MACH
®
Gas Fired Boiler
15
•
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 (1100 mm
2
/kW) of total boiler input is required.
NOTICE!
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 ¼”
3. Motorized louvers shall be interlocked with the appliance so that they are proven open prior to main burner
ignition and operation.
Table of US Minimum area of ventilation openings per boiler (sq inches)
MACH
®
Boiler MODEL
AIR SOURCE
INDOOR AIR SUPPLY
OUTDOOR AIR SUPPLY
SAME
FLOOR
DIFF
FLOORS
ONE
OPENING
TWO OPENINGS
DIRECT
VERT
DUCT
HORIZ
DUCT
C750
750
1500
250
188
188
375
C900
900
1800
300
225
225
450
C1050
1050
2100
350
263
263
525
3.5.2.2
Air Inlet Requirements – Canada (CAN/CSA B149.1)
A. Ventilation of the space occupied by fuel burning appliance(s) or equipment shall be supplied by a ventilation
opening at the highest practicable point communicating with the outdoors. The total cross sectional area of the
ventilation opening must be either 10% of the net free area required for combustion air or 10 sq. in. (6500 mm
2
),
whichever is greater.
B. Use the following opening calculation for MACH
®
or MODU-FIRE
®
FD boilers:
When combustion air is supplied for a forced draft burner by natural airflow from the outdoors and there is no draft
regulator or draft hood in the same space, there shall be a permanent opening with a cross sectional area not less
than 1 sq. in/ 30,000 Btu/Hr (70 mm
2
/kW) of the total rated input to the burner(s). This opening must not interfere
with the ventilation air opening defined in paragraph A.
C. Use the following opening calculation for P-K THERMIFIC
®
boilers or other natural draft or fan-assist appliances:
When combustion air is supplied for natural or fan-assisted burners by natural airflow from the outdoors, there
shall be a permanent opening with a cross sectional area not less than 1 sq. in/ 7000 Btu/Hr (321 mm
2
/kW) up to
and including 1,000,000 Btu/Hr plus 1 sq. in. / 14,000 Btu/Hr (155 mm
2
/kW) in excess 1,000,000 Btu/Hr. This
opening must be either located at or ducted to a point not more than 18 in. (450 mm) nor less than 6 in. (150 mm)
above floor level. This opening is in addition to the ventilation air opening defined in paragraph A.
D. When combustion air is supplied by natural airflow into a space containing both types of appliance described in
paragraphs B and C, the cross sectional area of the opening shall be not less than the sum of the cross sectional
areas for all appliances in the space as calculated by the applicable method . This opening is in addition to the
ventilation air opening defined in paragraph A.