Where in the system is an oil separator installed?

Where in the system is an oil separator installed?

• A. In the discharge line leaving the compressor
• B. In the suction line
• C. In the liquid line after the condenser
• D. In the expansion line

Answer: (A)

Oil separators are used to remove lubricant from the refrigerant vapor after it leaves the compressor so the oil can return to the compressor while the refrigerant continues to the condenser. Placing the separator in the discharge line makes this separation effective right where the oil is carried in the high-temperature, high-pressure vapor that the compressor expels. If you put the separator in the suction line, you’d be trying to capture oil from vapor returning to the compressor, which isn’t where the oil is predominantly carried yet; the suction line is low-pressure and carries refrigerant returning from the evaporator, so the separator wouldn’t function properly. In the liquid line after the condenser, separating oil would occur after the refrigerant has already condensed, which defeats the purpose of returning the oil to the compressor and can complicate flow and pressure. In the expansion line, the flow is metered and throttled; an oil separator there would disrupt the metering and wouldn’t effectively separate oil from vapor. So the best placement is in the discharge line leaving the compressor, where it can effectively separate oil from the hot vapor and route the oil back to the compressor while sending clean vapor to the condenser.

Oil separators are used to remove lubricant from the refrigerant vapor after it leaves the compressor so the oil can return to the compressor while the refrigerant continues to the condenser. Placing the separator in the discharge line makes this separation effective right where the oil is carried in the high-temperature, high-pressure vapor that the compressor expels.

If you put the separator in the suction line, you’d be trying to capture oil from vapor returning to the compressor, which isn’t where the oil is predominantly carried yet; the suction line is low-pressure and carries refrigerant returning from the evaporator, so the separator wouldn’t function properly. In the liquid line after the condenser, separating oil would occur after the refrigerant has already condensed, which defeats the purpose of returning the oil to the compressor and can complicate flow and pressure. In the expansion line, the flow is metered and throttled; an oil separator there would disrupt the metering and wouldn’t effectively separate oil from vapor.

So the best placement is in the discharge line leaving the compressor, where it can effectively separate oil from the hot vapor and route the oil back to the compressor while sending clean vapor to the condenser.