Heating, ventilation and air conditioning (HVAC) pumping systems include both heating and cooling systems. Heating systems include hot water heating and steam heating systems, and cooling systems include chilled water, condenser/cooling tower systems and waterside economizer systems. Additionally, there may be other supporting pump systems, like chemical feed.
To focus on just one of the HVAC pumping systems, hot water heating or processes utilize pumps to transfer energy (heat) from the source (such as a boiler) to the demand load (such as radiators used to heat a space). Hot water heating distribution systems are responsible for directing the hot water to the load and back to the heating source. The most common hot water distribution systems use primary-secondary arrangement, where a primary loop includes a pump/pumps sized for the boiler and the secondary loop has a pump/pumps sized for the distribution system. The primary and secondary loops are connected with a common pipe that allows hot water from the loops to mix, which enables primary hot water to mix with cooled return water to elevate the temperature of the water entering the boiler. This limits condensation and shock. Depending on design and heating needs, the primary and secondary pumps can be constant or variable speed, but more often than not, the secondary pumps serve a variable load and can be optimized with variable-speed pumping.
The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) has published ASHRAE 90.1, which covers the minimum energy efficiency requirements for commercial buildings and provides guidance on HVAC applications that should utilize variable-speed pumping to reduce energy consumption. For information on HVAC pumping systems and more details on primary-secondary pumping, refer to the Hydraulic Institute’s Pump Application Guideline for Commercial Building Services.
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