Rheem Gas Domestic Indoor Water Heater Installation And Owner's Manual page 22

INSTALLATION
SECONDARY FLUE
A secondary flue must be installed with an indoor water heater to discharge
combustion products outside the building.
The water heater is supplied with a draught diverter and adaptor assembly,
designed to receive a 75 mm diameter flue.
Remove the draught diverter and adaptor assembly from the protective
packaging.
Fit the assembly by inserting the tabs on the legs of the draught diverter into
the slots in the top of the water heater.
The secondary flue must:
be seated inside of the adaptor of the draught diverter.
be self supporting and not impose a load on the water heater.
use a slip joint or similar to allow for disconnection.
be designed to run vertically for the maximum possible distance, and not
less than 600 mm, before any change of direction.
The flue design and installation must comply with AS 5601 or AS/NZS 5601.1.
VENTILATION
The ventilation of a room or an enclosure such as a cupboard, where the water
heater is installed must comply with AS 5601 or AS/NZS 5601.1.
If the water heater is installed in a room or an enclosure, where the total
thermal input of the water heater and any other gas burning appliance(s)
exceeds 3 MJ / h for each cubic metre of room or enclosure volume, an
adequate air supply must be provided.
For efficient water heater operation allow two permanent openings into the
room or enclosure, each of at least:
2
15,000 mm for a 25 MJ model
2
18,000 mm for a 30 MJ model
The distance between the top of the upper opening and the ceiling and the
distance between the bottom of the lower opening and the floor must not
exceed 5% of the total height of the room or enclosure.
The water heater must not be installed in an area with a corrosive atmosphere
where chemicals are stored or where aerosol propellants are released.
Remember the air may be safe to breathe, but when it goes through a flame,
chemical changes take place which may attack the water heater.
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