Title: Time delayed shut-down circuit for recirculation pump

Abstract: A circuit is provided for shutting off the motor of an intermittently activated, electrically powered fluid recirculation pump to prevent the pump motor from burning out its windings or bearings. A power control relay is energized to activate the pump motor for a predetermined period of time, allowing the pump to reach steady state flow condition, after which a time delay relay opens and current flows to the power control relay through a pressure switch. The pressure switch opens to shut-off the recirculation pump motor whenever the pump discharge pressure falls below a predetermined minimum.

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Inventors: Curtis, George C. (Portland, OR, US)

Application Number: 450300
Filing Date: 1974-03-12
Publication_date: 1976-06-15
Assignee:
Primary Class(es): 417/12 417/38
Other Classes:
US Patent Ref:

2661697	Dec, 1953	Long	417/12.
2741986	Apr, 1956	Smith	417/12.
2741987	Apr, 1956	Murphy	417/44.
2765743	Oct, 1956	Hollinshead	417/44.
2981195	Apr, 1925	Payne et al.	417/12.
3030890	Apr, 1962	Galik	318/484.

Other Refs:
Primary Examiner: Freeh, William L.
Assistant Examiner: La Pointe, G. P.
Attorney: