I can't make sense of the existing Alarm wiring


I am in the process of installing a Konnected board and trying to make sense of the current (legacy) alarm system wiring.

My house apparently has 7 "zones" (7 different sensors, from motion sensor to door/window sensors) , 2 keypads (that show the status of each "zone") and a bell.

So far, so good. Then I looked at the existing alarm board and tried to map each of the cables to its "zone"/sensor. This is where things stop making sense to me:

I can count 10 cables that go out of the alarm board:

- 1 is the AC power.

- 1 is the bell/siren.

- 1 is the phone line.

- 5 connect to each of the Z1..5 screw connectors on the board (and are, I suppose connected to the various sensors)

- 2 are connected on the same YEL/GRN screw connector, and from what I gather, these are the 2 keypads (it would make sense as those show the exact same status apparently).

Now what bothers me is the 5 "Z" ports but I have 7 distinctively working sensors. The existing alarm can detect each of the 7 sensors/"zone" individually and uniquely. It's not a case of sensors wired in series (I suppose). But how can the system handle 7 sensors when only 5 "Z" ports are connected ?

One of my theories is that the YEL/GRN pair for the keypads are actually some sort of data wires (not unlike USB cables) that use an encoding of some sort and are not just dumb closed/opened circuits. Since each of the keypad is close to a monitored door, I also assume the door sensors are actually connected to the keypads.

But this is all conjecture and I don't know much about this. Could anyone explain/emit a theory as to how these currently works? Also, how can I plug that to Konnected (I would be okay in discarding one of the motion sensors to get down to 6 zones btw).

Thank you.

  • The legacy alarm board

  • Hi Julien.  I am not at all an alarm expert.  I have ADT/ademco equipment.  That being said, I never heard of hooking sensors directly to the keypads.  Obviously the keypads have power and data as you identified.  The zones are probably ganged up outside the box somewhere.  Probably grouped by location.  Mine were mostly connected inside the box, with a few in the attic.  You may have resisters at the far ends of the zones for anti-tamper.  I think your best bet is to map out what you have, either by tracing or tripping sensors and making a chart.  Just concentrate on the zone connections and you should be able to figure it out.  That is what I did and found I did not like how sensors were grouped and needed more zones for a smoke detector.  I just used my pro panel without paralleling.   I have mixed feelings about only having the cell phone to arm/disarm.  I kept the old panel board for the power supply and battery back up.  You do know you need the paralleling boards to keep using your keypads?  Glass breaks and motion detecters will use power and zone.  You can google all of your equipment and get manuals on each piece if you don't already have them.  My next step is to use wall mounted tablets as status monitors.  

  • Hey Jon, thanks for the reply.

    I actually checked the panels and this confirmed my initial idea: each door sensor (close to the panels) is directly wired to the alarm panels. I confirmed that with my voltmeter in resistance mode and opening/closing the door. This behaves exactly like the only other door sensor that is not close to an alarm panel (in terms of resistance/open-close circuitry).

    There seem to be quite the amount of logic in each alarm panel, so I would not be surprised if the data connection between the panels and the central board was used to encode information about directly-connected sensors.

    In any case, I feel I have a complete mapping now and will be able to hook things up soon! The only thing I need to figure out is why the supposedly 12V aux outputs actually output 13.6V. I hope it's not to account for tension drops along the lines or if it is, I hope the output of the power supply will be enough to power-up the motion sensors.

  • 12 volt power sources are never 12 volts.  Lead acid batteries are 13.8 volts charged.  Makes sense that your system is 13.6.  

    Sounds like you are on track.  You might pull out the keyboards and see if there are other two conductor wires attached.  I would be surprised if there were.  

    Double check your contacts and see if opening two doors, windows, or a combination trip that zone.

    I have a lot of powered sensors, so I ended up bringing 12 volts (+ and -) out to  buss bars to distribute.

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