Unit installation

Operating
56 SCXF-SVX01K-EN
Compressor Safety Devices
If a compressor low pressure cutout opens during
compressor start-up, the UCM will not shut the
compressor off during the first two to three minutes after
start-up.This prevents possible nuisance trips during low
ambient start conditions. See Table 36, p. 56.
Each compressor’s discharge line contains a high pressure
cutout. Under abnormal operating conditions, the cutout
will open to stop compressor operation.
Low Ambient Compressor Lockout
This function will lock out the compressor if the outdoor air
temperature sensor reads an outdoor temperature below
the low ambient compressor lockout temperature
setpoint.This setpoint is adjustable at the human interface
panel. Compressors will lock out when outdoor air
temperature falls below that selected temperature and will
start again when the temperature rises 5°F above the
setpoint.
Evaporator Coil Frost Protection FROSTAT™
The FROSTAT™ system eliminates the need for hot gas
bypass. It utilizes an evaporator temperature sensor
mounted on the suction line near theTXV bulb of each
circuit to protect the evaporator from freezing.
If the evaporator temperature approaches the specified
setpoint (adjustable between 25 and 35°F at the HI) the
compressor(s) will cycle off.The supply fan remains on to
help de-ice the coil.The compressors will restart when the
evaporator temperature has risen 10°F above the specified
cutout temperature and when the compressor(s) have
been off a minimum of three minutes.This prevents rapid
cycling of the compressors.
Service Valve Option
If ordered, service valves are factory installed on each
circuit before and after the compressor to allow
compressor isolation for servicing.
Waterside Components
Waterside components consist of water piping, water
valves, water flow switch option, water cooled condensers
(SXWF only), and the economizer option.
SXWF 65, 72 Independent 15 15 15 10 B/BD/ABD/ABCD A/AD/ACD/ABCD
SXWF 80 Independent 15 15 15 15 B/BD/ABD/ABCD A/AC/ABC/ABCD
SXRF 60 Manifolded 15 15 15 15 B/BD/ABD/ABCD A/AC/ABC/ABCD
SCWF 90 Independent 15 15 15 15 15 A/AB/ABC/ABCDE C/CDE/ACDE/BCDEF
SCWF 100 Independent 15 15 15 15 10 10 A/AB/ABCD/ABCDEF CD/CDEF/ACDEF/ABCDEF
SCWF C1 Independent 15 15 15 15 15 15 A/AB/ABCD/ABCDEF CD/CDEF/ACDEF/ABCDEF
Table 35. Compressor stage (continued)
Unit
size
Refrigerant
circuit type
Compressor by stage
Compressor
staging
Compressor
stagingABCDEF
Figure 35. Typical pulldown curve for unit operating
properly within control band
Figure 36. Typical pulldown curve for unit operating
improperly outside control band
1
3
5
2
4
6
Set
Point
Control Band
Control Response
1 - Stage On
2 - Stage Off
3 - Stage On
4 - Stage Off
5 - Stage On
6 - Stage Off
Table 36. Pressure cutouts (open/close)
Unit Model
High Pressure
Cutout
Low Pressure
Cutout
SXWF 553/424 49/74
SXRF 650/500 36/61