ADDITIONAL CHARGE
SPECIAL PRECAUTIONS WHEN CHARGING UNIT WITH SCROLL COMPRESSORS
The refrigerant is pre-charge in the outdoor unit. If the piping length is less than 7.5m, then additional charge after vacuuming
is not necessary. When the piping length is more than 7.5m, use the table below.
Cooling only
Example:
FDM30JEV1K & RD30JEV1K with 13m piping length, additional piping length is 5.5m. Thus,
Additional charge = 5.5[m] x 55[g/m]
= 302.5[g]
Model
Indoor
FDM50JEV1K
FDM60JEV1K
Outdoor
RD50JEY1K
RD60JEY1K
Additional charge [g/m]
54
102
Model
Indoor
FDM20JEV1K FDM25JEV1K FDM30JEV1K FDM40JEV1K FDM40JEV1K
Outdoor
RD20JEV1K
RD25JEV1K
RD30JEV1K
RD40JEV1K
RD40JEY1K
Additional charge [g/m]
19
38
55
65
65
These precautions are intended for use with Scroll compressors only with R22 and R410A refrigerants but are not applied to
others competitive Scroll compressors.
Scroll compressors have a very high volumetric ef
Þ
ciency and quickly pump a deep vacuum if there is insuf
Þ
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
ß
anks and tips and generates additional
heat. The combination of heat of compression 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
Þ
rst few hours or the damage done during
Þ
eld charging may show up some time later. Other typical
Þ
eld charging
problems include undercharging, overcharging, moisture or air in the system etc. In time each one of these problems can
cause compressor failure.
Minimal equipment is required for
Þ
eld charging. The minimum equipment required to do a satisfactory job is:-
1. Set of service gauges
4. Vacuum gauge
2. Hoses
5. Scales
3. Vacuum pump
6. Thermometer
The proper refrigerant charge should follow the volume as recommended by manufacturer and recommendation should be
followed by the installer.
1. Charging procedures – Single phase compressors
Evacuate the system to -760mmHg. To reduce evacuation time, use short, large diameter hoses and connect to unrestricted
service ports on the system. Quality of vacuum cannot be determined by time – a reliable vacuum gauge must be used. (etc.
electronic vacuum gauge)
Turn the refrigerant cylinder upside down, purge the charging hose and charge liquid through the liquid line charging port
until refrigerant no longer
ß
ows or until the correct charge has been weighed in. If additional charge is required start the
system and slowly bleed liquid into the suction side until the system is full.
It recommends charging liquid in a CONTROLLED manner into the suction side until the system is full
.
This recommendation does not hold true for reciprocating compressors where liquid charging into the suction side could
cause severe damage.
Carefully monitor the suction and discharge pressures – ensure that the suction pressure does not fall below 25 psig (1.7
bar) at any time during the charging process.
Dip-pipe
Liquid withdrawal
Invert cylinder
without dip-pipe
