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XC14 SERIES
CHECKING AIR FLOW AT INDOOR COIL
Check airflow using the Delta−T (
DT) process using the illustration in figure 20.
1. Determine the desired DTMeasure 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 coilMeasure 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 adjustmentIf 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 speedSee 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 20. Checking Indoor Airflow over Evaporator Coil using Delta−T Chart
WEIGH IN
Liquid Line
Set Diameter
Ounces per 5 feet (g per 1.5 m)
adjust from 15 feet (4.6 m) line set*
3/8" (9.5 mm)
3 ounce per 5’ (85 g per 1.5 m)
*If line length is greater than 15 ft. (4.6 m), add this amount. If
line length is less than 15 ft. (4.6 m), subtract this amount.
Refrigerant Charge per Line Set Length
NOTE The above nameplate is for illustration purposes only. Go to actual nameplate on outdoor unit for charge information.
CHARGING METHOD
NOTE Insulate liquid line when it is routed through areas where the surrounding ambient temperature could become higher than the
temperature of the liquid line or when pressure drop is equal to or greater than 20 psig.
CALCULATING SYSTEM CHARGE FOR OUTDOOR UNIT VOID OF CHARGE
If the system is void of refrigerant, first, locate and repair any leaks and then weigh in the refrigerant charge into the
unit. To calculate the total refrigerant charge:
Amount specified on
nameplate
Adjust amount. for variation
in line set length listed on
line set length table below.
Total charge
+
=
64ºF (17.7ºC) and Below
Figure 21. Using HFC−410A Weigh In Method
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