Harman® • PF-120 Installation Manual_R1 • 2014 -___ • 03/14
14
3-90-08121i
F. Avoiding Smoke and Odors
Negative Pressure, Shut-down, and Power Failure:
T
o reduce the probability of back-drafting or burn-back in
the pellet burning appliance during power failure or shut-
down conditions, the stove must be able to draft naturally
without exhaust blower operation. Negative pressure in the
building will resist this natural draft if not accounted for in the
pellet appliance installation.
Heat rises and leaks out at upper levels. This air must be
replaced with cold air from outdoors, which flows into lower
levels of the building.
Vent Pipe
Be sure to use approved pellet vent pipe wall and ceiling
pass- through fittings to go through combustible walls and
ceilings. Be sure to use a starting collar to attach the venting
system to the furnace. The starting collar must be secured
to the flue stub with at least three screws, and sealed with
high temp silicone caulking.
Pellet venting pipe (also known as PL vent) is constructed
of two layers with air space between the layers. This air
space acts as an insulator and reduces the outside surface
temperature to allow a clearance to combustibles of only 1
inches. The sections of pipe lock together to form an air tight
seal in most cases; however, in some cases a perfect seal
is not achieved. For this reason and the fact that the PF-120
operates with a positive vent pressure, we specify that the
joints also be sealed with silicone.
Where passing through an exterior wall or roof, be sure to use
the appropriate pass-through device providing an adequate
vapor barrier. Venting manufacturers generally provide these
pas-through devices.
D. Draft
Draft is the pressure difference needed to vent appliances
successfully. When an appliance is drafting successfully, all
combustion by products are exiting through the chimney.
Considerations for successful draft include:
• Preventing negative pressure
• Location of appliance and chimney
To measure the draft or negative pressure on your appliance
use a magnahelic or a digital pressure gauge capable of
reading 0 - 1 inches of water column (W.C.).
The appliance should be running on high for at least 30
minutes for the test of high burn draft.
With the furnace running on high you should have a negative
pressure equal to or greater than the number given in the
chart below. If you have a lower reading than you find on the
chart, your appliance does not have adequate draft to burn
the fuel properly.
Cold draft test should be done prior to lighting unit. Minimum
should be:
Minimum Vacuum Requirements:
.35
INSPECT FLUE PIPES, FLUE PIPE JOINTS, AND
FLUE PIPE SEALS REGULARLY TO ENSURE THAT
SMOKE AND FLUE GASES ARE NOT DRAwN INTO,
AND CIRCULATED BY, THE AIR-CIRCULATION
SYSTEM.
WARNING
!
E. Negative Pressure
Negative pressure results from the imbalance of air available
for the appliance to operate properly. It can be strongest in
lower levels of the house.
Causes include:
• Combustion air requirements for furnaces, water heaters
and other combustion appliances
• Location of return-air vents to furnace or air conditioning
• Imbalances of the HVAC air handling system
• Upper level air leaks such as:
- Recessed lighting
To minimize the effects of negative air pressure:
• Install the outside air kit with the intake facing prevailing
winds during the heating season
• Ensure adequate outdoor air for all combustion appliances
and exhaust equipment
Risk of Asphyxiation!
Negative pressure can cause
spillage of combustion fumes and soot.
WARNING
!
• 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 a “sealed can” design
• Attic hatches weather stripped or sealed
• Attic mounted duct work and air handler joints and seams
taped or sealed
NOTICE:
Hearth & Home Technologies assumes no
responsibility for the improper performance of the chimney
system caused by:
• Inadequate draft due to environmental conditions
• Downdrafts
• Tight sealing construction of the structure
• Mechanical exhausting devices
