1

Air ConditioningAir Conditioning

ChargingCharging

2

Adding or Replacing a ChargeAdding or Replacing a Charge• Methods for adding • Weighing in with digital scale-Best• Measuring (graduated cylinder or Dial-

a-charge)• Operating pressure charts (using charts

to find pressure at a given ambient temperature

• Superheat/Sub-cooling-Manufacturers Literature

• Sight Glass

• Methods for adding • Weighing in with digital scale-Best• Measuring (graduated cylinder or Dial-

a-charge)• Operating pressure charts (using charts

to find pressure at a given ambient temperature

• Superheat/Sub-cooling-Manufacturers Literature

• Sight Glass

3

Liquid Charging to the High Side.Liquid Charging to the High Side.– Usually done in the liquid line

through the service valve. – System is OFF, and in a vacuum.

100% of the charge can usually be added.

– If the refrigerant stops flowing, the rest must be added to the low side while the unit is running.

• ****HIGH SIDE ONLY****

– Usually done in the liquid line through the service valve.

– System is OFF, and in a vacuum. 100% of the charge can usually be added.

– If the refrigerant stops flowing, the rest must be added to the low side while the unit is running.

• ****HIGH SIDE ONLY****

4

Vapor charging through the Low SideVapor charging through the Low Side– Vapor charging into the low (Suction) side

of the system while running (never with any R-4..)

– If the cylinder is cold it may need to be warmed to raise the pressure above the suction line pressure

– Advantages are it is the easiest way to top off a fully charged system

– Disadvantages are it is a slow process or adding large quantities.

– Vapor charging into the low (Suction) side of the system while running (never with any R-4..)

– If the cylinder is cold it may need to be warmed to raise the pressure above the suction line pressure

– Advantages are it is the easiest way to top off a fully charged system

– Disadvantages are it is a slow process or adding large quantities.

5Liquid charging through the Low SideLiquid charging through the Low Side• System must be running,

compressor will pull refrigerant in

• When adding liquid to the low side, throttle in slowly, not allowing the pressure to go up more than 10 PSIG at a time.

• System must be running, compressor will pull refrigerant in

• When adding liquid to the low side, throttle in slowly, not allowing the pressure to go up more than 10 PSIG at a time.

6

• Advantages are that it is faster than charging with vapor.

• Disadvantages are that it is easy to overcharge or damage compressor.

• Advantages are that it is faster than charging with vapor.

• Disadvantages are that it is easy to overcharge or damage compressor.

Liquid charging through the Low SideLiquid charging through the Low Side

7

Charge SymptomsCharge Symptoms

8

Low ChargeLow Charge– Insufficient cooling– Long running time– Low suction pressure– Low discharge pressures

•

– Insufficient cooling– Long running time– Low suction pressure– Low discharge pressures

•

9

Low Charge Cont…Low Charge Cont…

• Bubbles in sight glass• Higher than normal compressor

and discharge line temp• Low compressor amps• Subcooling lower than normal• In fixed bore systems, a starved

evaporator-High superheat

• Bubbles in sight glass• Higher than normal compressor

and discharge line temp• Low compressor amps• Subcooling lower than normal• In fixed bore systems, a starved

evaporator-High superheat

10

Over ChargeOver Charge

• High discharge pressure• High suction pressure• High compressor amps• High condenser sub-cooling

• High discharge pressure• High suction pressure• High compressor amps• High condenser sub-cooling

11

• Flooded evaporator in fixed bore systems-Little or no superheat.

• Compressor sweating (flooding with liquid)

• Flooded evaporator in fixed bore systems-Little or no superheat.

• Compressor sweating (flooding with liquid)

12

WEIGHING REFRIGERANTWEIGHING REFRIGERANT

• Weighing the correct charge into the system can be accomplished with an electronic scale – Very accurate– Automatically displays amount of

refrigerant removed from cylinder– Some units dispense a predetermined

amount of refrigerant and then shut off

• Weighing the correct charge into the system can be accomplished with an electronic scale – Very accurate– Automatically displays amount of

refrigerant removed from cylinder– Some units dispense a predetermined

amount of refrigerant and then shut off

13

USING CHARGING CHARTS USING CHARGING CHARTS

• Curves and/or charts supplied by manufacturers• Used to help technicians properly charge systems• Since charts and curve vary for manufacturer to

manufacturer, always follow directions carefully• Uses superheat values for fixed bore systems• Uses subcooling values for TXV systems• Charge carefully! It is always easier to add

refrigerant than remove it

• Curves and/or charts supplied by manufacturers• Used to help technicians properly charge systems• Since charts and curve vary for manufacturer to

manufacturer, always follow directions carefully• Uses superheat values for fixed bore systems• Uses subcooling values for TXV systems• Charge carefully! It is always easier to add

refrigerant than remove it

14

CHARGING ZEOTROPIC BLENDSCHARGING ZEOTROPIC BLENDS

• Dew point value–Where saturated vapor begins to

condense–Used for superheat calculations

• Bubble point values–Where saturated liquid begins to boil–Used for subcooling calculations

• Dew point value–Where saturated vapor begins to

condense–Used for superheat calculations

• Bubble point values–Where saturated liquid begins to boil–Used for subcooling calculations