User manual

19
Hearth & Home Technologies • BV4236DBI, BV4842DBI • 2209-900 Rev. N • 9/12
Figure4.2
E. NegativePressure
WARNING! Asphyxiation Risk! Negative pressure can
cause spillage of combustion fumes and soot. Fireplace
needs to draft properly for safety.
Draft is the pressure difference needed to vent replaces
successfully. Considerations for successful draft include:
• Preventing negative pressure
• Location of replace and chimney
Negative pressure results from the imbalance of air
available for the replace to operate properly. Causes for
this imbalance 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 to furnace or air conditioning
• Imbalances of the HVAC air handling system
• Upper level air leaks (recessed lighting, attic hatch
opening, duct leaks)
To minimize the effects of negative air pressure, the fol-
lowing must be considered:
• Install the fresh 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 combustion
appliances and exhaust equipment.
• Ensure furnace and air conditioning return vents are not
located in the immediate vicinity of the replace.
• Avoid installing the replace 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.
• Basement installations should be avoided due to stack
effect. Stack effect creates negative pressure in lower
levels. Hearth & Home Technologies recommends the
use of direct vent replaces in basements.
Location of the replace and chimney will affect perfor-
mance. As shown in Figure 4.2, the chimney should:
• Be installed through the warm space enclosed by the
building envelope. This helps to produce more draft,
especially during lighting and die-down of the re.
• Penetrate the highest part of the roof. This minimizes
the effects of wind turbulence.
• Be located away from trees, adjacent structures, uneven
roof lines and other obstructions.
Offsets can restrict draft so their use should be minimized.
Consider the replace location relative to oor and ceiling
and attic joists.
Recommended
Location
Marginal
Location
Location
Not
Recommended
Recommended
Location
Location NOT
Recommended
Multi-level Roofs
Windward
Leeward