MACH® Series
Gas-Fired Boiler
Installation
14
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.
E. When a duct is used to meet the requirement for combustion air supply, as described in paragraphs A through D,
above, the opening of the duct shall be located so there is no possibility of cold air affecting steam or water piping,
electrical equipment or mechanical equipment.
F. When combustion air is supplied by mechanical means, an airflow-sensing device must be installed. It must be
wired into the pre-ignition limit string to prevent the burner from starting or to stop an operating burner in case of
air supply failure.
G. When all combustion air is supplied through a make-up air heater, and the appliance is interlocked to the heater,
the requirements of paragraphs A through F do not apply.
NOTE:
1. The free area of a combustion air supply opening is calculated by deducting the blockage area of any fixed
louvers, grilles or screens from the total 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 Canadian Minimum Area of Combustion and Ventilation Air Openings
MACH
®
Required Combustion Air
Opening
Ventilation Air Opening
Model Input
(Btu/Hr)
in
2
mm
2
in
2
mm
2
C2500 2,500,000
83
53,548
10
6,452
3.5.3
Flue Venting
This boiler is not certified for use with Type "B" vent nor with CPVC/PVC venting.
This boiler is a Category IV appliance (condensing – positive pressure) as it is defined in ANSI Z21.13/CSA 4.9, latest
edition. The vent material must be as listed in the Table of Acceptable Materials for Venting Systems above. The
exhaust vent can be run horizontally or vertically.
Vent installations shall be in accordance with NFPA54/ANSI Z223.1, the
National Fuel Gas Code
, or CAN/CSA-
B149.1, the
Natural Gas and Propane Installation Code
, or applicable provisions of the local building codes.
3.5.3.1 VENT
SIZING
The vent must be sized in accordance with the ASHRAE Systems and Equipment handbook, Chapter 30 or according
to the vent manufacturer’s recommendations. When using manufactured venting systems, consult your vent supplier
for correct sizing and structural support requirements.
