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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.
This unit is NOT approved for use with coils which use capillary tubes or fixed orifices as a refrigerant metering device.
Check airflow using the Delta-T (DT) process shown below..
AIRFLOW
INDOOR COIL
DRY
BULB
C
53º
All temperatures are expressed in ºF
Use the following procedure to adjust for optimal air flow across the indoor coil:
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
3. Determine if fan needs adjustment — If the difference between the measured T
DT (T
–DT) is within +3º, no adjustment is needed. See example below:
Drop
Assume DT = 15 and A temp. = 72º, these C temperatures would necessitate stated actions:
T
–
DT
Cº
Drop
19 –
15
53º
14 –
15
58º
10 –
15
62º
4. Adjust the fan speed — See indoor unit instructions to increase/decrease fan speed.
Temperature of air
entering indoor
coil ºF
A
T
Drop
19º
air flow
) = A minus C.
Drop
=
ºF ACTION
=
4 Increase the airflow
=
-1 (within +3º range) no change
=
-5 Decrease the airflow
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
Wet-bulb ºF
57 58 59 60 61 62 63 64 65 66 67 68 69 70
air flow
INDOOR COIL
Changing air flow affects all temperatures; recheck
temperatures to confirm that the temperature drop
and DT are within +3º.
Page 26
DT
B
A
72º
B
64º
DRY BULB
WET BULB
and the desired
Drop
31-5000749 Rev. 0
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