06-06
D. FAN VOLUMETRIC CONTROLS (SUPPORT AREAS): For fan volumetric controls
of the VAV (variable air volume) systems. The following guidelines
shall apply:
1. Variable Speed Drive Package: For air handling units of 280
m3/min. (10,000 CFM) and larger capacities, the package of the
volumetric controls shall consist of the variable speed drives for
the supply and return air fans and the control accessories
comprising of the air flow measuring devices and static pressure
sensor(s).
The preferred sequence of operation is described in VA
Standard Details Nos. 15900-11,11A,11B,11C.
2. Constant Speed Operation:
For air handling units smaller than 280
m3/min (10,000 CFM) capacity, the individual room temperature
control shall involve variation in the supply air volume.
However, the supply and return air fans shall continue to operate
at constant speed.
During part load conditions, the bypass type
of room air terminal units will divert (and relieve) the supply
air into the ceiling air plenum, where, after mixing with the room
return air, it will find its way into the return air system.
E. Heating Controls: See Article 4.
F. Cooling Controls: See Article 5.
3.6 SMOKE AND FIRE CONTROL
The smoke control for the HVAC systems shall be designed in accordance
with NFPA 90a to affect system shutdown in the event of smoke
detection. The systems shall be incorporated with the following
features:
A. SMOKE DETECTORS AND SMOKE DAMPERS:
1. SMOKE DETECTORS: A duct mounted smoke detector shall be installed
in the main supply air duct, on the downstream side of the after
filters and prior to any duct takeoff, of all supply air systems
of capacities greater than 56 m3/min. (2,000 CFM). Upon smoke
detection, the duct detector (through its auxiliary contacts)
shall:
a. Stop the supply and associated return air fan; the building
exhaust air fan(s) shall continue to run.
b. Sound an alarm at the fire alarm system.
c. Sound an audible alarm and print an alarm message at the
central engineering control center (ECC).
2. SMOKE DAMPERS: In addition to the supply air duct detector listed
in Paragraph 1, for air handling units with capacities larger than
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