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INSTALLATION
INSTRUCTIONS
ML193UHE
507863-02
10/2021
Supersedes 06/2020
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.
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.
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.
© 2021 Lennox Industries Inc.
Dallas, Texas USA
MERIT
®
SERIES GAS FURNACE
UPFLOW / HORIZONTAL AIR DISCHARGE
Contents
Unit Dimensions - inches (mm) ......................................2
ML193UHEGas Furnace ................................................3
Shipping and Packing List ..............................................3
Safety .............................................................................3
Use of Furnace as a Construction Heater ......................4
General ...........................................................................5
Combustion, Dilution, Ventilation Air...............................5
Setting Equipment ..........................................................8
Filters ............................................................................13
Duct System .................................................................13
Pipe Fittings Specications...........................................14
Joint Cementing Procedure .......................................... 15
Venting Practices ..........................................................16
Gas Piping ....................................................................33
Electrical .......................................................................36
Integrated Control .........................................................39
Unit Start-Up .................................................................40
Gas Pressure Measurement.........................................41
Proper Combustion.......................................................42
High Altitude .................................................................42
Testing For Combustion Air Non-Direct Vents ..............43
Other Unit Adjustments.................................................44
Service..........................................................................45
Repair Parts List ...........................................................46
Start Up Checklist .........................................................47
Blower Data ..................................................................51
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