Sequencing of variable primary flow chiller system
AssigneeAmerican Standard International Inc.
InventorsLee R. Cline, Michael C.A. Schwedler
Life of this patent
Estimating the term…
Abstract
To provide chilled water, a variable-primary-flow system includes two variable speed pumps that pump water through a first chiller and a second chiller. A control energizes the second chiller in response to a cooling demand exceeding that what can be met by the first chiller operating alone, and de-energizes the second chiller upon the cooling demand decreasing to a level below the first chiller's maximum capacity. When both chillers are operating, the capacities of the chillers are modulated in unison to meet the cooling demand. Likewise, when both pumps are running, their speed is modulated in unison to provide a desired pressure.
Claims29
A method of controlling a chiller system that includes a first chiller and a second chiller through which water can be pumped to meet a cooling demand, comprising:
- pumping the water through the first chiller at a first flow rate to meet the cooling demand;
- increasing the cooling demand;
- in response to increasing the cooling demand, pumping the water through the first chiller at a second flow rate that is less than the first flow rate;
- and
- in response to increasing the cooling demand, pumping the water through the second chiller at a third flow rate, wherein the first flow rate is substantially equal to a sum of the second flow rate plus the third flow rate.
A method of controlling a chiller system that includes a first chiller and a second chiller for meeting a demand for chilled water, wherein the first chiller is selectively operable at a first full load and a first range of partial loads, and the second chiller is selectively operable at a second full load and a second range of partial loads, wherein the chiller system further includes a chilled water circuit, a first pump for forcing the chilled water through the first chiller at a first flow rate that may vary, a second pump for forcing the chilled water through the second chiller at a second flow rate that may vary, a bypass valve, a first heat exchanger, and a second heat exchanger, wherein the chilled water circuit connects the first chiller, the second chiller, the bypass valve, the first heat exchanger, and the second heat exchanger in parallel flow relationship with respect to the flow of chilled water, the method comprising:
- increasing the demand for chilled water;
- in response to increasing the demand for chilled water, changing the operation of the first chiller from operating at the first full load to operating within the first range of partial loads;
- in response to increasing the demand for chilled water, reducing the first rate at which the first pump forces chilled water through the first chiller;
- and
- in response to increasing the demand for chilled water, energizing the second chiller to begin operating the second chiller in the second range of partial loads.
A method of controlling a chiller system that includes a first chiller and a second chiller for meeting a demand for chilled water, wherein the first chiller is selectively operable at a first full load and a first range of partial loads, and the second chiller is selectively operable at a second full load and a second range of partial loads, wherein the chiller system further includes a chilled water circuit, a first pump for forcing the chilled water through the first chiller at a first flow rate that may vary, a second pump for forcing the chilled water through the second chiller at a second flow rate that may vary, a bypass valve, a first heat exchanger, and a second heat exchanger, wherein the chilled water circuit connects the first chiller, the second chiller, the bypass valve, the first heat exchanger, and the second heat exchanger in parallel flow relationship with respect to the flow of chilled water, the method comprising:
- establishing a chilled water temperature target;
- establishing a chilled water pressure target;
- selectively operating the chiller system in a high demand mode and a low demand mode to meet the chilled water temperature target;
- in the low demand mode, leaving the second chiller inactive while selectively operating the first chiller in the full load and the first range of partial loads to meet the chilled water temperature target;
- in the low demand mode, leaving the second pump inactive while modulating the pressure of the chilled water by controlling the operation of the first pump to meet the chilled water pressure target;
- in the high demand mode, operating the first chiller at a first partial load while operating the second chiller at a second partial load;
- and
- in the high demand mode, modulating the pressure of the chilled water by controlling the operation of the first pump and the second pump to meet the chilled water pressure target.
A method of controlling a chiller system that includes a first chiller and a second chiller for meeting a demand for chilled water, wherein the first chiller is selectively operable at a first full load and a percent of the first full load ranging from zero to one hundred percent, and the second chiller is selectively operable at a second full load and a percent of the second full load ranging from zero to one hundred percent, wherein the chiller system further includes a chilled water circuit, a first pump for forcing the chilled water through the first chiller at a first flow rate that may vary, a second pump for forcing the chilled water through the second chiller at a second flow rate that may vary, a bypass valve, a first heat exchanger, and a second heat exchanger, wherein the chilled water circuit connects the first chiller, the second chiller, the bypass valve, the first heat exchanger, and the second heat exchanger in parallel flow relationship with respect to the flow of chilled water, the method comprising:
- establishing a chilled water temperature target;
- establishing a chilled water pressure target;
- selectively operating the chiller system in a high demand mode and a low demand mode to meet the chilled water temperature target;
- in the low demand mode, leaving the second chiller inactive while operating the first chiller to meet the chilled water temperature target;
- in the low demand mode, leaving the second pump inactive while modulating the pressure of the chilled water by controlling the operation of the first pump to meet the chilled water pressure target;
- in the low demand mode, modulating the pressure of the chilled water by controlling the operation of the first pump and the second pump to meet the chilled water pressure target;
- in the high demand mode, modulating the first chiller at a percentage of the first full load;
- and
- in the high demand mode, modulating the second chiller at a percentage of the second full load and in unison with the first chiller, whereby the percentage of the first full load is substantially equal to the percentage of the second full load.
A chiller system comprising:
- a first chiller wherein the first chiller is selectively operable at a first full load and a first range of partial loads;
- a second chiller for meeting a demand for chilled water, wherein the second chiller is selectively operable at a second full load and a second range of partial loads;
- a first pump for forcing the chilled water through the first chiller at a first flow rate that may vary,
- a second pump for forcing the chilled water through the second chiller at a second flow rate that may vary;
- a bypass valve;
- a first heat exchanger;
- a second heat exchanger;
- a chilled water circuit, the chilled water circuit connects the first chiller, the second chiller, the bypass valve, the first heat exchanger, and the second heat exchanger in parallel flow relationship with respect to the flow of chilled water;
- means for establishing a chilled water temperature target;
- means for establishing a chilled water pressure target;
- means for selectively operating the chiller system in a high demand mode and a low demand mode to meet the chilled water temperature target;
- means for, in the low demand mode, leaving the second chiller inactive while selectively operating the first chiller in the full load and the first range of partial loads to meet the chilled water temperature target;
- means for, in the low demand mode, leaving the second pump inactive while modulating the pressure of the chilled water by controlling the operation of the first pump to meet the chilled water pressure target;
- means for, in the high demand mode, operating the first chiller at a first partial load while operating the second chiller at a second partial load;
- and
- means for, in the high demand mode, modulating the pressure of the chilled water by controlling the operation of the first pump and the second pump to meet the chilled water pressure target.
A chiller system comprising:
- a first chiller wherein the first chiller is selectively operable at a first full load and a percent of the first full load ranging from zero to one hundred percent;
- a second chiller for meeting a demand for chilled water, wherein the second chiller is selectively operable at a second full load and a percent of the second full load ranging from zero to one hundred percent;
- a first pump for forcing the chilled water through the first chiller at a first flow rate that may vary;
- a second pump for forcing the chilled water through the second chiller at a second flow rate that may vary;
- a bypass valve;
- a first heat exchanger;
- a second heat exchanger;
- a chilled water circuit wherein the chilled water circuit connects the first chiller, the second chiller, the bypass valve, the first heat exchanger, and the second heat exchanger in parallel flow relationship with respect to the flow of chilled water;
- means for establishing a chilled water temperature target;
- means for establishing a chilled water pressure target;
- means for selectively operating the chiller system in a high demand mode and a low demand mode to meet the chilled water temperature target;
- means for, in the low demand mode, leaving the second chiller inactive while operating the first chiller to meet the chilled water temperature target;
- means for, in the low demand mode, leaving the second pump inactive while modulating the pressure of the chilled water by controlling the operation of the first pump to meet the chilled water pressure target;
- means for, in the low demand mode, modulating the pressure of the chilled water by controlling the operation of the first pump and the second pump to meet the chilled water pressure target;
- means for, in the high demand mode, modulating the first chiller at a percentage of the first full load;
- and
- means for, in the high demand mode, modulating the second chiller at a percentage of the second full load and in unison with the first chiller, whereby the percentage of the first full load is substantially equal to the percentage of the second full load.
Dependencies are inferred from the claim text.