3100 Wood Stove Series (ACC)

R

C. Negative Pressure

Draft is the pressure difference needed to vent appliances successfully. Considerations for successful draft include:

Preventing negative pressure

Location of appliance and chimney

Negative pressure results from the imbalance of air avail- able for the stove to operate properly. Causes for this imbal- ance include:

Exhaust fans (kitchen, bath) etc.)

Range hoods

Combustion air requirements for furnaces, water heaters and other combustion appliances

Clothes dryers

Location of return-air vents to furnace or air condi- tioning

Imbalances of HVAC air handling system

Upper level air leaks

To minimize the affects of negative air pressure the following must be considered:

Install the outside air kit. Install the intake on the side of the house towards prevailing winds during the heating season.

Ensure adequate outdoor air is supplied for combus- tion appliances and exhaust equipment.

Ensure furnace and air conditioning return vents are not located in the immediate vicinity of the appli- ance,

Avoid installing the appliance near doors, walkways or small isolated spaces.

Recessed lighting should be of “sealed can” design; attic hatches weather stripped or sealed; and attic mounted duckwork and air handler joints and seams taped or sealed.

Recessed lighting

Attic hatch opening

Duct leaks

WARNING

Asphyxiation Risk.

Negative pressure can cause spillage of com- bustion fumes, soot and carbon monoxide.

Appliance needs to draft properly for safety.

 

 

 

Recommended Location:

 

 

 

Recommended Location:

• Above peak

 

 

 

 

Above peak

• Inside heated space

 

 

 

 

 

 

 

Marginal Location:

 

 

 

Marginal Location:

Wind loading possible

 

 

 

• Below peak

 

 

 

Location NOT recommended:

 

 

 

 

 

Not the highest point of the roof

 

 

 

 

 

Wind loading possible

 

 

 

 

 

 

 

 

 

 

Location NOT recommended:

 

 

 

 

 

Too close to tree

 

 

Recommended:

 

 

Below adjacent structure

 

 

• Insulated exterior chase

 

Lower roof line

 

 

in cooler climates

 

Avoid outside wall

 

Windward

 

 

 

 

 

 

 

 

 

 

 

Leeward

 

Recommended:

 

Multi-level Roofs

 

NOT recommended:

 

 

 

 

 

Outside Air Intake

 

 

 

Outside Air Intake

 

on windward side

 

 

 

on leeward side

Figure 6.1

Page

7033-277F

September 1, 2008

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Hearth and Home Technologies 31ST-ACC, 31M-ACC-MBK Wood Stove Series ACC Negative Pressure, 7033-277F September 1