Subcooling Charging & Refrigerant Adjustment in Cooling ModeUpdated 11 days ago

Introduction

This article explains the process for subcooling charging and refrigerant adjustment in Cooling mode.

Subcooling is the only recommended charging method when the outdoor ambient temperature is between 68-113°F (20-45°C) and the indoor ambient temperature is between 68-89°F (20-32°C).

If either temperature is out of the range, use the weigh-in method. For information, see this article.

Note: When the outdoor ambient temperature is higher than 68°F (20°C), make sure to return in spring or summer in order to accurately charge the system in Cooling mode.

Steps

1. Begin by checking the ambient temperature.

2. Activate Forced Cooling mode by starting the system in Cooling mode, then pressing and holding the "SET" button until the symbol "dC" displays. After entering Forced Cooling mode, the symbol "dC" and current compressor frequency will show alternatively on the digital display.

Note: The Forced Cooling mode will automatically stop after 1 hour. The mode can be exited by pressing and holding the "SET" button again.

3. After Forced Cooling mode has started, wait 20 minutes for the system to stabilize. The compressor will maintain a specific frequency in this mode.

4. Determine the optimum subcooling value, which is based on the measured liquid line temperature and pressure below in the following table:

Liquid Line Temp. (°F/°C)	Subcooling Value (°F/°C)
	6	7	8	9	10	11	12	13
	Liquid Gauge Pressure (PSI)
55°F / 13°C	164	167	170	172	175	178	181	184
60°F / 15.5°C	178	181	184	187	191	194	197	200
65°F / 18°C	194	197	200	203	206	210	213	217
70°F / 21°C	210	213	217	220	223	227	230	234
75°F / 24°C	227	230	234	238	241	245	249	252
80°F / 27°C	245	249	252	256	260	264	268	272
85°F / 29°C	264	268	272	276	280	284	288	292
90°F / 32°C	284	288	292	297	301	305	309	314
95°F / 35°C	305	309	314	318	323	327	332	336
100°F / 38°C	327	332	336	341	346	351	355	360
105°F / 40.5°C	351	355	360	365	370	375	380	385
110°F / 43°C	375	380	385	390	396	401	406	412
115°F / 46°C	401	406	412	417	422	428	433	439
120°F / 49°C	428	433	439	445	450	456	462	468
125°F / 52°C	456	462	468	474	480	486	492	498

5. If the calculated subcooling value is lower than the recommended design subcooling value in the following table, add refrigerant. If the calculated subcooling value is higher than the value shown in the table, recover refrigerant.

Subcooling (°F/°C)		Ambient Temperature (°F/°C)
Subcooling (°F/°C)		68~77 / 20~25	77~86 / 25~30	86~95 / 30~35	95~104 / 35~40	104~113 / 40~45
Model	24K	10±2	8±2	8±2	6±2	6±2
	36K	10±2	8±2	8±2	6±2	6±2
	48K	8±2	8±2	8±2	6±2	6±2
	60K	8±2	8±2	8±2	6±2	6±2

6. Wait 5 minutes for the system to stabilize and repeat the steps above until the subcooling value matches the design subcooling value in the table above.

7. Remove the service tools.

8. Press and hold the "SET" button to exit Forced Cooling mode. The symbol "dC" will disappear when exiting the Forced Cooling mode.

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