Lennox Merit 14ACX−018−230 Installation Instructions Manual page 26

START: Measure outdoor ambient temperature
USE WEIGH-IN METHOD
Weigh-in or remove refrigerant
based upon line length
SUPERHEAT RFC
If refrigerant is
REMOVED, retest to
confirm that unit is
properly charged.
If value is LESS than
shown, then REMOVE
refrigerant.
°F
−40
−35
−30
−25
−20
−15
−10
−5
0
5
10
15
20
25
30
35
40
45
50
55
506645−01
ABOVE or
40ºF
(4.4ºC) and
Above
SHº (Superheat) Values (+/−5ºF)
Wet Bulb (air entering indoor coil)
ºF* 50 52 54 56 58 60 62 64 66 68 70 72 74 76
40 15 18 20 23 26 29 32 34 38 41 43 46 48 51
45 13 16 18 21 24 27 30 33 36 39 41 44 46 49
50 11 14 16 19 22 25 28 31 34 37 39 42 44 47
55 9 12 14 17 20 23 27 30 33 36 38 40 42 44
60 7 10 12 15 18 21 24 27 30 33 35 38 40 43
65 - 6 10 13 16 19 21 24 27 30 33 36 38 41
70 - - 7 10 13 16 19 21 24 27 30 33 36 39
75 - - - 6 9 12 15 18 21 24 28 31 34 37
80 - - - - 5 8 12 15 18 21 25 28 31 35
85 - - - - - - 8 11 15 19 22 26 30 33
90 - - - - - - 5
95 - - - - - -
100 - - - - - -
105 - - - - - -
110 - - - - - -
115 - - - - - -
* Dry−bulb temperature (ºF) of entering outdoor ambient air.
MORE or
LESS
Figure 24. HFC−410A Superheat RFC Method
Table 3. HFC−410A Temperature
°C Psig
−40.0 11.6
−37.2 14.9
−34.4 18.5
−31.7 22.5
−28.9 26.9
−26.1 31.7
−23.3 36.8
−20.6 42.5
−17.8 48.6
−15.0 55.2
−12.2 62.3
−9.4 70.0
−6.7 78.3
−3.9 87.3
−1.1 96.8
1.7 107
4.4 118
7.2 130
10.0 142
12.8 155
39ºF
(3.8ºC) and
Below
BELOW
9 13 16 20 24 27 31
- 6 10 14 18 22 25 29
- - 8 12 16 21 24 28
- - 5 9 13 17 22 26
- - - 6 11 15 20 25
- - - - 8 14 18 24
If value is MORE
than shown, then
ADD refrigerant.
Pressure (Psig)
°F
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
Page 26
1. Confirm proper airflow across coil using figure 19.
2. Compare unit pressures with table 4, Normal
Operating Pressures.
3. Use SUPERHEAT to correctly charge unit or to
verify the charge is correct.
4. Set thermostat to call for heat (must have a cooling
load between 70-80ºF (21−26ºC)
5. Connect gauge set.
6. When heat demand is satisfied, set thermostat to
call for cooling.
7. Allow temperatures and pressures to stabilize.
8. Measure the suction line pressure and use the use
value to determine saturation temperature (table
3):
SATº =_________
9. Record suction line temperature:
VAPº =_________
10. Subtract to determine superheat (SHº):
VAPº − _____ SATº ______ = SHº______
11. Record the wet bulb temperature (air entering
indoor coil):
WB =_______
12. Record outdoor ambient temperature.
13. Compare results with table to the left.
NOTE − Do not attempt to charge system where a
dash appears, system could be overcharged.
Superheat is taken at suction line service port.
Suction line superheat must never be less than 5ºF
at the suction line service port.
If refrigerant is
ADDED, retest to
confirm that unit is
properly charged.
°C
15.6
18.3
21.1
23.9
26.7
29.4
32.2
35.0
37.8
40.6
43.3
46.1
48.9
51.7
54.4
57.2
60.0
62.8
65.6
Psig
170
185
201
217
235
254
274
295
317
340
365
391
418
446
476
507
539
573
608