Lennox International Inc 2SCU13 Approach Values for TXV Systems, Outdoor Ambient Temp Superheat

Superheat Values for Fixed Orifice Systems (80°DB/67°WB Return Air)

Outdoor Ambient Temp.	Superheat
°F	°F
60	38
65	35
70	30
75	26
80	22
85	18
90	12
95	8
100	5
105	0

Table 7

Pressures higher than those listed indicate that the system is overcharged. Pressures lower than those listed indicate that the system is undercharged. Verify adjusted charge using the approach method.

4.Use the same digital thermometer to check liquid line temperature.

5.Subtract the outdoor ambient temperature from the liquid line temperature to determine the approach temperature.

_____ ° Liquid Line Temperature °F

–_____ ° Outdoor Ambient Temperature °F = _____ ° Approach Temperature °F

6.Compare the approach value with those shown in Table 8. If the values to do not agree with those provided in Table 8, add refrigerant to lower the approach temperature or recover refrigerant from the system to increase the approach temperature.

Check Charge Using Normal Operating Pressures

Use Table 9 to perform maintenance checks. Table 9 is not a procedure for charging the system. Minor variations in these pressures may be due to differences in installa- tions. Significant deviations could mean that the system is not properly charged or that a problem exists with some component in the system.

Approach Values for TXV Systems

Model	-18	-24	-30	-36	-42	-48	-60
Temp.	6	10	11	9	5	5	8
°F

Approach value is the liquid line temperature minus the outdoor ambient temperature (±1°F).

NOTE: For best results, use the same digital thermometer to check both outdoor ambient and liquid temperatures.

Table 8

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