1 City Place is a 35 story luxury apartment building located in downtown White Plains, NY. The building had a triplex constant speed water pressure booster system which was installed when the building was first built. This · constant speed water pressure booster system was grossly oversized, equipped with three 25 HP direct coupled multi stage centrifugal pumps. The control mechanism was very complex and included obsolete controls like a Hydraulic control valve, hot water recirculation system, pressure switches, cycle timers etc. The control mechanism was adversely affecting pump performance because when the pressure switch activated the pumps they operated at full 3500 RPM to bring the pressure up, however, this pressure was· regulated down by the hydraulic control valve which acted against the pump, thus bringing down the overall system efficiency.
Another issue faced by the maintenance technicians was the lack of technical help and spare parts for the pumps which needed constant maintenance. The system outlived its use resulting in excessive wear and tear caused by the constant full load operation.
Towle Whitney LLC designed a replacement system using Variable Frequency Drives that govern centrifugal pumps thus eliminating the need for complex and obsolete control mechanisms mentioned above. Some of the advantages of VF drives were i) The VF drive controlled motor speed and torque by controlling the frequency and voltage supplied to the motor, the speed of the motor was varied based on the pressure drop due to water demand. At low demands the system operated at lower RPM and ramped up and down depending on variation in volume which allowed for significant amount of energy savings. ii) The VF drive enabled the pump to maintain constant pressure and not a range, this value of pressure was also easily adjustable. iii) The VF drive protected the pump against harmful conditions such as loss of incoming water supply, loss of power, short cycling, over voltage / current etc. iv) The VF drive enabled the pump to ramp up/ down in a controlled manner, thus reducing cavitation, turbulence in the piping and reduces water hammer.
Towle Whitney LLC installed a HILO Triplex variable speed booster system with two 20HP pumps and one 1 0HP pump, replacing the old constant speed system. The 1 0HP pump handles the off-peak demand with takes care of 80% of the load during an entire day and at peak demand one of the 20HP pumps helps the 1 0HP pump to handle the load. The second 20HP pump serves as an inline standby pump at all times to provide redundancy.
The savings in energy consumption are two fold: i) The VF drive enables the pump to operate at an optimum frequency based on the demand, if operating at 100% load the energy consumption is 100%; however, when operating at 80% load the energy consumption drops to 50%. ii) Lowering the pump HP automatically lowers the power consumption due to reduced amperage draw.
Energy savings of up to 80% have been recorded after installation of the Towle Whitney booster system. Towle Whitney solutions are proven and at a fraction of the cost compared to others.