4
Merrimack Large Insert
30004671
SAFETY NOTICE: IF YOUR MERRIMACK IS NOT
PROPERLY INSTALLED, A HOUSE FIRE MAY RE-
SULT. TO REDUCE THE RISK OF FIRE, FOLLOW THE
INSTALLATION INSTRUCTIONS. CONTACT LOCAL
BUILDING OR FIRE OFFICIALS ABOUT RESTRICTIONS
AND INSTALLATION INSPECTION REQUIREMENTS IN
YOUR AREA.
Requirements for Existing Fireplaces
The Merrimack Large Insert is listed for installation within
a properly built masonry or heat circulating, masonry-type
fireplace that is constructed in accordance with the require
-
ments 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 structurally
sound. Have them inspected by a qualified professional
chimney sweep, a mason, or your Vermont Castings'
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 chim
-
ney. However, the fireplace should not be modified in any
way without first checking with your local 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 instal-
lation in factory-built fireplaces.
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
2' (610 mm) higher than any portion of a building within
10' (3 m). (Fig. 2)
DO NOT CONNECT YOUR MERRIMACK LARGE IN-
SERT TO A CHIMNEY FLUE SERVING ANOTHER
APPLIANCE.
Installation
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.,
Vermont Castings Group strongly recommends
that a full stainless steel chimney liner be installed
for the insert to the chimney top to increase overall
performance and to ease and reduce yearly main-
tenance.
•
A masonry chimney must be well-constructed and
must meet minimum code requirements. The chim-
ney flue should have a
code-approved liner made of
masonry or pre-cast refractory tiles
, straight or flex
-
ible 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" (152
mm) diameter or 28 square inches (181 cm
2
) but no
greater than 3 times larger or 85 square inches (548
cm
2
). A chimney larger than this must be re-lined.
Be aware that a chimney originally designed for fireplace
use may perform differently when used to vent an air-
controlled appliance such as your Merrimack Large Insert
- even if the flue is less than 3 times larger than the flue
collar. For example, a chimney on an outside wall may
not heat up enough to sustain an adequate draft. Such a
flue can often be improved if it is relined to reduce its size
and/or insulated to keep it warmer.
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 2'-3'-10' rule for chimneys.
