Class change on a Gent 4 zone fire alarm panel

[markysparky108]

A bit flummoxed here guys, any advice gratefully accepted.
I need to sound the bells on a Gent 4 zone panel for class changes in a school. To do this, I must short out terminals C1 & C2 within the panel from a remote timer. The timer is an approx 70mtr cable run away. I have run a 1.5mm 2c swa cable between the two points.
When I stand at the Gent panel and short C1 & C2,with a short piece of wire, the bells ring, so no problem there. My problem is that when the timer shorts the swa pair connected across C1 & C2, the bells wont ring. I have even twisted the wires together at the timer end, and still the bells wont ring.
So I thought, maybe the length of run was the problem, so I measured the loop and I have 1.5ohms across it. So I`m thinking, well maybe it’s not enough of a “short” to link the terminals. So out of interest I put a resistance of 10 ohms directly across C1 & C2, and low and behold the bells rang !!!
So 1.5 ohm loop wont short C1 & C2, yet a 10 ohm loop will !!!
My brain has gone foggy, Am I missing something stupid here guys ??

 

[D Skelton]

You have a break in one of the conductors, simples

Good luck finding it!

 

[markysparky108]

Oh if only it were that simple. No break. Have checked all that. Shorted out far end, and continuity test shows 1.5 ohms loop, which over a 70mtr run is about right for the size of cable. I measured a 100m coil of T&E and got a loop of 3.4 ohms.
Thats the whole point, its doing my head in

 

[tazz]

The gent panel requires a pulsed one second short, if using a relay this will not pulse. You need a digital pulsed relay set at one second intervals.

 

[markysparky108]

Thanks for that Tazz. I`ll try it.
Not sure how though, when I just short it manually at the panel with a short piece of wire, and hold the wires on, it rings and stays ringing.

 

[tazz]

At the end of your run short out cables briefly and see if you get a one second ring

 

[stranded]

That should be correct, most class change signals in schools etc seem to do about 5-10 1 second bursts, so that seems to make sense.

 

[markysparky108]

No joy I`m afraid. When I short out the C1 C2 terminals at the panel, the bells ring uninterrupted for as long as I hold the short in place. Totally baffling !!!

 

[stranded]

No joy I`m afraid. When I short out the C1 C2 terminals at the panel, the bells ring uninterrupted for as long as I hold the short in place. Totally baffling !!!

Is their a non- latching zone on the panel? Try using that with the timer?

 

[Engineer54]

Is this normal, to use the fire alarm bells for class changes??
And there was i thinking that Fire Alarms were only to be used for fire evacuations, and that any other bells systems etc had to be distinguishable from a fire alarm bell/sounder!! lol!!

 

[stranded]

Is this normal, to use the fire alarm bells for class changes??
And there was i thinking that Fire Alarms were only to be used for fire evacuations, and that any other bells systems etc had to be distinguishable from a fire alarm bell/sounder!! lol!!

Then again, i suppose your right, but ive been loads places where they use the bell as the fire alarm and vice versa. My old high school used a gent vigilon compact, does about 10 1 sec blasts on a steady tone, then alternating/hi low sound for fire alarm, but since its Addressable its alot easier. Pity it wasnt sounders on the system like fulleon roshnis or somthing then the second tone could be wired in which is just a steady tone...... im stuck really....

 

[Engineer54]

Then again, i suppose your right, but ive been loads places where they use the bell as the fire alarm and vice versa. My old high school used a gent vigilon compact, does about 10 1 sec blasts on a steady tone, then alternating/hi low sound for fire alarm, but since its Addressable its alot easier. Pity it wasnt sounders on the system like fulleon roshnis or somthing then the second tone could be wired in which is just a steady tone...... im stuck really....

Well it's not something i would even contemplate doing. As far as i'm concerned a Fire Alarm system is for one purpose only, and certainly not as a dammed class time sounder!!

 

[stranded]

Well it's not something i would even contemplate doing. As far as i'm concerned a Fire Alarm system is for one purpose only, and certainly not as a dammed class time sounder!!

You might find a fire engineer could help you out, im not an engineer but know a bit about systems. (hopefully an apprentice spark soon). Even ring a local firm and ask their advice? I never seemed to think it was a problem because ive never seen a proper dedicated class change system, it always seems to be with the alarm, hence why some panels have class change conections, but i think the non lathing zone is your best option to try, no reason it shouldnt work.

 

[tazz]

This is were the name Class Change comes from, as all fire alarms used to do just that.
Back to Gent, now Im totally baffled, acording to gent the max length of cable run is 100m, to the push button or pulsed timer, and the zone cannot be programmed for non latching

 

[markysparky108]

With a class change timer, the bells will sound on and off every couple of seconds for about 10 seconds only. TOTALLY distinguishable from a fire alarm. Virtually every school I have ever worked in uses this type of system. If you read the Gent literature that comes with their panels, they actually state that terminals C1 & C2 are for use as a class change facility.

Getting off the point here, I was hoping someone would see something that I am not getting. As said, I can short C1 & C2 at the panel, and hey presto, the bells ring, but when I short C1 & C2 from a distance ( read the first post ) bells don't ring !! It doesnt make sense to me, but then what do I know, Ive only been a sparks for 35 years lol

 

[stranded]

This is were the name Class Change comes from, as all fire alarms used to do just that.
Back to Gent, now Im totally baffled, acording to gent the max length of cable run is 100m, to the push button or pulsed timer, and the zone cannot be programmed for non latching

Ahh... i wasnt sure if they had non-lathing zones or not, think i was thinking of a ctec cfp... this is a tricky one... surley there is a way some how...

 

[tazz]

Can only now suggest trying a length of cable, just to test

 

[Richard Burns]

OK so try a different cable as a test to see if there is a problem somehow with your installed cable, take a reel of cable and use it to provide the "short" if it works then you need to look at your connections for the installed SWA.
If the SWA and connections are OK then you could try installing a local relay that is switched by the SWA and that relay provides the C1 C2 connection.

 

[Engineer54]

If that's is indeed the case, then i stand corrected!! but personally, i still wouldn't use a fire alarm panel as a class change bell ringing facility!!

 

[tazz]

If that's is indeed the case, then i stand corrected!! but personally, i still wouldn't use a fire alarm panel as a class change bell ringing facility!!

Then it has no other use

 

[D Skelton]

As I said earlier, there is a break in one of the conductors for sure! Get a 100m drum of 1mm and use that to short C1 and C2. You know where you stand then if that works.

 

[stranded]

As I said earlier, there is a break in one of the conductors for sure! Get a 100m drum of 1mm and use that to short C1 and C2. You know where you stand then if that works.

Best idea i think so far

 

[markysparky108]

Yes I`ll try that, but I am absolutely certain that I dont have a break in the 2 cores of the SWA. When shorted at the far end I am getting 1.5 ohms across the two open ends. The same test on a 100 m coil of 1.0mm T&E gave me 3.5ohms.
That is what is so baffling about this. Also, as stated previously, I put a 10 ohm resistor across the terminals and the bells rang. Will try it tomorrow and come back here.

 

[D Skelton]

Silly me, I must have missed that. Well the only thing I can think of now is the potential current loss due to the fact that you essentially have a single line conductor running in a steel wire armoured cable for as near as makes no difference 200m.

As a ferrous material the steel in your armour could potentially be causing significant power loss due to the eddy current. I'd try the 100m roll of T+E and if that works then you know what the problem is. Alternatively, you could use an earth leakage clamp meter to measure the current to earth from the armour?

If I'm right (and that's a big 'IF' lol) one solution could be to use AWA. Another could be to use unarmoured cable or to move your timer relay closer to the alarm panel.

Anyone else care to speculate as to what the cause could be if it isn't down to inductance?

I'm very interested to know how you get on so do keep us posted

 

[tazz]

It is a strange one....but the reel of cable test will prove one way or the other.