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–EIMWC00408-16EN - 21/60
Total friction loss for discharge line from 20 to 40 kPa is considered good design. Carefully consideration must be given
for sizing each section of piping so that gas velocities are sufficient at all operating conditions to carry oil.
If the velocity in a vertical discharge riser is to low, considerable oil can collect in the riser and horizontal header, causing
compressor to lose oil and it can result in compressor damage due to lack of oil. When the compressor load (and the gas
velocity in the discharge line) increase the oil collected during reduced load can be carried out in a slug back to the
compressor causing damage.
Any discharge lines coming into and horizontal header should rise above the centerline of the header.
The discharge lines should pitch downward, in the direction of the hot gas flow, at the rate of 6 mm per meter of
horizontal run. This is necessary to move by gravity any oil lying in the header. Oil pockets should be avoided because
oil would collect at such points an the compressor can become starved.
If the chiller unit is below condenser, loop the discharge line to at least 2.5 cm above the top of the condenser. A
pressure tap valve should be installed at the condenser to facilitate measuring pressure for service.
A relief valve should be installed on the discharge line.
Reference for discharge line sizing is shown in Table 9. It has to be used for reference only, for circuit working with
evaporator leaving temperature equal to 7°C and condensing temperature equal to 55°C. Line dimensioning is
responsibility of plant designer, use ASHRAE Refrigeration Handbook or other suitable design guide.
Table 4 - Discharge line sizes
Circuit
Capacity
kW
Total Equivalent Length (meters)
5
10
15
20
25
30
40
50
60
300
2-1/8
2-1/8
2-1/8
2-5/8
2-5/8
2-5/8
3-1/8
3-1/8
3-1/8
350
2-1/8
2-1/8
2-5/8
2-5/8
3-1/8
3-1/8
3-1/8
3-1/8
3-1/8
400
2-1/8
2-5/8
2-5/8
3-1/8
3-1/8
3-1/8
3-1/8
2 x 2-5/8
2 x 2-5/8
450
2-5/8
2-5/8
2-5/8
3-1/8
3-1/8
3-1/8
2 x 2-5/8
2 x 2-5/8
2 x 3-1/8
Oil Charge
In remote condenser application the oil charge into the compressor has to take into account that a percentage of oil
around 1% is usually mixed into the refrigerant, so some oil has to be added to the standard charge if the refrigerant
charge exceed the standard charge of the unit. What is important, during the unit operation, is that the oil level in the oil
separator is not lower than the ¼ of the upper sideglass.
The compressor of the EWLD and Liquid Receiver version units are shipped with their proper charge of oil. The
refrigerant circuits mustn’t remain open to the air for more than 15 minutes. If this happens you need to replace the
oil
charge and the oil filter as described in the “Procedure to replace oil filter” of this manual.
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