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START: Determine how refrigerant is metered
WHEN TO CHARGE?
S
Warm weather best
S
Can charge in colder weather
CHARGE METHOD? Determine by:
S
Metering device type
S
Outdoor ambient temperature
REQUIREMENTS:
S
Sufficient heat load in structure
S
Indoor temperature between 70‐80ºF (21-26ºC)
S
Manifold gauge set connected to unit
S
Thermometers:
- to measure outdoor ambient temperature
- to measure liquid line temperature
- to measure suction line temperature
CHECKING AIR FLOW AT INDOOR COIL
Temp.
80
24 24 24 23 23 22 22 22 20 19 18 17 16 15
of air
entering
78
23 23 23 22 22 21 21 20 19 18 17 16 15 14
indoor
76
22 22 22 21 21 20 19 19 18 17 16 15 14 13
coil ºF
74
21 21 21 20 19 19 18 17 16 16 15 14 13 12
A
72
20 20 19 18 17 17 16 15 15 14 13 12 11 10
70
19 19 18 18 17 17 16 15 15 14 13 12 11 10
Wet-bulb ºF
57 58 59 60 61 62 63 64 65 66 67 68 69 70
T
Drop
C
19º
53º
air flow
DRY
BULB
All temperatures are
expressed in ºF
Figure 14. Checking Indoor Airflow over Evaporator Coil using Delta-T Chart
START: Measure outdoor ambient temperature
USE SUBCOOLING
METHOD
Refrigerant Charge per Line Set Length
Liquid Line
Ounces per 5 feet (g per 1.5 m)
adjust from 15 feet (4.6 m line set*
Set Diameter
3/8" (9.5 mm)
3 ounces per 5' (85 g per 1.5 m)
NOTE - *If line length is greater than 15 feet (4.6 m), add this
amount. If line length is less than 15 feet (4.6 m), subtract this
amount.
506 11/2012
Figure 13. Determining Charge Method
Delta−T
B
A
72º
B
air flow
64º
DRY
BULB
INDOOR
WET
BULB
COIL
ABOVE or
65ºF
BELOW
(18.3ºC) and
ABOVE
Figure 15. HFC-410A Weigh In
OUTDOOR AMBIENT
TEMPERATURE
65ºF (18.3ºC)
AND ABOVE
APPROACH OR
SUBCOOLING
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: (T
) = A minus C.
Drop
3. Determine if fan needs adjustment—If the difference between the
and the desired DT (T
measured T
Drop
justment is needed. See examples: Assume DT = 15 and A temp. =
72º, these C temperatures would necessitate stated actions:
DT
Cº
T
–
Drop
53º
19
–
15
58º
14
–
15
62º
10
–
15
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 +3º.
64ºF (17.7ºC)
and BELOW
Page 16
TXV
64ºF (17.7ºC)
AND BELOW
WEIGH‐IN
–DT) is within +3º, no ad
Drop
=
ºF ACTION
=
4
Increase the airflow
=
-1 (within +3º range) no change
=
-5 Decrease the airflow
1. Check Liquid and suction line pressures
2. Compare unit pressures with table 3 or 6.
3. Conduct
leak
check;
evacuate
previously outlined.
4. Weigh in the unit nameplate charge plus
any charge required for line set differences
over feet.
This nameplate is for illustration purposes
only. Go to actual nameplate on outdoor
unit for charge information.
as
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