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LENNOX HEARTH PRODUCTS • MERIT PLUS
GENERAL INFORMATION
(continued)
BTU Input
These electronic models come standard with a
remotely-modulated gas valve; flame appear-
ance and heat output cannot be controlled at the
gas valve. The BTU Input for these appliances
is shown in Table 1.
Input (BTU/HR) Gas Valves (all models)
Input Rate (BTU / HR)
Models
Nat. Gas
MPDP35
25,000
MPDP40
31,000
Table 1
Gas Pressure - All Models
Tables 2 and 3 show the appliances' inlet and
manifold gas pressure requirements:
Inlet Gas Supply Pressure
(all models)
Fuel #
Minimum
4.5" WC
Natural Gas
(1.12 kPa)
11.0" WC
Propane
(2.74 kPa)
Table 2
Manifold Gas Supply Pressure
(all models)
Fuel #
Low
Natural
(Lo) 1.6" WC
(Hi) 3.5" WC
Gas
(0.40 kPa)
(Lo) 6.3" WC
(Hi) 10.0" WC
Propane
(1.57 kPa)
Table 3
Green Wire
(From DFC Wire
Harness)
Manifold (Out)
Test Port
Line (In) Test Port
Orange Wire
(From DFC Wire
Harness)
Figure 1
DIRECT VENT GAS FIREPLACES (MPDP35/40) • CARE AND OPERATION INSTRUCTIONS
®
Test gauge connections are provided on the
front of the electronic gas control valve (identi-
fied 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
(refer to Figure 1).
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.
The appliance and its appliance main gas
Prop. Gas
valve must be disconnected from the gas
22,000
supply piping system during any pressure
testing of that system at test pressures in
29,000
excess of 1/2 psi (3.5 kPa).
The appliance must be isolated from the gas
supply piping system by closing its equipment
shutoff valve during any pressure testing of
the gas supply piping system at test pres-
sures equal to or less than 1/2 psi (3.5 kPa).
Orifice Sizes - Sea Level to High Altitude
(All Models)
Maximum
10.5" WC
These appliances are tested and approved for
(2.61 kPa)
installation at elevations of 0-4500 feet (0-1372
meters) above sea level using the standard burner
13.0" WC
orifice sizes (marked with an "*" in Table 4 ).
(3.23 kPa)
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
High
by either using gas that has been derated by
the gas company or by changing the burner
(0.87 kPa)
orifice to a smaller size as regulated by the
local authorities having jurisdiction and by the
(2.49 kPa)
(USA) National Fuel Gas Code NFPA 54/ANSI
Z223.1 - latest edition or, in Canada, the CAN/
CSA-B149.1 codes - latest edition.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
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.
Flame breadth, height and width will diminish
4% for every 1,000 feet of altitude.
Burn-in Period
During the first few fires of 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 YOUR HOUSE WELL VENTILATED
DURING THE CURING PROCESS. THE ODOR
AND HAZE EMITTED DURING THE CURING
PROCESS CAN BE QUITE NOTICEABLE AND
MAY SET OFF A SMOKE DETECTOR.
Do not turn on the blower during the burn-in
period.
Connect GTMS
Wire Harness
Pressure
Regulator
Tower
Yellow Ground Wire
(From DFC Wire
Harness)
SIT Proflame Valve
Burner Orifice Sizes
Elevation 0-4500 feet ( 0-1372 meters)
Model
Nat.Gas
Series
drill size (inches)
drill size (inches)
#42 (.093")*
MPDP35
H3721•
#36 (.1065")*
MPDP40
18L40•
* Standard size installed at factory
Table 4
• Part /Cat. Number
NOTICE:
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); otherwise, the white film
will bake onto the glass and become
difficult to remove.
See glass cleaning instructions on
Page 11.
Propane
#54 (.055")*
99K79•
#52 (.063")*
21L01•
7
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