Lennox 13ACX Installation And Service Procedure page 29

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 (
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.
Figure 17. Checking Indoor Airflow over Evaporator Coil using Delta-T Chart
DT)
process using the illustration in figure 17.
Temperature of air
entering indoor
coil ºF
A
T
Drop
19º
air flow
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
57 58 59 60 61 62 63 64 65 66 67 68 69 70
Wet-bulb ºF
INDOOR COIL
) = A minus C.
Changing air flow affects all temperatures; recheck
temperatures to confirm that the temperature drop
and DT are within +3º.
Page 29
DT
B
air flow
B
64º
and the desired
Drop
A
72º
DRY BULB
WET BULB
13ACX
SERIES