Situation/challenge: Domestic Cold Water Booster Pumps
This case study is about a 30 year-old, 27 story, 118 unit condominium high rise complex. Domestic cold water is pumped through the building by three 25HP pumps staged to run, as necessary, at full speed to maintain a set discharge pressure through regulation valves.
One of the three pumps is enough to carry the building load; one had failed requiring total replacement and a second required the motor and pressure regulation valve to be replaced. Because of the age, efficiency and maintenance required on the system, it was decided to replace with a new variable speed duplex pumping system. Estimates were obtained in the range of $38,000 to $45,000.
Gittleman Maintenance Solution
Pooling the knowledge and interest of our master electricians, pipefitters and plumbers, we engineered a retrofit conversion of the existing pumping system. The burned out motor was replaced with a high efficiency unit and the pressure regulation valve was removed and replaced with a simple check valve. We then installed and programmed a pressure sensor and variable frequency drive to maintain a set pressure, varying the pump speed according to demand. This modified pump was set as the lead pump with the other functioning constant speed pump set to a slightly lower discharge pressure that would automatically start in the event the lead variable speed pump could not keep up or failed.
Cost Savings / Client Benefit
This conversion was performed with no downtime or inconvenience to homeowners at a total cost of less than $6,000. We will be converting the second pump to variable speed at a later date, at a cost of approximately $4,000, resulting in savings to the association of about $28,000.
The newly converted pump idles at 0% when there is no demand in the building, smoothly ramping up to about 45 to 50% during higher load conditions, resulting in considerable annual energy savings and an ROI of less than two (2) years. We have successfully performed similar conversions at other buildings with more being planned.