2.Close manifold gauge set valves. Connect the center manifold hose to an upright cylinder of R410A.
3.If room temperature is below 70°F, set the room thermo- stat to call for heat. This will create the necessary load for properly charging the system in the cooling cycle.
4.Use a digital thermometer to record the outdoor ambient temperature.
5.When the heating demand has been satisfied, switch the thermostat to cooling mode with a set point of 68°F. When pressures have stabilized, use a digital thermometer to record the liquid and suction line temperatures.
6.The outdoor temperature will determine which charg- ing method to use. Proceed with the appropriate charging method.
Charge Using Weigh-In Method
If the system is void of refrigerant, or if the outdoor ambient temperature is cool, first locate and repair any leaks then use the
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, use one of the following procedures to charge the unit.
Charge Using Subcooling Method –
Outdoor Temperatures Below 65°F
When the outdoor ambient temperature is below 65°F, the subcooling method can be used to charge the unit. It may be necessary to restrict the air flow through the outdoor coil to achieve pressures in the
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 the temperature/pressure chart (Table 5 on page 14) to determine the saturation temperature for the liquid line pressure reading.
Blocking Outdoor Coil
Outdoor coil should be blocked one side at a time with cardboard or plastic sheet until proper testing pressures are reached.
Cardboard or Plastic Sheet
Figure 12
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 on page 14. If subcooling is greater than shown, recover some refrigerant. If subcooling is less than shown, add some refrigerant.
Charge Using Approach Method –
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 8 on page 15. 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. 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.
Issue 1008 | Page 13 |
