Dual evaporator defrost system for an appliance

1. An appliance comprising:

a first refrigerated enclosure;

a second refrigerated enclosure;

a compression stage;

a condensation stage;

an evaporation stage comprising:

a first evaporator for the first refrigerated enclosure; and

a second evaporator for the second refrigerated enclosure;

a condensation stage bypass line positioned between an output of the compression stage and the second evaporator;

a first valve in the condensation stage bypass line and being operative to allow a supply of refrigerant to bypass the condensation stage during a defrost mode;

a line from the second evaporator to the compression stage;

a second valve positioned in the line from the second evaporator to the compression stage and being operative to block a supply of refrigerant from the second evaporator to the compression stage during the defrost mode;

an additional line positioned between the second evaporator and the first evaporator, the additional line carrying the supply of refrigerant from the second evaporator to the first evaporator in the defrost mode; and

a third valve positioned in a line from the condensation stage to the evaporation stage, the third valve being operative to block a supply of refrigerant from the condensation stage to either the first evaporator, the second evaporator or both the first evaporator and the second evaporator, and wherein the third valve is operative to direct refrigerant from the second evaporator to the first evaporator during the defrost mode.

2. The appliance of claim 1 , wherein the condensation stage bypass line is positioned between the output of the compression stage and an output of the second evaporator, and the additional line is positioned between an input of the second evaporator and an input of the first evaporator.

3. The appliance of claim 1 , wherein the condensation stage bypass line is positioned between the output of the compression stage and an input of the second evaporator, and the additional line is positioned between an output of the second evaporator and an input of the first evaporator.

4. The appliance of claim 1 , wherein the second evaporator is configured to provide cooling to sub-freezing temperatures during non-defrost operation.

5. The appliance of claim 1 , wherein the first evaporator is configured to provide refrigeration temperatures to the first refrigerated enclosure in the defrost mode.

6. The appliance of claim 1 , wherein the appliance comprises a refrigerator.

7. The appliance of claim 1 , wherein the first evaporator and the second evaporator are independently controllable.

8. The appliance of claim 1 , wherein the third valve comprises a three-way valve.

9. A control system for a refrigerator, comprising:

a compression stage;

a condensation stage;

an evaporation stage comprising:

at least one first evaporator configured to providing cooling at above a freezing temperature; and

at least one second evaporator configured to provide cooling temperatures below the freezing temperature;

a condensation stage bypass line configured to direct a supply of refrigerant from the compression stage directly to the at least one second evaporator in a defrost mode of the control system;

a first valve positioned between the at least one second evaporator and the compression stage and being operative to block the supply of refrigerant from the at least one second evaporator to the compression stage during the defrost mode;

a line positioned between the at least one second evaporator and the at least one first evaporator configured to direct the supply of refrigerant to the at least one first evaporator during the defrost mode;

a second valve positioned in the condensation stage bypass line and being operative to allow the supply of refrigerant to flow to the at least one second evaporator during the defrost mode; and

a third valve positioned in a line from the condensation stage to the evaporation stage, the third valve being operative to block a supply of refrigerant from the condensation stage to either the first evaporator, the second evaporator or both the first evaporator and the second evaporator, and wherein the third valve is operative to direct refrigerant from the second evaporator to the first evaporator during the defrost mode.

10. The control system of claim 9 , further comprising a controller coupled to the first valve and the second valve to control an actuation of each valve to implement the defrost mode.

11. The control system of claim 9 , wherein the at least one first evaporator is configured to provide cooling at above the freezing temperature during the defrost mode.

12. The control system of claim 9 , wherein the third valve comprises a three-way valve.

13. A control system for a refrigerator including two independently controllable evaporators, comprising:

a compression stage, a condensation stage and an evaporation stage that includes a first evaporator for refrigerator compartment cooling and a second evaporator for freezer compartment cooling;

a condensation stage bypass line positioned between the compression stage and the second evaporator, the condensation stage bypass line being configured to carry a supply of refrigerant from the compression stage to the second evaporator in a defrost mode of the refrigerator;

a line between the second evaporator and the first evaporator and configured to carry the supply of refrigerant from the second evaporator to the first evaporator in the defrost mode;

a valve positioned between the second evaporator and the compression stage, the valve being configured to block the supply of refrigerant to the compression stage from the second evaporator during the defrost mode; and

another valve positioned at an output of the condensation stage, the another valve being configured to block a supply of refrigerant to either the first evaporator, the second evaporator or both the first evaporator and the second evaporator, and facilitate refrigerant flow from the second evaporator to the first evaporator during the defrost mode.

14. The control system of claim 13 , wherein the another valve comprises a three-way valve.