SCXF-SVX01Q-EN
63
mounted on the suction line near the TXV 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.
Water Purge
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This user-definable feature allows the user to select a
purge schedule to automatically circulate water
through the economizer and condensers periodically
during non-operational times. This allows fresh
chemicals to circulate in waterside heat exchangers.
This feature is on all units and is defined at the HI.
Water Piping Options
Water piping is factory-installed with left-hand
connections on units without a waterside economizer.
Units can be ordered with either basic piping or
intermediate piping. Also, units with waterside
economizers can be set for either variable or constant
water flow at the HI. See Figure 33, p. 64 and Figure
34, p. 64 for detailed piping configuration information.
With compatible piping configurations, the unit can be
configured to provide:
• Constant water flow with basic or intermediate
piping
or
• Variable water flow (head pressure control) with
intermediate piping only.
Constant water flow is for condenser pumping systems
that are not capable of unloading the water-pumping
system. Variable water flow maximizes energy saving
by unloading the water pumping system.
Basic Water Piping
This option is available on units without a waterside
economizer and with condenser water applications
above 54°F (12.2°C) that do not require condensing
pressure control. Left hand water connections and
piping are extended to the unit exterior. Manifold
piping is factory installed.
Intermediate Water Piping
This option provides condensing temperature control
when the unit is configured (user defined at the HI) for
variable water flow with or without a waterside
economizer. A two-way modulating control valve is
wired and installed in the unit to maintains a specific
range of water temperature rise through the condenser
when entering fluid temperature is less than 58°F (15°
C).This option allows the compressor to operate with
entering fluid temperature down to 35°F (2°C).The
minimum valve position to maintain minimum
condenser flow rates is user-defined at the HI. This
valve drives closed if the unit shuts down or if a power
failure occurs.
Water Flow Switch Option
A water flow switch is factory installed in the
condenser water pipe within the unit. Whenever the
flow switch detects a water flow loss prior to or during
mechanical cooling, compressor operation locks out
and a diagnostic code displays. If water flow is
restored, the compressor operation automatically
restores.
Water-Cooled Condensers
Units that are set up for variable water flow will
modulate a water valve to maintain a user-defined
condensing temperature setpoint. Condensing
temperature will be referenced utilizing factory
installed sensors located at each condenser.
Table 36. Condenser water piping connection sizes
Unit size
Inlet pipe
Outlet
pipe
SXWF 20, 22, 25, 29, 32, 35, 38
2 1/2 NPT 2 1/2 NPT
SXWF 42, 46, 52, 58, 65, 72, 80,
90, 100, 110
3 NPT 3 NPT
Waterside Economizer Option
The waterside economizer option takes advantage of
cooling tower water to either precool the entering air to
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