Special Precautions For R407C - McQuay MWM 007G 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 compositionR32(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 Hence when charging R407C, ensure that only liquid is being withdrawn from the cylinder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.
73