McQuay M5WM 007G, Manual

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c) Ensure that the compressor is not expose to open air for more than the recommended time specified by
its manufacturer (typically less than 10 minutes). Removed 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e) When charging R407C, ensure that only liquid is being withdrawn from the cylinder or can.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.
Composition of R407C in vapour phase
is different from liquid phase.
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 leak, the top up method, commonly practiced for R22 system, is not recommended for
R407C system. Unlike R22 where the refrigerant is of a single component, the composition of R407C,
which made up of three different components, may have changed during the leak. Consequently, a top
up may not ensure that the R407C in the system is of original composition. This composition shift may
adversely affect the system performance. It is recommended that the system should be evacuated
thoroughly before recharging with R407C.
74
R32/R125/R134
33% / 33% / 34%
23% / 25% / 52%
Dip-pipe
Liquid
withdrawal
Invert cylinder
without dip-pipe