desA
15-04-2009, 06:09 AM
I'm currently working through a new air-to-water heat pump design, for South-East Asian operating conditions.
I'd like to ask opinions & thoughts on whether a suction accumulator is essential in the system.
There seem to be two opposing viewpoints in the Copeland Application Engineering Bulletins:
1. AE-1300-R1 (rev: June 1996) "Application guidelines for 1.5 to 4 ton Quantum ZR*K3 and ZR*KC model Copeland compliant scroll compressors"
Accumulators
Due to the Compliant Scroll's inherent ability to handle liquid refrigerant in flooded start and defrost cycle operation, operation, no accumulator is required for durability below system charge levels listed in the Scroll Compressor Application Diagram (Table 1). However, large volumes of liquid refrigerant which repeatedly flood back to the compressor during normal off cycles or excessive liquid refrigerant floodback during steady operation can dilute the oil in any compressor to the point that bearings are inadequately lubricated and wear may occur. To test for these conditions, see the section entitled EXCESSIVE LIQUID REFRIGERANT FLOODBACK TESTS at the end of this Bulletin.
The Table 1 cut-off limit for using an accumulator is 10 lb (4.54kg).
2. AE-1247 (Dec 15, 1975) "Suction accumulators for heat pump applications
One of the most critical areas of air to air and air to water heat pump application is the proper control of liquid refrigerant under low ambient heating conditions.
System design must maintain a delicate balance between sufficient flooding to adequately cool the compressor, while avoiding excessive flooding which would adversely affect lubrication. When coil defrost is required, the compressor is exposed to sudden surges of liquid that can create extreme stresses in the compressor.
Both laboratory testing and field experience indicate that a properly designed suction accumulator can provided excellent protection against both potential hazards.
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My thoughts
My expected gas charge (from experimental tests) will be around 1.2-1.3kg of R-134A. This is far less than the 4.54kg recommended compressor cut-off limit.
Under South-East Asian design conditions, evaporator coil frosting is not expected as a routine occurrence (if ever).
My question
In the experience of RE members, what would your sound advice be on whether to use a suction accumulator, or not?
Links to additional field information, references, literature would be gratefully appreciated.
I'd like to ask opinions & thoughts on whether a suction accumulator is essential in the system.
There seem to be two opposing viewpoints in the Copeland Application Engineering Bulletins:
1. AE-1300-R1 (rev: June 1996) "Application guidelines for 1.5 to 4 ton Quantum ZR*K3 and ZR*KC model Copeland compliant scroll compressors"
Accumulators
Due to the Compliant Scroll's inherent ability to handle liquid refrigerant in flooded start and defrost cycle operation, operation, no accumulator is required for durability below system charge levels listed in the Scroll Compressor Application Diagram (Table 1). However, large volumes of liquid refrigerant which repeatedly flood back to the compressor during normal off cycles or excessive liquid refrigerant floodback during steady operation can dilute the oil in any compressor to the point that bearings are inadequately lubricated and wear may occur. To test for these conditions, see the section entitled EXCESSIVE LIQUID REFRIGERANT FLOODBACK TESTS at the end of this Bulletin.
The Table 1 cut-off limit for using an accumulator is 10 lb (4.54kg).
2. AE-1247 (Dec 15, 1975) "Suction accumulators for heat pump applications
One of the most critical areas of air to air and air to water heat pump application is the proper control of liquid refrigerant under low ambient heating conditions.
System design must maintain a delicate balance between sufficient flooding to adequately cool the compressor, while avoiding excessive flooding which would adversely affect lubrication. When coil defrost is required, the compressor is exposed to sudden surges of liquid that can create extreme stresses in the compressor.
Both laboratory testing and field experience indicate that a properly designed suction accumulator can provided excellent protection against both potential hazards.
-----------------
My thoughts
My expected gas charge (from experimental tests) will be around 1.2-1.3kg of R-134A. This is far less than the 4.54kg recommended compressor cut-off limit.
Under South-East Asian design conditions, evaporator coil frosting is not expected as a routine occurrence (if ever).
My question
In the experience of RE members, what would your sound advice be on whether to use a suction accumulator, or not?
Links to additional field information, references, literature would be gratefully appreciated.