Oil management for micro booster supermarket refrigeration system

1. A refrigeration system comprising:

at least one first compressor fluidly connected to a first suction line and a first discharge line;

at least one second compressor fluidly connected to a second suction line and a second discharge line, the second suction line being fluidly connected to the first discharge line;

a condenser operable to receive refrigerant from the at least one second compressor;

a first evaporator operable to receive refrigerant from the condenser and discharge refrigerant to the first suction line;

a second evaporator operable to receive refrigerant from the condenser and discharge refrigerant to the second suction line; and

an first oil separator comprising a first inlet fluidly connected to the first discharge line, a first refrigerant outlet fluidly connected the second suction line, a first oil outlet fluidly connected to a first sump of the at least one first compressor, a first horizontal plane intersecting the first refrigerant outlet, wherein:

the first oil separator is adapted to receive refrigerant and oil from the at least one first compressor through the first inlet and separate at least a portion of the oil from the refrigerant;

a first portion of the first oil separator below the first horizontal plane is configured to collect separated oil;

the first portion is sized to have a volume equal to a first compressor oil supply, the first compressor oil supply being greater than or equal to 100% of a first compressor initial oil charge and less than or equal to 250% of the first compressor initial oil charge;

the at least one first compressor is configured to receive oil from the first oil outlet when an amount of oil in the first portion is less than or equal to the first compressor oil supply; and

the at least one second compressor is configured to receive oil from the first refrigerant outlet when the amount of oil in the first portion is greater than the first compressor oil supply.

2. The refrigeration system of claim 1 , further comprising a second oil separator comprising a second inlet fluidly connected to the second discharge line, a second refrigerant outlet fluidly connected the condenser, and a second oil outlet fluidly connected to a second sump of the at least one second compressor, wherein:

the second oil separator is adapted to receive refrigerant and oil from the at least one second compressor through the second inlet and separate at least a portion of the oil from the refrigerant; and

the at least one second compressor is configured to receive oil from the second oil outlet.

3. The refrigeration system of claim 2 , wherein the first oil separator and the second oil separator are both completely charged.

4. The refrigeration system of claim 1 , wherein the first oil separator further comprises a sight glass and a second horizontal plane, wherein:

the second horizontal plane is disposed within the first portion and extends parallel to the first horizontal plane such that greater than or equal to 90% of a volume of the first portion is disposed below the second horizontal plane; and

a center of the sight glass is aligned with the second horizontal plane.

5. The refrigeration system of claim 1 , wherein:

the first sump is configured to contain the first compressor initial oil charge; and

the first compressor oil supply is greater than or equal to 100% of the first compressor initial oil charge and less than or equal to 225% of the first compressor initial oil charge.

6. The refrigeration system of claim 5 , wherein the first compressor oil supply is greater than or equal to 175% of the first compressor initial oil charge and less than or equal to 225% of the first compressor initial oil charge.

7. The refrigeration system of claim 1 , further comprising a valve disposed between the first evaporator and the first suction line, wherein:

the first suction line receives refrigerant from the first evaporator when the valve is in a first position;

the second suction line receives refrigerant from the first evaporator when the valve is in a second position; and

the at least one first compressor is bypassed when the valve is in the second position.

8. The refrigeration system of claim 7 , further comprising:

a first refrigeration case operable to be cooled by the first evaporator within a first temperature range when the valve is in a first position and within a second temperature range when the valve is in the second position, the first temperature range being lower than the second temperature range; and

a second refrigeration case operable to be cooled by the second evaporator within the second temperature range.

9. A refrigeration system comprising:

at least one first compressor fluidly connected to a first suction line and a first discharge line;

at least one second compressor fluidly connected to a second suction line and a second discharge line, the second suction line being fluidly connected to the first discharge line;

a condenser operable to receive refrigerant from the at least one second compressor;

a first evaporator operable to receive refrigerant from the condenser and discharge refrigerant to the first suction line;

a second evaporator operable to receive refrigerant from the condenser and discharge refrigerant to the second suction line;

a first valve disposed between the first evaporator and the first suction line; and

an oil line extending between a first oil sump of the at least one first compressor and a second oil sump of the at least one second compressor, the oil line comprising a two-way pump configured to move oil in a first direction from the second oil sump to the first oil sump or a second direction from the first oil sump to the second oil sump, wherein:

the first suction line receives refrigerant from the first evaporator when the first valve is in a first position;

the second suction line receives refrigerant from the first evaporator when the first valve is in a second position;

the at least one first compressor is bypassed when the first valve is in the second position; and

the refrigeration system is free of a distinct oil separator.

10. The refrigeration system of claim 9 , further comprising:

a first refrigeration case operable to be cooled by the first evaporator within a first temperature range when the first valve is in a first position and within a second temperature range when the first valve is in the second position, the first temperature range being lower than the second temperature range; and

a second refrigeration case operable to be cooled by the second evaporator within the second temperature range.

11. The refrigeration system of claim 10 , wherein:

the first refrigeration case comprises a walk-in freezer;

the second refrigeration case comprises a walk-in cooler;

the first refrigeration case and the second refrigeration case are disposed directly adjacent to one another within a retail space; and

the at least one first compressor and the at least one second compressor are disposed directly adjacent to one another in the retail space.

12. The refrigeration system of claim 11 , wherein:

the at least one first compressor is at least one of disposed within the first refrigeration case, disposed on the first refrigeration case, disposed under the first refrigeration case, disposed adjacent to the first refrigeration case, and attached to the first refrigeration case; and

the at least one second compressor is at least one of disposed within the second refrigeration case, disposed on the second refrigeration case, disposed under the second refrigeration case, disposed adjacent to the second refrigeration case, and attached to the second refrigeration case.

13. The refrigeration system of claim 9 , wherein the at least one first compressor comprises two first compressors having respective first oil sumps, the first oil sumps being connected by an oil balance tube.

14. The refrigeration system of claim 9 , wherein the at least one second compressor comprises two second compressors having respective second oil sumps, the second oil sumps being connected by an oil balance tube.

15. A refrigeration system comprising:

a single first compressor fluidly connected to a first suction line and a first discharge line;

at least one second compressor fluidly connected to a second suction line and a second discharge line, the second suction line being fluidly connected to the first discharge line, the at least one second compressor comprising a lead second compressor and a secondary second compressor;

a condenser operable to receive refrigerant from the at least one second compressor;

a first evaporator operable to receive refrigerant from the condenser and discharge refrigerant to the first suction line;

a second evaporator operable to receive refrigerant from the condenser and discharge refrigerant to the second suction line;

a first valve disposed between the first evaporator and the first suction line;

an oil line extending between a first oil sump of the single first compressor and a second oil sump of the lead second compressor; and

an oil balance tube connecting the second oil sump and a third oil sump of the secondary second compressor, wherein:

the first suction line receives refrigerant from the first evaporator when the first valve is in a first position;

the second suction line receives refrigerant from the first evaporator when the first valve is in a second position; and

the single first compressor is bypassed when the first valve is in the second position.

16. The refrigeration system of claim 15 , wherein the lead second compressor and the secondary second compressor are connected in parallel.