The Masonry Fireplace's Draft Control System; Positioning The Unit - Osburn 2200 Owner's Manual

2.4 The masonry fireplace's draft control system

If the fireplace's draft control system gets in the way of the installation of the insert, you must either block it in
the open position or remove it entirely. If you remove draft control system from the masonry hearth, you will
need to install the metal plate (27009), supplied with the owner's manual kit, indicating that the masonry hearth
has been modified. It must be secured inside the masonry hearth, in a visible place and easy to locate.

2.5 Positioning the unit

In addition to ensuring compliance of the masonry fireplace hearth extension (see Compliance of the
masonry fireplace section ), it is necessary to have a floor protection made of non-combustible materials
that meets the measurements specified in table FLOOR PROTECTION. To determine the need to add a
floor protection (D) beyond the hearth extension, you must do the following calculation using the data in
Table Data for floor protection calculation: D = B - (A - C). If the value (D) is negative or zero, you do not
have to add more floor protection in front of the unit, because the masonry fireplace hearth extension is long
enough. If the value (D) is positive, you will need a floor protection in front of the hearth extension at least
equivalent to the result (D).
Here is a sample calculation to determine the need to add a non-combustible materials floor protection. For
someone whose fireplace opening is less than 6 ft
room (C) the calculation would be:
Value D = B - (A - C)
Value D = 21 5/8" - (16" - 3")
Value D = 21 5/8" - 13"
Value D = 7 3/8"
This person should install a non-combustible floor protection of at least 7 3/8" (187 mm) in front of the
hearth.
If a non-combustible material floor protection needs to be added in front and level with the hearth extension
masonry fireplace (see Figure 2.5a), an R factor equal to or greater than 1.00 is required. If the extension of
the masonry hearth is raised at least 4" from the floor protection, a non-combustible material is sufficient.
The use of an R value is convenient when more than one material is going to be used in the hearth extension
to cover the combustible surface. This is because R values are additive, whereas K values are not. To find
the corresponding R factor to use for some selected materials, please see table Thermal characteristics of
common floor protection materials.
Example:
Required floor protection R of 1.00. Proposed materials: four inches of brick and one inch of
®
Durock board
Four inches of brick (R = 4 x 0,2 = 0,8) plus 1 inch of Durock
This R value is larger than the required 1.00 and is therefore acceptable
2
and which the insert would protrude 3" (76 mm) into the
0.8 + 0.52 = 1.32.
®
(R = 1 x 0.52 = 0.52).
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