Friday, January 13, 2006

ABS Sizing Standards

I often get questions on how ABS sizes duct, wire and pipe. Well I guess it has happened enought that I have written it all out for you. Read on and all shall be revealed.

Duct sizing is derived from the ASHRAE Fundamentals Handbook 1997 and can be based on Air Velocity or Static Pressure Drop (Friction) per 100 feet of duct. Roughness Coefficient and Air Density can be set by the user.

HVAC Load Calcs

HVAC Load Calcs can be performed using data from inside of the ABS model. That information can be exported in a gbxml or ddxml format to any load calculating software that accepts this standard format. Software that accepts gbxml and ddxml include; Trace 700 for heating and cooling load analyses and Varitrane Duct Designer and Elite Duct Size to calculate optimal duct sizes using static regain, equal friction, or constant velocity methods.


Mechanical MvParts (rooftop units, VAV boxes, etc) The sizes of MvParts in ABS were chosen based off of standard manufactures parts. When similar parts are not the same, ABS uses the larger size.

Electrical MvParts are based on leading manufacturers.

Duct and fittings
Duct and fittings are based on the ASHRAE Duct Fitting Database (1994), Round, Rectangular, and Oval Duct Industrial Construction Standards published by SMACNA, and are augmented by offerings from the leading manufacturer of duct and fitting in the United States.

Pipe and Pipe Fittings

Pipe and Pipe Fittings Pipe identification, outer dimensions, and nominal dimensions are referenced against ANSI B36.19 and ANSI B36.19 as published in Crane's Technical Paper No. 410. Pipe fittings are referenced against various applicable standards:
· Flange ANSI/ASME B16.5
· Socket Weld and Threaded ANSI/ASME B16.11
· Cast iron ANSI/ASME B16.12 and B16.13
· Butt Welded ANSI/ASME B16.9
· Grooved Not described in standard. Based off leading manufacturer.
· Brazed ANSI/ASME B16.18, B16.22, B16.23, and B16.29 (and others)

Plumbing Pipe

Plumbing Pipe Sizing is based on the Uniform Plumbing Code-2000, Cranes Technical Paper No. 410, American Society of Plumbing Engineers (ASPE) chapter interpretations, and engineering judgment. Also used are the Hazen-Williams friction loss formula and a derivation of the Hunters Curve referenced from ASPE.
Sanitary sizing is based on the Uniform Plumbing Code 2000.

Wire is sized from the ampacity table in the wire database (ampacity.mdb) arrange similar to NEC table 310-16 and 250-122. An additional table (ambients.mdb) contains correction factors based on NEC 310-16.

Conduit and Cable Tray
Conduit and Cable Tray are based on NEMA FB1 (conduit) and NEMA VE1 - 1998 (Cable Tray).
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