Page 295 - Mechanical Engineers' Handbook (Volume 4)

284 Energy Auditing

Areas for HVAC maintenance that are important to check include heat exchanger sur-
faces, fuel-air mixture controls in combustors, steam traps, and temperature controllers. Scale
on the water side of boiler tubes and chiller condenser tubes reduces the efficiency of heat
transfer. Losses of efficiency can also be caused by the buildup of dirt on finned-tube air-
cooled condensers. Improper control of fuel-air mixtures can cause significant losses in com-
bustors. Leaky steam traps are a common cause of energy losses. Figure 2 shows the annual
rate of heat loss through a leaky trap as a function of the size of the trap orifice and steam
pressure. Poorly maintained room thermostats and other controls such as temperature reset

Figure 2 Steam loss through leaking steam traps as a function of stem pressure and trap orifice size. 3