u201d also known as u201c primary secondary chilled boiler water circuit u201d in this case in the plant loop 701 a two plant pumps in the combination of 705 a and 706 a or 705 a and 707 a or 706 a and 707 a of identical or similar capacity are deployed to transport the produced chilled boiler water through the plant loop water circuit 701 a also known as u201c primary loop u201d if only one chiller boiler 703 a or 704 a is operating at the mean time and the other remains on standby in accordance with the current loading the respective two predetermined pumps the predetermined combination of 705 a 706 a and 707 a are connected in parallel and operate in predetermined equal reduced speed or almost equal reduced speed or similar reduced speed simultaneously the pumps and the corresponding driving motors are controlled by corresponding variable speed drive vsd 730 a corresponds to plant pump 705 a 731 a corresponds to plant pump 706 a 732 a corresponds to plant pump 707 a and the said drives 730 a 731 a 732 a are commanded by a controller 733 a the controller 733 a monitors the present loading on the water system either by measuring the present power consumption of operating chiller 39 s 703 a or 704 a compressor using a power sensor or the speed of the operating chiller 39 s 703 a or 704 a compressor using a tachometer or measuring discharged chilled boiler water temperature by temperature sensor located in appropriate location in the water circuit or some other means from which loading can be inferred based on that loading signal 734 a an algorithm calculates.