US 4,977,751 A · Refrigeration system having a modulation valve which also performs function of compressor throttling valve

Abstract

A refrigeration system having a modulation valve which controls refrigerant flow to a compressor according to a control algorithm. The need for a compressor throttling valve is eliminated by a load control circuit which operates the modulation valve to perform the function of the throttling valve when load reduction is required. An overload condition of a compressor prime mover overrides the control algorithm and selects a predetermined load control position of the modulation valve. A timer ensures that a predetermined recovery time is provided, before switching back to the control algorithm. The timer also selects the load control position of the modulation valve upon start-up. A heating or defrost mode automatically selects the load control position of the modulation valve for the duration of the mode, as does an ambient air temperature sensor when the ambient exceeds a predetermined value.

Claims13

Dependent claims

A method of controlling a refrigeration system having a compressor, with the compressor being driven by a prime mover, comprising the steps of:

providing a controllable modulation valve which is open in the absence of electrical current flow,
disposing the modulation valve in the refrigeration system in a position which enables the modulation valve to control the amount of refrigerant flow to the compressor,
controlling the modulation valve in a predetermined range near a selected set point temperature according to a predetermined control algorithm, with the control algorithm otherwise allowing the modulation valve to remain open,
causing the modulation valve to provide a predetermined restriction in the flow of refrigerant to the compressor for a predetermined period of time following start-up of the compressor, overriding the control algorithm,
providing an overload signal in response to a predetermined overload condition of the prime mover,
and causing the modulation valve to provide said predetermined restriction in the flow of refrigerant to the compressor in response to the overload signal, overriding the control algorithm.

3 more elements

In a refrigeration system for controlling the temperature of a served space via heating and cooling modes, wherein the refrigeration system includes a compressor driven by a prime mover, a refrigerant circuit which includes a condenser and an evaporator, a modulation valve in the refrigerant circuit positioned to restrict refrigerant returning to the compressor when operated from an open position towards a closed position, and modulation control for controlling the modulation valve according to a predetermined control algorithm which includes restricting the flow of refrigerant returning to the compressor in a predetermined range near a selected set point temperature and otherwise maintaining the modulation valve in an open position, the improvement comprising:

control means having first and second positions, with said first position connecting the modulation valve in a circuit which causes the modulation valve to provide a predetermined restriction in the flow of refrigerant returning to the compressor, and with said second position connecting the modulation valve to the modulation control,
and sensor means for providing an overload signal in response to a predetermined overload condition of the prime mover,
said control means being responsive to said overload signal, switching from said second position to said first position, if in said second position when said overload signal is provided.

Dependencies are inferred from the claim text.

Refrigeration system having a modulation valve which also performs function of compressor throttling valve

Life of this patent

Refrigeration system having a modulation valve which also performs function of compressor throttling valve

Life of this patent

Abstract

Claims13