1.3.15.3 PIPE SIZING CRITERIA
(a) All piping required for HVAC systems shall be sized based on the
criteria listed in the following subparagraph.
(b) Water losses, pressure loss, etc., for sizing piping shall be based
on "Cameron Hydraulic Data": With C = 100 for open (cooling tower)
systems and C = 150 for closed systems. For closed systems, the maximum
friction loss shall be 1200 mm (4 ft) of water per 30 m (100 ft) of
pipe with maximum velocity of 1.2 m/s (4 fps) for systems in occupied
areas, and up to 2.4 m/s (8 fps) for mains and large branches. For open
systems, the maximum friction loss shall be 1200 mm (4 ft) of water per
30 m (100 ft) of pipe and a maximum velocity of 2.4 to 3.0 m/s (8 to 10
fps). The minimum pipe size shall be 20-mm (3/4-inch).
1.3.15.4 DUCT SIZING
(a) Duct systems should be designed in accordance with the general
rules outlined in the latest ASHRAE Guide and Data Books, SMACNA
Manuals and Design Guide Section of the Associated Air Balance Council
Manual.
(b) Supply duct system, with total external static pressure 50 mm (2
inches) and larger, shall be designed for a maximum duct velocity of
12.75 m/s (2500 fpm) for duct mains and a maximum static pressure of
6.4 mm (0.25 inch) of water gage per 30 m (100 ft). Static pressure
loss and regain shall be considered in calculating the duct sizes. Size
supply branch ducts for a maximum duct velocity of 7.60 m/s (1500 fpm).
(c) All other duct systems such as return and exhaust, including branch
ducts, shall be designed for a maximum velocity of 7.60 m/s (1500 fpm)
for the duct mains and a maximum static pressure of 0.10 inch of water
gage per 30 m (100 ft), with the minimum duct area of .19 sq m (48 sq
in), that is, 203 mm x 152 mm (8 in x 6 in) size. See Article 2.11 for
exceptions.
(d) Indicate Duct Static Pressure Construction Classification according
to SMACNA (1/2", 1", 2", 3" and 4") on drawings.
1.4 CONTRACT DRAWINGS
1.4.1 GENERAL
1.4.1.1 Refer to the following Design and Construction Procedures in
VHA Program Guide PG-18-3:
(a) Topic 2, Drawings
(b) Topic 7, Piping, Ducts and Electrical Conduits
1.4.1.2 Refer to VA Standard Details, VA National CAD Standard
Application Guide, and National CAD Standard for symbols and
abbreviations, which are to be used on all drawings and submissions. To
avoid confusion and dispute, nomenclature on the drawings shall
correspond exactly to nomenclature in the VA Master Specifications.
Sheet notes and general type notes should be listed on the right hand
HVAC DESIGN MANUAL
1-18
GENERAL REQUIREMENTS
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