Lennox International Inc 2SCU13 warranty Subcooling Values for Fixed Orifice or TXV Systems

Charge Using Weigh-In Method (Fixed Orifice/TXV Systems)

If the system is void of refrigerant, or if the outdoor ambient temperature is cool, first locate and repair any leaks then use the weigh-in method to charge the unit.

1.Recover the refrigerant from the unit.

2.Conduct a leak check, then evacuate as previously outlined.

3.Weigh in the charge according to the total amount shown on the unit nameplate.

If weighing facilities are not available or if unit is being charged during warm weather, follow one of the other procedures outlined below.

Charge Using Subcooling Method (Fixed Orifice/TXV Systems) – Outdoor Temperatures 65°F or Above

If charging a fixed orifice or TXV system when the outdoor ambient temperature is 65°F or above, the subcooling method can be used to charge the unit.

1.With the manifold gauge hose on the liquid service port and the unit operating stably, use a digital ther- mometer to record the liquid line temperature.

2.At the same time, record the liquid line pressure reading.

3.Use a temperature/pressure chart for HCFC-22 to determine the saturation temperature for the liquid line pressure reading.

4.Subtract the liquid line temperature from the satura- tion temperature (according to the chart) to determine subcooling.

_____ ° Saturation Temperature °F

–_____ ° Liquid Line Temperature °F = _____ ° Subcooling Value °F

5.Compare the subcooling value with those shown in Table 6. If subcooling is greater than shown, recover some refrigerant. If subcooling is less than shown, add some refrigerant.

Charge Using Superheat Method (Fixed Orifice Systems) – Outdoor Temperatures 65°F or Above

1.With the manifold gauge hose on the suction service port and the unit operating stably, use a digital ther- mometer to record the suction line temperature.

2.At the same time, record the suction line pressure reading.

# 48283B006

Subcooling Values for

Fixed Orifice or TXV Systems

Outdoor		Liquid Subcooling (±1°F)
Temp.
	-18	-24	-30	-36	-42	-48	-60
°F
65	13	13	7	14	15	9	13
75	10	11	5	13	13	9	12
85	8	10	5	11	11	9	11
95	7	10	4	9	9	9	10
105	6	9	3	8	7	9	9
115	3	6	2	6	5	8	8

Table 6

3.Use a temperature/pressure chart for HCFC-22 to determine the saturation temperature for the suction line pressure reading.

4.Subtract the saturation temperature (according to the chart) from the suction line temperature to determine the superheat.

_____ ° Suction Line Temperature °F

–_____ ° Saturation Temperature °F = _____ ° Superheat Value °F

5.Compare the superheat value with those shown in Table 7 on page 12. If superheat is greater than shown, add some refrigerant. If superheat is less than shown, recover some refrigerant.

Charge Using Approach Method (TXV Systems)

– Outdoor Temperatures 65°F or Above

The following procedure is intended as a general guide and is for use on expansion valve systems only. For best results, indoor temperature should 70°F to 80°F. Monitor system pressures while charging.

1.Record outdoor ambient temperature using a digital thermometer.

2.Attach high pressure gauge set and operate unit for several minutes to allow system pressures to stabilize.

3.Compare stabilized pressures with those provided in Table 9 on page 13. Minor variations in these pres- sures may be expected due to differences in installa- tions. Significant differences could mean that the system is not properly charged or that a problem exists with some component in the system.

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