Specifications
32
c) Ensure that the compressor is not exposed to open air for more than the recommended time
specied by its manufacturer (typically less than 10 minutes). Remove the seal-plugs only when the
compressor is about to be brazed.
d) The system should be thoroughly vacuumed to 1.0 Pa (-700mmHg) or lower. This vacuuming level is
more stringent than R22 system so as to ensure no incompressible gas and moisture in the system.
e) When charging R407C, ensure that only liquid is being withdrawn from the cylinder or can. This is to
ensure that only the original composition of R407C is being delivered into the system. The liquid
composition can be different from the vapor composition.
f) Normally, the R407C cylinder or can is being equipped with a dip-pipe for liquid withdrawal.
However, if the dip -pipe is not available, invert the cylinder or can so as to withdraw liquid from the
valve at the bottom.
g) When servicing leaks, the top-up method, commonly practiced for R22 system, is not recommended
for R407C systems. Unlike R22 where the refrigerant is of a single component, the composition of
R407C (which is made-up of three different components) may have changed during the leak.
Consequently, atop-up may not ensure that the R407C in the system is of the original composition.
This composition shift may adversely affect the system performance. It is recommended that the
system be evacuated thoroughly before recharging with R407C.
Composition of R407C in vapour phase
is different from liquid phase.
R32/R125/R134
33% / 33% / 34%
23% / 25% / 52%
Dip-pipe
Invert cylinder
without dip-pipe
Liquid
withdrawal