The newest version of our control board has a master override or interlock. The interlock, which is now required by some building codes, effectively disables the WHF by closing the damper doors and turning off the fans. It is often used in conjunction with smoke detectors or mechanical systems located in the attic. The idea is that if the furnace turns on or the smoke detector goes off the WHF will shut down. This could slow down the spread of a fire or save $$$ if the furnace was accidentally turned on.
The interlock is integrated into our 24v digital controls on V4 of our control board. To use the interlock simply remove the two-pin shunt and run low voltage wire from the interlock screw terminals to the relay on the device that will disable the WHF. To activate the interlock the relay should interrupt the 24v current. Do not wire 120v to the interlock.
When activated a solid red LED will illuminate on the WHF control board. The fans will turn off and the damper doors will close. Once the interlock is disengaged, the LED will go out. The WHF can be restarted by flipping the wall switch off and on again or by using your remote.