Lennox 13HPX Series Unit Information page 12

Then, apply the measurements taken in following formula
to determine CFM:
Amps x Volts x 3.41
CFM =
1.08 x Temperature rise (F)
SETUP FOR CHARGING
Connect the manifold gauge set to the unit's service ports.
S
low pressure gauge to vapor service port
S
high pressure gauge to liquid service port
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 4. Checking Indoor Airflow over Evaporator Coil using Delta−T (DT) Chart
CHECK
EXPANSION VALVE
LOW HUGH
PRESSURE PRESSURE
GAUGE
MANIFOLD
TO
HFC−410
A DRUM
NOTE − USE GAUGE PORTS ON VAPOR LINE VALVE AND LIQUID VALVE FOR EVACUATING REFRIGERANT
LINES AND INDOOR COIL. USE VAPOR GAUGE PORT TO MEASURE VAPOR PRESSURE DURING
CHARGING.
Figure 5. 13HPX Cooling Cycle (Showing Gauge Manifold Connections)
DT
B
A
72º
B
air flow
64º
DRY BULB
INDOOR WET
BULB
COIL
DISTRIBUTO
BIFLOW
FILTER /
OUTDOOR
DRIER
COIL
MUFFLE
R
LIQUID
SERVICE
PORT
LIQUID
LINE
VALVE
COMPRESSO
R
Close manifold gauge set valves. Connect the center man-
ifold hose to an upright cylinder of HFC−410A.
CALCULATING CHARGE
If the system is void of refrigerant, first, locate and repair
any leaks and then weigh in the refrigerant charge into the
unit. To calculate the total refrigerant charge:
Amount Adjust amt. for
specified variation in line set
on length (table in
nameplate figure 6)
+
Step 1. Determine the desired DT Measure entering air tempera-
ture using dry bulb (A) and wet bulb (B). DT is the intersecting value
of A and B in the table (see triangle).
Step 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
Step 3. Determine if fan needs adjustment If the difference be-
tween the measured T
Drop
+3º, no adjustment is needed. See examples: Assume DT = 15 and
A temp. = 72º, these C temperatures would necessitate stated ac-
tions:
DT =
Cº T –
Drop
=
53º 19 – 15
=
58º 14 – 15
=
62º 10 – 15
Step 4. Adjust the fan speed See indoor unit instructions to in-
crease/decrease fan speed.
Changing air flow affects all temperatures; recheck temperatures to
confirm that the temperature drop and DT are within +3º.
OUTDOOR UNIT
R
REVERSING VALVE
VAPOR
SERVICE
PORT
VAPOR
LINE
VALVE
CHECK EXPANSION VALVE
Page 12
Additional charge
specified per indoor
unit matchup tables.
+ =
and the desired DT (T
–DT) is within
Drop
ºF ACTION
4 Increase the airflow
−1 (within +3º range) no change
−5 Decrease the airflow
NOTE − ARROWS INDICATE DIRECTION
OF REFRIGERANT FLOW
INDOOR UNIT
INDOOR
COIL
Total
charge