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timing when the discharge pressure rises above the Fan
ON Press. The fan stage is decremented, unless the 5
second timer between fan stages is still timing when
the discharge pressure falls below the Fan OFF Press.
When a fan stage is incremented, the fan delay timer is
set to 5 seconds, and the Fan ON pressure is ramped 20
PSIG over the original ON, point back to the original
value over the next 20 seconds. When a fan stage is
Optimized IPLV Fan Control
155
150
145
140
135
130
125
120
`
115
110
105
100
95
90
75
85
95
105
Ambient Air Temp (°F)
FIG. 43 - HIGH IPLV FAN CONTROL
VSD TEMPERATURE CONTROL, OPERATION OF THE COOLANT PUMP,
The Coolant pump and VSD Cabinet Cooling Fans will
run to cool the VSD whenever any of the following
conditions are met:
· VSD Comp IGBT Baseplate Temperature on a 2 or
4 compressor unit is greater than 10°F below the
cutout (Cutout [218°F]-10°F =208°F). When the
VSD internal ambient falls below the restart tem-
perature (Cutout [218°F] - 15°F = 203°F), the fans
and pump will turned off without a time delay.
· VSD Comp IGBT Baseplate Temperature on a 3
compressor unit is greater than 10°F below the
cutout (Cutout [232°F] - 10°F = 222°F).
the VSD internal ambient falls below the restart
temperature (Cutout - 15°F = 217°F), the fans and
pump will be turned off without a time delay.
· Pre-charge Enable 1 from the Chiller Logic Board
is ON.
· Pre-charge Enable 2 from the Chiller Logic Board
is ON.
JOHNSON CONTROLS
CONDENSOR FAN CONTROL (CON'T)
Fan On Press
Fan Off Press
115
125
LD10634
AND VSD CABINET COOLING FANS
When
decremented, the fan delay timer is set to 5 seconds,
and the Fan OFF pressure is ramped 20 PSIG below the
original Fan OFF point, back to the original value over
the next 20 seconds. The ON and OFF points will vary
as ambient temperature changes. FIG. 43 shows the fan
ON and OFF points relative to ambient temperature.
High VSD Cabinet Ambient Temperature
Fan Operation
All condenser fans on all systems will run when the
chiller is off and enabled to run, if the VSD internal
ambient temperature is higher than 5°F below the VSD
Cabinet Ambient Temperature Cutout of 158°F (158°F
- 5°F = 153 °F). When the fans turn on in this situa-
tion, the fan outputs will cycle one at a time with a 100
ms delay between fan starts. When the VSD internal
ambient falls below the "Restart Temperature" (158°F
Cutout - 10°F = 148 °F), the fans will all be turned off
without a delay.
· VSD Internal Ambient Temp > 158°F (Cutout)
– 10°F = 148°F. When the Internal Ambient Temp
falls < 158°F (Cutout) - 15°F = 143 °F the VSD
cooling fans and glycol pump will turn off.
· Condenser Fans (as needed) and VSD coolant pump/
fans will run whenever a compressor is running.
Under these conditions, the condenser fans will run
to control discharge pressure and the VSD coolant
pump/fans will run to cool the IGBT baseplate and
internal cabinet. Additional condenser fans will be
brought on, if the IGBT baseplate temperatures or
internal cabinet ambient rises to 5°F below the cut-
out. Condenser fans will turn off, if the compressor
turns off provided VSD cooling is not required. The
glycol pump and cabinet fan may continue to run,
if VSD cooling is required.
· Glycol Pump and Cabinet Cooling Fans will also
run in the Service Mode if the Fan/Pump Run Bit
is Set.
FORM 201.21-NM3 (616)
7
227
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