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Combustion air and vent system requirements – A.O. Smith 12 40GPC T 100 User Manual

Page 10

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• The connector must be firmly attached and

sealed to prevent it from falling out.

• To aid in removing the connector, a thimble or

slip joint may be used.

• The connector must not extend beyond the

inner edge of the chimney as it may restrict

the space between it and the opposite wall of

the chimney

Chimney Termination Vent System

Seal

Do Not Extend

Vent Beyond Edge

Of Chimney

Maintain

Clearance*

Support Strap

3 FT.

Minimum

2 FT. Minimum Above Any Object

Within 10 FT. Horizontally

Slope Up

1/4 Inch

Per Foot

Minimum

Vent

Connector

Figure 8.

Do not reduce the vent to less than the draft

hood outlet diameter. Do not terminate the vent

connector in a chimney that has not been certified

for this purpose. Some local codes may prohibit

the termination of vent connectors in a masonry

chimney.
Vertical Exhaust Gas Vent: Vertical exhaust

gas vents must be installed with U.L. listed type

B vent pipe according to the vent manufacturer’s

instructions and the terms of its listing.
It must be connected to the water heater’s draft

hood by a listed vent connector or by directly

originating at the draft hood opening.
Vertical gas vents must terminate with a listed cap

or other roof assembly and be installed according to

their manufacturer’s instructions.
Gas vents must be supported to prevent damage,

joint separation, and maintain clearances to

combustible materials.
IMPORTANT: This gas vent must be terminated in a

vertical position to facilitate the removal of the burnt

gases.
An unused chimney fl ue or masonry enclosure

may be used as a passageway for the installation

of a gas vent. NOTE: The chimney fl ue or masonry

enclosure size may be too large to allow proper

venting.
Common (combined) venting is allowable with

vertical type B vent systems and lined masonry

chimneys as long as proper draft for the water

heater is established under all conditions of

operation. CAUTION: DO NOT common vent this

water heater with any power vented appliance.

The following fi gures are examples of vent pipe

system installations and may or may not be typical

for your specifi c application. Consult the “National

Fuel Gas Code”, NFPA 54, ANSI Z223.1-current

edition and the guidelines set forth by prevailing

local codes.

Maintain

Clearance*

Support Strap

3 FT.

Minimum

Vent

Connector

Slope Up

1/4 Inch

Per Foot

Minimum

**Maintain

Specified

Clearance

Venting Gas Vent System With Type B Double Wall Vent Pipe.

2 FT. Minimum Above

Any Object Within

10 FT. Horizontally

Type B Double
Wall Vent Pipe

Figure 9.

Consult the table found in the “National Fuel Gas

Code”, NFPA 54, ANSI Z223.1-current edition to

determine the minimum height from roof to lowest

discharge opening.

Seal

Maintain

Clearance*

Support Strap

Specified Minimum Clearance

Vent

Connector

Slope Up

1/4 Inch

Per Foot

Minimum

Vent Connector

**Maintain

Specified

Clearance

Venting Through Chimney With Type B Double Wall Vent Pipe.

Unused Chimney

Flue Or Masonry

Enclosure

Maintain Manufacturer’s

Listed Vent Cap

Figure 10.

* Maintain vent pipe clearance requirements to local,

state and/or the “National Fuel Gas Code”, ANSI

Z223.1(NFPA 54)-current edition.

** NFPA 211, Standard for Chimneys, Fireplaces,

Vents, and Solid Fuel-Burning Appliances states

that these chimneys are intended to be installed

in accordance with the installation instructions

provided with each chimney support assembly.

Minimum air space clearance to combustible

materials should be maintained as marked on the

chimney sections.

COMBUSTION AIR AND VENT SYSTEM REQUIREMENTS

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