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XC16 SERIES
CHECKING AIR FLOW AT INDOOR COIL
Check airflow using the Delta−T (
D
T)
process using the illustration in figure 17.
1. Determine the desired
D
T
Measure entering air temper-
ature using dry bulb (
A
) and wet bulb (
B
).
D
T
is the intersect-
ing 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
). Tem-
perature Drop Formula: (
T
Drop
) =
A
minus
C
.
3. Determine if fan needs adjustment
If the difference between
the measured
T
Drop
and the desired
D
T
(T
Drop
–
D
T)
is within
+3º, no adjustment is needed. See examples: Assume
D
T
=
15 and
A
temp. = 72º, these
C
temperatures would necessi-
tate stated actions:
Cº
T
Drop
–
D
T
=
ºF
ACTION
53º
19
–
15
=
4
Increase the airflow
58º
14
–
15
=
−1
(3º range) no change
62º
10
–
15
=
−5
Decrease the airflow
4. Adjust the fan speed
See 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
D
T are within
+3º.
D
T
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 flow
air flow
All temperatures are
expressed in ºF
Figure 17. 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 18. Using HFC−410A Weigh In Method
