General Information
900414-00 12/2015
Innovative Hearth Products
MHD 35/40 Series Direct-Vent Gas Fireplaces
10
Orifice Sizes—Sea Level to High Altitude
These fireplaces are tested and approved for installation at elevations of 0–4500 ft (0–1372 m) above sea level
using the standard burner orifice sizes
(
Table 5
)
. For elevations above 4500 ft, contact your gas supplier or qualified
service technician.
Table 5 - Burner Orifice Sizes, Elevation 0–4500 ft ( 0–1372 m)
Model
Natural Gas
drill size
Propane
drill size
35” Models
#48 (0.076”)*
#56 (0.046”)*
40” Models
#44 (0.086”)*
#55 (0.052”)*
* Standard size installed at factory
Deration
At elevations above 4500 ft, the amount of BTU fuel value delivered must be reduced by either:
• Using gas that has been derated by the gas company.
• Changing the burner orifice to a smaller size as regulated by the local authorities having jurisdiction and by the
(USA) National Fuel Gas Code NFPA 54/ANSI Z223.1—latest edition or, in Canada, the CAN/CGA-B149.1 codes—
latest edition.
NOTE:
Flame breadth, height and width will diminish 4% for every 1,000 ft of altitude.
IN CANADA—CAN/CGA-2.17-M91 (HIGH ALTITUDE):
THE CONVERSION SHALL BE CARRIED OUT BY A MANUFACTURER’S AUTHORIZED REPRESENTATIVE,
IN ACCORDANCE WITH THE REQUIREMENTS OF THE MANUFACTURER, PROVINCIAL OR TERRITORIAL
AUTHORITIES HAVING JURISDICTION AND IN ACCORDANCE WITH THE REQUIREMENTS OF THE CAN/
CGA-B149.1 OR CAN/CGA-B149.2 INSTALLATION CODES.
COMMONWEALTH OF MASSACHUSETTS REQUIREMENTS
These appliances are approved for installation in the U.S. state of Massachusetts if the following additional
requirements are met:
• Install this appliance in accordance with Massachusetts Rules and Regulations 248 C.M.R. Sections 4.00
through 8.00.
• Installation and repair must be done by a plumber or gas fitter licensed in the Commonwealth of Massachusetts.
• The flexible gas line connector used shall not exceed 36” (92 centimeters) in length.
• The individual manual shutoff must be a T-handle type valve.
Massachusetts Horizontal Vent Requirements
In the Commonwealth of Massachusetts, horizontal terminations installed less than seven (7) ft above the finished
grade must comply with the following additional requirements:
• A hard wired carbon monoxide detector with an alarm and battery back-up must be installed on the floor level
where the gas fireplace is installed. The carbon monoxide detector must comply with NFPA 720, be ANSI/UL
2034 listed and be ISA certified.
• A metal or plastic identification plate must be permanently mounted to the exterior of the building at a minimum height
of eight (8) ft above grade and be directly in line with the horizontal termination. The sign must read, in print size no
less than one-half (1/2) inch in size,
GAS VENT DIRECTLY BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS.
COLD CLIMATE INSULATION
For cold climate installations, seal all cracks around your fireplace with noncombustible material and wherever cold
air could enter the room. It is especially important to insulate outside chase cavity between studs and under floor on
which fireplace rests, if floor is above ground level. Gas line holes and other openings should be caulked or stuffed
with unfaced fiberglass insulation.
NOTE:
Do not use loose, or blown-in insulation in the cavity surrounding the fireplace.
If the fireplace is being installed on a cement slab in cold climates, a sheet of plywood or other raised platform can
be placed underneath to prevent conduction of cold transferring to the fireplace and into the room. It also helps to
seal inside surfaces and tape for maximum air tightness and caulk firestops.
