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INSTALLER'S GUIDE
SUbcooLING cHARGING IN cooLING AbovE 55°f oD AMbIENT
American Standard has always recommended installing approved
matched indoor and outdoor systems.
All American Standard split systems are AHRI rated with only
TXV indoor systems.
The benefits of installing approved indoor and outdoor split
systems are maximum efficiency, optimum performance and the
best overall system reliability.
The following charging methods are therefore prescribed for
systems with indoor TXV's.
1.
Subcooling (in the cooling mode) is the only recommended
method of charging above 55°F outdoor ambient temperatures.
2.
For best results - the indoor temperature should be kept
between 70°F to 80°F. Add system heat if needed.
3.
At startup, or whenever charge is removed or added, the
system must be operated for a minimum 20 minutes to stabilize
before accurate measurements can be made.
4.
Measure Liquid Line Temperature and Refrigerant Pressure
at service valve.
5.
Determine total refrigerant line length, and height (lift) if
indoor section is above the condenser.
6.
Determine the Design Subcool Charging Temperature from
the unit nameplate.
7.
Locate this value in the appropriate column of the Subcool-
ing Charging Table. Locate your liquid line temperature in the
left column of the table, and the intersecting liquid line pressure
under your nameplate subcool value column. Add refrigerant to
raise the pressure to match the table, or remove refrigerant to
lower the pressure. Again, wait for 20 minutes for the system
conditions to stabilize before adjusting charge again.
8.
When system is correctly charged, you can refer to System
Pressure Curves (in Service Facts) to verify typical perfor-
mance.
SUBCOOL CHARGING TABLE CORRECTIONS FOR LINE LENGTH AND RISE
SUbcooLING cHARGING bELow 55°f oD AMbIENT - IN HEATING oNLy
1.
The Subcool Charging Method in cooling is not recommended
below 55°F outdoor ambient.
2.
The only recommended method of charging at outdoor am-
bients below 55°F, is to weigh in the charge in the heating
mode.
3.
Use Nameplate charge plus standard charge adders for line
length.
PAGE 6
60
50
40
30
25
20
15
Use Design Subcool Value from Table
10
0
Subtract 10 psig from S.C. Table Pressure
10
20
TOTAL REFRIGERANT LINE LENGTH (FEET)
R-410A SUbcooLING cHARGING TAbLE
LIQUID
TEMP. (°F)
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
Add 10 psig to Subcool Charging Table Pressure
25
30
40
4.
Check liquid line temperature and pressure (at the OD
valves) to obtain a minimum of 10°F subcooling.
5.
Add charge if a minimum of 10°F subcooling is not obtained
with the nameplate charge plus line length correction.
6.
It is important to return in the spring or summer to accurately
charge the system in the cooling mode at outdoor ambients
above 55°F.
DESIGN SUBCOOLING VALUES (°F)
8
10
12
LIQUID LINE PRESSURE (psi)
179
185
191
195
201
208
211
218
225
229
236
243
247
255
263
267
275
283
287
296
304
309
318
327
331
341
351
355
365
376
381
391
402
407
418
429
435
446
458
464
476
488
495
507
520
From Dwg. D154557P01 Rev. 1
60
80
Pub. No. 11-BC08D1-7
14
198
215
232
251
271
291
313
336
360
386
413
441
470
501
533