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Check that compressor RLA corresponds to values shown
in Appendix B. RLA draw can be much lower than values
listed at low load conditions and low ambient condensing
temperatures. Values in Appendix B can slightly exceed
at high load conditions and high ambient condensing
temperatures.
EXAMPLE:
a. Liquid Line Pressure = 417 PSI
b. Corresponding Temp. = 120°F
c. Thermometer on Liquid line = 109°F.
To obtain the amount of subcooling, subtract 109°F
from 120°F. The dierence is 11° subcooling. See the
specication sheet or technical information manual for the
design subcooling range for your unit.
a. Suction Pressure = 143 PSI
b. Corresponding Temp. = 50°F
c. Thermometer on Suction Line = 59°F
To obtain the degrees temperature of superheat, subtract
50.0 from 59.0°F. The dierence is 9° Superheat. The
9° Su¬perheat would fall in the ± range of allowable
superheat.
For TXV systems, to adjust superheat, unscrew the
cover from the expansion valve, locate the adjustment
screw, and turn it clockwise (in) to increase superheat
or counterclockwise (out) to decrease superheat. It is
recommended to make small adjustments at a time, 1/8-1/4
turn increments. Replace adjustment cap. Wait a minimum
of 15 minutes between adjustments to allow time for the
TXV and pressures to stabilize.
8. With all safety devices closed, the system will
continue cooling operation until the thermostat is
satised.
9. Disconnecting the jumper wire between R and Y1 and
Y2 and between R and G on TB1 terminal block will
simulate a satised thermostat. The compressors
will cycle o and IIC (pin 12) will initiate its time delay
cycle. The compressor and the supply fan will cycle
o.
10. After a time delay of approximately 3 minutes, the
compressor control circuits will be ready to respond to
a subsequent call for cooling from the wall thermostat.
11. Open disconnect switch. Reconnect the eld
thermostat wire at terminal R on terminal block TB1.
1. Check to see if all supply and return air grilles are
adjusted and the air distribution system is balanced
for the best compromise between heating and cooling.
2. Check for air leaks in the ductwork. See Sections on
Air Flow Adjustments.
3. Make sure the unit is free of “rattles”, and the tubing
in the unit is free from excessive vibration. Also make
sure tubes or lines are not rubbing against each other
or sheet metal surfaces or edges. If so, correct the
trouble.
4. Set the thermostat at the appropriate setting for
cooling and heating or automatic changeover for
normal use.
5. Be sure the Owner is instructed on the unit operation,
lter, servicing, correct thermostat operation, etc.
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