Navien NR-180(A) Operation & Installation Manual page 41

The additional safety issues outlined below must also be followed
completely when installing this Navien Water Heater:
Vent terminal should not be pointing toward any opening of the building or
windows. Do not install the Water Heater in crevices to prevent gas from
accumulating.
Prevent debris, liquid or flammable gas from entering the Water Heater
intake air pipe terminal. It may cause damage to the Water Heater and
warranty will be avoided.
Install the Water Heater outdoor under the overhang with 3 feet or more
from the eaves to the top of the Water Heater vent terminal. Water heater
must have open space around all 3 sides.
Water heater vent terminal should be 1ft(united state)/3ft(Canada) or more
from windows and doors (refer to P35)
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