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CHECKING AIR FLOW AT INDOOR COIL
Check airflow using the Delta-T (
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 18. Checking Indoor Airflow over Evaporator Coil using Delta-T Chart
START: Measure outdoor ambient temperature
USE SUBCOOLING
METHOD
Refrigerant Charge per Line Set Length
g per 1.5 m) adjust from 4.6 m line
Liquid Line
Set Diameter
9.5 mm
NOTE - *If line length is greater than 4.6 m, add this amount. If
line length is less than 4.6 m, subtract this amount.
START: Measure outdoor ambient temperature
USE WEIGH‐IN METHOD
Weigh‐in or remove refriger
ant based upon line length
If refrigerant is added
or
removed,
verify
charge
using
the
Subcooling Method.
If value is LESS
than shown, add
refrigerant.
507994-01 11/19
DT)
process using the illustration in figure 18.
Delta−T
B
A
72º
B
air flow
64º
BULB
INDOOR
WET
BULB
COIL
65ºF
(18.3ºC) and
ABOVE
set*
85 g per 1.5 m)
Figure 19. HFC-410A Weigh In
ABOVE or
BELOW
64ºF and
BELOW
If value is MORE
than shown, remove
refrigerant.
APPº (Approach) Values(F:+/-1.0° [C: +/-0.6°])
MORE or
ºF (ºC)*
LESS
Any
*Temperature of air entering outdoor coil
Figure 20. HFC-410A Approach TXV Charge
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
measured T
Drop
justment is needed. See examples: Assume DT = 15 and A temp. =
72º, these C temperatures would necessitate stated actions:
Cº
T
–
Drop
53º
19
–
58º
14
–
62º
10
–
DRY
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
ABOVE or
BELOW
1. Confirm proper airflow across coil using figure 18.
2. Compare unit pressures with Table 3, Normal Operating Pressures.
3. Set thermostat to call for heat (must have a cooling load between
70‐80ºF (21-26ºC).
4. Connect gauge set.
5. When heat demand is satisfied, set thermostat to call for cooling.
65ºF and
6. Allow temperatures and pressures to stabilize.
ABOVE
7. Record outdoor ambient temperature:
AMBº =_________
8. Record liquid line temperature:
LIQº = __________
9. Subtract to determine approach (APPº):
LIQº_____ - AMBº _____ = APPº_____
10. Compare results with table below.
-036
-042
-048
11 (6.1)
9 (5.0)
8 (4.4)
Page 20
and the desired DT (T
–DT) is within +3º, no ad
Drop
DT
=
ºF ACTION
=
15
4
Increase the airflow
=
15
-1 (within +3º range) no change
=
15
-5 Decrease the airflow
1. Check Liquid and suction line pressures
2. Compare unit pressures with table 3 or 6.
3. Conduct
leak
check;
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.
-060
9 (5.0)
evacuate
as
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