1. Retrofitting CFC/HCFC systems into HFC
UNIVERSITY OF HONG KONG
Department of Electrical & Electronic Engineering
M.Sc.(Eng) in Building Services Engineering
MEBS 6013 Testing & Commissioning
Retrofitting CFC/HCFC systems into HFC
K.F. Chan (Mr.)
MEBS
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2. UNIVERSITY OF HONG KONG
Department of Electrical & Electronic Engineering
M.Sc.(Eng) in Building Services Engineering
MEBS 6013 Testing & Commissioning
Gaskets
HFC’s have higher penetrating power than CFC’s and HCFC’s, therefore, the gaskets of the system have to be replaced by those suitable for HFC’s.
K.F. Chan (Mr.)
MEBS
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3. UNIVERSITY OF HONG KONG
Department of Electrical & Electronic Engineering
M.Sc.(Eng) in Building Services Engineering
MEBS 6013 Testing & Commissioning
Lubricants
HFC’s have much higher affinity for water than CFC’s and HCFC’s. Moreover, the polyester based oil used in HFC systems also have higher water affinity than those mineral oils and alkylbenzenes used in traditional CFC systems. Thus different types of filter dryers, having higher affinity for water, are required for HFC systems.
Refrigeration compressors compressing HFC vapours need polyester based oil, while traditional mineral or alkylbenzene oils usually suffice for CFC’s and HCFC’s systems.
Those polyester based oils used in HFC systems absorb moisture readily up to several hundreds ppm when exposed to open atmosphere. Hydrocarbon lubricants such as mineral oils and alkylbenzenes do not absorb moisture so readily and their saturation limit was about 60 ppm at 50% RH, 210C. This indicated that the lubricants in HFC system have higher water affinity than lubricants used in traditional CFC/HCFC systems.
K.F. Chan (Mr.)
MEBS
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4. UNIVERSITY OF HONG KONG
Department of Electrical & Electronic Engineering
M.Sc.(Eng) in Building Services Engineering
MEBS 6013 Testing & Commissioning
Depth of oil sumps
When compared with traditional CFC’s or HCFC’s systems, the fluctuation in level in the oil sump is larger in HFC systems.
Refrigeration compressors compressing HFC vapours need polyester based oil, while traditional mineral or alkylbenzene oils usually suffice for CFC’s and HCFC’s systems. Solubility of HFC’s in polyester oils is higher when compared with CFC’s or HCFC’s in traditional lubricants.
When the refrigeration system is running, the dissolved HFC’s will evaporate as the oil sump gets hot, so more lubrication oil is carried into the piping circuit, together with the evaporated refrigerant, from the compressor oil sump (or crankcase). However, on shut down, more refrigerant vapour will dissolve back in the oil (because of the lower oil temperature during shutdown), and the extent of this is larger for HFC’s.
Therefore, when compared with traditional CFC’s or HCFC’s systems, the fluctuation in level in the oil sump is bigger in HFC systems. So when converting CFC or HCFC systems into HFC’s, full attention must be paid to the depth of the existing compressor oil sump and make sure that low oil level or low oil pressure alarm will not be actuated inadvertently during compressor start up.
K.F. Chan (Mr.)
MEBS
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5. UNIVERSITY OF HONG KONG
Department of Electrical & Electronic Engineering
M.Sc.(Eng) in Building Services Engineering
MEBS 6013 Testing & Commissioning
Lubricants handling
once opened, each can of lubricant should be used immediately
As mentioned above, lubricants used in HFC systems absorb moisture readily. Therefore, it is very important that once opened, each can of lubricant is used immediately.
K.F. Chan (Mr.)
MEBS
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6. Evacuation level K.F. Chan (Mr.) MEBS6013 2011 UNIVERSITY OF HONG KONG
Department of Electrical & Electronic Engineering
M.Sc.(Eng) in Building Services Engineering
MEBS 6013 Testing & Commissioning
Evacuation level
Higher vacuum level is also required during system evacuation of HFC refrigeration systems.
1000 microns vs “30 inches Hg”
K.F. Chan (Mr.)
MEBS
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7. R22 converted into R134a system
UNIVERSITY OF HONG KONG
Department of Electrical & Electronic Engineering
M.Sc.(Eng) in Building Services Engineering
MEBS 6013 Testing & Commissioning
R22 converted into R134a system
Capacity
Power factor
If a R22 system is converted into a R134a system, it must be noted that the same compressor running on R134a outputs only about 60% of its R22 capacity. Thus sufficiency of the cooling capacity must be thoroughly checked.
Moreover, the compressor also consumes less power, leading to a lower power factor; this may affect the reactive component of the electricity load. Power factor correction devices may be needed.
K.F. Chan (Mr.)
MEBS
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8. Temperature glide K.F. Chan (Mr.) MEBS6013 2011
UNIVERSITY OF HONG KONG
Department of Electrical & Electronic Engineering
M.Sc.(Eng) in Building Services Engineering
MEBS 6013 Testing & Commissioning
K.F. Chan (Mr.)
MEBS
All rights reserved

9. R22 converted into R407c system
UNIVERSITY OF HONG KONG
Department of Electrical & Electronic Engineering
M.Sc.(Eng) in Building Services Engineering
MEBS 6013 Testing & Commissioning
R22 converted into R407c system
Extra superheat
Extra subcooling
When R22 system is converted into R407c, it should be noticed that R407c is a blend of 3 different refrigerants – R32/R125/R134a – these boil and condense at slightly different temperatures. This is called temperature glide. Additional sub-cooling in the condenser and additional super-heating in the evaporator (the latter requires different adjustment of the expansion device) have to be considered as well.
K.F. Chan (Mr.)
MEBS
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