Page 299 - Mechanical Engineers' Handbook (Volume 4)

288 Energy Auditing

of the pipes. Figure 3 shows the percentage of the heat in steam that is lost due to condensate
flashing at various pressures. Raising temperatures in chilled-water distribution systems also
saves energy in two ways. Heat gain through pipe surfaces is reduced, and the chiller’s
efficiency increases due to the higher suction head on the compressor (see Fig. 4).
A PM program is needed to ensure that energy-using systems are operating efficiently.
Among the activities that should be conducted regularly in such a program are cleaning of
heat exchange surfaces, surveillance of steam traps so that leaky traps can be found and
repaired, combustion efficiency testing, and cleaning of light fixtures. Control equipment
such as thermostats, time clocks, and reset controllers need special attention. This equipment
should be checked and adjusted frequently.

3.2 Capital-Intensive Energy Conservation Measures
Major additions, modifications, or replacement of energy-using equipment usually require
significant amounts of capital. These measures consequently undergo a more detailed scrutiny
before a facility’s management will decide to proceed with them. While the fundamental
approach of eliminating unnecessary tasks and minimizing the work required for necessary
tasks is unchanged, the auditor must pay much more attention to the tasks of estimating
costs and savings when considering capital-intensive conservation measures.
This subsection will describe only a few of the many possible capital-intensive measures.
These measures have been chosen because they illustrate some of the more common ap-
proaches to energy saving. However, they are not appropriate in all facilities and they will
not encompass the majority of savings in many facilities.
Energy Management Systems
An energy management system (EMS) is a centralized computer control system for building
services, especially HVAC. Depending on the complexity of the EMS, it can function as a
simple time clock to turn on equipment when necessary, it can automatically cycle the
operation of large electrical equipment to reduce peak demand, and it can program HVAC
system operation in response to outdoor and indoor temperature trends so that, for example,
the ‘‘warm-up’’ heating time before a building is occupied in the morning is minimized.
While such a system can be a valuable component of complex building energy service
systems, the energy auditor should recognize that the functions of an EMS often duplicate
the services of less costly equipment such as time clocks, temperature controls, and manual
switches.

Air-Conditioner Economizers
In many areas, outdoor temperatures are lower than return air temperatures during a large
part of the cooling season. An air-conditioner economizer uses outside air for cooling during

Figure 3 Percentage of heat that is lost due to
condensate flashing at various pressures.