1.3.13 VIBRATION CRITERIA
Refer to VA Master Specification, Section 15200, NOISE AND VIBRATION
CONTROL. See Article 5.3.
1.3.14 SEISMIC BRACING CRITERIA
See Article 2.15, Seismic Requirements (HVAC).
1.3.15 HVAC EQUIPMENT SIZING CRITERIA
1.3.15.1 AIR HANDLING EQUIPMENT: To compensate for the duct air leakage
and any future space internal heat gain, the equipment must be sized in
accordance with the following guidelines:
(a) Load Calculations: Heat gain calculations must be done in
accordance with the procedure outlined in the latest ASHRAE Handbook of
Fundamentals. The calculations performed either manually or with a
computer program shall not include any built-in safety factors.
(b) The calculated supply air shall be the sum of all individual peak
room air quantities without any diversity, even for the variable air
volume systems.
(c) Safety Margin: A safety factor of 5 percent shall be applied to the
calculated room air quantity to allow for any future increase in the
room internal load.
(d) The adjusted supply air shall be, thus, 5 percent in excess of the
calculated supply air.
(e) Air leakage: The air leakage through the supply air distribution
ductwork shall be computed on the basis of the method described in the
SMACNA Air Duct Leakage Test Manual. The maximum leakage amount shall
not exceed 4 percent of the adjusted supply air.
(f) Supply Air Fan Capacity: The capacity of the supply air fan shall
be calculated per the following example:
(1) Calculated Supply Air Volume
= 560 Cu M/Min (20,000 CFM)
(2) Safety Margin = 5 percent of item (1)= 28 Cu M/Min (1,000 CFM)
(3) Adjusted Supply Air Volume = 588 Cu M/Min (21,000 CFM)
(4) Duct Air Leakage = 4 percent of item (1)= 24 Cu M/Min (840 CFM)
(5) Supply Air Fan Capacity = 612 Cu M/Min (21,840 CFM)
(g) Equipment Selection: selection of the supply air fan, cooling coil,
preheat coil, energy recovery coil (if any), filters, louvers, dampers,
etc., shall be based on the supply fan capacity, 612 Cu M/Min (21,840
CFM) calculated in the example above. A psychrometric chart shall be
prepared for each air-handling unit. Make sure heat gains due to the
fan motor and duct friction losses are taken into account for sizing
cooling coils.
HVAC DESIGN MANUAL
1-16
GENERAL REQUIREMENTS
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