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SECTION C: Installation
10
CAUTION: Combustion air must not be contaminated
by corrosive chemical fumes which can damage the
heater and void the warranty. (See Section H.)
NOTICE: It is recommended that the intake vent be
insulated to minimize sweating.
Optional Construction Air Filter
An optional construction air filter is available for use.
The filter should be removed after construction is fin-
ished to allow for unrestricted air flow to the heater.
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. 24 (horizontal) or Fig. 25 (vertical) of
this manual (pages 26 & 27 respectively).
2. Provide adequate ventilation of the space occupied
by the heater(s) by an opening(s) for ventilation air
at the highest practical point communicating with
the outdoors. The total cross-sectional area shall be
at least 1 in.
2
of free area per 20,000 BTUH (111
mm
2
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 shall be at
least 1 in.
2
of free area per 10,000 BTUH (222
mm
2
per kW) of total input rating of all equipment
in the room when the opening is communicating
with the outdoors through horizontal duct(s).
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 non-
operating hours.
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 rear of the
heater, using three or four sheet metal screws (not sup-
plied) equally positioned around the circumference of
the duct. The screen assembly should be removed be-
fore attaching any air duct to the heater. The screws
and duct connection point must be sealed with RTV
(not supplied). TruSeal is generally used when damag-
ing contaminants are present in the mechanical room.
All ducting should be self-supported.
CAUTION: Use TruSeal combustion air if damaging
airborne contaminants are or may be present in the
heater area. See Section H of this manual regarding air
contamination.
Conventional Combustion Air Supply
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
combined 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 determination.
Each opening shall have a minimum free area of 1 in.
2
per 1,000 BTUH (2,225 mm
2
per kW) of the total input
rating of all gas utilization equipment in the confined
space, but not less than 100 in.
2
(645 cm
2
). One open-
ing 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 minimum
dimension of air openings shall be not less than 3 in.
(76 mm) in any direction.
All Air from Outdoors
The confined space shall communicate with the out-
doors in accordance with one of the methods below.
The minimum dimension of air openings shall not be
less than 3 in. (76 mm) in any direction. Where ducts
are used, they shall be at least of the same cross-
sectional area as the net free area of the openings to
which they connect.
1. Two permanent openings, one commencing
within 12 in. (305 mm) of the top, and one com-
mencing within 12 in. (305 mm) of the bottom of
the enclosure, shall be provided. The openings
shall communicate directly, or by ducts, with the
outdoors or spaces (crawl or attic) that freely
communicate with the outdoors.
a. Where directly communicating with the out-
doors or where communicating to the outdoors
through vertical ducts, each opening shall
have a minimum free area of 1 in.
2
per 4,000
BTUH (550 mm
2
per kW) of total input rating
of all equipment in the enclosure.