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506601−01
ADDING OR REMOVING REFRIGERANT
This system uses HFC−410A refrigerant which operates at
much higher pressures than HCFC−22. The pre−installed
liquid line filter drier is approved for use with HFC−410A
only. Do not replace it with components designed for use
with HCFC−22.
COOLING MODE INDOOR AIRFLOW CHECK
Check airflow using the Delta−T (
D
T)
process using the
illustration in figure 20.
HEATING MODE INDOOR AIRFLOW CHECK
Blower airflow cubic feet per minute (CFM) may be
calculated by energizing electric heat and measuring:
S
Temperature rise between the return air and supply air
temperatures at the indoor coil blower unit,
S
Measuring voltage supplied to the unit,
S
Measuring amperage being drawn by the heat unit(s).
Then, apply the measurements taken in following formula
to determine CFM:
CFM =
Amps x Volts x 3.41
1.08 x Temperature rise (F)
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
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
TEMPERATURE OF AIR
ENTERING INDOOR COIL ºF
INDOOR COIL
DRY BULB
DRY
BULB
WET BULB
B
T
DROP
19º
A
DR
Y−BULB
WET−BULB ºF
A
72º
B
64º
C
53º
AIR FLOW
AIR FLOW
All temperatures are expressed in ºF
1.
Determine the desired DT
Measure entering air temperature using dry bulb (
A
) and wet bulb (
B
).
D
T
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
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 3º, no adjustment
is needed. See example below:
4.
ADJUST THE FAN SPEED
See indoor unit instructions to increase/decrease fan speed.
ASSUME
D
T
= 15 AND
A
TEMP. = 72º, THESE
C
TEMPERATURES WOULD NECESSITATE STATED ACTIONS:
AIRFLOW
Use the following procedure to adjust for optimal air flow across the indoor coil:
INDOOR COIL
Changing air flow affects all temperatures; recheck temperatures to
confirm that the temperature drop and
D
T are 3º.
Figure 20. Checking Indoor Airflow over Evaporator Coil using Delta−T Chart
