40
FORM 145.32-IOM5
ISSUE DATE: 04/08/2019
SECTION 2 – STARTUP AND OPERATION
Superheat
Only check superheat after establishing the steady state
operation of the unit, pulling down the discharge air tem-
perature to within the control range, and running the unit
in a fully loaded condition.
The superheat is calculated as the difference between
the actual temperature of the refrigerant gas in the suc-
tion line and the temperature corresponding to the suc-
tion pressure as shown in Table 25.
For example, when the suction pressure is 130 psig and
the suction line temperature is 57.0°F:
• Saturation Temperature for 130 psig = 45.0°F
• Evaporator Superheat = Suction Line Temperature
(57.0°F) minus Saturation Temperature (45.0°F)
= 12.0°F
When adjusting the expansion valve, do not turn the
adjusting screw more than one turn at a time This al-
lows sufficient time (approximately 15 minutes) be-
tween adjustments for the system and the thermal ex-
pansion valve to respond and stabilize.
The superheat setting should be adjusted to 8.0–11.0°F
at design conditions.
Leak Checking
Leak check compressors, fittings, and piping to ensure
there are no leaks. Verify the evaporator distributor
tubes do not have bare copper touching each other or
are against a sheet metal edge. If leak checking a unit
charged with R-410A, ensure the leak test device is ca-
pable of sensing refrigerant R-410A.
Startup (Cooling)
Prestart Checklist
After installation has been completed, make the fol-
lowing checks:
1. Check the electrical supply voltage. Ensure that it
is the same as listed on the unit nameplate.
2. Set the room thermostat to the OFF position.
3. Turn ON the unit electrical power.
4. Set the room thermostat fan switch to ON.
5. Check the indoor blower rotation.
6. Check the blower drive belt tension.
7. Check the unit's supply air (CFM).
• Liquid Line Subcooling = Saturation Temperature
(108.0°F) minus Liquid Line Temperature (95.0°)
= 13.0°F
Subcooling should be 10.0–14.0°F at design conditions.
TABLE 25 - R-410A PRESSURE AND TEMPERA-
TURE CHART
PSIG TEMP ˚F PSIG TEMP ˚F
0 -60 78 20
2 -58 80 21
4 -54 85 24
6 -50 90 26
8 -46 95 29
10 -42 100 32
12 -39 105 34
14 -36 110 36
16 -33 115 39
18 -30 120 41
20 -28 125 43
22 -26 130 45
24 -24 135 47
26 -20 140 49
28 -18 145 51
30 -16 150 53
32 -14 160 57
34 -12 170 60
36 -10 180 64
38 -8 190 67
40 -6 200 70
42 -4 210 73
44 -3 220 76
46 -2 225 78
48 0 235 80
50 1 245 83
52 3 255 85
54 4 265 88
56 6 275 90
58 7 285 92
60 8 295 95
62 10 305 97
64 11 325 101
66 13 355 108
68 14 375 112
70 15 405 118
72 16 500 134
74 17 600 149
76 19 700 159
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