Technical Manual - Page 37
Furthermore, the controller will learn the current status of the limit switches and the direction of the sleeve
motor. However if both limit switches are closed during any stage of operation, the controller will only be
able to operate the sleeve motor.
FAILURE MODE, PCB PROGRAMMING
The software for the vent is designed so that when the sleeve motor is travelling upwards, it will only look for
the UPPER LIMIT switch. The software is designed this way so that the mechanical arrangement of the limit
switch will not be a determining factor of the sleeveʼs operation.
However in the situation when the UPPER LIMIT switch fails to close due to either broken wire connection
or malfunctioning of the limit switch, the sleeve motor will continue to operate until either the UP/DOWN is
pressed again or the power is switched off.
To prevent the above situation from occurring, two timers are incorporated into the software. The sleeve will
take 8 seconds to travel from its lowest position to its fully raised position; hence a 15 and a 30-second
timer are used.
If the 15 second timer times out before the corresponding limit switch, the microprocessor will assume the limit
switch fails to close. It will assume the sleeve motor is now moving in the opposite direction than it was before,
due to the mechanical set up of the sleeve, therefore the microprocessor will try to detect the other limit switch.
If the 30-second timer has timed out before the limit switch closes, the microprocessor will stop the sleeve motor
and all operation will be disabled until a power reset is applied.
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