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INSTALLATION
INSTRUCTIONS
ML180DFE
506734-03
01/2023
Supersedes 03/2022
THIS MANUAL MUST BE LEFT WITH THE
HOMEOWNER FOR FUTURE REFERENCE
This is a safety alert symbol and should never be
ignored. When you see this symbol on labels or in man-
uals, be alert to the potential for personal injury or death.
WARNING
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, personal
injury or loss of life. Installation and service must be
performed by a licensed professional HVAC installer or
equivalent, service agency, or the gas supplier.
CAUTION
As with any mechanical equipment, contact with sharp
sheet metal edges can result in personal injury. Take
care while handling this equipment and wear gloves and
protective clothing.
© 2023 Lennox Industries Inc.
Dallas, Texas USA
MERIT
®
SERIES GAS FURNACE
DOWNFLOW DISCHARGE AIR
Contents
Unit Dimensions - inches (mm) ......................................2
ML180DFE Gas Furnace................................................3
Shipping and Packing List ..............................................3
Safety .............................................................................3
Use of Furnace as a Construction Heater ......................4
General ...........................................................................4
Combustion, Dilution, Ventilation Air...............................5
Setting Equipment ..........................................................9
Filters ............................................................................10
Duct System ................................................................. 11
Venting ......................................................................... 11
Gas Piping ....................................................................17
Electrical .......................................................................19
Integrated Control .........................................................22
Unit Start-Up .................................................................24
Gas Pressure Measurement.........................................25
Proper Combustion.......................................................25
High Altitude .................................................................25
Other Unit Adjustments.................................................26
Service..........................................................................28
Repair Parts List ...........................................................30
Start-Up and Performance Checklist ............................ 31
Blower Data ..................................................................33
DOWNFLOW
AIR FLOW
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