Time delayed shut-down circuit for recirculation pump

Claim 1

A circuit for controlling the application of electrical power to a pump motor, comprising a plurality of electrical conductors adapted to be connected to an electrical pump motor for applying electrical power thereto, a first relay having a pair of cooperating contacts in at least one of said conductors for controlling the flow of current therethrough, a second relay having a coil connected between two of said conductors, said second relay thereby being actuated upon the application of an electrical potential between said two conductors, one end of the coil of said first relay being connected to a first of said two conductors and the other end thereof being connected to a first fixed contact of said second relay, said other end of said coil of said first relay also being connected to a second fixed contact of said second relay through a pressure-sensitive switch adapted to sense the output pressure of a pump driven by such motor, said pressure-sensitive switch being adapted to open and interrupt the connection between said first relay coil and said second fixed contact of said second relay for sensed pressures less than a predetermined minimum, and a movable contact on said second relay connected to a second of said two conductors and contacting said first fixed contact when said second relay is first actuated, said second relay being adapted to return to a de-energized condition upon the expiration of a predetermined period of time, moving said movable contact into contact with said second fixed contact, whereby energization of an associated pump motor is assured for a predetermined period of time irrespective of the output pressure of the associated pump, after which period of time the pump motor will be de-energized when such output pressure drops below a predetermined level.