Issue with “water alarm” zone configured as “type 1” (NC)

[Marko Vulovic]

Hello.  I have an M1 that has a zone with definition 25 (Water Alarm) and type 1 (Normally Closed).  There is no EOL resistance.  When the zone sensor is in its normal (shorted) state, the voltage at the zone input on the M1 is measured as 0V (as expected) and the M1 properly indicates the zone as “normal” (not violated).  However when the zone sensor is in its triggered state (open), the M1 improperly indicates that the zone is in a “trouble” state.  The voltage reported by the M1 for the zone is 13.8V.  For a type 1 (normally-closed) zone, I would expect 13.8V at the zone input to be interpreted as “violated”.  Additionally, since a zone configured as Type 1 doesn’t have any EOL resistance, it should *never* be able to report “trouble”.  Is this a bug?  Am I doing something wrong?

I am running the latest FW (5.3.36) on the M1.

[Brad Weeks]

For a Water Sensor you should be using a Normally Open sensor and install the 2.2KΩ across the contacts so you get the three states Normal secure, Alarm when the contacts short and “Trouble” in the event the loop opens (cut wire for example).

[Marko Vulovic]

Hi Brad.  Thanks for your response.

The water sensor I am using is the GRI 2600, which is a very common, NC sensor.  Unfortunately I cannot change that.  But I realized that even in mode 1 it’s expecting a parallel 2.2kOhm EOL resistor and was treating the open condition as a trouble state.  Rookie move on my part.  I added the parallel resistor and it’s working as expected now.

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