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Weighing the charge
- Must be used for all charging operations
- Charge weight is known or determined through another method
- Used for full or partial charge replacement
- Charge level is monitored with the use of a scale
- Net weight – total amount of refrigerant in cylinder
- Tare weight – weight of container
- Gross weight – tare weight + refrigerant weight
- Water capacity (WC) – amount of water cylinder can hold
- Tank holds 80% with oil separated – 60% if not separated
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Sight glass Method
- May be used when system is equipped with sight glass
- Charge until no bubbles appear in the sight glass
- Used for full or partial charge replacement
- Consider distance of sight glass from metering device
- Danger of under or over charging
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Graduated charging Cylinder
- When used for full charge replacement it is an accurate method of charging small systems
- Match scale to refrigerant, and temperature to find volume
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Super Heat
- Used for fixed metering systems (capillary tube) Heat pump
- Measure full load super heat, SST minus Evaporator outlet temperature
- Only accurate when measured at full load condition
- Compare to manufactures recommendations
- Limitation: require OEM recommendation
- 1% charge = 3 F change in Superheat
- Sensing element must make good contact
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Sub cooling
- Used for TXV systems
- Measure full load subcooling, SDT minus condenser outlet temperature
- Compare to manufactures recommendations
- Limitation OEM recommendations
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Liquid Level Indication
- Used with systems with liquid level indicators in the receiver
- Often used on systems which employ condenser flooding capacity control
- Charge Refrigerant until proper liquid level is achieved in the receiver
- Level based on the ambient condition at the time of charging
- Compare Manufacturers Recommendations
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Charging Chart Method
- Use manufactures charging charts and recommendations to achieve proper charge level
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