2.5.3
Controls
A circuit breaker, magnetic starter, and manual-off-automatic selector
switch for each blower motor, and timers required for automatic operation
shall be provided. When in the automatic mode of operation, the blowers
shall operate alternately for 1-hour periods. Controls shall conform to
NEMA ICS 1. All controls shall be housed in a NEMA 250, Type 4 enclosure.
2.5.4
Air Pressure Gauges
An air pressure gauge shall be provided on the discharge line from each
blower. The gauge shall comply with ASME B40.100 and shall have a scale
range to include the full range of expected operation and up to 125
percent, but not more than 150 percent of maximum. The gauges shall be
mounted in the blower enclosure and shall be easily read with the enclosure
open.
2.5.5
Pressure Relief Valve
A pressure relief valve shall be provided in the discharge piping from each
blower. The valve shall vent pressure to the atmosphere when system
pressure exceeds [_____] kPa psi and shall reset automatically when
pressure drops below [_____] kPa psi. Volumetric release rate shall be 1.5
times the rated capacity of the blower. Relief valves shall have threaded
connections and shall be constructed and installed in compliance with ASME
BPVC SEC IV.
2.5.6
Air Filter-Silencer
Filter-silencers shall be used on blowers of 0.094 cubic meters per second
200 cfm or less. Provide separate silencer and air filter as well as a
discharge silencer on blowers over 0.094 cubic meters per second 200 cfm.
Filters shall be of the cleanable element type. Collection efficiency
shall be at least 90 percent of particulates 5 micrometers microns in
diameter and larger. Pressure drop through a clean unit shall not exceed
50.8 Pa 0.2 inches of water at rated capacity of blower. If filters are
mounted outside, provide weatherproof enclosures. Silencers shall be
heavy-duty, all welded chamber absorption types with double wall
construction to prevent high frequency ringing.
2.5.7
Mounting
Blowers and motors shall be rigidly mounted on a steel baseplate or
framework. Motor mount shall provide for adjustment of V-belt tension.
2.5.8
Enclosure
Blowers and motors shall be housed in a weatherproof enclosure constructed
of a corrosion-resistant material such as aluminum or galvanized steel, or
shall be factory painted with one prime coat and two finish coats of baked
enamel. The enclosure shall have wall louvers adequate to provide air for
cooling and, if the intake is in the enclosure, for blower supply.
Construction of the enclosure shall allow access to the blowers and motors
for maintenance.
2.6
AIR-DIFFUSION EQUIPMENT
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SECTION 11390
Page 18
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