4
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT
®
SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • INSTALLATION INSTRUCTIONS
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
Test gauge connections are provided on the
front of the gas control valve, identified
IN
for
the inlet and
OUT
for the manifold side (see
Figures 1 and 2).
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.
GAS VALVE dIAGRAMS
See Figure 1 for millivolt models and Figure 2
for electronic models.
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 asterisk
(
*
) in Table 4, below).
For elevations above 4500 feet, contact your
gas supplier or a qualified service technician.
deration
At higher elevations, 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/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 of altitude.
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
REqUIREMENTS fOR THE
COMMONWEALTH 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.
• Installation and repair must be done by a
plumber or gas fitter licensed in the Com-
monwealth of Massachusetts.
• The flexible gas line connector used shall
not exceed 36 inches (92 centimeters) in
length.
• The individual manual shut-off must be a
T-handle type valve.
NEW YORK CITY APPROVAL
New York City, NY (MEA)
These fireplaces are approved for installation
in New York City in the US state of New York
if the following additional requirement is met:
• An Outside Combustion Air Kit (FOAK-4,
FOAK-4LD, or DK-4) must be installed. See
Step 5 on Page 14.
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
GAS PRESSURE REqUIREMENTS
(All Models)
Tables 2 and 3
show the appliances' inlet and
manifold gas pressure requirements:
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).
Burner Orifice Sizes
Elevation 0-4500 feet ( 0-1372 meters)
Model
Series
Nat.Gas
drill size (inches)
Propane
drill size (inches)
MLBV-35
#48 (0.076")*
H1236•
#56 (0.046")*
62L37•
MLBV-40
#43 (0.089")*
99K75•
#55 (0.052")*
19L52•
Table 4
*
Standard size installed at factory.
•
Part /Catalog Number.
H I
LO
W
HT
PT
HT
PT
PILO
T
PI
LO
T
ON
it
OFF
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
