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Controls
CAB-PRC001-EN 25
Sequence of
Operation
Sequence of Operation
Fan Speed Switch
Off: Fan is turned off, two-position
damper option spring-returns closed.
High, Medium, Low: Fan runs continu-
ously at the selected speed. The two-
position damper option opens to an
adjustable mechanical stop-position.
ZN.010 and ZN.510
Off: Fan is off; control valves and fresh air
damper option close.
Auto (Fan Cycling): Fan and fresh air
damper cycle with control valve option to
maintain setpoint temperature. In cooling
mode, the fan cycles from off to medium
and in heating mode it cycles from off to
low (factory default that can be field-
adjusted using Rover service software).
When heating is not required, the fan is
off and the fresh air damper option
closes. The fan can also be field-config-
ured (using Rover) to run at a user-
defined speed when the fan speed switch
is in the auto position.
Low, Medium, High (Continuous Fan): Fan
operates continuously while control valve
option cycles to maintain setpoint
temperature. Fresh air damper option is
open.
ZN.520
Off: Fan is off; control valve options and
fresh air damper options close.
Auto
:
Fan speed control in the auto
setting allows the modulating (three-wire
floating point) control valve option and
three-speed fan to work cooperatively to
meet precise capacity requirements,
while minimizing fan speed (motor/
energy/acoustics) and valve position
(pump energy). As the capacity require-
ment increases at low fan speed, the
water valve opens. When the low fan
speed capacity switch point is reached,
the fan switches to medium speed and
the water valve repositions to maintain an
equivalent capacity. The reverse se-
quence takes place with a decrease in
required capacity.
Low, Medium, High: The fan will run
continuously at the selected speed and
the valve option will cycle to meet
setpoint.