Page 14
Revised 05−2009
TPA*S4
Cooling mode indoor airflow check
Check airflow using the Delta−T (
D
T)
process (figure 15).
Heating mode indoor airflow check
Blower airflow (CFM) may be calculated by energizing
electric heat and measuring:
S
temperature rise between the return air and supply air
temperatures at the indoor coil blower unit,
S
measuring voltage supplied to the unit,
S
measuring amperage being drawn by the heat unit(s).
Then, apply the measurements taken in following formula
to determine CFM:
CFM =
Amps x Volts x 3.41
1.08 x Temperature rise (F)
Setup for Charging
Connect the manifold gauge set to the unit’s service ports
(see figure 16):
S
low pressure gauge to
vapor service port
S
high pressure gauge to
liquid service port
Close manifold gauge set valves. Connect the center
manifold 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
specified
on
nameplate
Adjust amt. for
variation in
line set length
(table 6)
Additional charge
specified per
indoor unit matchup
(table 8)
Total
charge
+
+
=
Weigh−in Charging Method
Weigh−in:
1.. Recover the refrigerant from the unit.
2.. Conduct leak check; evacuate as previously outlined.
3.. Weigh in the unit nameplate charge plus any charge
required for line set differences from 15 feet and any
extra indoor unit matchup amount per table 8. (If
weighing facilities are not available, use the subcooling
method.)
Table 6. Charge per Line Set Lengths
Liquid Line
Set Diameter
Oz. per 5 ft. (g per 1.5m) adjust from
15 ft. (4.6m) line set*
3/8 in. (9.5mm)
3 ounce per 5 ft. (85g per 1.5m)
NOTE − *If line length is greater than 15 ft. (4.6 m), add this amount.
If line length is less than 15 ft. (4.6 m), subtract this amount.
Subcooling Charging Method
Requirements
these items are required for charging:
S
Manifold gauge set connected to unit.
S
Thermometers for measuring outdoor ambient, liquid
line, and vapor line temperatures.
When to use cooling mode
When outdoor temperature
is 60°F (15°C) and above, use cooling mode to adjust
charge.
When to use heating mode
When the outdoor
temperature is below 60°F (15°C), use the heating mode to
adjust the charge.
Adding Charge for Indoor Matchups
Table 8 lists all
the Lennox recommended indoor unit matchups along with
the charge levels for the various sizes of outdoor units.
Table 7. Normal Operating Pressures − 10 and Vapor +5 PSIG*
IMPORTANT
Use table 4 as a general guide when performing maintenance checks. This is not a procedure for charging the
unit (Refer to Charging / Checking Charge section). Minor variations in these pressures may be expected due
to differences in installations. Significant differences could mean that the system is not properly charged or that
a problem exists with some component in the system.
TPA*S4N43Y
Mode
5
F (
5
C)**
TPA036S4
TPA036S4
TPA036S4
TPA036S4
Liquid / Vapor
Liquid / Vapor
Liquid / Vapor
Liquid / Vapor
Cooling
65 (18)
260 / 136
231 / 135
246 / 134
256 / 116
75 (24)
303 / 140
267 / 138
286 / 136
298 / 123
85 (29)
348 / 143
314 / 140
330 / 138
345 / 131
95 (35)
398 / 145
367 / 143
379 / 140
395 / 135
105 (41)
452 / 148
414 / 146
432 / 143
450 / 138
115 (45)
512 / 151
473 / 148
492 / 146
512 / 141
Heating
60 (15)
350 / 131
366 / 129
348 / 119
379 / 127
50(10)
331 / 111
348 / 110
334 / 105
361 / 109
40 (4)
314 / 91
333 / 91
312 / 84
341 / 89
30 (−1)
303 / 74
317 / 70
300 / 73
323 / 71
20 (−7)
290 / 62
298 / 58
286 / 60
310 / 60
*These are most−popular−match−up pressures. Indoor match up, indoor air quality, and indoor load cause pressures to vary.
**Temperature of the air entering the outside coil.
