Daikin MAGNITUDE WME-D, Installation Operation & Maintenance, Page: 38 / 56

OPERATION
MAGNITUDE WME-D MAGNETIC BEARING CHILLER DAIKIN APPLIED
38
Within each variation of the Auto and Auto Efficiency, a PD loop
determines a tower capacity loop output (TCLO) value that goes
from -100 to 100, where -100 is reducing tower capacity as
quickly as possible, 0 is leaving tower capacity unchanged, and
100 is increasing tower capacity as quickly as possible.
• Tower bypass valve
— steps open above 10 TCLO
— steps closed below -40 TCLO
• Tower fan on/off events limited in frequency by timers for
staging up and staging down
• For a given number N of tower fan stages, all VFD
controlled:
— all stages run at the same speed
— VFD speed steps up from minimum speed setting to
maximum speed setting when above 15 TCLO and
tower bypass valve position is > 90% of Valve Control
Range - Max
— VFD speed steps down below -5 TCLO
• For a given number N of tower fan stages, where one stage
is VFD controlled:
— VFD speed steps up from minimum speed setting to
maximum speed setting above 0 TCLO and tower valve
> 90% of Valve Control Range - Max
— speed steps down below 0 TCLO
— VFD speed -100%/N stages when adding 2nd and or
3rd stage
— VFD speed +80%/N stages when dropping 2nd and or
3rd stage
• For one tower fan stage:
— turn on at 90 TCLO if tower bypass valve position is >
90% of Valve Control Range - Max
— turn off at 20 TCLO
• For multiple tower fan stages:
— (E)nable threshold = 90 / N stages
— (D)isable threshold = 20
— For 2 stages:
— • 1 on E*1 TCLO and tower valve > 90%, 2 on E*2
TCLO and tower valve = 100%
— • 2 off D*2 TCLO, 1 off D*1 TCLO
— For 3 3 stages:
— • 1 on E*1 TCLO and tower valve > 90%, 2 on E*2
TCLO and tower valve = 100%, 3 on E*3 TCLO and
tower valve = 100%
— • 3 off D*2 TCLO, 2 off D*1 TCLO, 1 off D*.5 TCLO
Figure 45: Chiller Unit Tower Control
BAS Tower Control
In the above control strategies, the chiller unit controller is directly
controlling the cooling tower fan stages, variable frequency
drives, and bypass valve. As an alternative, a BAS can control
these components based on the 0-10 VDC signals for the tower
fan VFD and tower bypass valve or condenser pump VFD. See
Figure 46 .
Figure 46: BAS Tower Control
Figure 47: Settings View - Valves
Condenser
MicroTech
®
Controller
0-10 VDC
Signal
Bypass Line
0-10 VDC Signal
Bypass
Valve
Cooling Tower
Fan Staging
(Up to 2 fans)
Tower
Control
Panel
w/ Fan
VFD
Condenser
MicroTech
®
Controller
Bypass Line
0-10 VDC Signal
BAS
Tower
Control
Panel
w/ Fan
VFD