Napco Gemini 1632

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Old 06-29-18, 04:54 PM
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Napco Gemini 1632

Napco 1632 system. I've had the system about 14 years and it's been flawless. Never had a false trip or malfunction on any of the zones. Yesterday the system was armed (set on instant) and one of the window zones went into alarm for no reason. No one had opened the window causing the alarm to go off. The window in question is a bathroom awning window in the shower area which does get some moisture. The magnet is installed on the bottom of the window frame and makes contact with the wired contact inside of the frame when the window closes. I shut off and rearmed the system and it did not go off again. Later in the day I replaced the window contact, magnet, and the resistor in the panel to try and eliminate any issues. What would cause the zone to trip? I checked all of the terminal connections and everything was tight. I'm hoping that the computer board is not going to start malfunctioning and causing problems with false trips. Is this the start of problems with the main computer board?
 
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Old 06-30-18, 12:35 AM
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It's not that unusual for a system to develop a falsing problem after many trouble-free years. All houses shift and settle over the years, and the statistically most likely cause of a perimeter (door/window) contact falsing is a change in spacing (distance) or alignment between the switch and magnet. They could have been on the threshold of falsing for years before actually going over the edge.

The least likely cause, statistically, is failure of the control panel. If the old switch in the frame and the magnet on the bottom of the sash had drifted out of alignment and/or too far apart, replacing them in exactly the same place might not stop the falsing--unless the new switch is more sensitive or the new magnet is stronger.

The simple fix for this problem is to make the magnetic field stronger next to the switch by adding a 2nd magnet beside the existing one. It's important to orient the new magnet with the old, with the same polarity, so that they're trying to push apart from each other.

Sorry I can't be more specific, but I don't know what kind of window you're working with there--your description could fit double-hung, sliding, or casement. Also, you mention the magnet being ON the sash rather than in it, so I'm assuming the magnet is surface-mounted rather than recessed. A picture(s) of the switch/mag would be helpful.
 
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Old 06-30-18, 03:51 AM
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The inside of a typical contact is a reed switch the size of a pencil lead. Over time, simple metal fatigue can cause the switch to fail.
 
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Old 06-30-18, 07:56 AM
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The magnet is a surface mount on an awning window. The wired portion of the contact sits inside of a space under the wood trim where the window mechanism draws into when the window closes which also hides the contact. The contacts are very close together if not actually touching. I used an ohmmeter to test continuity with the new contact and I slowly drew the magnet away and there was almost 2 inches before it broke contact. I bought the new contact at a local supplier and the seller was adamant that the contacts cannot lose magnetism over time but I've heard differently from several alarm techs. Hopefully the problem is solved.
Thanks for the help.
 
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Old 07-01-18, 11:27 AM
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Back in the late 70's or early 80's there was an urban myth circulating among alarm techs in the DC Metro Area that magnets lose 10% of their strength every year. At that time, reed switches were relatively new (in common use) and we had thousands of systems installed years and decades earlier that use the old unsealed clunky mag switches that needed stronger magnets to work. The prediction was that in a few years, we'd have to go around replacing _all_ the old magnets.

Of course, that didn't happen, because magnets made to last don't lose any appreciable strength over time, as long as you don't heat them over a flame or repeatedly drop them.

At the time, we didn't have the Internet or Google or Wikipedia or Snopes.com to check on urban legends. Now we do, but we still have some of those old urban legends in circulation, in _spite_ of the empirical evidence of millions of alarm systems installed decades ago that haven't needed all their magnets replaced.

If you want to know about magnets losing their strength, Google and Wikipedia are your friends.

EDIT: Look up lodestones. There are lodestones in museums holding onto nails hundreds (thousands?) of years after being dug up.
 
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Old 07-01-18, 02:24 PM
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The _magnet_ is rarely the problem. The _reed switch_ however, is a simple mechanical device, and sooner, or later, the law of entropy has it's way.

It's _very_ rare, but here in Florida, mostly on South facing metal window/door frames; I've found a _few_, generally older (10+ years), magnets that appear to have lost noticeable amounts of magnetic strength from the repeated solar heating of the metal frame they are attached to. Again, I could count the number on two hands, over a 20 year career.
 
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