A refrigeration circuit includes a primary loop, a secondary loop connected to the primary loop, a first expansion valve connected to the secondary loop, and a second expansion valve. The second expansion valve is connected to the secondary loop and is in parallel with the first expansion valve to control thermal communication between the refrigeration circuit and a first heat load independent of thermal communication between the refrigeration circuit and a second heat load. Environmental control systems and methods of controlling refrigerant flow in refrigeration circuits are also described.