Specifications

INSTALLATION, OPERATION & MAINTENANCE INSTRUCTIONS
4
FAN DELAY DEFROST TERMINATION CONTROL
This control located on the coil plate senses the
coil temperature. To provide fan delay, the defrost
thermostat must be turned off.
1. Set thermostat between 20ºF and 30ºF
or above.
2. Adjust defrost timer up to maximum
of 45 minutes.
3. Set the thermostat between 55 to 60ºF
to defrost unit coolers operating between
–40 to –20ºF. To defrost unit coolers
operating between –10 to 10ºF, set the
thermostat between 60 to 65ºF.
F
AN DELAY DRAIN PAN CONTROL
The fan delay drain pan control senses the general
coil temperature.
• With temperature rise, the fan delay thermostat
de-energizes the fan and energizes the electric
pan heaters.
• After defrost cycle, the coil temperature drops
and the fan delay thermostat energizes the motor
and de-energizes the heaters.
• Defrost timer must be set long enough to
completely melt the ice in the unit cooler. Set
the thermostat at 20 to 25ºF and the differential
at minimum.
CHECK SUPERHEAT
After the temperature has reached the desired
temperature, the unit cooler superheat should be
checked and adjustments made if necessary.
Generally, systems with a design temperature
difference (TD) of 10ºF should have a superheat
value of 6 to 10ºF for maximum efficiency. For
systems operating at higher TD, the superheat
can be adjusted to 12 to 15ºF as required.
IMPORTANT
After correcting a faulty defrost cycle, it is
essential that the coil, drain pan and unit cooler
be free and clear of ice before placing the unit
cooler back on automatic operation.
To ensure unit cooler performance, the expansion
valve must be set at the proper superheat and
at the lowest temperature in which the system is
expected to operate.
STEP 7 - WIRING
All systems wiring must be in compliance with all
applicable local and national codes.
All internal wiring of fan motors, tubular heaters and
combination defrost termination fan delay control
have been factory connected. All wiring connections
terminate on a single terminal block in the wiring
compartment and are clearly labeled.
START-UP
L
EAK TESTING AND EVACUATION
Leak testing and evacuation must be done in
accordance with local and national codes.
Once all refrigerant connections are made, leak test
all joints before charging the system with refrigerant.
After leak testing, all moisture and non-condensable
gas must be evacuated from the system. Attach high
vacuum line pump and gauge on both high and low
pressure sides of the system. A minimum vacuum
level of 100 microns is required to effectively
remove moisture.
Be sure all valves such as compressor, hot gas,
receiver, and liquid solenoid valves are open. Break
the vacuum in the system with the refrigerant to
be used. Always charge the refrigerant into the
system through a new 16 cu. in drier (field supplied)
in the charging manifold line.
F
AN MOTOR
The fan motor may restart on automatic thermal
protection if the coils are frozen. The fan motor may
cycle if the coil is blocked. Check the supply voltage
at the motor leads if motor is inoperable.
CAUTION
Before starting unit cooler, be sure wire fan
guards are secured in place over each fan.
IMPORTANT
The use of a calibrated pressure gauge and
regulator must always be used with nitrogen
gas cylinders.
Drain traps on low temperature unit coolers must
be outside of refrigerated enclosures. In the instance
where traps are subject to freezing temperatures,
wrap the traps with heat tape and insulation.
Always trap drain lines individually to prevent
vapor migration.
S
TEP 5 - REFRIGERANT CONNECTIONS
All refrigerant system components must be installed
in accordance with applicable local and national
codes using proper engineering practices.
Use top quality refrigeration tubing that is internally
free of dirt, humidity or other contaminants. Unsealed
tubing should not be used. Long radius elbows are
recommended.
Dry nitrogen must be swept through the lines while
joints are brazed to avoid oxidation and carbon
deposits.
All external piping must be well supported. The unit
cooler will not support external piping or valves.
If the condition arises where the suction line
must be raised to a point higher than the suction
connection on the unit cooler, a suction line trap
must be installed on the unit cooler.
Horizontal suction lines should slope away from the
evaporator toward the compressor. Leak check and
evacuate the system using a two-stage deep vacuum
pump.
S
TEP 6 - EXPANSION VALVE CONNECTION
All unit coolers are supplied with a 1/2 in. OD
sweat expansion valve connection. Expansion valves
are field supplied.
LS, LP & LA unit coolers require the use of an
externally equalized expansion valve and are
provided with a 1/4 in. OD equalizer line.
Check the operation of the expansion valve after the
system has reached the desired cooler temperature.
If the coil is not receiving enough refrigerant, reduce
the superheat setting on the expansion valve.