Lightning setting off my alarm system

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Old 08-14-19, 01:59 PM
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Lightning setting off my alarm system

Hi everyone... 1st time poster, glad to be a member.

I have a Vista 20P which I programmed myself. I've been having a curious problem lately where by my lower level, hardwired lower level window zone has been "opening" during thunderstorms.

I replaced the contact sensors (they are the "hidden" type in the frame/sash) a few years ago (when I replaced the windows).

The latest event occurred at 2AM and indeed a thunderstorm was taking place. After checking everything was OK, I observed that the lower level window zone opened for like 3-5 seconds (it was more than a brief open/close) when I saw a flash of lighting. The thunderous boom sound had not occurred yet given the storm was kinda far away when this happened. So I convinced myself something electrical is going on and it wasn't caused by the vibrations of a "boom".

This is a new phenomenon, the system has worked untouched for years now without having this problem. Now it has happened a few times in the past few months during thunderstorms.

Wondering if anyone has any thoughts on what I could do to mitigate the problem? I was going to replace the contact sensors and an "easy" thing to try but not sure how a contact sensor could fail in such a way that this became a problem.

Could the panel be bad?

Anything I can do to minimize the effects of suspected induced current from lightning strikes on the zone?

Thanks so much.
 
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08-14-19, 04:18 PM
MrRonFL
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The switch in these things is about the size of a coarse human hair. The temper of the springy metal can, and does get weaker, so that even a mild voltage or vibration can pop it open for a split second.

They are inexpensive enough, that replacing the contact is a cheap first step.
 
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Old 08-14-19, 04:18 PM
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The switch in these things is about the size of a coarse human hair. The temper of the springy metal can, and does get weaker, so that even a mild voltage or vibration can pop it open for a split second.

They are inexpensive enough, that replacing the contact is a cheap first step.
 
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Old 08-14-19, 05:06 PM
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Now it has happened a few times in the past few months during thunderstorms.
What a coincidence. I'm an installer. I have a customer with a mansion on the side of a hill..... fairly close to the top. This house eats mini magnetic press-in switches. Picture 40+ windows. I've had them blasted open and go intermittent. I just a got a call a few days ago with one window swinging open and closed. Luckily, I did the installation so that every window is on its own zone and I know exactly which one has the problem. This problem seems to happen during storms. It can go a year in between problems and it picks a random switch. Some were already replaced twice and others first failure.

Here's an even stranger issue. I've had switches permanently open and intermittent right out of a brand new bag of 10. It can really try your patience.
 
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Old 08-15-19, 06:08 AM
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Thanks for the input... as I suspected; swapping out the contacts is a cheap 1st step. Interestingly, before I replaced the windows, the house still had the contacts installed from 20+ years ago - never had an issue with them. Presuming they are bad, the new ones are toast after a few years.

I've the "delay" time (or whatever it is called) cranked up pretty high but like I mentioned, that zone opened for like 3+seconds while I was watching the panel with there was a lightning strike...

I might look at setting them up as individual zones but I suspect that will become a wiring nightmare.

Do you guys recommend one brand of contacts over another? I am using recessed contacts in the window sill/dash.
 
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Old 08-15-19, 07:40 AM
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Just a left field thought, the sensors used, NO reed switch only, or includes builtin shock sensor?
I have issues with some door/window contacts that include the shock sensor.
 
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Old 08-15-19, 01:51 PM
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I believe them to be good ole NO reed switches.

I don't understand how induced current on the wiring would cause the zone to open. The panel is putting current/voltage thru the zone and should only open when there no more current flowing.

Was thinking of putting a resistor on the zone for no other reason than to add some impedance.

Also, I presume that is DC flowing thru the zone circuits. If it was A/C, I would try putting a capacitor inline to block any induced DC.
 
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Old 08-15-19, 06:28 PM
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There is supervision voltage on the circuit; and you can't add extra resistance because the system expects a specific resistance value in the loop.

Basically, the wiring, especially in exterior walls, is a big antenna. The induced voltage is enough to either weld the reed switch, or create enough current flow to force it to flex. It's kinda funky physics; but again, that metal "reed" is really tiny.
 
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Old 08-16-19, 05:23 AM
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As MrRonFL mentioned, the voltage on the zone wires (3VDC for DSC panels), is there so the panel can inspect the voltage returning and identify (0V = open, 3V =Closed, etc).

The reed switch is simply open and closed via the magnet pulling it closed or releasing it when moved away.
With that being said, the switch is a super tiny soft piece and over time, abuse or over current, can be damaged.
If over voltage or current did occur however, there should be a log in the panel for it depending on what the panel logs.

I did mention the shock sensor as some guys would install the door/window contacts that also contained a shock sensor. I personally do not like these and only use them if required for ULC purposes (or if customer is dead set to have it).
 
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Old 08-16-19, 11:47 AM
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My vista panel will support zone doubling so as I understand things, I could add a specific resistor to the zone and be OK.... my thinking here, which maybe wrong, is having a load in the circuit would minimize voltage spikes from the micro amps being induced in the wiring.

I would think the reed switches would be "slammed" against their contact from the magnet and thus unable to bend from voltage/current spikes....

Regardless, I ordered some new contacts and will install to see if it resolves my problem. I will keep you posted.
 
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Old 08-16-19, 01:07 PM
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There's an old-school solution to just about any sort of transient flakiness on a hardwired zone loop, but it involves putting a relay between the panel zone terminals and the zone loop. it has usually been a bulletproof fix, but takes time & trouble and needs to be done right.

If new contacts don't solve the problem, let us know and I'll elaborate.
 
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Old 08-16-19, 01:55 PM
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I would suggest just replacing the switches.
Zone doubling can get confusing and will not help the problem you are having.
 
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Old 08-16-19, 02:49 PM
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Sadly, this is a known phenomenon with reed switches, especially if installed in metal framed doors and windows. Compared with the glitches of plunger, roller, and ball switches, these are relatively care free.

Just remember, the second law of thermodynamics will always win, in the end.
 
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