Cooling Towers. Multiple cell towers and isolated basins
economizer. A manual shutdown for the fan shall be
are required to facilitate operations, maintenance and
provided. If cooling towers operate intermittently during
redundancy. The number of cells shall match the number
sub-freezing weather, provisions shall be made for
of chillers. Supply piping shall be connected to a manifold
draining all piping during periods of shutdown. For
to allow for any combination of equipment use. Multiple
this purpose indoor drain down basins are preferred to
towers shall have equalization piping between cell basins.
heated wet basins at the cooling tower. Cooling towers
Equalization piping shall include isolation valves and
with waterside economizers and designed for year-
automatic shutoff valves between each cell. Cooling towers
round operation shall be equipped with basin heaters.
shall have ladders and platforms for ease of inspections
Condenser water piping located above-grade and down
and replacement of components. Variable speed pumps
to 3 feet below grade shall have heat tracing. Cooling
for multiple cooling towers shall not operate below 30
towers shall be provided with BACnet or LONWORKS
percent of rated capacity.
microprocessor controls, capable of connecting to central
building automation systems.
Induced draft cooling towers with multiple-speed or
variable-speed condenser fan controls shall be provided.
See Chapter 7, Fire Protection Engineering & Life Safety,
Induced draft towers shall have a clear distance equal to
for fire protection provisions for cooling towers.
the height of the tower on the air intake side(s) to keep
Chilled Water and Condenser Water Pumps. Pumps shall
the air velocity low. Consideration shall be given to piping
be of a centrifugal type and shall generally be selected to
arrangement and strainer or filter placement such that
operate at 1750 RPM. Both partial load and full load must
accumulated solids are easily removed from the system.
fall on the pump curve. The number of primary chilled
Clean-outs for sediment removal and flushing from basin
water and condenser water pumps shall correspond to
and piping shall be provided.
the number of chillers, and a stand-by pump shall be
The cooling tower's foundation, structural elements and
designed for each chilled water and condenser water
connections shall be designed for a 45 m/s (100 mph)
circuit. Variable volume pumping systems shall be
wind design load. Cooling tower basins and housing shall
considered for all secondary piping systems with pump
be constructed of stainless steel.
horsepower greater than 11.2 kW (15 hp). The specified
pump motors shall not overload throughout the entire
If the cooling tower is located on the building structure,
range of the pump curve.
vibration and sound isolation must be provided. Cooling
towers shall be elevated to maintain required net positive
Each boiler cooling tower and chiller group pumps shall
suction head on condenser water pumps and to provide a
be arranged with piping, valves, and controls to allow
1.2 m (4 ft) minimum clear space beneath the bottom of
each chiller-tower group to operate independently of the
the lowest structural member, piping or sump, to allow
other chiller and cooling tower groups.
reroofing beneath the tower.
Freeze Protection. Propylene glycol manufactured
Special consideration shall be given to de-icing cooling
specifically for HVAC Systems is used for freeze
tower fills if they are to operate in sub-freezing weather,
protection, primarily in low temperature chilled water
such as chilled water systems designed with a water-side
146 F A C I L I T I E S S T A N D A R D S
FOR THE
PUBLIC
BUILDINGS
SERVICE
5.11 Primary Cooling Systems
Revised March 2005 PBS-P100
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