Daikin RDT Installation And Maintenance Manual page 138

Servicing Refrigerant Sensors or
Switches
Variable Speed Inverter Compressor
The VFD is factory-programmed and should not be modified
in the field. Any modifications will void the warranty.
Compressors are compatible with the manufacturer's VFD
only.
The Daikin Rooftop unit includes the following refrigerant
sensors or switches.
1. Low refrigerant pressure sensing, operating switch,
automatic reset
a. Disables their associated compressors on a drop in
suction pressure. Units with Fantrol, setpoint = 70
psig. Units with Speedtrol, setpoint = 50 psig (low
ambient).
b. Enables their associated compressors on a rise in
suction pressure. Units with Fantrol, setpoint = 120
psig. Units with Speedtrol, setpoint = 90 psig.
2. High refrigerant pressure, protective switch, manual
reset, reset by breaking control power to the S1 control
switch.
a. All R-410A high pressure switches disable their
associated compressors on a rise in discharge
pressure to 650 psig.
b. The switches have a differential of 150 psig.
The low pressure and SpeedTrol sensors/switches sense
refrigerant pressure through Shrader fittings that contain cores.
The cores are stop valves that do not allow refrigerant to flow
through the Shrader unless the device is in place. Therefore
the low pressure and SpeedTrol sensors/switches can be
replaced without reclaiming the refrigerant.
The Shrader that serves the high pressure switch does not
contain a core in order to maximize the functionality of the
safety. Therefore it cannot be replaced unless the refrigerant
has already been reclaimed.
IM 893-10 • ROOFPAK SINGLEZONE UNITS
WARNING
Winterizing Water Coils
Coil freeze-up can be caused by such things as air stratification
and failure of the outdoor dampers and/or preheat coils.
Routine draining of water cooling coils for winter shutdown
cannot be depended upon as insurance against freeze-up.
Severe coil damage may result. It is recommended that all coils
be drained as thoroughly as possible and then treated in the
following manner.
• Fill each coil independently with an antifreeze solution
using a small circulating pump and again thoroughly
drain.
• Check freezing point of antifreeze before proceeding
to next coil. Due to a small amount of water always
remaining in each coil, there will be a diluting effect. The
small amount of antifreeze solution remaining in the coil
must always be concentrated enough to prevent freeze-
up.
NOTE: Carefully read instructions for mixing antifreeze
solution used. Some products have a higher freezing
point in their natural state than when mixed with
water.
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aInTenanCe
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