Daikin Magnitude, Installation, Operation And Maintenance Manual

Page: 43 / 70

www.DaikinApplied.com 41 IOM 1210-7 • MAGNITUDE
®
MODEL WMC CHILLERS
o
peraTIon
Stage Differential (Temp) 3.0 °F 1.0 to 10.0 °F M Fan staging deadband with SP1=Temp
Fan Stage Down Time 5 min 1 to 60 min M Time delay between stage up/down event and next stage down
Fan Stage Up Time 2 min 1 to 60 min M Time delay between stage up/down event and next stage up
Cooling Tower Stages 2 1 to 4 M Number of fan stages used
Twr Bypass Valve/Fan
VFD [SP2]
None
None, Valve SP,
Valve Stage, VFD
Stage, Valve SP/
VFD Stage
M
None: No tower valve or VFD
Valve SP: Valve controls to VALVE SP2(4) & 3(5)
Valve Stage: Valve control setpoint changes to fan stage setpoint
VFD Stage: 1st fan is VFD controlled, no valve
Valve SP/VFD Stage: Both valve and VFD
Cooling Tower Control
[SP1]
None
None, Temperature,
Lift
M
None: No tower fan control Temperature: Fan and valve controlled by EWT Lift: Fan and
valve controlled by lift pressure
Tower Valve Type
NC (To
Tower)
NC, NO T Normally closed (NC) or normal open (NO) to tower
Explanation of Tower Control Settings
There are five possible tower control strategies: (I) NONE ,
(II) VALVE SP , (III) VALVE STAGE , (IV) VFD STAGE , and
(V) VALVE SP / VFD STAGE . These control strategies are
selected from the TOWER Setpoint Screen (see Figure 35
on page 40 ) using Setpoint 2. (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. See "Setting Tower Control Using the HMI Panel"
on page 43 for details on how to set these tower control
strategies.
(I) NONE: This control strategy is tower fan staging only.
This is not a recommended strategy . In this mode
the tower fan staging (up to four stages) is controlled by
either the condenser Entering Water Temperature (EWT)
or LIFT pressure (difference between the condenser and
suction pressure). Tower bypass or fan speed are not
controlled. See Figure 36 and Figure 36 .
Figure 36: TOWER Setpoint - SP2 - (I) NONE (I) NONE
Figure 37: Temperature vs. Fan Stages
(II) VALVE SP: This control strategy is tower staging (up to
four stages) with a low-limit controlled bypass valve. The
tower fans are controlled as in (I), plus a tower bypass
valve is controlled to provide a minimum condenser EWT.
There is no interconnection between the fan control and
the valve control. See Figure 38 and Figure 38 .
Figure 38: TOWER Setpoint - SP2 - (II) VALVE SP (II)
Figure 39: VALVE SP - Valve Opening vs. Temperature
As shown in Figure 38 , the default temperature at which the
valve opens completely is 65°F. This temperature is the Valve
SP (also called Valve Target) and is adjustable.
(III) VALVE STAGE: This control strategy is tower staging (up
to four stages) with a stage-controlled bypass valve. In
this mode, the bypass valve controls between fan stages
Condenser
Cooling Tower
Fan Staging
(Up to 4 fans)
Tower
Control
Panel
MicroTech
®
II
Controller
65
70
75
80
85
90
95
0 1 2 3 4 5
Te
m
pe
ra
tur
e (
°F)
Fan Stages
Condenser
Bypass Line
0-10 VDC Signal
Bypass
Valve
Cooling Tower
Fan Staging
(Up to 4 fans)
MicroTech ® II
Controller
Tower
Control
Panel
0
20
40
60
80
100
60 65 70 75 80 85 90
Va
lv
e O
pe
ni
ng
(%
)
Temperature (°F)