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Controls
UNT-PRC001-EN32
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. Low air tempera-
ture detection option is still active.
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 no heating or cooling is required,
the fan is off and the fresh air damper
option closes. The fan can also be field-
configured (using Rover) to run at a
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. The low
air temperature detection option is still
active.
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/chilled water reset). As the
capacity requirement 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 sequence 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.