McQuay MWM09J Manual page 21

Application Information
Special Precautions When Dealing With Refrigerant R410A Unit
(1) What is new refrigerant R410A?
R410A is a new HFC refrigerant which does not damage the ozone layer. The working pressure of this
new refrigerant is 1.6 times higher than conventional refrigerant (R22), thus proper installation / servicing
is essential.
(2) Components
Mixture weight composition R32(50%) and R125(50%)
(3) Characteristic
• R410A liquid and vapor components have different compositions when the fl uid 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 R410A.
• When refrigerant R410A is used, the composition will differ depending on whether it is in gaseous or
liquid phase. Hence when charging R410A, ensure that only liquid is being withdrawn from the cylinder
or can. This is to make certain that only original composition of R410A is being charged into the system.
• POE oil is used as lubricant for R410A compressor, which is different from the mineral oil used for R22
compressor. Extra precaution must be taken not to expose the R410A system too long to moist air.
(4) Check list before installation / servicing
• Tubing
Refrigerant R410A 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 R410A
• Tools (size of service port is different from R22 system)
Tools specifi cally for R410A only (must not be used for R22 or other refrigerant)
i) Gauge manifold 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 R410A 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 its hydroscopic
POE oil, additional precautions must be taken to ensure optimum and trouble free system operation.
(a) 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.
(b) Ensure that the compressor is not exposed to open air for more than the recommended time specifi ed
by its manufacturer (typically less than 10 minutes). Removed the seal plugs only when the compressor
is about to be brazed.
(c) 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.
19
MWM-J_(ii)