Class change on a Gent 4 zone fire alarm panel

[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.

 

[D Skelton]

Any news yet?

 

[jaresquire]

I would be checking for earth faults on the class change pair or similar if the conductors test as intact.

 

[stranded]

Any joy then?

 

[R G]

you say a 10ohm resistor works , why dont you put that in series with the SWA with a switch on the end or whatever

 

[D Skelton]

you say a 10ohm resistor works , why dont you put that in series with the SWA with a switch on the end or whatever

That's a fair point, there may need to be a minimum resistance between the two terminals? Doubtful but it's worth exploring.