Here's a weird one. I have an old Ademco hard-wired alarm panel which has been running well since 1985. Recently it went into alarm condition but would not shut off. (For a momentary opening of the closed loop, it's supposed to shut off after 12 minutes. The closed loop contains a Dual Tec PIR/microwave combo unit which has a very low false alarm rate. When it false alarmed recently, I forgave it, but the alarm stayed on so I assumed it was "latching" due to some failure and not shutting off. I replaced it with a second unit, and watched the LED's carefully. The new one was clearly working properly. On testing the system, I simulated an alarm condition and watched the LEDs turn on and off, so I knew the OC was momentary. I even checked the output with a meter. The alarm did not turn off after
12 minutes!!!!! I then did a manual open and reclose of the loop with the Dual Tec out of the circuit. The alarm cut off after 12 minutes. What is going on here? The Ademco recognizes the opening of the loop but does not recognize the closing, but *only* when the closing is done by the Dual Tec and not manually. Ideas? I'd say the relay on the DT is not re-closing properly but the other unit apparently did the same thing. The panel must think it sees something other than a closed loop! A real hair tearer. (Thanks for help.) P.S. The loop has a 2000 ohm terminating resistor.- posted
11 years ago