Combustion Air; Ducted Combustion Air - Watts Aerco Benchmark OMM-0116 Installation And Start-Up Manual

Benchmark 750-3000 Installation & Startup Manual
SECTION 2 – INSTALLATION

2.13 COMBUSTION AIR

The Benchmark Venting and Combustion Air Guide, TAG-0022 (GF-2050) MUST be consulted
before any inlet air venting is designed or installed. Air supply is a direct requirement of ANSI
223.1, NFPA-54, CSA B149.1 and local codes. These codes should be consulted before a
permanent design is determined.
The combustion air must be free of chlorine, halogenated hydrocarbons or other chemicals that
can become hazardous when used in gas-fired equipment. Common sources of these
compounds are swimming pools, degreasing compounds, plastic processing, and refrigerants.
Whenever the environment contains these types of chemicals, combustion air MUST be
supplied from a clean area outdoors for the protection and longevity of the equipment and
warranty validation.
If combustion air is supplied directly to the unit(s) though air duct(s), see section 2.13.1 below.
If combustion air is not supplied through air ducts, it must be supplied to the unit(s) through two
permanent openings. These two openings must have a free area of not less than one square
2
inch (6.5 cm ) for each 4000 BTUs (1.17 kW) input for each unit. The free area must take
into account restrictions such as louvers and bird screens.
For Canada installations, refer to the requirements specified in CSA B149.1-10, sections 8.4.1
and 8.4.3.

2.13.1 DUCTED COMBUSTION AIR

For ducted combustion air installations, the air ductwork must be attached directly to the air inlet
connection on the sheet metal enclosure. Consult the Benchmark Venting and Combustion Air
Guide, TAG-0022 (GF-2050) when designing combustion air ducting.
In a ducted combustion air application, the combustion air ducting pressure losses must be
taken into account when calculating the total maximum allowable venting run. When using the
unit in a ducted combustion air configuration, the minimum diameter connection at the unit is:
TABLE 2-4: Air Duct Minimum Diameter
Benchmark Model
BMK 750
BMK 1000
BMK 1500
BMK 2000
BMK 2500
BMK 3000
• •
OMM-115_D GF-200 5/9/2019
Duct Diameter
6 inch (15.2 cm) diameter connection
8 inch (20.3 cm) diameter connection
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