Charge Checks; Capillary Tube/Fixed Orifice System; Superheat Determination; Expansion Valve System - McQuay ACU018ARAY Installation And Maintenance Manual

CHARGE CHECKS

Capillary Tube/Fixed Orifice System

1. Fully open both base valves.
2. Connect service gauge manifold to base-valve service ports
to purge lines. Run system at least 10 minutes to allow
pressure to stabilize.
3. Temporarily install thermometer on suction (large) line
near condensing unit. Provide good contact between the
thermometer and line. Wrap thermometer with insulating
material to provide an accurate reading.
4. Refer to Table 3 for proper system superheat. Add charge
to lower superheat. Remove charge to raise superheat.
5. Remove gauge lines carefully.
CWARNING
Escaping liquid refrigerant can cause burns. Wear
protective gloves, gear and eyewear.
Table 3: System Superheat
AMBIENT CONDENSER INLET
o
TEMPERATURE ( F DB)
100
95
90
85
80
75
70
65
60

Superheat Determination

1. Read suction pressure. Using Table 4, determine saturated
suction temperature.
2. Read suction line temperature.
3. Use the following formula to determine superheat:
Superheat = Suction Line Temp. - Saturated Suction Temp.
Table 4: Saturated Suction Pressure (R-22)
SUCTION PRESSURE PSIG
50
53
55
58
61
63
66
69
72
75
78
81
Page 8
o
RETURN AIR TEMPERATURE ( F DB)
65 70 75 80
5
5 7
7 12
5 10 17
5 12 21
5 10 17 25
5 14 20 28
13 19 26 32
17 25 30 33
SATURATED SUCTION
o
TEMPERATURE F
26
28
30
32
34
36
38
40
42
44
46
48

Expansion Valve System

1. Fully open both base valves.
2. Connect service gauge manifold to base-valve service parts
making sure lines are purged. Run system at least 10 min-
utes to allow pressure to stabalize.
3. Temporarily install the thermometer to liquid (small) line
near condensing unit. Provide good contact between ther-
mometer and line. Wrap thermometer with insulating
material to provide an accurate reading.
4. Referring to Table 5, adjust charge to obtain a temperature
12-15°F below the saturated liquid temperature.
Example:
If the Liquid Pressure is 260 psig then the Saturated Tempera-
ture will be 120°F. Adjust the Saturated Temperature by sub-
tracting 12-15°F. This will give you a Liquid Line
Temperature of 105° - 108°F.
Table 5: Saturated LIquid Temperature
LIQUID PRESSURE PSIG
200
210
85
220
5
230
9
240
18
250
20
260
26
270
29
280
32
290
35
300
37
SPECIAL NOTE: For systems with more than 15' of inter-
connecting tubing, please refer to Table 6 for line charge
allowance per foot of tubing.
Table 6: Line Charge Allowance (R-22 - oz./ft.)
LINE O.D. (IN)
1/4
3/8
1/2
5/8
3/4
7/8
1 1/8
1 3/8
NOTE: Systems with over 50' separation between condens-
ing unit and evaporator may require oil charge adjustment
(Table 7).
Table 7: Oil Charge Adjustment
UNIT MODEL
(TONS)
1 - 1 1/2
2 - 5
*Use either Texaco WF-32 (formerly cappella B) or Suniso 3G-S oil.
SATURATED TEMPERATURE
102
105
108
111
114
117
120
123
126
128
131
LIQUID LINE SUCTION LINE
0.22
0.58
1.14
1.86
ADDITIONAL OIL CHARGE PER EACH ADDI-
TIONAL 10' OF LINE (OZ)*
0.25
0.5
o
F
0.04
0.06
0.08
0.15
0.22
IM-800