Return to the Electrical Wiring Forum | Post a Follow-Up

 o
alarm system goes off every year during vacation

Posted by w0lley32 (My Page) on
Mon, Aug 29, 11 at 13:00

Hi! I have a DSC PC1500 alarm system that for the past three years has triggered a false alarm while I was away on vacation. It's always zone 4 (bedrooms) which have 2 motion detectors on it and nothing else. When I called my installer (an independent guy who works on his own) three years ago, he said he opened the motion detector cover in the master bed and found a spider inside the housing, and attributed it to that. Last year, it went off again during my vacation, and he attributed it to the backup battery being bad intermittently (which my electromechanics background makes me doubt very seriously). This year, he says it's my battery again. When I asked him if the sensors themselves could be at fault, he said just because when he waves his hand at them the little green light goes on, they can't be bad!

That being said, I wanted to do my own diagnostics, so I removed the mouldings that hide the wiring to inspect it, and everything is fine visually. An ohm test proved negative as well, and all the connexions are clean and tight.

Since there seems to be only two possibilities (bad motion sensors or bad control board), please help me know a bit more about motion sensors.

First, do these sensors have a limited life like smoke detectors? If so, what's the average life of such sensors? Is it better to have the same brand sensors and main panel? I have one "no name" sensor and a paragon sensor on zone 4. Could excessive heat buildup in the house have triggered one or both sensors? Finally, zone 4 is the zone with the longest wiring run (around 50 ft); could that be too long? The wiring does not come close to any power cables.

Finally, while I don't think it's very likely, can the DSC control boards fail in the way that I describe? The system was purchased in 1998 if that matters, but the motion sensors on zone 4 were replaced in 2004.

Can you please help me answer some of my questions and help me troubleshoot my system? Any help would be appreciated. Thanks.


Follow-Up Postings:

 o
RE: alarm system goes off every year during vacation

I don't know the answer to your problem, but it the system is monitored, the monitoring company should replace the sensors for free. If not, I would replace the "no-name" as that's the first area of questionable concern. When in doubt, replace.

As for heat, if those rooms face south and are heating up more than the rest of the house, that also could be suspect, all else being equal.


 o
RE: alarm follow-up

One other thought, you could try switching the wires from one zone to another. If the system false alarms again and the fault is still in the same zone (bedrooms) it's the controller. If it changes, it's in the wiring or sensors.


 o
RE: alarm system goes off every year during vacation

Thanks for you reply. I was going to replace both sensors anyway since the're cheap and more than likely the cause of the problem, but I still would like to know more about them, especially if they their internal components degrade over time, and when I replace them, are they "plug and play" or do I have to calibrate them? If so, can you please tell me the procedure?

Thanks.


 o
RE: alarm system goes off every year during vacation

Technically, everything degrades over time, but the lifespan of an alarm sensor should be pretty long.

They're pretty much plug-and-play. You may find a "sensitivity" adjustment.


 o
RE: alarm system goes off every year during vacation

INFRARED DETECTORS HAVE MULTIPLE ZONES EACH SET OF ZONES HAS A POSITIVE & NEGATIVE-TO ACTIVATE THAT ZONE. IT TAKES TWO THINGS TO ACTIVATE A ZONE, SOMETHING HAS TO PASS THRU THE POSITIVE & NEGATIVE FIELD & ALSO BE MORE THAN PLUS OR MINUS 6 (USUALLY)DEGREES OF WHAT THAT FIELD WAS SEEING.INITIAL POSITIONING OF DETECTORS IS CRUCIAL TO THERE FUNCTION.ARE ANY OF YOUR DETECTORS FACING A EAST OR WEST WINDOW? IF SO THEY SHOULD BE MOVED AS THE SUN & MOVEMENT OF CLOUDS CAN CAUSE A FALSE ALARM AS THEY CAN TRIGGER THE + OR - 6 DEGREE & SHOW MOVEMENT THRU THE FIELDS.IF SPIDERS ARE GETTING IN A DETECTOR THAT MEANS A WIRE HOLE IN THE REAR OF THE DET NEEDS TO BE PLUGGED.ALSO CHECK THAT THE DETECTOR FIELDS ARE NOT LOOKING AT A HEAT REGISTER OR ANYTHING ELSE THAT MIGHT SHOW AN IMMEDIATE INCREASE, OR DECREASE IN HEAT OR COLD, OR MOVEMENT(SUCH AS BLINDS OR DRAPES)I HAVE HAD DETECTORS IN HOMES FOR OVER 15 YEARS THAT ARE STILL WORKING GREAT BUT THE NEW DETECTORS ARE MUCH BETTER & FAR CHEAPER. HOPE THIS HELPS.


 o
RE: alarm system goes off every year during vacation

ALRIGHT THEN!!!!!


 o
RE: alarm system goes off every year during vacation

Thanks for your replies. One detector is at the corner of the west and south walls in the master bed (with a window on the west wall) and the other is in the office in the corner of the north and west walls. There is a window on the east wall, but both windows have wooden blinds and they were closed. As far as the spider is concerned, the alarm guy said he saw it, but I was right beside him and I never saw it. I think that he made that up since day 1.

Anyways, I have replaced the sensors for good measure, but I have realized that the false alarms always occur on the 11th or 12th day of vacancy. To my knowledge, there are no power cables in the vicinity of the alarm wiring, but if there are some that I didn't know about, could they be causing the false triggering?

What is the typical current draw of such sensors when "idle"? Could the 50-foot run of 24 AWG wire not handle the current draw, causing the wire to heat up, causing more voltage drop, leading to more heat, until there's not enough voltage present at the detector?

Thanks for your help.


 o
RE: alarm system goes off every year during vacation

I know for sure that I'm not killing the power to that circuit ( the hall lights are on that circuit, and when I come home from my trip it's usually night), and when I return everything on that circuit works so I know the breaker didn't trip. Besides, the "trouble" light on the keypad lights up as soon as the power is lost.


 o
RE: alarm system goes off every year during vacation

I still believe the 11 or 12 day element is
key to diagnosing this problem. What could
be happeining on the 11th or 12th day that
would trigger the sensors? Are there any
'wireless' components in the system that
could be receiving spurious signals? Also
check out anything that might be on a timer,
and see if there is any way it could possibly
effect the security system. I'll bet the
answer is something that is
simple and obvious, once you discover what it is.
Good luck and please post your solution, once
you find it.


 o
RE: alarm system goes off every year during vacation

Since it occurred to me that all false alarms occur after 11 or 12 days, I'm almost positive that it's the key to the answer. The fact that it's always zone 4 that causes problems makes me look for something different about that zone. One thing that's different from the other zones is that the wire runs are about 25 feet longer than the other zones.

To answer your questions, there are no wireless components on the system, and I don't even think they have that capability. I don't like wireless systems because I have never seen them work to my satisfaction. I still plug my laptop into an RJ-45 jack. I have no timers as well. The circuit powering the system has the hall lights and outlets, the front outside lights (controlled by an ordinary toggle switch), the living room outlets and a receptacle that I installed in the basement next (about a foot to the left) to the alarm system. Alarm system plugs into that receptacle with an SVT cord, and I am positive that the receptacle is always hot.

What would happen if something on zone 4 caused the voltage to continually drop ever so slightly and became too low to power the sensors after 11 days? What's a typical cable length between a motion sensor and the control panel?

Now that I think of that control panel and where it's located, it struck me in the face that the keypad is right next to the door, about 8 inches above a 3-gang switch box. the keypad cable runs beneath the door casing, parallel and approximately one foot away from the power cables going to the switches, and that's also where I took my power for the basement receptacle. Would those power cables be too close? They run parallel for about 4 feet. Have you got any other suggestions? Thanks.


 o
RE: alarm system goes off every year during vacation

Are you changing your HVAC settings when you leave?


 o
RE: alarm system goes off every year during vacation

I have electric baseboard heaters and a window A/C (which I turn off before leaving). I take my vacation in August so the baseboard heaters have been shut off months before. No HRV or anything else that could displace air inside the house.


 o
RE: alarm system goes off every year during vacation

As Enigma2 has already suggested, swap the
sensors between zone 4, with another zone
and see if the problem is still there. That
would eliminate the board as being at fault.
Put some tape over the motion sensors, so that
you can rule out the fact that they are doing
what they are designed to do.


 o
RE: alarm system goes of every year during vacation

Just to be clear, when it was suggested to swap
the sensors with another zone, the swap was to be
done with the wires at the control board, and not
with the actual sensors themselves.


 o
RE: alarm system goes off every year during vacation

you probably have a cat stuck in the house.


 o
RE: alarm system goes off every year during vacation

Thanks for your replies. I was aware to swap the wires at the control board, to see if the problem transfers to the other zone. As for cats, I don't have any pets, and I am not aware of any rodents.

If I go by your replies, it looks like wire length or its proximity to power cables has nothing to do with my problem? Thanks.


 o
RE: alarm system goes off every year during vacation

I'm an alarm tech. Apart from things, bugs (silicone the holes in the back of the motion sensor to seal where the wire comes in) triggering it, a moving blind or curtain can trigger it too. A wall hanging could also, if the hvac makes it move. This is why it's not desirable to have two motions on one zone. If it faces a window or something sometimes that can cause falsing. If it's curtains, you can mask the back of the motion's fresnel to block that part off, the motion installers's sheet will explain it (you can usually download these.) Brands generally don't mind being mixed.

One thing you could do is disconnect the zone in the panel (are there resistors in there? Another possible issue) put a jumper wire in there across the zone, then put a small relay that's switched by the 'loop' - the sensor output from the motions - and a buzzer, if the bedrooms aren't in use. Watch it for a few days, and see if you can figure out what's causing it.

This is an intriguing issue.

Another thing that can trigger them is if the dc to the motions is interrupted...they go through a warm up cycle and of course, because they're probably Normally Closed, when the current to the motion is interrupted, the panel sees it as an alarm event. What could be causing it is a loose connection or damage to the wire in the wall. If there's enough slack at both ends, very carefully restrip the outer sheath an inch or two and remake all connections. If it's typical alarm wire, station z (old style 4 conductor phone wire) it's quite easy to nick one of the conductors when stripping the outer sheath, so a nick is likely close to the end.

How are the two motions wired together? Are there two wires that run to the panel and are connected in series? Does one motion run to the other and have a splice inside? There may also be a splice in the wall, in which case it could be bad, but I don't know why it takes 2 weeks to have an issue.

There are a lot of possibilities here. Timers and electrical interference are two, but unlikely - alarms are generally robust and simple. As for cable length, there ARE limits but in practice some runs can be hundreds of feet without issues.

I've attached a link to an alarm forum, you might try for some fresh ideas there.

Another thing to try is to remove and bypass one motion, then the other, either reprogramming the motion as a door so you can chime it, or using the buzzer as I suggested. A word to the wise about programming, none of the systems are terribly user-friendly, so you may not want to do that yourself.

Another possibility is to see what that zone is programmed as. Also, can the motions see out of the bedrooms into a hallway, and could something in there be tripping them?

Here is a link that might be useful: DIY security forum


 o
RE: alarm system goes off every year during vacation

2004 isn't super-old for PIRs, but they do get better all the time.

Was that a Paragon sensor, or a Paradox? They are pretty cheap and you might want to consider replacing them. The latest DSC and Honeywell (Ademco) sensors are pretty good. You need to make sure they're adjusted properly. Check that yours are set to "hostile" environment or less sensitive.


 o
RE: alarm system goes off every year during vacation

Thanks Alan for you reply. You brought very good suggestions, and it is quite timely, because I recently went away for 15 days, and the alarm went off again, on the 11th day. Last year, I had re-done all the connections both at the sensors and in the panel, and swapped zone 4 with zone 5. I am the one who installed the wires; I used 4-wire telephone wire and each sensor is wired back to the panel and connected in series there. Zone 4 and zone 5 both have two identical yes - Paradox not Paragon - sensors. I did not splice any wires at all. Every run from a sensor to the panel is one continuous piece of wire from a 500ft spool. The spool has a sticker with ULC and CSA listings and does not appear to be cheap. I wrote in my first post that it's been doing this only for the past 3 years, but I never quit the house for more than 10 days before that, so I don't know if it's a new condition or not.

I do not have any central HVAC or air handler, only electric baseboard heaters and a window A/C. The baseboard heaters are obviously off at this time of year and I shut off the window A/C before I left.

Now please consider this: I have had this system since 2004, and the only 4 false alarms I had consistently occured after exactly 11 days of being armed continuously. I don't know about the first two years, but the last 2 false alarms not only occurred 11 days after I left the house, they occured at the same time of day also; in 2011 I left the house and armed the system at 5:54 AM and it went off at 5:54 AM 11 days later, and last August I left the house at 12:06 PM and I had a false alarm 11 days later at 12:06 PM.

I think that this is not a coincidence, but I may be wrong. Would you have any ideas beyond the ones you already gave me? Thanks a lot!


 o
RE: alarm system goes off every year during vacation

That is interesting, the 11 days. I suppose that's beyond coincidence, really. To the minute? I'm going to ask around.

I guess those periods are the longest times the system's continually armed. I'm wondering if there's some odd programming thing there that could be causing it, since it's so exact. Some sort of failed reporting thing (they can be programmed to phone home periodically etc)

I am going to ask around, but I have these thoughts: Messed up programming or firmware, or an issue with the clock or panel itself. It doesn't explain the zone 4 thing. If you have more than one motion sensor on a different zone, you could swap them.

Personally, I'd make really good labels on all the zones, disconnect and jumper them, and arm the system (you could disconnect the siren, but DSC panels have built-in siren supervision so you'll need to leave a resistor across the siren terminal in parallel or you'll get an error code. I'm not sure offhand what the value of the resistor is, there should be one there already, in the panel, or at the siren.

If it goes off 11 days later, you know the panel's bad.

Good news is, they're not very expensive, +-$100 or so, and the newer ones - PC1832 etc offer a few neat features like some support for self-monitoring etc.

You could jump to this step anyway, if you like. Maybe your installer will give you a deal.

Since this seems to happen 11 days to the minute, I'm leaning towards a problem with the panel itself, not the motions, not the keypad.

I suppose since it's 11 days to the minute, you can be prepared for it, put a reminder on your cellphone

Problem is the 11 days needed. U


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!


Return to the Electrical Wiring Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.


Learn more about in-text links on this page here