Operation
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IOM 1274-3 • CENTRIFUGAL WATER CHILLERS
Figure 56: Settings View - Tower
Tower Control Settings
There are five possible tower control strategies: (I)
VFD
STAGE
, (II)
VALVE SP
, (III)
VALVE STAGE
, (IV)
NONE
, and
(V)
VALVE SP / VFD STAGE
. These control strategies are
selected from the TOWER Setpoint Screen
(see
Table 16 on
page 50
) using
the
Tower Valve/Fan VFD Strategy setting.
(In the following pages, “SP” means “Setpoint.”) An explanation
of each control strategy follows this paragraph. Along with each
explanation is a diagram and graph to help illustrate the control
strategy. Note that these graphs illustrate the default conditions
for each strategy.
Setting Tower Control Using the HMI
Panel
MicroTech® may assist in the head control either directly
or through inputs to a BAS to optimize performance and
efficiency. Using the MicroTech® controller, up to three Digital
Outputs of Tower Staging along with two Analog Outputs (0-10
VDC) are available. The two Analog Outputs are as follows:
1. Bypass Valve signal
2. Tower Fan VFD signal
Setup for any tower control will be accomplished on the HMI
using the TOWER Setpoint Screen (see
Table 16 on page
50
and see
Table 16 on page 50
).
Setpoint for Cooling Tower Control on the TOWER Setpoint
Screen sets the type of control. NONE is selected as default.
Choose TEMPERATURE for entering condenser water control
or LIFT to define the lift pressure between the Evaporator
Pressure and the Condenser Pressure.
Setpoint for Tower Valve / Fan VFD Strategy on the TOWER
Setpoint Screen defines if and how the two MicroTech® Analog
Outputs (Bypass Valve signal and Tower Fan VFD signal)
will be used with the Staging selected for the tower. A BAS or
other control may monitor these outputs to understand when or
how much the MicroTech® would recommend for proper head
control on the WSC unit. Setup instructions for each of the five
tower control strategies are provided next.
Setpoint 3 (Cooling Tower Stages) on the TOWER Setpoint
Screen sets the number of tower stages that the tower has.
Strategy (I) VFD STAGE (Default):
In this mode, a VFD controls the first fan. Up to two more fans
are staged on and off and there is no bypass valve. See
Figure
57
and
Figure 58
.
To set up in HMI,
A. The TOWER Setpoint setting for Cooling Tower Control
strategy should be NONE. Tower Valve/VFD should be
changed to VFD STAGE for control of the VFD speed
based on temperature or lift.
Figure 57: Strategy (I) - VFD STAGE
Condenser
0-10 VDC
Signal
Cooling Tower
Fan Staging
(Up to 3 fans)
MicroTech
®
Controller
Tower
Control
Panel
w/ Fan
VFD
Содержание WSC
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