HVAC: Peeling Back the Layers
Part 1: Facilities Can Take Greater Advantage of BAS Features
Part 2: Focus on Ventilation and Scheduling Pays Energy Dividends
Part 3: Energy Efficiency Can Flow from Attention to Pumps, Fans
Energy Efficiency Can Flow from Attention to Pumps, Fans
By Todd Dorius - September 2011 - BAS Energy Efficiency
A facility's centrifugal pumps and fans also offer energy-saving opportunities. Fan pressure increases by the square of the fan's speed, and the power increases by the cube of its speed. Fan or pump speed is directly proportional to the flow rate. So any reduction of the flow rate dramatically reduces energy use.
Managers also must consider pressure drops in the system. The access doors in one building were difficult to open, due to extremely high pressure drops across a filter bank. When the filter bank area increased, the access doors open more easily, the fan horsepower dropped, and filter life increased.
Many existing buildings also have leaky ductwork related to poor installation or aged components. Technicians can visually identify these situations, while others require the aid of an infrared scanner or temperature-sensing tool.
A leak in ductwork generally means a loss of conditioned air to a return plenum or the outdoors. Even if the leak is in a conditioned space with exposed ductwork, the conditioned air is wasted, since it is not directed where occupants need it. This situation equates to wasted energy.
Finally, technicians can identify leaks in exposed hydronic systems by stains on the outer insulation jacket. This condition represents not just a loss of conditioned water but the potential for damage to the building and the loss of insulation performance, leading to energy losses.
Todd Dorius, P.E., is a project manager with Facility Engineering Associates. He has more than 15 years of experience in designing HVAC systems for large data centers, campus utilities, central plants, resorts, office buildings, and medical and retail facilities.
