FCU 500, FCU 505 · Edition 02.17
32
Furnace zone control
The zone FCUs (FCU 505) control the zone capacity.
After checking the safety interlocks (after expiry of the
switch-on delay time) and when the fan run-up time
is started, the furnace FCU signals to the zone FCUs
via the input at terminal 66 that they should move
the actuators to purge position. After the purge (and
the tightness test if applicable) has been ended, the
furnace FCU signals to the zone FCUs via the input at
terminal 46 that burner start is enabled. When they
receive this signal, the zone FCUs move the valves to
ignition position for starting the burners and then issue
the enable signal to the burner control units to start the
burners.