Verify Sensor Performance-- Using an ohmmeter
and a thermometel, compare measured temperature to tile re-
sistance shown in Table 34.
Table 34 -- Sensor Temperature/Resistance
Values
TEMPERATURE (F) RESISTANCE (ohms)
-58 200,280
-40 100,680
-22 53,010
-4 29,091
14 16,590
32 9,795
50 5,970
68 3,747
77 3,000
86 2,416
104 1,597
122 1,060
140 740
158 525
176 376
185 321
194 274
212 203
230 153
248 116
257 102
266 69
284 70
302 55
_'!] [_ljlll[[']_
Economizer Operation During Power Fail-
ure -- Dampo.'s have a spring return. [n event of power fail-
ure, &_mpers will return to fully closed position until power is
restored. Do not manually ol?emte damper moto;:
Evacuation -- Proper evacuation of the system will m-
move noncondensables and ensure a tight, dq system before
charging. Evacuate from both high and low side ports. Never
use the system compressor as a vacuum pump. Refrigerant
tubes and indoor coil should be evacuated to 500 microns.
Always break a vacuum with dry nitrogen. The two possible
methods are the deep vacuum method and the triple evacuation
method.
DEEP VACUUM METHOD- The deep vacuum method
requires a vacuum pump capable of pulling a minimum vacu-
um of 500 microns and a vacuum gage capable of accurately
measuring this vacuum depth. The deep vacuum method is the
most positive way of assuring a system is free of air and liquid
water. (See Fig. 30.)
TRIPLE EVACUATION METHOD -- The triple evacuation
method should only be used when vacuum pump is capable of
pumping down to 28 in. of mercury and system does not con-
tain any liquid watel: Proceed as follows:
1. Pump system down to 28 in. of mercmy and allow pump
to continue operating for tin additional 15 minutes.
2. Close service v_dves and shut off vacuum pump.
3. Connect a nitrogen cylinder and regulator to system and
open until system pressure is 2 psig.
4. Close service valve and allow system to stand for 1 hi:
During this time, dry nitrogen will be able to diftuse
throughout the system, absorbing moisture.
5. Repeat this procedure. System will then contain minimal
amounts of contaminants and water vapol:
Refrigerant Charge -- Amount of refrigerant charge is
listed on unit nameplate. Refer to Carder GTAC II; Module 5;
Charging, Recovery. Recycling, and Reclmnation section for
chtuging methods and procedures. Unit panels must be in place
when unit is operating during charging procedure.
Puron® (R-410A) refrigerant cylindeLs contain a dip tube
which ;dlows liquid refrigerant to flow from the cylinder in an
upright position. Charge units with cylinder in the upright posi-
tion and a commerci;d type metering device in the manifold hose.
This system uses Puron refrigerant which has higher
pressures than R-22 and other refrigerants. No other refrig-
erant may be used in this system. Gage set, hoses, and
recovery system must be designed to handle Puron refrig-
erant. If unsure about equipment, consult the equipment
manufacturel: Dmnage to equipment or peLsonal injury
may result.
NOTE: Do not use recycled refrigerant as it may contain
contaminants.
NO CHARGE -- Use standard evacuating techniques. After
evacuating system, weigh in the specified amount of refriger-
ant (refer to unit nameplate).
LOW CHARGE COOLING -- Using cooling charging chart
(see Fig. 31-35), add or remove refrigerant until conditions of
the chart are met. An accurate pressure gage and temperature-
sensing device is required. Charging is accomplished by
ensuring the proper amount of liquid subcooling. Connect
pressure gage to the compressor discharge service v;dve.
Connect temperature sensing device to the liquid line between
the condenser and the TXV (thermostatic expansion valve) and
insulate it so that ambient temperature does not affect reading.
TO USE THE COOLING CHARGING CHART -- Use the
above temperature and pressure readings, and find the intersec-
tion point on the cooling charging chart. If intersection point on
chtut is above line, add refrigerant. If intersection point on
chtut is below line, carefully recover some of the charge. Re-
check suction pressure as charge is adjusted.
NOTE: Indoor-air cfm must be within normal operating range
of unit. All outdoor fans must be operating.
The TXV is set to maintain between 10 and 15 degrees of
superheat at the compressors. The v;dves are factory set and
cannot be adjusted. Do not use a TXV designed for use with
R-22 refrigerant.
03
z
o
cc
Q)
LEAK IN
SYSTEM
TIGHT
TOO WE_
TIGHT
DRY SYS I EM
0 1 2 3 4 5 6 7
MINUTES
Fig. 30 -- Deep Vacuum Graph
4O
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