Venting Installation, Typical B-Vent Configuration

VENTING INSTALLATION

A B-type venting system must be connected to the appliance for venting to the outside of the building.

The following section is provided as a guide to a standard B-type vent installation.

Standing codes requirements concerning B-type vent installations may vary within your state, province or local codes jurisdiction. Therefore, it is recommended that you check with your local building codes for specific requirements or in absence of local codes, follow Section 7.0 of the current National Fuel Gas Code ANSI Z223.1/NFPA 54 and in Canada with CAN/CGA B149 for Category I systems using double wall B-1 vent pipe.

This gas appliance must be vented to the outdoors only and may not be terminated into an attic space or into a chimney flue servicing a solid-fuel burning appliance.

This appliance may be vented through a manufactured chimney system or a masonry chimney using a B-vent adapter or a chimney liner system if all are listed, inspected and approved by local codes and/or building authorities.

The examples shown in Figure 10 are typical of most B-vent installations and codes practices.

Example 1: Shows the minimum allowable system height and lateral offset for a 60° degree or greater inclination. Code specifies that offsets at 60° degrees or greater are considered horizontal and must follow the 75% percent rule for lateral to total vertical system height. Codes also allows only one offset in the total system when at 60° degrees or greater. The total vertical height in this example represents the minimum height of 8 feet and therefore the allowable lateral is 6 feet when the 75% percent rule applies. If the lateral length must exceed 75% then the system must be sized in accor- dance with the Category I venting tables.

Example 2: Shows a multiple offset each at 45° degrees of inclination. Multiple offsets are permitted if they do not exceed 45° degrees of inclination. The total lengths of the two offsets are not required to meet the 75% percent allowable rule.

Example 3: Shows a single offset at 45° degrees of inclination and therefore the lateral length at 10 feet of offset does not have to meet the 75% percent rule.

In each case the offsets must be supported and firestops must be positioned wherever the vent must pass through a sub-floor, ceiling joist or an attic overhang. The vent pipe must terminate vertically into a listed type vent cap and extend a sufficient height through an approved roof flashing, roof jack or a roof thimble. At all points the listed clearances must be maintained.

		Listed
		Vent Cap			Listed	Listed
					Vent Cap	Listed
					Vent Cap	Vent Cap
						Vent Cap
	Maintain		Maintain
	Maintain		Listed				Maintain
	Listed		Listed				Maintain
	Listed		Clearance		Maintain		Listed
	Clearance		Clearance		Maintain		Listed
	Clearance		Support Each		Listed		Clearance
			Support Each		Listed		Clearance
			Lateral At		Clearance
			Least Every	45°
		60°	Six (6) Feet	45°	12' Min.
		60°
	8'					45°	10'
	8'	6'				45°	10'
12' Min.	Position	6'		45°	Position		12' Min.
12' Min.	Position		Position	45°	Position		12' Min.
	Firestop		Firestop		Firestop
	Firestop		Firestop
		Maintain		Maintain			Maintain
		Listed		Listed			Listed
		Clearance		Clearance			Clearance