Not understanding zone reporting behaviour
AJAX sensors only report zone status through Modbus TCP when the system is armed or in night mode. Setting devices to Always Active enables daytime reporting, but also means those zones will trigger the alarm when the system is disarmed. Plan which zones genuinely need 24/7 Modbus TCP reporting.
Not inviting Elausys as Security Company
Area control (arm/disarm from Modbus TCP) will not work without inviting Elausys as a Security Company in the AJAX app. Internet access is also required for arming/disarming commands.
Incorrect area count with AJAX groups
Match Partition Mode and the number of areas on the gateway web interface to the AJAX group configuration. Check these settings if individual group commands behave incorrectly.
Expecting disarm to exit Night Mode
Disarming a group does not disable Night Mode when groups are enabled. You must explicitly send a Partial Arm (OFF) command to disable Night Mode. Design your controller logic to handle this independently.
Ethernet connection loss
If the Ethernet connection between the gateway and the AJAX Hub drops, the Connected LED will turn off. Detector status coils will hold their last known state until communication is restored.
Modbus TCP connection timeout
The gateway automatically closes idle Modbus TCP connections after 60 seconds of inactivity. Ensure your Modbus master is configured with a polling interval shorter than 60 seconds to maintain the connection.
Writing to read-only coils
Attempting to write to status coils (addresses 0x000B and above) will return a Modbus exception code 0x02 (Illegal Data Address). Only command coils (0x0000–0x000A) accept write operations.