Special Precautions For R407C - McQuay MDB075D Owner's Manual

Special Precautions For R407c

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Hence when charging R407C, ensure that only liquid is being withdrawn from the cylinder or can.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)
i) Manifold gauge and charging hose
ii) Gas leak detector
iii) Refrigerant cylinder/charging cylinder
iv) Vacuum pump c/w adapter
v) Flare tools
vi) Refrigerant recovery machine
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.
112