Table of Contents
Advertisement
3.4
Accumulators
CAUTION
Inadequate lubrication! Bearing destruction! Minimise liquid refrigerant
returning to the compressor. Too much refrigerant dilutes the oil. Liquid
refrigerant can wash the oil off the bearings leading to overheating and bearing
failure.
Irrespective of system charge, oil dilution may occur if large amounts of liquid refrigerant repeatedly
flood back to the compressor, for example during:
▪
normal off cycles;
▪
defrost;
▪
varying loads.
In such a case an accumulator must be used to reduce floodback to a safe level that the compressor
can handle. The use of accumulators is dependent on the application. If an accumulator must be
used,
the oil-return orifice should be from 1 to 1.4 mm in diameter, depending on compressor size
and compressor floodback results.
The size of the accumulator depends upon the operating range of the system and the amount of
subcooling and subsequent head pressure allowed by the refrigerant control. If an accumulator is
used, it is recommended that it be sized to hold from 50% to 70% of the system charge.
Figure 8: Oil dilution chart for operation
Note 1: Low load operation may be acceptable in the yellow marked area. For further
information, please contact the Application Engineering department.
3.5
Screens
CAUTION
Screen blocking! Compressor breakdown! Use screens with at least
0.6 mm openings.
The use of screens finer than 30 x 30 mesh (0.6 mm openings) anywhere in the system should be
avoided with these compressors. Field experience has shown that finer mesh screens used to protect
thermal expansion valves, capillary tubes or accumulators can become temporarily or permanently
plugged with normal system debris and block the flow of either oil or refrigerant to the compressor.
Such blockage can result in compressor failure.
3.6
Mufflers
External mufflers, normally applied to piston compressors in the past, may not be required for
Copeland Scroll compressors. Individual system tests should be performed to verify acceptability of
sound performance. If adequate attenuation is not achieved, use a muffler with a larger cross-
sectional area to inlet area ratio. A ratio of 20:1 to 30:1 is recommended.
A hollow shell muffler will work quite well. Locate the muffler at minimum 15 to maximum 45 cm from
the compressor for the most effective operation. The farther the muffler is placed from the
compressor within this range, the more effective. Choose a muffler with a length of 10 to 15 cm.
10
C6.2.7/1007-0619/E
Advertisement
Table of Contents
