035-19946-001 Rev. B (0804)
Unitary Products Group
7
SECTION VI: EVACUATION
It will be necessary to evacuate the system to 500 microns or less. If a
leak is suspected, leak test with dry nitrogen to locate the leak. Repair
the leak and test again.
To verify that the system has no leaks, simply close the valve to the vac-
uum pump suction to isolate the pump and hold the system under vac-
uum. Watch the micron gauge for a few minutes. If the micron gauge
indicates a steady and continuous rise, it’s an indication of a leak. If the
gauge shows a rise, then levels off after a few minutes and remains
fairly constant, it’s an indication that the system is leak free but still con-
tains moisture and may require further evacuation if the reading is
above 500 microns.
SECTION VII: SYSTEM CHARGE
The factory charge in the outdoor unit includes enough charge for the
unit and the highest sales volume evaporator. Some indoor coil
matches may require additional charge. See tabular data sheet pro-
vided in unit literature packet for charge requirements.
The “TOTAL SYSTEM CHARGE” must be permanently stamped on the
unit data plate.
Total system charge is determined as follows:
1.
Determine outdoor unit charge from tabular data sheet.
2.
Determine indoor coil adjustment from tabular data sheet.
3.
Calculate the line charge using the tabular data sheet if line length
is greater than 15 feet.
4.
Total system charge = item 1 + item 2 + item 3.
5.
Permanently stamp the unit data plate with the total amount of
refrigerant in the system.
Use the following charging method whenever additional refrigerant is
required for the system charge.
Measurement Method
If a calibrated charging cylinder or accurate weighing device is avail-
able, add refrigerant accordingly.
Check flare caps on service ports to be sure they are leak tight. DO
NOT OVERTIGHTEN (between 40 and 60 inch - lbs. maximum).
Superheat Charging Method
NOTE:
Use this method only during system maintenace and repair.
1.
Operate system until temperatures and pressures stabilize (mini-
mum of 10 minutes).
2.
Measure and record indoor wet bulb (WB) temperature using a
sling psychrometer and the outdoor dry bulb (DB) temperature
using a thermometer.
3.
Measure and record the suction pressure at the suction service
valve port.
4.
Using Table 1, note the superheat value corresponding to the
intersection of the indoor wet bulb and the outdoor dry bulb.
5.
With the superheat value obtained in step 4 and the suction pres-
sure value from step 3, find the intersection of the values in Table
2. This is the required suction tube temperature at the suction ser-
vice valve.
To bring the tube temperature in line with the required value from Table
2, add refrigerant to the service port to cause the tube temperature to
fall and reclaim refrigerant to cause the temperature to rise.
Do not leave the system open to the atmosphere.
Refrigerant charging should only be carried out by a qualified air
conditioning contractor.
Compressor damage will occur if system is improperly charged. On
new system installations, charge system per tabular data sheet for
the matched coil and follow guidelines in this instruction.
TABLE 1:
Superheat Value
INDOOR WB
°
F
1
OUTDOOR DB
°
F
55
60
65
70
75
80
85
90
95
100
105
110
115
50
9
7
52
12
10
6
54
14
12
10
7
56
17
15
14
10
6
58
20
18
16
13
9
5
60
23
21
19
16
12
8
6
62
26
24
22
19
16
12
8
5
64
29
27
24
21
18
15
11
9
6
66
32
31
30
24
23
18
15
11
9
6
68
35
33
30
27
24
21
19
16
14
12
9
6
70
35
33
30
28
25
22
20
18
15
13
11
8
72
35
33
30
28
26
24
20
20
17
15
14
74
34
31
30
27
25
23
22
20
18
76
35
33
31
29
27
26
25
23
1. Evaporator Entering Air °F
