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Air Filter
An air filter is supplied standard with the heater. This
filter is shipped loose for field installation. Refer to the
Air Filter Kit Installation Instructions (Part No. 241338)
for details.
Fig. 8: Air Filter Box
Direct Vent
If outside air is drawn through the intake pipe directly
to the unit for combustion:
1. Install combustion air direct vent in accordance
with Fig. 33 (horizontal) or Fig. 34 (vertical) of this
manual (pages 31 and 32, respectively).
2. Ventilation of the space occupied by the heater(s)
is recommended and can be provided by an open-
ing(s) for ventilation air at the highest practical
point communicating with the outdoors. The total
cross-sectional areas should be at least 1 in.² of
free area per 20,000 BTUH (111 mm² per kW) of
total input rating of all equipment in the room,
when the opening is communicating directly with
the outdoors or through vertical duct(s). The total
cross-sectional area should be at least 1in.² of free
area per 10,000 BTUH (222 mm² per kW) of total
input rating of all equipment in the room, when the
opening is communicating with the outdoors
through horizontal duct(s). Damage to the equip-
ment due to inadequate ventilation of the space is
not a warrantable failure.
3. In cold climates, and to mitigate potential freeze-
up, Raypak highly recommends the installation of
a motorized sealed damper to prevent the circula-
tion of cold air through the heater during the
non-operating hours.
Motorized Combustion Air Dampers or
Louvers
When dampers or louvers are communicating directly
with outside combustion air, they must be interlocked
with each appliance in the equipment room, to ensure
proper operation. See field wiring connection section
of this manual for proper wiring instructions, using
Fan/Damper dry contacts and external interlock.
TruSeal™ Combustion Air
In addition to the 3 previous steps, combustion air may
be ducted directly to the heater by using PVC, CPVC
or sealed single-wall galvanized ducting. The duct will
attach directly to the air collar located on the inline Air
Filter Box (shipped loose), using 3-4 sheet metal
screws (not supplied) equally positioned around the
circumference of the duct. The screen assembly
should be removed before attaching any air duct. The
screws and duct connection point must be sealed with
RTV (not supplied). TruSeal is generally used when
damaging contaminants are present in the mechanical
room.
All ducting MUST be self-supported.
Conventional Combustion Air
Supply
CAUTION: Use TruSeal combustion air if
damaging airborne contaminants are or may be
present in the heater area. See the Appendix of this
manual regarding air contamination.
U.S. Installations
All Air from Inside the Building
The confined space shall be provided with TWO per-
manent openings communicating directly with an
additional room(s) of sufficient volume so that the com-
bined volume of all spaces meets the criteria for a
room large in comparison (NFGC). The total input of all
gas utilization equipment installed in the combined
space shall be considered in making this determina-
tion. Each opening shall have a minimum free area of
1 in.
per 1,000 BTUH (2,225 mm
2
input rating of all gas utilization equipment in the con-
fined space, but not less than 100 in.
opening shall commence within 12 in. (305 mm) of the
top, and one opening shall commence within 12 in.
(305 mm) of the bottom of the enclosure. The mini-
mum dimension of air openings shall be not less than
3 in. (76 mm) in any direction.
11
per kW) of the total
2
(645 cm
). One
2
2
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