Lennox EL16XC1 Series Installation And Service Procedure page 28

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 15. Checking Indoor Airflow over Evaporator Coil using Delta-T Chart
DT)
process using the illustration in figure 15.
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
=
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
Wet-bulb ºF
57 58 59 60 61 62 63 64 65 66 67 68 69 70
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 28
B
air flow
B
64º
and the desired
Drop
A
72º
DRY BULB
WET BULB