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Combustion Air
• Provide two permanent openings to allow
circulation of combustion air.
• Make each opening 194 square inches if they
provide indoor air, and 100 square inches for
outdoor air.
• If the unit is installed in a mechanical closet,
provide a 24" clearance in front of the unit to
the door.
• If combustion air will be provided through a
duct, size the duct to provide 60 cubic feet of
fresh air per minute.
8.
Gas Piping
The appliance and its individual shutoff valve must be disconnected from the gas supply piping system
during any pressure testing of that system at test pressures in excess of
The Appliance must be isolated from the gas supply piping system by closing its individual manual shutoff
valve during any pressure testing of the gas supply piping system at test pressures equal to or less than
psig (3.5 kPa).
The appliance and its gas connections must be leak tested before placing the appliance in operation.
The inlet gas pressure must be within the range specified. This is for the purposes of input adjustment.
In order to choose the proper size for the gas line, consult local codes or the National Fuel Gas Code ANSI
Z223.1.
Gas Pressure
Size the gas line according to total btuh demand
of the building and length from the meter or
regulator so that the following supply pressures
are available even at maximum demand:
Natural Gas Supply Pressure
Min. 5" WC
Max. 10.5" WC
LP Gas Supply Pressure
Min. 10.5" WC
Max. 14" WC
Supply combustion air to the units as per the National Fuel Gas Code, ANSI Z223.1.
10"
20"
20"
10"
Openings supplying indoor air
Follow the instructions from the gas supplier.
1
⁄
Gas Meter
Select a gas meter capable of supplying the entire
btuh demand of all gas appliances in the building.
Gas Connection
• Do not use piping with a diameter smaller than
the inlet diameter of the water heater.
• Gas flex lines are not recommended unless they
are rated for 194,000 btuh.
• Install a gas shutoff valve on the supply line.
• Use only approved gas piping materials.
psig (3.5 kPa).
2
1
⁄
2
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