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KHA180, 240
differences in installations. Significant differences
could mean that the system is not properly charged
or that a problem exists with some component in the
system.
Correct any system problems before
proceeding.
6− If discharge pressure is high, remove refrigerant from
the system. If discharge pressure is low, add
refrigerant to the system.
Add or remove charge in increments.
Allow the system to stabilize each time
refrigerant is added or removed.
7− Use the following approach method along with the
normal operating pressures to confirm readings.
TABLE 3
KHA180 NORMAL OPERATING PRESSURES
Outdoor
Coil En-
tering
Air Temp
Circuit 1
Circuit 2
Dis. +10
psig
Suc. +5
psig
Dis. +10
psig
Suc. +5
psig
65
F
270
138
270
135
75
F
312
139
312
135
85
F
356
142
356
136
95
F
403
144
404
138
105
F
455
147
458
140
115
F
512
147
515
145
TABLE 4
KHA240 NORMAL OPERATING PRESSURES
Outdoor
Coil En-
tering
Air Temp
Circuit 1
Circuit 2
Dis. +10
psig
Suc. +5
psig
Dis. +10
psig
Suc. +5
psig
65
F
275
135
278
135
75
F
315
138
318
136
85
F
359
140
364
138
95
F
407
142
413
140
105
F
457
144
466
141
115
F
517
146
527
145
C−Charge Verification − Approach Method − AHRI Testing
1− Using the same thermometer, compare liquid
temperature to outdoor ambient temperature.
Approach Temperature = Liquid temperature (at
condenser outlet) minus ambient temperature.
2− Approach temperature should match values in table
5. An approach temperature greater than value
shown indicates an undercharge. An approach
temperature less than value shown indicates an
overcharge.
3− The approach method is not valid for grossly over or
undercharged systems. Use table 3 or 4 as a guide
for typical operating pressures.
TABLE 5
APPROACH TEMPERATURES
Unit
Liquid Temp. Minus Ambient Temp.
1st Stage
2nd Stage
180 & 240
12°F + 1
(6.7°C + 0.5)
12°F + 1
(6.7°C + 0.5)
D−Compressor Controls
1− High Pressure Switches (S4, S7)
Compressor circuits are protected by a high pressure
switch which cuts out at 640 psig + 10 psig (4413 kPa
+ 70 kPa).
2− Freezestats (S49, S50)
Switches de−energize compressors when indoor coil
temperature falls below 29
F (−2
C) to prevent coil
freeze−up. Switches reset when indoor coil
temperature reaches 58
F (15
C).
3− Defrost Switches (S6, S9)
Defrost switches close to initiate defrost when liquid
line temperature falls to 35
F (1.7
C). The defrost
switch is located on the liquid line between the
outdoor expansion valve and the distributor
4− Defrost Termination Switches (S46, S104)
Defrost pressure switches open to terminate defrost
when vapor line (discharge pressure during cooling
and defrost) pressure reaches 450 psig (3103 kPa).
5− Defrost Controls (CMC1, CMC2)
Defrost is liquid line temperature initiated and
operates for 14 minutes unless terminated by vapor
line pressure drop.
When the liquid line temperature drops below 35°F,
the defrost switch closes and signals the
defrost
control
that a defrost cycle is needed. If the defrost
switch is still closed after 60 minutes (default), a
defrost cycle begins and operates for 14 minutes.
The defrost pressure switch can terminate the defrost
cycle before the 14 minutes elapses if vapor line
pressure reaches 450 + 10 psi
.
6− Electric heat is energized during defrost to maintain
discharge air temperature.
