4
Merrimack Large Insert
30004671
Installing the Merrimack Large Insert into an existing
masonry fireplace is an effective way to add an efficient
heater to your home. The existing fireplace and chim-
ney must meet certain requirements.
Requirements for existing Fireplaces
The Merrimack Large Insert is listed for installation
within a properly built masonry or heat circulating, ma-
sonry-type fireplace that is constructed in accordance
with the requirements of recognized building codes. A
heat-circulating masonry-type fireplace must conform
to building code standards for masonry fireplaces, and
must consist of a factory-built metal firebox with air
circulation pathways that are surrounded by masonry
materials. Air circulation pathways must not be blocked
by the insert or surround panels.
The fireplace and chimney must be clean and structur-
ally sound. Have them inspected by a qualified profes-
sional chimney sweep, a mason, or your Vermont Cast-
ings’ Authorized Dealer before the Merrimack Large
Insert is installed. Any deterioration (cracks, loose
mortar or loose bricks) must be repaired.
Codes may permit removal of the damper in order to
make a positive vent connection between the firebox
and the chimney. However, the fireplace should not be
modified in any way without first checking with your lo-
cal building inspector or fire marshal. Provision should
be made to restore the fireplace to its original condition
if the insert is removed. Do not remove bricks or mortar
that may jeopardize the compliance of the fireplace with
local building codes.
The Merrimack Large Insert is not approved for
installation in factory-built fireplaces.
Installation
Requirements for existing chimneys
Chimney requirements differ for the U.S. and Canada.
Specifications for each are listed below. Connect the
insert to the chimney in accordance with local codes
and the requirements of the listing agency as specified
in this manual.
chimney height / U.S. and canada
Chimney height should be no less than 15’ (4.5 m)
above the hearth and no more than 35’ (10.5 m).
The chimney should extend at least 3’ (914 mm) above
the highest point where it passes through a roof, and at
least ’ (610 mm) higher than any portion of a building
within 10’ (3 m). (Fig. )
Do not connect your Merrimack Large insert to a
chimney flue serving another appliance.
U.S.
In the U.S. (aNSI/NFpa 211, 1988), when
installed in a masonry fireplace:
•
A connector must extend from the flue collar
to the flue liner.
•
The cross sectional area of the flue must be less
than or equal to three times the area of the flue
collar. If larger, the chimney must be re-lined.
•
Means must be provided to prevent room air
passing to the chimney cavity.
•
Provision must be made for removal of the
insert to clean the chimney flue.
general considerations / U.S.
•
While not required in most jurisdictions in the
U.S., MHSC strongly recommends that a full
stainless steel chimney liner be installed for the
insert to the chimney top to increase overall per-
formance and to ease and reduce yearly mainte-
nance.
•
A masonry chimney must be well-constructed
and must meet minimum code requirements.
The chimney flue should have a code-approved
liner made of masonry or pre-cast refractory
tiles, straight or flexible stainless steel pipe, or a
poured-in-place liner. An unlined chimney must
be relined professionally.
•
The chimney must have a nominal flue size of
6” (15 mm) diameter or 8 square inches (181
cm
) but no greater than 3 times larger or 85
square inches (548 cm
). A chimney larger than
this must be re-lined.
2' Min.
2' Min.
3'
Min.
0 To 10'
3'
Min.
0 To 10'
AC617
RLTSKC8
2/11/98
AC617
Reference
Point
Fig. 2
The ’-3’-10’ rule for chimneys.
