Thomas & Betts RGM 405 Vent Pipe and Joints, Venter Flue Outlet, Vent Pipe Diameter and Length

7. Venting and Combustion Air (cont'd)

7B. Venting and Combustion Air Requirements for Power Vent Drawing Combustion Air from THE INSIDE SPACE and Venting Flue Products to the Outdoors (vent cap is required)

If the environment has a positive pressure and is such that it is not detrimental to combustion air, this system may be installed. To provide combustion air to the heater sufficient air must enter the equipment location to replace that exhausted through the heater vent system. In the past, the infiltration of outside air assumed in heat loss calculations (one air change per hour) was assumed to be sufficient. However, current construction methods using more insulation, vapor barriers, tighter fitting and gasketed doors and windows, weather-stripping, and/or mechanical ex- haust fans may now require the introduction of outside air through wall openings or ductwork to the equipment room.

The requirements for combustion and ventilation air depend upon whether the unit is located in a confined or unconfined space. An "unconfined space" is defined as a space whose volume is not less than 50 cubic feet per 1000 BTUH of the installed appliance. Under all conditions, enough air must be provided to ensure there will not be a negative pressure condition within the equip- ment room or space. Follow the specific requirements below for a confined space installation.

Confined Space Installation - Do not install a unit in a con- fined space without providing wall openings leading to and from the space. Provide openings near the floor and ceiling for ventila- tion and air for combustion as shown in Figure 7, depending on the combustion air source as noted in Items 1, 2, and 3 below.

Figure 7 - Confined Space:

A space whose volume is less than 50 cubic feet per 1000 BTUH of the installed appliance input rating

Add total BTUH of all appliances in the confined space and divide by figures below for square inch free area size of each (top and bottom) opening.

1.Air from inside the building -- openings 1 square inch free area per 1000 BTUH. Never less than 100 square inches free area for each opening. See (1) in Figure 7.

2.Air from outside through duct -- openings 1 square inch free area per 2000 BTUH. See (2) in Figure 7.

3.Air direct from outside -- openings 1 square inch free area per 4000 BTUH. See (3) in Figure 7.

NOTE: For further details on supplying combustion air to a confined space, see the National Fuel Gas Code ANSI Z223.1a (latest edition).

Specific Venting Requirements (read all

before installing)

1) Venter (Flue) Outlet
Venter
	Model Size	150, 200, 250	300, 350, 400
Outlet
	Outlet Diameter	5"	6"
Size:
Venter Outlet Attachment Requirements:

•A minimum of 12" of straight pipe is required at the venter outlet before installing an elbow in the vent system. An elbow should never be attached directly to the venter. An elbow attached to the straight pipe can be in any position at or above horizontal. See Figure 8.

Figure 8 - Alternate

Vent in any	Vent Directions
position above
horizontal

A minimum of 12" of straight pipe is required before an elbow

•Do not install dampers or any other type of flue restrictor device.

2)Vent Pipe Diameter and Length

Maximum Vent Length - minimum length is 5 ft (1.5M)

CAUA	Pipe	Maximum		90° Elbow			45° Elbow
	Diameter		Length		Equals*		Equals*
150-250	5"	50	ft (15.2M)	5	ft	(1.5M)	2.5	ft (.8M)
300-400	6"	50	ft (15.2M)	5	ft	(1.5M)	2.5	ft (.8M)

*Reduce by this amount for each elbow.

Note: If the system contains all vertical pipe or a combination of horizontal and vertical vent pipe, the Maximum Permissible Vent Length may be in- creased one foot (305mm) for each foot (305mm) of vertical rise up to a maximum increase of ten feet (3M).

3)Vent Pipe and Joints

Provide field-supplied vent pipe as specified in the Table on page 4.

•If using single wall, 26-gauge or heavier galvanized pipe, secure slip-fit connections using sheet metal screws or rivets. Seal pipe joints either with tape suitable for 550°F (such as Option FA1, P/N 98266) or high-tem- perature silicone sealant.

•If using Category III vent pipe, follow pipe manufacturer's instructions for joining pipe sections. When attaching Category III pipe to the venter outlet or the vent cap, make secure, sealed joints following a procedure that best suits the style of Category III pipe being used.

•If using double-wall (Type B) vent pipe (at least 1/2 of the equivalent vent length must be vertical), follow pipe manufacturer's instructions for join- ing pipe sections. For joining double-wall pipe to the venter outlet collar, single-wall pipe, and/or the vent cap, follow the instructions below:

Instructions for attaching double-wall (Type B) vent pipe to the ven- ter outlet, a single-wall pipe run, or to the vent cap (use these in- structions for either full length double-wall or terminal only):

Hardware and Sealant Required: 3/4" long sheetmetal screws; and a tube of high temperature silicone sealant

1)Look for the "flow" arrow on the vent pipe; attach according to the arrow. Slide the pipe so that the venter outlet, the single-wall pipe, or the vent cap is inside the double-wall pipe.

2)Drill a hole through the pipe into the outlet collar, the single-wall pipe, or the vent cap. (Hole should be slightly smaller than the sheet metal screw being used.) Using a 3/4" long sheet metal screw, attach the pipe. Do not overtighten. Repeat, drilling and inserting two additional screws evenly spaced (120° apart) around the pipe.

3)Use silicone sealant to seal any gaps. If there is an annular opening, run a large bead of sealant in the opening. The bead of sealant must be large enough to seal the opening, but it is not necessary to fill the full volume of the annular area.

4)Vent System Support

Lateral runs should be supported every six feet (1.8M) using a non-combus- tible material, such as strap steel or chain. Do not rely on the heater for support of either horizontal or vertical vent pipe.

Form 405, Page 10