Rheem Gra Series Installation Instructions Manual page 18

Method 2
(Not Shown)
One permanent opening, located
within 12 inches of the top of the
enclosure, shall be permitted
where the equipment has
clearances of at least 1 inch from
the sides and back and 6 inches
from the front of the appliance.
The opening shall directly
communicate with the outdoors or
communicate through a vertical or
horizontal duct to the outdoors or
spaces (crawl or attic) that freely
communicate with the outdoors,
and shall have a minimum free
area of:
a. 1 square inch for each 3,000
BTUH of the total input rating of all
equipment located in the enclosure
and
FIGURE 14
COMBUSTION AIR FITTING
ATTACH DOUBLE ELBOW TO TOP INLET
AIR OPENING OR 90° ELBOW TO SIDE
INLET AIR OPENING TO PREVENT
ACCIDENTAL BLOCKAGE OF INTAKE
OPENING. PLUG OPENING NOT USED.
EXHAUST
18 18
BTUH
Input
45,000
60,000
75,000
90,000
105,000
120,000
b. Not less than the sum of the
areas of all vent connectors in the
confined space.
If unit is installed where there is an
exhaust fan, sufficient ventilation
must be provided to prevent the
exhaust fan from creating a negative
pressure.
Combustion air openings must not be
restricted in any manner.
CONSULT LOCAL CODES FOR
SPECIAL REQUIREMENTS.
UPFLOW
2" PVC
DOUBLE
ELBOW
TOP
OPTION
2" PVC ELBOW
SIDE
OPTION
I337
Free Area Round Pipe
Each Opening Size
15.00 square inches 4"
16.67 square inches 5"
25.00 square inches 6"
30.00 square inches 6"
35.00 square inches 7"
40.00 square inches 7"
DOWNFLOW/HORIZONTAL
2" PVC
DOUBLE
ELBOW*
COMBUSTION AIR
*NOTE: WHEN FURNACE IS INSTALLED IN A
HORIZONTAL POSITION ONLY ONE 90°
ELBOW IS REQUIRED. INSTALL THE ELBOW
SO THE OPEN END IS POINTED DOWNWARD.
CONNECTION TO
FURNACE
IMPORTANT: When indoor
combustion air is used, the inlet air
opening at the furnace must be
protected from accidental blockage.
On upflow models, install a 90° elbow
pointing downward in the side inlet air
opening or a double elbow pointing
downward in the top inlet air opening.
On downflow/horizontal models,
install a double elbow in the top inlet
air opening. See Figure 14.
ATTACH DOUBLE ELBOW TO INTAKE AIR
COLLAR AND SECURE WITH TWO SHEET
METAL SCREWS TO PREVENT ACCIDENTAL
BLOCKAGE OF INTAKE AIR OPENING.
EXHAUST
I336