Bosch GWH 425 EF - Manual (Page 4)

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MINIMUM INSTALLATION CLEARANCES FROM COMBUSTIBLE AND NON
COMBUSTIBLE MATERIALS FOR ALCOVE OR CLOSET INSTALLATIONS
FRONT VIEW SIDE VIEW
MODEL 425 EF
* On a combustible wall surface the unit should be mounted away
from the wall to provide adequate clearance of the vent pipe.
See page 5 for instructions.