Western Airconditioning Zeta Echos Technical Information Manual page 13

Energy savings in these conditions can be as high as 11% per year and sometimes even more!
Inverter Driven Pump operating logic:
Dp1: System side pressure drops
Dp2: Evaporator pressure drops
When all the utilities are in operation, the unit's pump runs at the nominal flow rate and with an
available head on the system side equal to Dp1 and evaporator pressure drops equal to Dp2.
The system's heat load drop causes the shut-off valves of the utilities to close, which results in an
increase in the pressure drops that the pump needs to overcome. At the same time, the inverter's
control logic will reduce the flow rate, which will determine lower evaporator pressure drops and bring
back the available head to the nominal Dp1 value.
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