Rheem GF901U Series Installation Instructions Manual page 27

COMBUSTION AIR FOR
DIRECT VENT
INSTALLATIONS
THE COMBUSTION AIR SYSTEM
DESIGNED FOR THIS FURNACE
MUST BE USED.
When this furnace is installed as a
direct vent forced air furnace, all
combustion air is supplied directly to
the burner through a special air inlet
system outlined in these instructions.
This system consists of field-supplied
Schedule 40 or 26 SDR-PVC pipe
and one of the following horizontal
vent termination kits: RXGY-D02,
RXGY-D03, RXGY-D04, or
RXGY-E03.
NOTE: Schedule 40 ABS-DWV pipe
and fittings may be used as an
alternate to PVC pipe for the
combustion air inlet and vent pipes.
The combustion air for this furnace is
supplied directly from the outdoors
through the combustion air inlet
system.
When the furnace is installed in the
same space with other gas
appliances, such as a water heater,
be sure there is an adequate supply
of combustion and ventilation air for
the other appliances. Do not delete or
reduce the combustion air supply
required by the other gas appliances
in this space. See Z223.1, National
Fuel Gas Code (NFPA54) for deter-
mining the combustion air
requirements for gas appliances. An
unconfined space must have at least
50 cubic feet (volume) for each
1,000 BTUH of the total input of all
appliances in the space. If the open
space containing the appliances is in
a building with tight construction
(contemporary construction), outside
air may still be required for the
appliances to burn and vent properly.
Outside air openings should be sized
the same as for a confined space.
STANDARD TERMINATIONS
STANDARD VERTICAL
TERMINATIONS
COMBUSTION AIR PIPING
Use two medium-radius sweep
elbows to keep the inlet downward to
prevent entry of rain. See Figure 22
for the proper relationship of
combustion air to exhaust
termination.
STANDARD HORIZONTAL
TERMINATIONS
COMBUSTION AIR PIPING
When 3-in. pipe is used between the
furnace and outside wall, reduce it
to 2 inches before penetrating the
wall. Up to 18 inches of 2-in. pipe
may be used inside the wall.
The standard horizontal intake air
termination for all models is a 2-in.
PVC coupling with a wind deflector
vane (provided) attached. Cut a
2 / -in. length of 2-in. PVC pipe.
1
4
Connect this pipe and another 2-in.
PVC coupling to the coupling at the
wall. The outer coupling must
terminate 4 inches from the wall. See
Figure 23, Detail B, for vane location.
Attach vane in vertical position with
PVC solvent.
IMPORTANT: To ensure proper
furnace operation, the supplied vane
must be installed in the vertical
position as shown in Figure 23, Detail
B.
The combustion air inlet terminal
must be located with respect to the
exhaust terminal as shown in Figure
23, Detail C.
IMPORTANT: All furnaces with
horizontal air intakes, except those
using concentric vent kit RXGY-E03,
must have a drain tee assembly and
trap installed as close to the furnace
as possible. This is to drain any water
that may be in the combustion air
pipe to prevent it from entering the
furnace combustion chamber.
These parts are included in kits
RXGY-D02 (for 2-in. pipe), RXGY-
D03 (for 3-in. pipe) and RXGY-D04
(special for the 120,000 BTU furnace
installed with the alternate horizontal
termination). Attach the trap to the
bottom of the tee with PVC solvent.
Connect the other end to a suitable
drain, as to the downstream of a
condensate trap on the furnace.
STANDARD VERTICAL
TERMINATIONS
EXHAUST VENT PIPING
Vertical through-the-roof vent
applications do not require an
exhaust terminal. The exhaust vent
must terminate at least 12 inches
above the combustion intake air
termination. The exhaust vent for
models with inputs of 90,000 through
120,000 BTUH is 2-in. PVC pipe
120,000 BTUH models with
excessively long runs require 2
Refer to Table 2 for proper
application. This must
be reduced to 1" or 1
12 inches for models with inputs of
45,000 through 75,000 BTUH.
See Figure 26.
STANDARD HORIZONTAL
TERMINATIONS
EXHAUST PIPING
For direct vent systems the standard
termination is 2-in. PVC pipe
extending 12 inches from the wall for
furnaces with inputs from 105,000 to
120,000 BTUH. Install a 2-in. coupling
at the outside wall to prevent the
termination from being pushed
inward. When 3-in. pipe is used
between the furnace and outside wall,
reduce to 2 inches before penetrating
the wall. The standard termination is
1 / -in. PVC pipe extending outward
1
2
12 inches from the wall for models
with inputs of 45,000 to 75,000
BTUH. Install a 2-in. to 1
coupling at the outside wall to prevent
pushing the termination back into the
wall. See Figure 23, Detail B.
The combustion air and exhaust
terminations must be at least 12
inches above grade and must be
oriented with respect to each other as
shown in Figure 23. Refer to section
on alternate venting options when
higher snow levels are anticipated.
ALTERNATE
TERMINATIONS
ALTERNATE HORIZONTAL
DIRECT VENT TERMINATIONS
KIT NOS. RXGY-D02, -D03
AND -D04
The combustion air and exhaust
terminations may be raised a
maximum of 60 inches above the
wall penetration to maintain the
required 12 inch clearance above
grade or snow level. See Figure 18.
Size the pipe length according to
Table 2.
IMPORTANT: The following
guidelines must be met when
extending beyond 24 inches of pipe
on the exterior of the structure:
• Size the entire vent system
according to the alternate, not
standard, termination shown in
Table 2.
1 / ".
2
1 / " the last
2
/ -in.
1
2
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