Manual for Refrigeration Servicing Technicians - UNEP - Division of ...

4
Servicing Practices
Electronic charging machines
During larger-scale manufacturing, equipment tends to be charged
using electronically controlled charging machines. These generally
measure refrigerant into a system using precise mass flow meters,
and are generally accurate to ±0.5g or better.
Vapour refrigerant charging
Vapour refrigerant charging is the process of moving vapour out of
the vapour space of the refrigerant cylinder to the low-pressure side
of the system. Charging while the system is running is acceptable as
cylinder, close the charging cylinder valve and operate the system
for 1-2 minutes until the low-pressure side reading indicates lower
reading than the charging
cylinder.
long as the suction pressure is closely checked during the charging
3 - Continue adding refrigerant by
process. Due to pressure difference consideration, the cylinder
opening the charging cylinder
pressure could become lower than
valve until the proper charge is
system suction pressure during
obtained.
charging. Using a hot water or
servicing charging heaters could
solve this problem. Never use a
brazing torch to heat cylinders.
121 PSIG
OPEN
196 PSIG
CLOSED OPEN
Before connecting any refrigerant
hose to a service or tap valve,
the hose should be briefly purged
(vented) with refrigerant from
In general, follow the same connection
the cylinder to ensure that air
scheme as in evacuation process and
replace the connection with vacuum pump
with the refrigerant charging cylinder as
shown here:
CHAPITRE 4
PAGE 18
VAPOUR REFRIGIRENT CHARGING
SUCTION PRESSURE
50 PSIG
Then:
1 - Open the low-pressure side valve then open refrigerant graduated
charging cylinder valve keeping eye on system pressure and
refrigerant weight scale.
2 - When the pressure has equalised between system and charging
121
PSIG
R-22
Vapour refrigerant charging
and moisture does not enter the
system.
105