Lennox Elite XC16 Installation Instructions Manual page 17

LOW HIGH
PRESSURE PRESSURE
GAUGE MANIFOLD
TO
HFC−410A
DRUM
Temp.
80 24 24 24 23 23 22 22 22 20 19 18 17 16 15
of air
entering
78 23 23 23 22 22 21 21 20 19 18 17 16 15 14
indoor
76 22 22 22 21 21 20 19 19 18 17 16 15 14 13
coil ºF
74 21 21 21 20 19 19 18 17 16 16 15 14 13 12
A 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
T
Drop
C
19º
53º
air flow
DRY
BULB
All temperatures are
expressed in ºF
Figure 28. Checking Indoor Airflow over Evaporator Coil using Delta−T Chart
START: Determine how refrigerant is metered
WHEN TO CHARGE?
S
Warm weather best
S
Can charge in colder weather
CHARGE METHOD? Determine by:
S
Metering device type
S
Outdoor ambient temperature
REQUIREMENTS:
S
Sufficient heat load in structure
S
Indoor temperature between 70-80ºF (21−26ºC)
S
Manifold gauge set connected to unit
S
Thermometers:
− to measure outdoor ambient temperature
− to measure liquid line temperature
− to measure suction line temperature
LIQUID LINE
SERVICE VALVE
FILTER
DRIER
Figure 27. Typical Manifold Gauge Connection Setup
Delta−T
B
A
72º
B
air flow
64º
DRY
BULB
INDOOR
WET
BULB
COIL
Figure 29. Determining Charging Method
OUTDOOR UNIT
OUTDOOR
COIL
SUCTION LINE
SERVICE VALVE
COMPRESSOR
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 ) = A minus C.
Drop
3. Determine if fan needs adjustment If the difference between the
and the desired DT (T
measured T
Drop
adjustment is needed. See examples: Assume DT = 15 and A temp. =
72º, these C temperatures would necessitate stated actions:
Cº T –
Drop
53º 19 –
58º 14 –
62º 10 –
4. Adjust the fan speed See indoor unit instructions to
increase/decrease fan speed.
Changing air flow affects all temperatures; recheck temperatures to
confirm that the temperature drop and DT are within +3º.
65ºF (18.3ºC)
and ABOVE
APPROACH OR
SUBCOOLING
(SECOND STAGE − HIGH
CAPACITY)
Page 17
(Uncased Coil Shown)
TXV
–DT) is within +3º, no
Drop
DT =
ºF ACTION
=
15 4 Increase the airflow
=
15 −1 (within +3º range) no change
=
15 −5 Decrease the airflow
TXV
OUTDOOR AMBIENT
TEMPERATURE
64ºF (17.7ºC)
and BELOW
WEIGH-IN
XC16 SERIES