Cathodic Protection. The need for corrosion protection
smaller buildings [circulation of less than 63.1 L/s
for underground metallic piping must be evaluated by a
(1,000 gpm)].
soils resistivity test. Cathodic protection or another means
In variable primary applications, many conventional
of preventing pipe corrosion must be provided if required
chillers and boilers may experience flow-related heat
by the Geotechnical Report.
exchange problems when a minimum flow is not
maintained. For this reason, all variable primary
Dielectric Unions. Dielectric unions must be provided
applications must follow manufacturers' recommended
when connecting dissimilar materials in piping systems.
practices to prevent equipment damage or failure.
Piping Material. Table 5-5 cites which commercial
Primary/Secondary Pumping. In this application,
standard shall be used for piping material.
primary and secondary circuits are separate, with neither
Isolation of Piping at Equipment. Isolation valves, shutoff
having an effect on the pumping head of the other. The
valves, by-pass circuits, flanges and unions shall be
primary circuit serves source equipment (chiller or
provided for piping at equipment to facilitate equipment
boiler), while the secondary circuit serves the load. The
repair and replacement. Equipment requiring isolation
primary loop and pumps are dedicated and sized to serve
includes boilers, chillers, pumps, coils, terminal units and
the flow and temperature differential requirements of the
heat exchangers. Valves shall also be provided for zones
primary source equipment. This permits the secondary
off vertical risers.
pump and loop to be sized and controlled to provide the
design flow rate and temperature differential required to
Flexible Pipe Connectors. Flexible pipe connectors shall
satisfy the heating or cooling loads. Primary/secondary
be fabricated from annular close pitched corrugated and
systems are recommended for larger buildings [circulation
braided stainless steel. All pumps, chillers, and cooling
of more than 63.1 L/s (1,000 gpm)] and campus facilities.
towers shall have flexible connectors.
Piping System and Equipment Identification. All pipes,
be used in appropriately sized manufactured products.
valves and equipment in mechanical rooms, shafts,
Air separators and vents must be provided on hot water
ceilings and other spaces accessible to maintenance
systems to remove accumulated air within the system.
personnel must be identified with color-coded bands and
Automatic bleed valves shall only be used in accessible
permanent tags indicating the system type and direction
spaces in mechanical rooms where they can be observed
of flow for piping systems or type and number for
by maintenance personnel and must be piped directly to
equipment, per ASHRAE Handbook. The identification
open drains. Manual bleed valves shall be used at terminal
system shall also tag all valves and other operable fittings.
units and other less accessible high points in the system.
Gas piping and sprinkler lines must be identified as
Air vents shall be provided at all localized high points of
prescribed by NFPA.
the piping systems and at each heating coil. Likewise,
system drains shall be provided at all localized low points
of the heating system and at each heating coil.
148 F A C I L I T I E S S T A N D A R D S
FOR THE
PUBLIC
BUILDINGS
SERVICE
5.12 Pumping and Piping Systems
Revised March 2005 PBS-P100
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