80
78
76
74
I Wet-bulb °F
Delta-T
24 24 24 23 23 22 22 22 20 19 18 17 16 15
23 23 23 22 22 21 21 20 19 18 17 16 15 14
22 22 22 21 21 20 19 19 18 17 16 15 14 13
21 21 21 20 19 19 18 17 16 16 15 14 13 12
20 20 19 18 17 17 161L_5._15 14 13 12 11 10
19 19 18 18 17 17 16 15 15 14 13 12 11 10
I
57 58 59 60 61 62 63 64 65 66 67 68 69 70 I
DRY
I
BULB
iNDOOR t WET
COIL BULB
1. Determine the desired DT--Measure entering air temperature
using dry bulb (A) and wet bulb (B). DT is the intersecting value of A
and B in the table (see triangle).
2. Find temperature drop across coil--Measure the coil's dry bulb
entering and leaving air temperatures (A and C). Temperature Drop
Formula: (TDrop) = A minus C.
3. Determine if fan needs adjustment--If the difference between the
measured TDrop and the desired DT (TDrop-DT} is within +3°, no ad-
justment is needed. See examples: Assume DT = 15 and A temp. =
72°, these C temperatures would necessitate stated actions:
C° TDrop- DT = °F ACTION
53° 19 - 15 = 4 Increase the airflow
58° 14 - 15 = -1 (within +3 ° range) no change
62° 10 - 15 = -5 Decrease the airflow
4. Adjust the fan speed--See indoor unit instructions to increase/de-
crease fan speed.
Changing air flow affects all temperatures; recheck temperatures to
confirm that the temperature drop and DT are within +3°.
Figure 27. Checking Indoor Airflow over Evaporator Coil using Delta-T Chart
(WHEN TO CHARGE?
• Warm weather best
• Can charge in colder weather
CHARGE METHOD? Determine by:
• Metering device type
• Outdoor ambient temperature
REQUIREMENTS:
• Sufficient heat load in structure
• Indoor temperature between 70-80°F (21-26°C)
• Manifold gauge set connected to unit
• Thermometers:
to measure outdoor ambient temperature
to measure liquid line temperature
to measure suction line temperature
APPROACH OR
SUBCOOLING
WEIGH-IN
Figure 28. Determining Charge Method
SUPERHEAT
BELOW
1. Check Liquid and suction line pressures
2. Compare unit pressures with Table 6,
Normal Operating Pressures.
3. Conduct leak check; evacuate as
previously outlined,
4. Weigh in the unit nameplate charge plus
any charge required for line set differences
over feet.
WE G
Refrigerant Charge per Line Set Length
Liquid Line Ounces per 5 feet (g per 1.5 m)
Set Diameter adjust from 15 feet (4.6 m) line set*
3/8" (9.5 mm) 3 ounce per 5' (85 g per 1.5 m)
NOTE - *If line length is greater than !5 ft. (4.6 m), add this
amount. If line length is less than 15 ft. (4.6 m), subtract this
amount.
LENNOX
This nameplate is for illustration purposes
only. Go to actual nameplate on outdoor
unit for charge information.
Figure 29. HCFC-22 Weigh In TXV Method
Page 15
13ACD SERIES
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