5
Finned copper tube gas boilers & water heaters – Boiler manual
FTXLF-IOM-HN-1-110308 Copyright 2008 Mestek, Inc.
Never operate the Futera XLF in an environment
subjected to a negative pressure unless it is Direct
Vented. Failure to comply with this warning can result
in excessive levels of carbon monoxide causing severe
personal injury or death!
All air from inside the building
If the Futera XLF is to be located in a confined space, the minimum
clearances listed in Table 1, page 4 must be maintained between it
and any combustible construction. When installed in a confined
space without the intake air option (as in Figure 5, page 10 through
Figure 8, page 13) two permanent openings communicating with
an additional room(s) are required. The combined volume of
these spaces must have sufficient volume to meet the criteria for
an unconfined space. The total air requirements of all gas utiliza-
tion equipment, fireplaces, wood stoves or any type of exhaust
fan must be considered when making this determination. Each
opening must have a minimum free area of 1 in
2
/1000 Btu/hr,
2200 mm
2
/kW based on the total input rating of ALL gas utilization
equipment in the confined area. Each opening must be no less than
100 in
2
, 64,516 mm
2
in size. The upper opening must be within
12 inches, 305 mm of, but not less than 3 inches, 76 mm from, the
top of the enclosure. The bottom opening must be within 12 inches,
305 mm of, but not less than 3 inches, 76 mm from, the bottom of
the enclosure.
All air from outside the building
When installed in a confined 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 inches, 305 mm of, but not less than 3 inches, 76 mm from, the
top of the enclosure. The bottom opening must be within 12 inches,
305 mm of, but not less than 3 inches, 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 horizontal 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 inch, 6.4 mm. If the free area through a
louver or grill is not known, ducts should be sized per Table 2.
Canadian installations must comply with CSA B149.1 when air sup-
ply is provided by natural air flow 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.
Make-up Air Louver Sizing
table 2
Input
MBH
Required cross-sectional area
Wire screen
¼ inch (6.4 mm)
Metal louvers
75% free area
Wooden louvers
25% free area
in
2
cm
2
in
2
cm
2
in
2
cm
2
3000
750
4838
1000
6452
3000
19354
4000
1000
6452
1334
8592
4000
25808
intake air option — General guidelines
This configuration provides combustion air directly to the boiler/
water heater’s air intake adapter using a dedicated pipe when using
the direct vent option. Combustion air can be drawn in horizontally
through the same outside wall which terminates the exhaust gases
or vertically through the roof, see Figure 1, page 8 through Figure 4,
page 9.
Common intake air systems may be used provided the
common duct is sized properly. An intake combustion
air damper should be installed if the common vent
option is used 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!
Intake air pipe sizing
table 3
Input
MBH
Vertical
Horizontal
in
mm
in
mm
3000
10
254
8
203
4000
12
305
10
254
All joints in metal intake air systems must be secured using
corrosion resistant fasteners and sealed using a suitable Sili-
cone caulk. If PVC or CPVC is used, the joints must be
cleaned with a suitable solvent and connected using a solvent based
PVC cement.
The combustion air system MUST be supported by the
building structure not the boiler/water heater.
A combustion air damper interlocked with the unit
should be installed in the intake air pipe when the
infiltration of subfreezing air could occur, otherwise
the unit could freeze up voiding the warranty!
intake air option – Vertical guidelines
The maximum equivalent length for the vertical intake air pipe is
100 ft, 30.5 m. Each 90
o
elbow and the intake air terminal are equal
to 10 linear ft, 3.0 m of pipe, see Table 3.
An approved, nonrestrictive intake air terminal must be used. The
intake air terminal must terminate as shown in Figure 3, page 9. The
penetration point in the roof must be properly flashed and sealed.
