604.3 Not Supplied with the Furnace. Where a furnace

plenum is not supplied with the furnace, any fabrication and installation instructions provided by the manufacturer shall be followed. The method of connecting supply and return ducts shall facilitate proper circulation of air. [NFPA 54:10.3.7.3]

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DUCT SYSTEMS

this section, then 40 percent of the total installed duct area shall be tested. Where the tested 40 percent fail to comply with the requirements of this section, then 100 percent of the total installed duct area shall be tested. Sections shall be selected by the building owner or designated representative of the building owner. Positive pressure leakage testing shall be permitted for negative pressure ductwork. The permitted duct leakage shall be not more than the following:

Lmax = CLP ^0.65 (Equation 603.9.2)

Where: Lmax = maximum permitted leakage, (ft ³ /min)/100

square feet [0.0001 (m ³ /s)/m ² ] duct surface area. CL = six, duct leakage class, (ft ³ /min)/100 square

feet [0.0001 (m ³ /s)/m ² ] duct surface area at 1 inch water column (0.2 kPa). P = test pressure, which shall be equal to the

design duct pressure class rating, inch water column (kPa). Exception: Transfer air duct operating at less than 1 inch of water column (0.25 kPa).

603.9.2.1 Duct Leakage Tests for Buildings that Meet Air Distribution System Duct Leak- age Sealing Criteria in Title 24, Part 6. For duct leakage testing, see California Energy Code Sec- tions 150.0(m)(11) for single family buildings, Sec- tion 160.3(b) for multifamily buildings, and Section 120.4(g) for nonresidential and Hotel Motel build- ings.