Page 1
INSTALLATION
INSTRUCTIONS
ML193UH
507278-04
02/2018
Supersedes 11/2017
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.
© 2018 Lennox Industries Inc.
Dallas, Texas USA
MERIT
®
SERIIES GAS FURNACE
UP/FLOW HORIZONTAL AIR DISCHARGE
AIR FLOW
UPFLOW
AIR FLOW
AIR FLOW
HORIZONTAL RIGHT
HORIZONTAL LEFT
Contents
Unit Dimensions - inches (mm) ......................................2
ML193UH Gas Furnace..................................................3
Shipping and Packing List ..............................................3
Safety Information ..........................................................3
Use of Furnace as Construction Heater .........................4
General ...........................................................................5
Combustion, Dilution & Ventilation Air ............................5
Shipping Bolt Removal ...................................................8
Installation - Setting Equipment ......................................8
Filters ............................................................................13
Duct System .................................................................13
Pipe Fittings Specications...........................................13
Joint Cementing Procedure .......................................... 15
Venting Practices ..........................................................16
Vent Piping Guidlines ...................................................16
Gas Piping ....................................................................33
Electrical .......................................................................36
Ignition Control .............................................................39
Unit Start-Up .................................................................40
Gas Pressure Adjustment .............................................41
Proper Cumbustion.......................................................42
High Altitude Information ..............................................42
Testing for Venting and Combustion Air 43
Other Unit Adjustments.................................................44
Twinning the ML193UH ................................................45
Service..........................................................................46
Repair Parts List ...........................................................47
Start-Up & Performance Check List .............................48
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