Specifications

17
Guidelines Of Field-charging Air Conditioning Systems With Scroll Compressors
These guidelines are intended for use with Scroll compressors only with R22, R407C, R134a, R404A, R507,
and R410A refrigerants. They do not apply to reciprocating compressors or competitive Scroll compressors.
Field-charging - Some Precaution Points
Scroll compressors have a very high volumetric efficiency and quickly pump a deep vacuum if there is insuffi-
cient refrigerant in the system or if refrigerant is added too slowly. Operation with low suction pressure will
quickly lead to very high discharge temperatures. While this process is happening, the scrolls are not being well
lubricated - scrolls depend on the oil mist in the refrigerant for lubrication. A lack of lubrication leads to high
friction between the scroll flanks and tips and generates additional heat. The combination of heat of compres-
sion and heat from increased friction is concentrated in a small localized discharge area where temperatures
can quickly rise to more than 300°C. These extreme temperatures damage the Scroll spirals and the orbiting
Scroll bearing. This damage can occur in less than one minute especially on larger compressors. Failure may
occur in the first few hours or the damage done during field charging may show up some time later.
Other typical field charging problems include undercharging, overcharging, moisture or air in the system etc. In
time each one of these problems can cause compressor failure.
Equipment
Minimal equipment is required for field charging. The minimum equipment required to do a satisfactory job is:-
Set of service gauges
Hoses
Vacuum pump
Vacuum gauge
Scales
Thermometer
Charging Hoses
Most field-charging is done using standard service hoses. Hoses are made in different colors with different
working pressures and with different leak rates but the most important point is the presence or absence of
Shredder valve depressors. Shredder valve depressors severely restrict the flow through the service hoses.
This slows evacuation and vapor charging dramatically. In most cases the Shredder depressor can be removed
but it is simpler to have one set of hoses with and one set without Shredder depressors.
Hose selection is important depending whether the system is being evacuated or charged. Charging liquid from
the cylinder into the liquid line should be carried out using an open hose connected to an unrestricted fitting. This
will reduce charging time.
Hose with Shredder valve Depressor Hose without Shredder valve Depressor