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                                   Basics of Pump Application for HVAC Systems

                                            Basics of Pump Application for HVAC Systems  297



































                    Figure 10.12 Wire-to-water efficiency curves for Tables
                    10.4, 10.5, and 10.6.

                      Figure 10.12 provides the data of Tables 10.4, 10.5, and 10.6 as
                    curves plotted with system gallons per minute. This figure demon-
                    strates the advantage of the three-pump variable-speed system
                    energy-wise over the two-pump variable-speed system. It also shows
                    the dramatic energy savings of either variable-speed system over the
                    constant-speed system. Not only do the variable-speed systems save
                    energy, but they also reduce appreciably the overpressure on the
                    water system and the radial thrust on the pumps themselves.
                      It should be noted that these tables are based on standard water at
                    50°F. If wire-to-water efficiencies are computed for liquids of other
                    densities or viscosities, the head inserted in the tables should be cor-
                    rected for the actual density and viscosity.


                    10.9 Wire-to-Water Efficiency Indication
                    Wire-to-water efficiency indication for an actual pumping system can
                    be developed easily through the recording of the system flow, net
                    pump head, and pumping system kilowatts. This instrumentation for




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