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Alarm Stays On

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.
Reply to
frank1492
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Is it wired backwards, by chance? Removing the sensor and just opening/closing the circuit makes the alarm work properly? Almost has to be a sensoe related problem.

Reply to
clare

You think after 25 years it re-wired itself to be backwards?

For the OP, it might be time to consider a new system. Anything electronic that is approaching 30 years of service is bound to have issues. Just simple things like electolytic caps for example. Another problem with a system of that vintage is that it's probably going to be impossible to program if you want to change anything, even if you have the codes. My old one of that vintage was programmed by blowing PROMS to set the thing up. You can get a whole new panel kit for $150.

Reply to
trader4

Being obtuse again, eh?? The unit was replaced. Always possible the first one was defective and the new one reversed, no??

Stranger things have happened. Smartass.

By his description and basic analysis it would APPEAR to be a sensor related problem - either function or installation, or interference.

Reply to
clare

How can you say that with such certainty our Canadian know-it-all ?

It could have more to do with changes in the resistance of the loop and how the old SOLID STATE electronics are dealing with that... Hence it is more pertinent to check for out of spec EOL resistors and components on that circuitry which is effecting the way the central controller is reacting to the sensor devices wired to it...

Reply to
Evan

Hey, I'm not saying NOT to check the resistors - but it APPEARS it is only the one sensor causing a problem, and if the sensor is removed from the circuit and a switch substituted, the system works as it is supposed to. This would lead ME to suspect it is an issue with the sensor.

Now,I don't pretend to know it all. However, many times, particularly with older tech solid state devices, reverse connections can have strange results, and unlike a simple switch type "sensor" like a door or window sensor, the microwave and PIR units ARE polarity sensitive.

ALSO

On any Honeywell Dual Tec I've seen there is a separate 7-16 (usually

12) volt power supply which is polarity sensitive, as well as the alarm contacts - which have 4 different programmable resistor values across the NC contacts if connected C to NC. and another 4 resistors across the NC tamper switch connections. On some you can connect C to EOL - I don't know what the rammifications would be if connected C to EOL.

Being Normally Closed contacts, if there is more than one sensor or switch on the loop, they are wired in series, with the EOL resistor across the terminals at the panel (generally) so with the whole string closed the resistance across the circuit is nominally ZERO ohms, and as soon as any contact is opened the panel sees the EOL resistance (in the OP's case, 2.2K ohms. If the sensor is installed jumpered to 2.2K ohms, the panel will see 4.4 k ohms with the sensor tripped - and the panel could "fault".

If he is using an external EOL resistor he needs to remove all of the jumpers.

If he has not removed the jumpers, it would very likely malfunction with the sensor connected, and work fine with it removed and replaced with a switch or jumper.

You can look for zebras and unicorns all day, but when you hear hoofbeats, it's much smarter to look for horses, ponies, or jack-asses first.

Reply to
clare

LMFAO -- I don't think you have ever seen one based on this explanation of alarm system workings.

x-posted to ASA for a good laugh.

Reply to
G. Morgan

Bwahahahahaha!!!

Why did you remove my x-post?

Reply to
G. Morgan

I've installed a few. Some over 30 years ago, The last ones about 15 years ago - wired and wireless - and I've worked on one of the new ones within the last 2 years - a whole lot more complex - a whole computer packed into the box, with complex programming up the ying yang. Other than moving the control panel (keypad) and a few sensors, I said "get the alarm company - it'll be cheaper than paying my time to figure out how to program it".

There's more than just open and closed switches and resistors in the new digital jobs. The old analog or "2 bit digital" systems WERE simple. The 30 year old ones were a lot simpler than the 15 year old ones - which were not "leading edge" at the time.

But (at least most of) the sensors from the 30 year old system still work on the new systems, and many of the new sensors work on the 30 year old ones as well.

Reply to
clare

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