Typical Arrangements
Figure 1 illustrates a typical piping arrangement involving a remote condenser located at a higher elevation, as commonly encountered when the condenser is on a roof and the compressor and receiver are on grade level or in a basement equipment room...
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In this case, the design of the discharge line is very critical. .If properly sized for full load condition, the gas velocity might be too low at reduced loads to carry oil up through the discharge line and condenser coil. .Reducing the discharge line size would increase the gas velocity sufficiently at reduced load conditions; however, when operating at full load, the line would be greatly undersized, and thereby create an excessive refrigerant pressure drop. .This condition can be overcome in one of two following ways:.
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1. .The discharge line may be properly sized for the desired pressure drop at full load conditions and an oil separator. installed at the bottom of the trap in the discharge line. from the compressor...
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2. .A double riser discharge line may be used as shown in. Figure 2. .Line“A” should be sized to carry the oil at minimum load conditions and the line “B” should be sized so.
that at the full load conditions both lines would have sufficient flow velocity to carry the oil to the condenser...
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For more complete information, refer to the ASHRAE Handbook on Systems..
Figure 1
Figure 2
Notes:
1. . All oil traps are to be as short in radius as possible. .Common practice is to fabricate the trap using three 90 degrees ells...
2. . Pressure relief valves are recommended at the condenser for protection of the coil...
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3. . A drain line check valve is recommended for applications where the condenser may be at a lower temperature than the receiver..
Installation, Refrigerant Piping
Install piping according to standard accepted refrigeration practice. .The following recommendations should be adhered to:.
1. . See Tables 1 and 2 for discharge and liquid
drain line sizes for remote condenser . connections...
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2. . Use only refrigeration grade copper tubing...
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3. . Soft solder joints are not acceptable...
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4. . Put dry nitrogen through lines while brazing...
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5. . Do not leave dehydrated piping or components. open to the atmosphere any longer than is. absolutely necessary. .
