Table of Contents
Advertisement
space inside the house, the slight negative pressure low in the house will compete against the desired
upward flow in the chimney.
There are two reasons why the
chimney in the house at right will
cold backdraft when it is cold
outside and there is no fire burning
in the fireplace. First, the chimney
runs up the outside of the house, so
the air in it is colder and denser
than the warm air in the house. And
second, the chimney is shorter than
the heated space of the house,
meaning the negative pressure low
in the house will pull outside air
down the chimney, through the
fireplace and into the room. Even
the finest fireplace will not work well
when connected to this chimney.
8.5 CHIMNEY INSTALLATION NOTES
If possible, install an interior chimney as it will provide better performance. In areas with continuous
temperatures below 18 C (0 F), the use of an exterior chimney increases the likelihood of operating
problems such as low draft, high rate of creosoting, and poor start-up characteristics. Exterior chimneys
are also prone to down-drafting and flow reversal. Installations, which are located on lower floors in the
house, such as in a basement, in combination with outside chimney, are especially prone to flow reversal.
The WFP-100 is listed only with chimney systems described in Table 3.
A chimney venting a fireplace shall not vent any other appliance.
The minimum chimney system height for a straight installation is 15 ft. (4.6 m) from the bottom of the
unit to the chimney cap. Note: If only the minimum chimney height is installed, operating conditions must
be optimal (interior chimney, minimum height of 18" before any offset, etc.). Additional height will increase
drafts and will decrease the tendency to smoke.
All chimney installations must include at least one support. Reducing the amount of chimney weight on
the fireplace will help avoid the noise created when the fireplace expands. This can be achieved by having
the chimney supported by the supports. The maximum chimney length that should be supported by the
fireplace is 9 ft. (2.75 m) for 2" Solid Pack Chimney and 12 ft. (3.7 m) for 1" Solid Pack Chimney.
The chimney must extend at least 3 ft. (92 cm) above its point of contact with the roof and at least 2 ft.
(61 cm) higher than any wall, roof or building within 10 ft. (3.1 m) of it. See the figures on point 11 bellow to
determine the configuration that applies to your roof (flat or sloped roof and the distance between the
chimney and the highest point of the roof and/or the nearest chimney).
Deviations should be avoided whenever possible, especially the most pronounced. Each deviation adds
some restriction to the chimney system and may lead to draft problems.
If the chimney extends higher than 5 ft. (1.5 m) above its point of contact with the roof, it must be
secured using a roof brace.
A rain cap must be installed on top of the chimney.
Cut and frame square holes in all floors, ceilings, and roof that the chimney will go through to provide a
2" (50 mm) minimum clearance between the chimney and any combustible materials. Do not fill this 2
space with insulation or any other combustible material.
Portions of the chimney which may extend through accessible spaces must be enclosed to avoid
contact with combustible materials or damage the chimney.
HearthStone Quality Home Heating Products, Inc ®
40
WFP-100 Model 8420
Advertisement
Table of Contents
