Vent Pipe Size, Vent Connectors | A.O. Smith 315456-002, GAHH-40

Align the legs of the draft hood with the slots provided. Insert the legs and secure the draft hood to the water heater’s top with the four screws provided as shown in Figure 9. Do not alter the draft hood in any way. If you are replacing an existing water heater, be sure to use the draft hood supplied with this water heater.

Vent Pipe Size

It is important that you follow the guidelines in these instructions for sizing a vent pipe system. If a transition to a larger vent size is required, the vent transition connection must be made at the draft hood outlet.

Vent Connectors

1.Type B, Double wall, U.L. Listed Vent Pipe.

2.Single wall Vent Pipe.

Maintain the manufacturer’s specified minimum clearance from combustible materials when using type B double wall vent pipe.

Vent connectors made of type B, double wall vent pipe material may pass through walls or partitions constructed of combustible material if the minimum listed clearance is maintained.

Maintain a six inch minimum clearance from all combustible materials when using single wall vent pipe.

IMPORTANT: Single wall vent pipe cannot be used for water heaters located in attics and may not pass through attic spaces, crawl spaces or any confined or inaccessible location. A single wall metal vent connector cannot pass through any interior wall.

When installing a vent connector, please note the following (See Figures 10-12):

•Install the vent connector avoiding unnecessary bends, which create resistance to the flow of vent gases.

•Install without dips or sags with an upward slope of at least 1/4-inch per foot.

•Joints must be fastened by sheet metal screws or other approved means. It must be supported to maintain clearances and prevent separation of joints and damage.

•The length of the vent connector cannot exceed 75% of the vertical vent height.

•The vent connector must be accessible for cleaning, inspection, and replacement.

•Vent connectors cannot pass through any ceiling, floor, firewall, or fire partition.

•It is recommended (but not mandatory) that a minimum 12 inches of vertical vent pipe be installed on the draft hood prior to any elbow in the vent system.

IMPORTANT: Existing vent systems must be inspected for obstructions, corrosion, and proper installation.

Chimney Connection

IMPORTANT: Before connecting a vent to a chimney, make sure the chimney passageway is clear and free of obstructions. The chimney must be cleaned if previously used for venting solid fuel appliances or fireplaces. Also consult local and state codes for proper chimney sizing and application or, in the absence of local and state codes, the “National Fuel Gas Code”, ANSI Z223.1(NFPA 54)-current edition.

•The connector must be installed above the extreme bottom of the chimney to prevent potentially blocking the flue gases.

•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 (Figure 10).

FT.

2 FT. Minimum Above Any Object

Within 10 FT. Horizontally

Support Strap

Minimum

Maintain

Seal

Clearance*

Do Not Extend

Vent Beyond Edge

Of Chimney

Vent

Connector

Slope

1/4 Inch

Per Foot

Minimum

Chimney Termination Vent System

FIGURE 10.

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 (Figures 11 and 12).

IMPORTANT: This gas vent must be terminated in a vertical position to facilitate the removal of the burnt gases.

An unused chimney flue or masonry enclosure may be used as a passageway for the installation of a gas vent (Figure 12).

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.

Figures 10-12 are examples of vent pipe system installations and may or may not be typical for your specific application. Consult the “National Fuel Gas Code”, NFPA 54, ANSI Z223.1-current edition and the guidelines set forth by prevailing local codes.