Bosch NG Installation And Operating Instructions Manual page 6

Appliances located in unconfined spaces:
a) An unconfined space is one whose volume is greater
than 50 cubic feet per 1000 Btu per hour of the combined
rating of all appliances installed in the space. That would
be 2000 cubic feet for the AquaStar 38B alone.
b) In unconfined spaces in buildings of conventional frame,
masonry, or metal construction, infiltration is normally
adequate to provide air for combustion, ventilation, and
dilution of flue gasses.
Identification labels are found on the shipping box, and on
the rating plate which is located on the right side panel of
the cover. Also, each burner orifice is stamped with a number
(79 for LPG and 120 for Natural Gas).
5 ½"
Fig. 1 - Mounting the Heater
6
WALL STUDS
SUPPORT BOARD
1" X 4"
SPACE BOARD
6 720 606 446