A.O. Smith AWH-35, Инструкция по эксплуатации, Страница: 28 / 48

CHECKING REFRIGERANT CHARGE
Servicing of the refrigeration circuit must only be performed
by agencies or individuals possessing Type II or Universal
certification as defined in Section 608 of the Clean Air Act. See
Qualifications on page 6.
This HPWH unit is factory charged with 134a refrigerant. See the
rating label on the HPWH unit and Table 9 for refrigerant charge
by weight. It should not be necessary to add or remove refrigerant
during installation or start up. Refrigerant lost during frequent
refrigerant pressure testing can cause low refrigerant conditions.
Air and water flow should always be checked first to eliminate
other potential problems before checking the refrigerant charge.
Check Air Flow
Ensure the air filters are clean. Ensure the evaporator coil is
clean. Ensure the blower motor belt is not worn or loose. See
Figure 1 on page 8 for component locations. Correct any
problems with air flow before checking the refrigerant pressures.
Check Water Temperature Rise
Always check water temperature rise through the HPWH unit’s
internal heat exchanger before checking the refrigerant charge.
See Start Up on page 23 for information on how to measure
the water temperature rise.
If the measured water temperature rise during start up was within
8°F to 12°F (4°C to 7°C) checking the charge is not necessary
unless other conditions warrant testing.
If the measured temperature rise through the HPWH unit is less
than 8°F (4°C) checking the charge is not necessary unless other
conditions warrant testing. Short water piping runs between the
HPWH and the storage tank will produce lower temperature rises
and are not problematic.
If the measured temperature rise through the HPWH unit is more
than 12°F (7°C) check for restrictions in the inlet and outlet water
piping connected between the HPWH unit and the storage tank.
On new installations ensure the maximum equivalent feet of inlet
and outlet piping was not exceeded. This is the most common
cause of excessive water temperature rise on new installations.
See number 11 on page 22.
SUBCOOLING CALCULATION
1. Measure and record the liquid pressure at the liquid line
pressure test port inside the unit.
2. Convert the recorded liquid line pressure to saturated
temperature using Table 10.
3. Measure the liquid line temperature near the liquid line
pressure test port inside the unit.
4. Compare the liquid line temperature to the saturated
temperature in Table 10.
5. The difference between saturated temperature and liquid
line temperature is the subcooling. Subcooling normal range
should be 5°F to 15°F (2.8°C to 8.5°C).
SUPERHEAT CALCULATION
1. Measure and record the suction pressure at the suction line
pressure test port inside the unit.
2. Convert the recorded suction pressure to saturated
temperature.
3. Measure the suction line temperature near the suction line
pressure test port inside the unit.
4. Compare the suction line temperature to the to the saturated
temperature in Table 10.
TABLE 10
R134A SATURATED TEMPERATURE CHART
SATURATED
TEMPERATURE °F
SATURATED
TEMPERATURE °C
REFRIGERANT
PRESSURE (PSI)
0 -18 7
5 -15 9
10 -12 12
15 -9 15
20 -7 18
25 -4 22
30 -1 26
35 2 30
40 4 35
45 7 40
50 10 45
55 13 51
60 16 57
65 18 64
70 21 71
75 24 79
80 27 87
85 29 95
90 32 104
95 35 114
100 38 124
105 41 135
110 43 146
115 46 158
120 49 171
125 52 185
130 54 199
135 57 214
140 60 229
145 63 246
150 66 263
155 68 281
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5. The difference between saturated temperature and sucti o n
line temperature is the superheat . Superheat normal range
should be 8°F to 12°F (4.4°C to 6.7°C).
TABLE 9
MODEL FACTORY CHARGE R134A
AWH-35 2lbs, 15oz
AWH-55 3lbs, 12oz
AWH-75 6lbs, 5oz
AWH-100 7lbs, 3oz
AWH-115 7lbs, 14oz
AWH-140 10lbs, 15oz
AWH-170 13lbs, 5oz