fire station alerting/wiring

[ocguard]

I'm looking at doing an overhaul on a portion of the fire station alerting system at work. Our station alerting is accomplished via our Motorola v7 P25 radio system SCADA and ACE3600 RTU. I'm not so much looking at changing anything on the radio end, but what happens after the radio.

Our RTU sends out a low-voltage signal to a vintage Gamewell gong, rings the gong, which is wired in series to an AC relay to activate the lights in the bunkroom and apparatus floor. Problem is, sometimes, the relay never trips. The gong is always consistently works, but the lights are very unreliable.

I know this is more of an electrical issue than a true radio issue, but hopefully someone has the knowledge of what I've described to give me some insight on how to make the entire system work more reliably.

 

[krokus]

Under the KISS principle: Is the relay in good condition? The contacts might be damaged, or windings might have shorted.

When testing relays, make sure they engage at the rated coil voltage, and hold their position, until at least 80% (ish) of their rated coil voltage.

Are you sure the relay and gong are wired in series? That would seem a bit odd. I would think they would be in parallel.

 

[ocguard]

Under the KISS principle: Is the relay in good condition? The contacts might be damaged, or windings might have shorted.

When testing relays, make sure they engage at the rated coil voltage, and hold their position, until at least 80% (ish) of their rated coil voltage.

Are you sure the relay and gong are wired in series? That would seem a bit odd. I would think they would be in parallel.

There is only one output leaving the RTU, then is disappears into the wall. At the gong, a wire comes out of the wall to the... solenoid? Or whatever you call that mechanism that trips the gong's actuator. Then goes back into the wall. So I assume they are run in series.

 

[W2NJS]

If the light relay is actually in series with the gong then the relay must have the same current draw as the gong. In the series alarm circuits the voltage is additive so the current must be uniform for each device on the circuit. What you most likely need is the services of a good fire alarm technician or an electrician who understands alarm circuitry.

 

[ocguard]

If the light relay is actually in series with the gong then the relay must have the same current draw as the gong. In the series alarm circuits the voltage is additive so the current must be uniform for each device on the circuit. What you most likely need is the services of a good fire alarm technician or an electrician who understands alarm circuitry.

We used to have dedicated fire alarm technicians on staff. Now we have Google, chewed bubble gum, and a house fund.

 

[Thayne]

Check what voltage & if it is AC or DC leaving the RTU, (Maybe it comes from a transformer somewhere near) then activate it and check the voltage at the gong, (You can tell if it is series or parallel at that connection) then anyone with some electrical knowledge can figure out where the problem is--bad relay or whatever.

 

[902]

Just from a quick read, two things come to mind: 1) simultaneous current draw, and 2) inductive "kick" from a solenoid or relay. Some very simple things to try which might negate your need for a PLC replacement - 1) place a diode across the relay/solenoid windings; 2) construct an emitter follower circuit that provides isolation between the two independent systems. No guarantees, but I'd say give it a shot.

Wouldn't the light output line be latched and the gong be momentary or a timed pulse?