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Overall Status
Status text
Description
Noise Reduction
Unit is running with the Quiet Mode activated. Active setpoint may differ from what has
been set as cooling setpoint.
Max Pulldn
Unit thermostat control is limiting the unit capacity because the water temperature is
dropping at a rate that could exceed the active setpoint.
Pumpdn
Unit is shutting down.
Prepare the unit to start
The unit starts only if all the enable setpoints/signals are active:
•
Unit Switch Enable (signal) = Enable
•
Keypad Enable (setpoint) = Enable
•
BMS Enable (setpoint) = Enable
5.2.2.1
Unit Switch Enable
Each unit is equipped with a Main selector installed outside the front panel of the unit switchbox. As shown in the pictures
below, for VZ units, two different positions can be selected: Local, Disable:
Local
With the Q0 switch in this position the unit is enabled. Pump will start if all other enable
signals are set to enable and at least one compressor is available to run.
Disable
With the Q0 switch in this position the unit is disabled. Pump will not start in normal
operational condition. Compressor are kept disabled independently from the status of the
individual enable switches.
5.2.2.2
Keypad Enable
The Keypad enable setpoint is not accessible by user password level. If it is set to
“Disable”, contact your local maintenance
service to check if it can be changed to Enable.
5.2.2.1
BMS Enable
The last enable signal is coming through the high level interface, that is from a Building Management System. The unit can
be enabled/disabled from a BMS connected to the UC using a communication protocol. In order to control the unit over the
network, the Control Source setpoint must be turned in “Network” (default is Local) and Network En Sp must be “Enable”
(4.2.2). If disabled, check with your BAS company how the chiller is operated.
5.3
Condensation Control (Optional)
Condenser Entering Water Temperature is controlled in order to achieve best chiller efficiency within compressor envelope
limits. To do this, application manages the outputs for the control of the following condensation devices:
•
Tower fan #1…4 by mean of 4 on/off signals. Tower fan # state is on when Cond EWT is greater than the Cond
EWT setpoint. Tower fan # state is off when Cond EWT is lower than Setpoint
– Diff. The picture below represents
an example of activation and deactivation sequence based on Cond EWT present value relation with set points
and differentials listed in 4.2.4.
