Charging System - Lennox Elite XC13 Installation Instructions Manual

INDOOR COIL AIRFLOW CHECK
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
Check indoor coil airflow using the Delta−T (

Charging System

DETERMINING CHARGE METHOD
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
506120−01 03/10
DT
B
A
72º
B
air flow
64º
DRY
BULB
INDOOR WET
BULB
COIL
DT)
process as illustrated.
Figure 33. Indoor Coil Airflow Check
TXV
A
64ºF
(17.7ºC) and
Below
WEIGH-IN
Figure 34. Determining Charge Method
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:
DT
Cº T –
Drop
53º 19 – 15
58º 14 – 15
62º 10 – 15
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.
Which indoor
metering
device?
B C
65ºF
(18.3ºC) and
Above
APPROACH OR
SUBCOOLING
Page 22
–DT) is within +3º, no
Drop
=
ºF ACTION
=
4 Increase the airflow
=
−1 (within +3º range) no change
=
−5 Decrease the airflow
FIXED
ORIFICE
D
40ºF
(4.4ºC) and (3.8ºC) and
Above
SUPERHEAT WEIGH-IN
E
39ºF
Below