engineers taking down sensors willy nilly when testing them with smoke pots, they just unscrew them. Do they put the panel into supervisor mode for this, or could I do this, if, say, a sensor was sending out the "oh sh** theres a fire here" message, when it should be sending the "its a lovely day, and no smoke here" message?

 

[breezer]

how can you test a fire alrm smoke detector if its not connected to the Fire alarm?

to test them you (should) use a smoke pole (its like a small bucket with a can of smoke on the bottom, any perssure on it and it releases "smoke")

this is one

can of smoke is inside the bottom red bit, there is also a sealing "circle" at the top

all smoke detectors are monitored for the fact has some person taken one down, so it depends on the panel how this is done / over ridden

addressable ones should send i am dusty and need cleaning first

some you can actualy "ask" the panel how clean / dirty a detecor is

 

[Steve]

breezer, I meant he presses that pot against them, then when they sound the alarm, he unscrews them and the alarm stops. He blows them out, then replaces them on the ceiling. All is well.

 

[plugwash]

I don't think panels tend to reset after an alarm without being manually reset. There is probablly someone at the panel hitting the silence button as soon as the sensor under test sets it off.

as for removing the detector without warning the panel that would probably come up as a fault on the panel.

 

[breezer]

steve, he blows the smoke out to stop it going off again.

it may have an auto reset for tesing.

when testing a hotel there has to be 2 of you, one by the panel one testing.

the one by the panel does as plugwash said reset it, but also he must know where the other bloke is, so if it goes off some where else (other than where his mate is) he lets it sound as it is a genuine activation

 

[Tim 77]

Some panels in OMT (One Man Test) mode will go into fire if it detects activations in 2 different zones at the same time. Me and a work mate discovered this this when testing a large warehouse together.

Check thses out for fire alarm test kits

http://www.detectortesters.com/site/home/

 

[Steve]

All I know about the panel in question was it had 5 buttons numbered 1-5. Each button also had a function on it. 3 was reset. It had a "everythings ok" light, and a "oh sh** theres a fire" light. It also had 2 zone lights IIRC

 

[Luke1]

think that makes a little more sense.
does any one know where there might be examples how these are wired?
Ive seen some that are a big loop and others that have a resistor at the end of the circuit and i dont really know which is which. Also is there a set method to wiring them, like sounders on one circuit, break glasses on another?

cheers