Special Maintenance Considerations - Effective Building Maintenance: Protection of Capital Assets - page 91

turn fan or a relief fan(s). Engineering investigation and analysis is
required to determine the most cost-effective approach.

• Use Water-Cooled or Evaporative Condensing : The vast majority of
direct expansion (DX) cooling systems utilize outdoor air as a “heat
sink” for condenser heat rejection. However, by using evaporative
cooling, there is a significant improvement in the cooling energy re-
quirement as shown by Table 4-1.

Table 4-1. Comparison of Condensing Energy Impact
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Typical

Type TypicalCondensing Compressor

kW/Ton
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OfCondensing Temperature(°F)

Air-Cooled 120-130 0.9-1.4

Evaporative 94-98 0.6-0.8
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Thus, evaporative condensing can reduce cooling energy con-
sumption by about 40% over air-cooled condensing. Existing air-
cooled equipment can be retrofitted with evaporative “pre-cooling”
pads or, as older air-cooled equipment reaches the end of its service
live, water-cooled replacements will typically be very cost effective.

• Convert Chilled Water System to Variable Flow : Primary-secondary
or variable flow primary piping configurations significantly reduce
chilled water pumping energy and improve the overall loading and
efficiency of multi-chiller systems.

• Install Waterside Economizer Cycle : The energy consumption by
the waterside economizer for the pumps and cooling tower is only
about 20-25% of the energy consumption by mechanical cooling.
Thus, for fancoil unit systems or other air systems that cannot utilize
an airside economizer cycle, winter cooling energy requirements
can be reduced by 75-80%.

• Improve Burner Efficiency: : Every burner, not matter what size,
should be maintained for maximum firing efficiency. However, for
larger systems (1,500,000 Btu/h input or greater), improvements