2.3.1
Pneumatic Controls
If pneumatic operation is provided, a regenerant desiccant air dryer unit
shall be provided. Boiler shall shut down on loss of control air pressure.
Pneumatic control systems shall conform to ASME B19.3. Air filter
regulator sets shall be installed at each control valve and transmitter in
the system. The master air filter regulator set on the control panel shall
be the dual type where one side can be cleaned and repaired while the other
is operating. Exterior control air piping and devices shall be protected
form freezing.
2.3.1.1
Air Compressor Unit
The air compressor unit shall be electric-motor driven,
polytetrafluoroethylene or carbon ring type automatic air compressor. The
compressor unit shall be sized to run not more than 60 percent of the time
when all controls are in service. The air compressor unit shall be
complete with necessary accessories including automatic pressure control
equipment, relief valves, check valves, air filters, moisture traps, and a
receiver with ample capacity for emergency operation of the controls for 15
minutes after compressor shutdown. Compressor speed shall not exceed 900
rpm. Motor speed shall not exceed 1750 rpm. The compressor air intake
shall be provided with a low drop type air suction filter/silencer suitable
for outdoor installation.
2.3.1.2
Air Receiver
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NOTE: The condensate drain line will be located in
such a manner as to prevent freezing.
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The air receiver shall be constructed in accordance with ASME BPVC SEC VIII
D1for unfired pressure vessels for 1379 kPa 200 psi working pressure, and
shall be equipped with inlet and outlet connections, valved drain
connection, minimum 150 mm 6 inch dial pressure gauge, pop safety valves,
and regulator connections.
2.3.2
Electrical controls
Electrical control devices shall be rated at [120] [24] volts and shall be
connected as specified in Section 16402 INTERIOR DISTRIBUTION SYSTEM.
2.3.3
Water Temperature Controller
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NOTE: If hot water boilers are not utilized, the
following paragraph will be deleted. Consideration
will be given to the utilization of outside air
reset controls. Outside air reset control is
typically used for boilers whose primary loads are
due to space heating applications. Information on
outdoor air reset controls for space heating
application is located in section 15950 HEATING,
VENTILATING AND AIR CONDITIONING (HVAC) CONTROL
SYSTEMS and TM 5-815-3. Consideration will be given
to the use of control based on return water
temperature rather than supply water temperature.
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SECTION 15569A
Page 27
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