Air conditioning control system for variable evaporator temperature

Claim 1

A method of controlling an air conditioning system, the air conditioning system being capable of treating a conditioned space by at least treating return air from the conditioned space in return air coils, the air conditioning system having at least one compressor and an evaporator and circulating a coolant through the return air coils, the return air coils having control valves capable of regulating coolant flow, and having a size that is able to be varied between a minimum and a maximum, wherein the method comprises the steps of: (a) setting desired temperature and humidity set points for the conditioned space; (b) setting desired maximum and minimum coolant velocity set points for the velocity of coolant through the return air coils; (c) measuring the conditioned space temperature and providing a temperature control signal computed from a deviation value of the conditioned space temperature from the temperature set point, the temperature deviation value being representative of changed sensible heat load requirements; (d) measuring the coolant velocity through the return air coils and providing a coolant velocity control signal computed from a deviation value of the coolant velocity from the maximum coolant velocity set point; (e) measuring the conditioned space humidity and providing a humidity control signal computed from a deviation value of the conditioned space humidity from the conditioned space humidity set point, the humidity deviation value being representative of changed evaporator temperature and latent heat load requirements; (f) in response to the temperature control signal, varying the coolant flow to the return air coils by regulating the control valves to meet the changed sensible heat load requirements; (g) in response to the coolant velocity control signal, varying the size of the return air coils such that the changed size prevents the coolant velocity from exceeding the maximum coolant velocity or from reducing below the minimum coolant velocity; (h) subsequent to a variation in size of the return air coils, providing an adjusted coolant velocity control signal; and (i) in response to the higher of the coolant velocity control signals and the humidity control signal, providing an evaporator temperature control signal to adjust the evaporator temperature to a maximum to thereby optimize input energy reduction.

Claim 2

A method of controlling an air conditioning system, the air conditioning system being capable of treating a conditioned space by at least treating return air from the conditioned space in return air coils, the air conditioning system having at least one compressor and an evaporator and circulating a coolant through the return air coils, the return air coils having control valves capable of regulating coolant flow, and having a size that is able to be varied between a minimum and a maximum, wherein the method comprises the steps of: (a) setting desired temperature and humidity set points for the conditioned space; (b) setting desired maximum and minimum coolant velocity set points for the velocity of coolant through the return air coils; (c) measuring the conditioned space temperature and providing a temperature control signal computed from a deviation value of the conditioned space temperature from the temperature set point, the temperature deviation value being representative of changed sensible heat load requirements; (d) measuring the coolant velocity through the return air coils and providing a coolant velocity control signal computed from a deviation value of the coolant velocity from the maximum coolant velocity set point; (e) measuring the conditioned space humidity and providing a humidity control signal computed from a deviation value of the conditioned space humidity from the conditioned space humidity set point, the humidity deviation value being representative of changed evaporator temperature and latent heat load requirements; (f) in response to the temperature control signal, varying the coolant flow to the return air coils by regulating the control valves to meet the changed sensible heat load requirements; (g) in response to the coolant velocity control signal, varying the size of the return air coils such that the changed size prevents the coolant velocity from exceeding the maximum coolant velocity or from reducing below the minimum coolant velocity; (h) subsequent to a variation in size of the return air coils, providing an adjusted coolant velocity control signal; and (i) in response to the higher of the coolant velocity control signals and the humidity control signal, providing an evaporator temperature control signal to adjust the evaporator temperature to a maximum to thereby optimize input energy reduction.

Claim 9

A method of controlling an air conditioning system, the air conditioning system being capable of treating a conditioned space by at least treating return air from the conditioned space, the air conditioning system having at least one compressor with a predetermined minimum compressor speed and an evaporator providing heat exchange with return air and outside air, the evaporator having a size that is able to be varied between a minimum and a maximum, wherein the method comprises the steps of: (a) setting desired temperature and humidity set points for the conditioned space; (b) measuring the conditioned space temperature and providing a temperature control signal computed from a deviation value of the conditioned space temperature from the temperature set point, the temperature deviation value being representative of changed sensible heat load requirements; (c) measuring the conditioned space humidity and providing a humidity control signal computed from a deviation value of the conditioned space humidity from the humidity set point, the humidity deviation value being representative of changed evaporator temperature and latent heat load requirements; (d) in response to the temperature control signal, varying flow of refrigerant in the evaporator such that the changed sensible heat load requirements are met; and (e) in response to the humidity control signal, providing an evaporator temperature control signal to adjust the evaporator temperature to a maximum to thereby optimize input energy requirements, said maximum evaporator temperature being limited such that the compressor speed does not reduce below the predetermined minimum compressor speed.

Claim 10

A method of controlling an air conditioning system, the air conditioning system being capable of treating a conditioned space by at least treating return air from the conditioned space, the air conditioning system having at least one compressor with a predetermined minimum compressor speed and an evaporator providing heat exchange with return air and outside air, the evaporator having a size that is able to be varied between a minimum and a maximum, wherein the method comprises the steps of: (a) setting desired temperature and humidity set points for the conditioned space; (b) measuring the conditioned space temperature and providing a temperature control signal computed from a deviation value of the conditioned space temperature from the temperature set point, the temperature deviation value being representative of changed sensible heat load requirements; (c) measuring the conditioned space humidity and providing a humidity control signal computed from a deviation value of the conditioned space humidity from the humidity set point, the humidity deviation value being representative of changed evaporator temperature and latent heat load requirements; (d) in response to the temperature control signal, varying flow of refrigerant in the evaporator such that the changed sensible heat load requirements are met; and (e) in response to the humidity control signal, providing an evaporator temperature control signal to adjust the evaporator temperature to a maximum to thereby optimize input energy requirements, said maximum evaporator temperature being limited such that the compressor speed does not reduce below the predetermined minimum compressor speed.

Claim 15

An apparatus for controlling an air conditioning system, the air conditioning system being capable of treating a conditioned space by at least treating return air from the conditioned space in return air coils, the air conditioning system having at least one compressor and an evaporator and circulating a coolant through the return air coils, the return air coils having a size that is able to be varied between a minimum and a maximum, the apparatus comprising: (a) a conditioned space humidity sensor, a conditioned space temperature sensor, and a coolant velocity sensor for determining the velocity of the coolant entering the return air coils; (b) an evaporator temperature controller; (c) means for providing a temperature control signal computed from a deviation value of conditioned space temperature from a temperature set point; (d) means for providing a humidity control signal computed from a deviation value of conditioned space humidity from a humidity set point; (e) means for providing a coolant velocity control signal computed from a deviation value of coolant velocity from a coolant velocity set point; (f) means for varying the return air coil size in response to the coolant velocity control signal; (g) means for varying the coolant velocity to the return air coils in response to the temperature control signal; and (h) control means capable of receiving the humidity control signal and the coolant velocity control signal, selecting the higher control signal and providing a control signal to the evaporator temperature controller to adjust the evaporator temperature to a maximum to thereby optimize input energy requirements.

Claim 16

An apparatus for controlling an air conditioning system, the air conditioning system being capable of treating a conditioned space by at least treating return air from the conditioned space in return air coils, the air conditioning system having at least one compressor and an evaporator and circulating a coolant through the return air coils, the return air coils having a size that is able to be varied between a minimum and a maximum, the apparatus comprising: (a) a conditioned space humidity sensor, a conditioned space temperature sensor, and a coolant velocity sensor for determining the velocity of the coolant entering the return air coils; (b) an evaporator temperature controller; (c) means for providing a temperature control signal computed from a deviation value of conditioned space temperature from a temperature set point; (d) means for providing a humidity control signal computed from a deviation value of conditioned space humidity from a humidity set point; (e) means for providing a coolant velocity control signal computed from a deviation value of coolant velocity from a coolant velocity set point; (f) means for varying the return air coil size in response to the coolant velocity control signal; (g) means for varying the coolant velocity to the return air coils in response to the temperature control signal; and (h) control means capable of receiving the humidity control signal and the coolant velocity control signal, selecting the higher control signal and providing a control signal to the evaporator temperature controller to adjust the evaporator temperature to a maximum to thereby optimize input energy requirements.

Claim 22

An apparatus for controlling an air conditioning system, the air conditioning system being capable of treating a conditioned space by at least treating return air from the conditioned space, the air conditioning system having at least one compressor with a predetermined minimum compressor speed and an evaporator providing heat exchange with return air and outside air, the evaporator having a size that is able to be varied between a minimum and a maximum, the apparatus comprising: (a) a conditioned space humidity sensor and a conditioned space temperature sensor; (b) an evaporator temperature controller; (c) means for providing a temperature control signal computed from a deviation value of conditioned space temperature from a temperature set point; (d) means for providing a humidity control signal computed from a deviation value of conditioned space humidity from a humidity set point; (e) means for varying the evaporator size in response to the temperature control signal; and (f) control means capable of receiving the humidity control signal and providing a control signal to the evaporator temperature controller to adjust the evaporator temperature to a maximum to thereby optimize input energy requirements, said maximum evaporator temperature being limited such that the compressor speed does not reduce below the predetermined minimum compressor speed.

Claim 23

An apparatus for controlling an air conditioning system, the air conditioning system being capable of treating a conditioned space by at least treating return air from the conditioned space, the air conditioning system having at least one compressor with a predetermined minimum compressor speed and an evaporator providing heat exchange with return air and outside air, the evaporator having a size that is able to be varied between a minimum and a maximum, the apparatus comprising: (a) a conditioned space humidity sensor and a conditioned space temperature sensor; (b) an evaporator temperature controller; (c) means for providing a temperature control signal computed from a deviation value of conditioned space temperature from a temperature set point; (d) means for providing a humidity control signal computed from a deviation value of conditioned space humidity from a humidity set point; (e) means for varying the evaporator size in response to the temperature control signal; and (f) control means capable of receiving the humidity control signal and providing a control signal to the evaporator temperature controller to adjust the evaporator temperature to a maximum to thereby optimize input energy requirements, said maximum evaporator temperature being limited such that the compressor speed does not reduce below the predetermined minimum compressor speed.