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Page 23
14ACX SERIES
CHECKING AIR FLOW AT INDOOR COIL
Check airflow using the Delta−T (
DT) process using the illustration in figure 19.
1. Determine the desired DTĊMeasure entering air temper-
ature using dry bulb (A) and wet bulb (B). DT is the intersect-
ing value of A and B in the table (see triangle).
2. Find temperature drop across coilĊMeasure the coil’s dry
bulb entering and leaving air temperatures (A and C). Tem-
perature Drop Formula: (T
Drop
) = A minus C.
3. Determine if fan needs adjustmentĊIf the difference between
the measured T
Drop
and the desired DT (T
Drop
–DT) is within
+
3º, no adjustment is needed. See examples: Assume DT =
15 and A temp. = 72º, these C temperatures would necessi-
tate stated actions:
Cº T
Drop
– DT = ºF ACTION
53º 19 – 15 = 4 Increase the airflow
58º 14 – 15 = −1 (within +3º range) no change
62º 10 – 15 = −5 Decrease the airflow
4. Adjust the fan speedĊSee indoor unit instructions to in-
crease/decrease fan speed.
Changing air flow affects all temperatures; recheck tempera-
tures to confirm that the temperature drop and DT are within
+
3º.
DT
80 24 24 24 23 23 22 22 22 20 19 18 17 16 15
78 23 23 23 22 22 21 21 20 19 18 17 16 15 14
76 22 22 22 21 21 20 19 19 18 17 16 15 14 13
74 21 21 21 20 19 19 18 17 16 16 15 14 13 12
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
57 58 59 60 61 62 63 64 65 66 67 68 69 70
Temp.
of air
entering
indoor
coil ºF
INDOOR
COIL
DRY
BULB
DRY
BULB
WET
BULB
B
T
Drop
19º
A
Dry−bulb
Wet−bulb ºF
A
72º
B
64º
C
53º
air flowair flow
All temperatures are
expressed in ºF
Figure 19. Checking Indoor Airflow over Evaporator Coil using Delta−T Chart
WHEN TO CHARGE?
S Best during warm weather
S Can charge in colder weather by determining
best charge method? Determine by:
A Metering device type
B 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
TXV
RFC
APPROACH OR
SUBCOOLING
WEIGH-INSUPERHEAT
65ºF
(18.3ºC) and
Above
START: Determine how refrigerant is metered
39ºF
(3.8ºC) and
Below
Which
metering
device?
WEIGH-IN
64ºF
(17.7ºC) and
Below
40ºF
(4.4ºC) and
Above
Figure 20. Determining Charge Method