Page 12
Manual 2100-292
Charging Instructions
Pressure Service Ports
High and low pressure service ports are installed on all units so
that the system operating pressures can be observed. Pressure
tables can be found later in the manual covering all models. It is
imperative to match the correct pressure table to the unit by model
number.
System Start-Up (Indoor Units Without
Expansion Valves)
Step 1.
Close disconnect switch(es) and set the thermostat to
cool and the temperature to the highest setting.
Step 2.
Check for proper airflow across the indoor coil by
referring to indoor unit installation.
Step 3.
Connect the service gauges and allow the unit to run for
at least 10 minutes or until pressures are stable. Check
pressures to the system pressure table attached to the
outdoor unit service panel. For optimum system
performance, go to Step 4.
Step 4.
Install a thermometer on the suction line approximately
6" to 10" from the compressor. Optimum system
performance will occur with a refrigerant charge
resulting in a suction line superheat as determined from
the following calculations.
A. Measure outdoor air dry bulb temperature ________ ºF
B. Measure indoor air wet bulb temperature ________ ºF
C. Measure suction pressure
________ PSIG
D. Measure suction line temperature
________ ºF
E. Determine optimum system superheat
from Table 9 using outdoor air dry bulb
(Step B) and indoor air wet bulb (Step A) ________ ºF
F. Determine saturated suction temperature
from suction pressure using Table 10
________ ºF
G. Determine system superheat:
Suction line temperature (Step D)
________ ºF
- Saturated suction temperature (Step F) - ________ ºF
= System superheat
= _______ ºF
H. Adjust the system superheat (Step G) to the optimum
system superheat (Step E) by adding charge to lower the
superheat or removing charge to raise the superheat.
I. Check final system operating pressures to the system
pressure tables as was done in Step 3.
Table 7 — System Superheat
Outdoor Ambient Return Air Temperature
Temperature º F — Wet Bulb
(º F Dry Bulb)
59
63
67
71
105
1
1
5
—
95
1
3
(8)
20
90
1
7
14
26
85
3
9
19
33
80
8
14
25
39
75
10
20
30
42
Table 8 — Saturated Suction Temperature (R-22)
Saturated Suction
Suction Pressure PSIG
Temperature (º F)
50
26
53
28
55
30
58
32
61
34
63
36
65
38
67
39
70
41
73
43
76
45
79
47
82
49
86
51
