DOMINATOR INSTALLATION AND OPERATION INSTRUCTIONSPage 6
All Air From Outside The Building
When installed in a confi ned space without utilizing
the intake air option two permanent openings
communicating directly with, or by ducts to, the outdoors
or spaces that freely communicate with the outdoors
must be present. The upper opening must be within 12
in, 305 mm of, but not less than 3 in, 76 mm from, the
top of the enclosure. The bottom opening must be within
12 in, 305 mm of, but not less than 3 in, 76 mm from,
the bottom of the enclosure.
Where directly communicating with the outdoors or
communicating with the outdoors through vertical ducts,
each opening shall have a minimum free area of 1 in
2
/
4000 Btu/hr, 550 mm
2
/kW of the total input rating of all
of the equipment in the enclosure.
Where communicating with the outdoors through hori-
zontal ducts, each opening shall have a minimum free
area of 1 in
2
/2000 Btu/hr, 1100 mm
2
/kW of the total input
rating of all of the equipment in the enclosure. When ducts
are used, they must have the same cross-sectional area
as the free area of the opening to which they connect.
When calculating the free area necessary to meet the
make-up air requirements of the enclosure, consideration
must be given to the blockage effects of louvers, grills and
screens. Screens must have a minimum mesh size of
1/4 in, 6.4mm. If the free area through a louver or grill is
not known, ducts should be sized per Table 3.
Table 3 - Make-up Air Louver Sizing
Required Cross Sectional Area
Input 1/4 in 6.4 mm
75% Free Area
25% Free Area
(MBH) Wire Screen
Metal Louvers
Wooden Louvers
in
2
cm
2
in
2
cm
2
in
2
cm
2
300 75 484 100 645 300 1935
400 100 645 133 860 400 2581
600 150 968 200 1290 600 3871
750 188 1210 250 1613 750 4839
900 225 1452 300 1935 900 5806
1050 263 1694 350 2258 1050 6774
1350 338 2177 450 2903 1350 8710
1500 375 2419 500 3226 1500 9677
1950 488 3145 650 4194 1950 12,581
2100 525 3387 700 4516 2100 13,548
Canadian installations must comply with CSA B149.1
when air supply is provided by natural air fl ow from
the outdoors for natural draft, partial fan-assisted, fan-
assisted, or power draft-assisted burners, there shall
be a permanent air supply opening(s) having a cross-
sectional area of not less than 1 in
2
per 7,000 Btuh
(310 mm
2
per kW) up to and including 1 million Btuh,
plus 1 in
2
per 14,000 Btuh (155 mm
2
per kW) in excess
of 1 million Btuh.
Intake Air Option - General Guidelines
This confi guration provides combustion air directly to the
boiler/water heater's air intake using a dedicated pipe
to obtain combustion air from the outdoors. Combustion
air can be drawn in horizontally through the same
outside wall which terminates the exhaust gases or
vertically through the roof, see Figures 4, 5, 6 & 7.
WARNING: Common intake air systems may be
used provided the common duct is sized properly
and an intake combustion air damper is installed
in the intake air pipe of each heater. Improper
installation can result in excessive levels of carbon
monoxide which can cause severe personal injury
or death!
Single wall galvanized smoke pipe, single wall aluminum
pipe or fl exible aluminum pipe can be used for the intake
air pipe. It must be sized per Table 4. All joints in metal
combustion air systems must be secured using
corrosion resistant fasteners and sealed using a suitable
Silicone caulk. The combustion air system MUST be
supported by the building structure not the boiler/
water heater.
Table 4 - Intake Air Pipe Sizing
Model Size Pipe Diameter
in
mm
300 & 400 6 152
600 & 750 8 203
900 & 1050 10 254
1350 - 2100 12 305
CAUTION: A stack damper interlocked with the unit
should be installed in the intake air pipe when the
infi ltration of sub-freezing air could occur, otherwise
the unit could freeze up voiding the warranty!
Intake Air Option - Horizontal Guidelines
The maximum equivalent length for the horizontal
combustion air pipe on installations that used the Direct
Vent option is 35 ft, 10.8 m. The maximum equivalent
length for the horizontal combustion air pipe on
installations that use the Horizontal Power Vent option is
100 ft, 30.5 m. Each 90° elbow and the combustion air
terminal are equal to 10 linear ft, 3.0 m of pipe. If
horizontal runs exceed 5 ft, 1.5 m they must be supported
at 3 ft, 0.9 m intervals with overhead hangers. The
certifi ed combustion air terminal from RBI must be used
and installed as shown in Figures 4 and 5.
Intake Air Option - Vertical Guidelines
The maximum length for the vertical combustion air pipe
is 30 ft, 9.1 m plus two 90° elbows. A listed,
nonrestrictive combustion air cap must be used. The
combustion air cap must terminate as shown in Figure
6. The penetration point in the roof must be properly
fl ashed and sealed.
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