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alarm wiring

918 Views 4 Replies 4 Participants Last post by  tomaquar
I want to move my door alarm from a recessed sensor on the interior door to a flush mount on the storm door. My alarm company is not very good so if I make a mistake Ill be without an alarm for a while.

Are there any pitfalls I need to be aware of ? Can I just install the flush sensor and connect the appropriate color wires?

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For added security, some sensors have an "End of Line Resistor" wired in at the sensor. If there is one there, you would need to move that as well.

Some sensors can be "normally open" or "normally closed". In one case a connection is completed when the door is closed. In the other case a connection would be completed when the door is opened. And with an "end of line resistor" wire loop, there can be 3 different states...

Connection open, a "middle state" (reading the value of the resistor), and a shorted state.

Note some alarms can be programmed so that a "delay entry door" causes a short to the wiring loop, however an open state on the same loop would cause an "instant" alarm. (middle state no devices activated - doors closed.)

And then there might be a cable with just two wires run to the sensor. And the sensor could be wired in "series" or "parallel" along with a resistor (depending on sensor type).

Or no resistor used and two wires going to the sensor.

Or there could be a 4 wire cable run to the sensor. Two of those wires could be shorted as a "24 hour supervisory loop" and the other two wires go to the sensor. Or all 4 wires are used for the sensor. Any wire color combination might be used!

High security sensors use 3 wires (not typically in a home).

And note they do all this different wiring intentionally so a burglar would never know for sure which wire is which. They DON'T want to have a "standard" wiring method for every house / business! The "Hollywood" scene of the burglar shorting an alarm wire is a bunch of HOOEY!

Bottom line: Pay close attention to how the existing sensor and wires are connected.
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