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®
MACH
Boiler
Model #
CM300
CM399
CM500
C750
C900
C1050
®
3.4.3 P-K MACH
Combustion Air Requirements
The table below summarizes the combustion air requirements for P-K MACH
®
P-K MACH
Model #
CM300
CM399
CM500
C750
C900
C1050
3.4.4 Direct Vent / Sealed Combustion Installations
®
The P-K MACH
series boilers are certified for operation in direct vent / sealed combustion systems,
which feature combustion air intake ductwork which sources the combustion air supply from outdoors.
The flow of combustion air through this ductwork is maintained by the appliance's combustion blower.
The combustion air intake ductwork can be constructed with PVC, CPVC, single wall galvanized steel,
or other suitable materials. The ductwork must be rigid enough to maintain the full required cross
sectional area under all operating conditions.
NOTE: The combustion air intake ductwork must be sufficiently rigid in order to prevent collapse
due to the potential for negative pressures inside the ductwork. If the ductwork collapses, this will
restrict the combustion air supply to the appliance which may prohibit operation.
Proper sealing of the combustion air intake ductwork is necessary to prevent infiltration of air from
conditioned space. For example, joints in PVC or CPVC piping must be cemented. For galvanized
duct, wrap each joint and seam with adhesive aluminum tape or other sealant. Patterson-Kelley
recommends installing a 1" x 1" or larger bird screen on the exterior termination. Ensure that the screen
does not become blocked with snow, ice, insects etc.
The combustion air supply must be free from dust, lint, etc. The presence of such materials in the air
supplied to the burner could cause nuisance "Low Air" shutdowns or premature burner failure. The
appliance should not be operated during construction while the possibility of drywall dust, demolition
dust, etc. exists.
The combustion air supply must be completely free of chemical fumes which may be corrosive when
burned in the appliance. Common chemicals which must be avoided are fluorocarbons and other
halogenated compounds, most commonly present as refrigerants or solvents, such as Freon
trichloroethylene, perchloroethylene, chlorine, etc. These chemicals, when burned, cause improper
combustion and premature appliance failure due to the formation of acids which quickly attack the heat
exchanger and the flue piping materials.
Sizing the Combustion Air Intake Ductwork
Revised: January 3, 2020
Released: January 3, 2020
Required Combustion Air
BTU/Hr
Opening
2
Input
in
300,000
10
399,000
13
500,000
17
750,000
25
900,000
30
1,050,000
35
Air Intake Connection
Patterson-Kelley 2020
All Rights Reserved.
Technical Service 1.877.728.5351
Ventilation Air Opening
2
mm
6,153
7,999
10,460
16,129
19,355
22,581
Required SCFM Combustion Air
5"
5"
5"
6"
6"
6"
1004905980 P-K MACH CM300-CM500&C750-C1050
Installation and Owners Manual (Rev F Jan-2020).docx
®
P-K MACH
Gas Fired Boiler
2
2
in
mm
10
6,452
10
6,452
10
6,452
10
6,452
10
6,452
10
6,452
®
boilers:
70
92
115
175
210
245
®
,
Page 23
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