Special Precautions For R407C - McQuay MCM 020 D Manual

Special Precautions for R407
Special Precautions When Dealing With Refrigerant R407C Unit
1) What is new refrigerant R407C?
R407C is a zeotropic refrigerant mixture which has Zero Ozone Depletion Potential (ODP = 0) and thus
conformed to the Montreal Protocol regulation. It requires Polyol-ester oil (POE) oil for its compressor's
lubricant. Its refrigerant capacity and performance are about the same as the refrigerant R22.
2) Components
Mixture weight composition R32(23%), R125(25%), R134a(52%)
3) Characteristic
•
R407C liquid and vapor components have different compositions when the fluid evaporates or
condenses. Hence, when leak occurs and only vapor leaks out, the composition of the refrigerant
mixture left in the system will change and subsequently affect the system performance. DO NOT add
new refrigerant to leaked system. It is recommended that the system should be evacuated thoroughly
before recharging with R407C.
•
When refrigerant R407C is used, the composition will differ depending on whether it is in gaseous or
liquid phase. Hence when charging R407C, ensure that only liquid is being withdrawn from the cylinder
or can. This is to make certain that only original composition of R407C is being charged into the
system.
•
POE oil is used as lubricant for R407C compressor, which is different from the mineral oil used for R22
compressor. Extra precaution must be taken not to expose the R407C system too long to moist air.
4) Check list before installation/servicing
•
Tubing
Refrigerant R407C is more easily affected by dust of moisture compared with R22, make sure to
temporarily cover the ends of the tubing prior to installation
•
Compressor oil
No additional charge of compressor oil is permitted.
•
Refrigerant
No other refrigerant other that R407C
•
Tools
Tools specifically for R407C only (must not be used for R22 or other refrigerant)
Manifold gauge and charging hose
i)
Gas leak detector
ii)
Refrigerant cylinder/charging cylinder
iii)
Vacuum pump c/w adapter
iv)
Flare tools
v)
Refrigerant recovery machine
vi)
5) Handling and installation guidelines
Like R22 system, the handling and installation of R407C system are closely similar. All precautionary
measures; such as ensuring no moisture, no dirt or chips in the system, clean brazing using nitrogen, and
thorough leak check and vacuuming are equally important requirements. However, due to zeotropic nature
of R407C and its hydroscopic POE oil, additional precautions must be taken to ensure optimum and
trouble-free system operation.
a) Filter-dryer must be installed along the liquid line for all R407C air conditioners. This is to minimise the
contamination of moisture and dirt in the refrigerant system. Filter-dryer must be of molecular sieve
type. For a heat-pump system, install a two-way flow filter dryer along the liquid line.
b) During installation or servicing, avoid prolong exposure of the internal part of the refrigerant system to
moist air. Residual POE oil in the piping and components can absorb moisture from the air.
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