CONTROL CIRCUIT FOR HEAT RECOVERY TYPE AIR COOLED HEAT PUMP TYPE REFRIGERATOR

摘要

PURPOSE:To prevent a discharge gas piping system from being turned into a closing state when operation modes are transferred by installing a time limit relay designed to receive an operation mode change over signal to a solenoid valve circuit which closes at the same time when operation mode is to be changed over by the change over of a four way valve, and connecting its contact with said solenoid valve in series. CONSTITUTION:When cooling operation or defrosting operation is canceled and turned to heating operation or heat recovery operation, a cooling operation signal (XC) or a defrosting operation command (XD) is opened so that an input signal to a time limit relay 22 may be shut down. After the shut down of the input signal, the time limit relay 22 is provided with a contact 22' designed to maintain an input signal receiving state during setting time, and maintains an energized state (valve open) of a solenoid valve 11. On the other hand, a four way valve 2 switches over its passage as the circuits of XC and XD are shut and moreover a heating operation command (XH) and heat recovery command (XR) are closed and energized. This construction makes it possible to prevent a sudden rise in discharge pressure without closing a discharge gas piping system by providing enough time required to change over a solenoid valve 6 and maintaining an opening state of the solenoid valve 11 by the contact of the time limit relay 22.