Before talking about pumps, take a look at another piece of equipment used to maintain comfort in a building: chillers. A chiller consists of a compressor, condenser, evaporator, expansion valve, power and controls unit, and many other ancillary items. When chillers were first introduced to the market, they were supplied as separate components, bringing many challenges during installation and commissioning. This is why manufacturers started manufacturing chillers as complete packages. Why should pump systems be any different? Pumping systems are comprised of pumps, motors, isolation valves, check valves, a power and control unit, and other ancillary items such as gauges and sensors. One could argue that pumps should be supplied as packages for the same reasons as chillers and boilers.
Operators can increase efficiency with packaged HVAC pump systems, inline multistage pumps, and advanced motors and controls.
Grundfos
08/19/2019
Image 1. Cost savings on NEMA Premium motors (Tables & images courtesy of Grundfos)
Table 1. Chilled water demand based on building cooling loads
If chilled water flow peak demand was 1,000 gallons per minute (gpm), this pumping system would be operating at around 72 gpm for over half of the pump system’s duty cycle. This low flow demand brings up questions when considering pump selection. Is this below the pump’s preferred operating region (POR)? And more importantly, is it below the pump’s allowable operating region (AOR)? What is the pump efficiency at this low flow range? Is this flow below the chiller’s minimum flow capacity? Would it be better to use three or four smaller pumps coupled in parallel?
When multiple pumps are to be considered, this is where providing them as a package can be beneficial.
Table 2. Design phase considerations
Users should examine the details closely for the multipump field-assembled system to be designed, purchased, installed and commissioned successfully. It is common for a miscommunication and/or details to be left out. Examples include: motors need to be 208 volt, but controls and drives were ordered at 460 volt; a missing gauge here, a sensor there; where a sensor should be located along with drive and control settings; the wrong type of valve; and so on. Oversights like these can delay the installation and commissioning process.