Hearth and Home Technologies 823-0170 - MBK owner manual Negative Pressure, Windward

R

Isle Royale Wood Stove

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

•Recessed lighting

•Attic hatch opening

•Duct 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 appliance,

•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 ductwork and air handler joints and seams taped or sealed.

WARNING

Asphyxiation Risk.

•Negative pressure can cause spillage of combustion fumes, soot and carbon mon- oxide.

•Appliance needs to draft properly for safety.

	Recommended Location:
Recommended Location:	•	Above peak
• Above peak	•	Inside heated space

Marginal Location:

• Below peak

Marginal Location:

• Wind loading possible

Location NOT recommended:

•Not the highest point of the roof

•Wind loading possible

Windward

Recommended: Outside Air Intake on windward side

	Location NOT recommended:
	•	Too close to tree
Recommended:	•	Below adjacent structure
• Insulated exterior chase	•	Lower roof line
in cooler climates	•	Avoid outside wall

Leeward

Multi-level Roofs

NOT recommended: Outside Air Intake on leeward side

Figure 6.1

Page 6 250-5763E November 22, 2011