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NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
Inlet Gas Supply Pressure
(all models)
Fuel # Minimum Maximum
Natural Gas
4.5" WC
(1.12 kPa)
10.5" WC
(2.61 kPa)
Propane
11.0" WC
(2.74 kPa)
13.0" WC
(3.23 kPa)
Table 2
Manifold Gas Supply Pressure
(all models)
Fuel # Low High
Natural
Gas
(Lo) 2.2" WC
(0.55 kPa)
(Hi) 3.5" WC
(0.87 kPa)
Propane
(Lo) 6.3" WC
(1.57 kPa)
(Hi) 10.0" WC
(2.49 kPa)
Table 3
Gas Valve Diagrams
See Figure 1 for Millivolt models and Figure 2
For Electronic Models.
H
I
L
O
W
H T P T H T P T
P
I
L
O
T
P
I
L
O
T
O
N
i
t
O
F
F
IN
OUT
HI/LO Variable
Flame Height
Adjustment
Figure 1 - SIT Millivolt Gas Valve
Manifold Pressure Tap
Inlet Pressure Tap
Pilot Adjustment
Screw
Main Gas Control Knob
OFF/PILOT/ON
Burner Orifice Sizes
Elevation 0-4500 feet ( 0-1372 meters)
Model
Series
Nat.Gas
drill size (inches)
Propane
drill size (inches)
MLDVTCD-35
#49 (0.073")
*
21L82 •
0.045"
**
75L10 •
Table 4
* Standard size installed at factory
** Standard size in LP conversion kit
• Part /Cat. Number
LENNOXHEARTHPRODUCTS•MERIT
®
SERIESDIRECT-VENTCONTEMPORARYDESIGNGASFIREPLACES•MODELMLDVTCD-35•INSTALLATIONINSTRUCTIONS
Gas Pressure - All Models
Tables 2 and 3 show the appliances' gas
pressure requirements:
Test gauge connections are provided on the
front of the millivolt and electronic gas control
valve (identified IN for the inlet and OUT for
the manifold side). The control valves have a
3/8" (10mm) NPT thread inlet and outlet side
of the valve.
Propane tanks are at pressures that will cause
damage to valve components. Verify that the
tanks have step down regulators to reduce the
pressure to safe levels.
These appliances must be isolated from the
gas supply piping system (by closing their
individual manual shut-off valve) during any
pressure testing of the gas supply piping
system at test pressures equal to or less
than 1/2 psig (3.5 kPa).
These appliances and their individual
shut-off valves must be disconnected from
the gas supply piping system during any
pressure testing of that system at pressures
greater than 1/2 psig (3.5 kPa).
These appliances must not be connected to a
chimneyorueservingaseparatesolidfuel
burning appliance.
Orifice Sizes - Sea Level to High Altitude
(All Models)
These appliances are tested and approved for
installation at elevations of 0-4500 feet (0-1372
meters) above sea level using the standard
burner orifice sizes (marked with an "*" in
Table
4)
. For elevations above 4500 feet, contact your
gas supplier or qualified service technician.
Deration - At higher elevations, the amount
of BTU fuel value delivered must be reduced
by either:
• Usinggasthathasbeenderatedbythegas
company.
• Changingtheburneroricetoasmallersize
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/CSA-B149.1
codes - latest edition.
Install the appliance according to the regulations
of the local authorities having jurisdiction and,
in the USA, the National Fuel Gas Code NFPA
54 / ANSI Z223.1 - latest edition or, in Canada,
the CAN/CSA-B149.1 - latest edition.
NOTE:
Flame appearance will diminish 4% per
thousand feet.
Figure 2 - Dexen Electronic Gas Valve
Pilot Stage
Terminal
Pressure-Tap
(Inlet)
Pilot Gas
Outlet
Supply
Gas
Inlet
Pressure-Tap
(Manifold)
Burner Stage
Terminal
Ground
(TP)
PILOT
OUT
VENT
LO
TH
TP
TH
TP
HI
IN
IN
Regulator
Mounting Screw
REQUIREMENTS FOR THE COMMON-
WEALTH OF MASSACHUSETTS
These fireplaces are approved for installation in
the US state of Massachusetts if the following
additional requirements are met:
• Install this appliance in accordance with
Massachusetts Rules and Regulations 248
C.M.R.
• Installationandrepairmustbedonebya
plumber or gas fitter licensed in the Com-
monwealth of Massachusetts.
• Theexiblegaslineconnectorusedshall
not exceed 36 inches (92 centimeters) in
length.
• Theindividualmanualshut-offmustbea
T-handle type valve.
Massachusetts Horizontal Vent Requirements
In the Commonwealth of Massachusetts, hori-
zontal terminations installed less than seven
(7) feet 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
installedontheoorlevelwherethegas
fireplace is installed. The carbon monoxide
detector must comply with NFPA 720, be
ANSI/UL 2034 listed and be ISA certified.
• Ametalorplasticidenticationplatemust
be permanently mounted to the exterior of
the building at a minimum height of eight (8)
feet 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.
NEW YORK CITY, NEW YORK (MEA)
Installation of these fireplaces are approved
for installation in New York City in the US state
of New York.