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COMPRESSOR PROTECTIVE DEVICES

OIL MANAGEMENT SYSTEMS

This guide is intended for Oil Management Systems installed with

scroll or reciprocating compressors using HCFC or HFC

refrigerants. For other systems, please contact Henry Technologies

Technical Support at 1-800-627-5148 for guidance.

A proper Oil Management System is essential to ensure compressor

lubrication and energy efficient cooling.

An Oil Management System is a cost effective alternative to replacing

expensive compressors due to incorrect lubrication. If selected and installed

correctly, an Oil Management System will give years of trouble free

operation, protecting the compressors from both low and excess oil levels,

with little or no maintenance. Excessive oil within the system can lead to a

slug of oil returning to the compressor. A slug of oil can be as damaging to a

compressor as a slug of liquid refrigerant.

By removing oil from the discharge gas, the system efficiency is increased.

Oil in a refrigeration or air conditioning system reduces the efficiency of the

system by:

1. A reduction in heat transfer due to oil coating of the condenser and

evaporator walls.

2. Displacing refrigerant volume resulting in a decrease in system

mass flow.

Oil does not change phase from liquid to gas and is therefore a very poor

refrigerant. A minimal amount of oil flowing through the system is necessary

to provide lubrication to valves, but a very small amount is needed.

SINGLE COMPRESSOR SYSTEM

Single Compressor System

A single Compressor has the most basic oil system. The Compressor (1)

discharge is piped to the inlet of an Oil Separator (2) and the outlet of the Oil

Separator is piped to the Condenser (3). A Discharge Check Valve (4)

should be fitted between the Separator and Condenser to ensure condensed

liquid refrigerant is not returned to the separator during off cycles. An Oil

Return Line (6) is connected from the Oil Separator through an Oil Strainer

(5), Oil Filter (10) or Oil Filter-Drier (11), to the compressor crankcase.

As oil collects in the separator, the float valve will open to return oil, under

discharge pressure, to the compressor crankcase. The float valve prevents

hot gas from bypassing to the crankcase by closing when the oil level falls.

It is recognized best practice to fit a solenoid valve, sight glass, and

shut-off valve in the oil return line. These components are not shown

in the diagram.

Refer to equipment list for further details on each

component in the oil system

LOW PRESSURE OIL MANAGEMENT SYSTEM

Low Pressure Oil Management System

This system is normally used for parallel compressors and uses three main

components; Oil Separator (2), Oil Reservoir (7) and Mechanical Oil Level

Regulators (9). The common discharge is piped to the inlet of the Oil

Separator and the outlet of the Oil Separator is piped to the Condenser. A

Discharge Check Valve (4) should be fitted between the Separator and

Condenser to ensure condensed liquid refrigerant is not returned to the

separator. An Oil Return Line is (6) connected from the Oil Separator to the

top valve of the Oil Reservoir (7). A Vent Line (8) is installed to the suction

line, using a Reservoir Pressure Valve (12), to reduce the pressure in the

Reservoir. This makes a low pressure system. The Reservoir Pressure Valve

will maintain the Reservoir at a set pressure above suction. Although

Mechanical Oil Level Regulators (9) are shown in the diagram, Electro-

mechanical and Optronic Oil Level Regulators can also be used.

The bottom valve of the Oil Reservoir is piped to the Oil Level Regulators

mounted on the compressor crankcases. These regulators open to feed oil

as the oil level drops and close as the oil level rises to the set level. In this

way, the oil level in each compressor is controlled. An Oil Strainer (5) should

be used on each Regulator to remove debris from the oil. Alternatively, the

Oil Strainers may be replaced by one Oil Filter (10) or Oil Filter-Drier (11)

installed between the Separator and Oil Reservoir. Due to the scavenging

nature of POE oil, it is recommended to install either an Oil Filter or Oil Filter-

Drier on a HFC/POE system instead of individual Oil Strainers.

On dual temperature and satellite systems, ensure that all regulators see

positive oil differential pressures within their allowable operating range.

It is recognized best practice to fit a solenoid valve, sight glass, and

shut-off valve in the oil return line. These components are not shown

in the diagram.

Refer to equipment list for further details on each

component in the oil system

1

5, 10, 11

3

6

2

4

12

4

7

8

6

6

10, 11

5

2

1

1

1

1

9

9

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