7
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
LENNOX HEARTH PRODUCTS • MERIT® SERIES B-VENT GAS FIREPLACES • MODELS MLBV-35, MLBV-40 • CARE AND OPERATION INSTRUCTIONS
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
GENERAL INFORMATION
The fireplace models covered in this manual are
B-vented decorative gas appliances designed
for residential application.
Millivolt appliances have a millivolt gas control
valve with piezo ignition system.
Electronic appliances have a battery backed-
up electronic intermittent pilot system. No
external electrical power is required to operate
these appliances; however, 120 VAC is recom-
mended (see Installation Instructions).
These appliances comply with National Safety
Standards and are tested and listed by ITS
(Report No. 100017854) to ANSI Z21.50 (in
Canada, CSA-2.22) and to CAN/CGA-2.17-M91
in both USA and Canada (latest editions at time
of manual publication) as vented gas fireplaces.
Installation must conform to local codes, or, in
the absence of local codes, with the National
Fuel Gas Code, ANSI Z223.1/NFPA 54 (latest
edition), or the Natural Gas and Propane Instal-
lation Code, CAN/CSA B149.1 (latest edition).
The appliance, when installed, must be electri-
cally grounded and wired in accordance with
local codes or, in the absence of local codes,
with the USA National Electrical Code, ANSI/
NFPA 70 (latest edition) or, in Canada, the Cana-
dian Electrical Code, CSA C22.1 (latest edition).

Burn-in Period

During the rst few res in this appliance,
there will be some odor due to the curing of
the paint and burning off of lubricants used in
the manufacturing process. Depending on your
use, the burn-in period may take a few hours
or a few days.
KEEP YOU R HOUS E WELL VENTI LATED
DURING THE BURN-IN PROCESS. THE ODOR
AND HAZE EMITTED DURING THE BURN-IN
PROCESS CAN BE QUITE NOTICEABLE AND
MAY SET OFF A SMOKE DETECTOR.

Gas Pressure Requirements

(All Models)
Gas pressure requirements are listed in
Tables 2 and 3.
Test gauge connections are provided on the
front of the gas control valve, identied IN for
the inlet and OUT for the manifold side (see
Figures 3 and 4).
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.
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

BTU Input

Millivolt and electronic models come standard
with a manually-modulated gas valve; flame
appearance and heat output can be controlled
at the gas valve. The BTU inputs for these ap-
pliances are shown in Table 1.
Input (BTU/HR) Manually Modulated
Gas Valves (all models)
Models Input Rate (BTU / HR)
Nat. Gas Prop. Gas
MLBV-35
17,000 high
13,000 low 17,000 high
14,000 low
MLBV-40 22,000 high
17,000 low 20,000 high
15,500 low
Table 1
IMPORTANT NOTE!

A white film may develop on the glass

enclosure panel during the first few

fires as part of the burn-in process.

The first few times you use the

fireplace, clean the glass after

each use (AFTER THE GLASS HAS

COMPLETELY COOLED); other wise,

the white film will bake onto the

glass and become difficult to

remove.

See “Clean Glass Enclosure Panel”

on Page 10.

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).

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 orice 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 orice 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.
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.

Gas Pressure Requirements

(continued)