P-K MACH
®
Gas Fired Boiler
Technical Service 1.877.728.5351
Revised: January 3, 2020
Released: January 3, 2020
Patterson-Kelley 2020
All Rights Reserved.
1004905981 P-K MACH C1500H-C4000 Installation and
Owners Manual (Rev F Jan-2020).docx
Page 26
Combustion Air
3.4.1 Air Inlet Requirements
– United States
Air inlet requirements for the United States are established by NFPA 54/ANSI Z223.1 & NFPA/ANSI
211. When air is supplied from inside the building, the total required volume shall be the sum of the
required volume for all the appliances located in the mechanical room. Adjacent rooms furnished with
fixed openings communicating directly with the mechanical room are considered part of the required
volume. The minimum volume is 50 ft
3
per 1,000 Btu/Hr (4.8 m
3
/kW) of installed appliance input
capacity.
Openings used to connect indoor spaces to obtain the required minimum volume shall be sized as follows
:
•
When rooms are on the same floor, each opening shall have an area equal to 1 square inch for
each 1,000 Btu/Hr (2,200 mm
2
/kW) of installed appliance input capacity, but not less than 100
square inches. One opening should commence less than 12 inches above the floor and the other
less than 12 inches below the ceiling. The minimum dimension of air openings shall be 3 inches
.
•
When rooms are on different floors, each opening shall have an area equal to 2 square inches for
each 1,000 Btu/Hr (4,400 mm
2
/kW) of installed appliance input capacity
.
When combustion air is supplied from outside the building, the boiler room shall be provided with one or two
openings to ensure adequate combustion air and proper ventilation
.
When using one permanent opening,
the opening shall commence within 12 inches of the ceiling and shall communicate directly with the
outdoors or through a vertical or horizontal duct that communicates to the outdoors
.
Minimum free area of
the opening is 1 square inch for each 3,000 Btu/Hr (700 mm
2
/kW) of installed appliance input capacity, and
not less than the sum of the areas of all vent connectors in the room.
Under no circumstances
shall the boiler room ever
be under a negative
pressure.
Particular care should be
taken when exhaust fans,
compressors, air-handling
units, or other equipment
may rob air from the boiler.
Note that this equipment
might be in rooms other
than the boiler room. This
applies to both sealed
combustion and
atmospheric room
combustion air applications.
When using two permanent openings, one opening shall commence within
12 inches above the floor and the other within 12 inches below the ceiling,
preferably on opposite walls. The openings shall communicate directly, or
by way of ducts, with free outdoor air. The minimum net free area of the
openings shall be calculated in accordance with the following
:
•
When air is taken directly from outside the building, each
opening (minimum of two, as outlined above), 1 square inch for
each 4,000 Btu per hour (550 mm
2
/kW) of total boiler input is
required
.
•
When air is taken from the outdoors through a vertical duct into
the mechanical room, 1 square inch per 4,000 Btu per hour
(550
mm
2
/kW) of total boiler input is required.
•
When air is taken from the outdoors through a horizontal duct
into the mechanical room, 1 square inch per 2,000 Btu per hour
(1,100 mm
2
/kW) of total boiler input is required.
1. The required size of openings for combustion and ventilation air shall be based
on the net free area of the opening.
2. Screens shall be not smaller than 1/4 inch.
3. Motorized louvers shall be interlocked with the appliance so that they are
proven open prior to main burner ignition and operation.
NOTES:
