Designing for Building Maintainability - Effective Building Maintenance: Protection of Capital Assets - page 150

1. Air-cooled condensing equipment rejects heat to the outdoor air
and, therefore, these units cannot be enclosed or placed in a posi-
tion where the rejected heat recirculates into equipment intakes.
There are three concerns relative to this equipment:
a. Provide space for the units, adequate separation between mul-
tiple units, and space around the units for maintenance and
air movement in accordance with the manufacturer's require-
ments.
b. Locate the equipment so as not to create a “heat trap” that im-
pairs performance of the equipment. Air-cooled equipment
should be located at least half the wall height away from ad-
jacent solid walls. Thus, if the wall height is 18 feet, the equip-
ment must be located at least 9 feet away from the wall. The
equipment cannot be located in an area defined by more than
two walls of the building (an inside corner). Putting equipment
in building recesses (3 building walls) or in wells (4 building
walls) is guaranteed to impair the performance of the equip-
ment, reduce its design service life, and increase maintenance
requirements.
c. Equipment screening must have at least 50% open area and
the screen height cannot exceed 1-2 feet above the height of the
equipment.
2. Cooling towers reject the heat removed from the building by the
chiller(s) to the outdoor air. This heat is rejected by spraying con-
denser water over a large heat transfer surface area, allowing a
percentage of the water to evaporate and cool the remaining water.
Cooling towers may be located on the roof or on the ground. If
located on the ground, they must be installed so that the operating
water level in the tower basin is higher than the condenser water
pump and all associated condenser water piping. This may make
the overall installed height significantly higher than envisioned.
The outdoor area requirement for cooling towers is approxi-
mately 0.5 sf per gsf of building area, plus the additional clearance
space for airflow and service shown by Figure 5-1.
Since the discharge of any cooling tower or evaporative con-
denser will contain a small percentage of respirable water drop-
lets, called “drift,” care must be taken to ensure that HVAC air
intakes are located well away from these discharges.