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© 2024 Lennox Industries Inc.
Dallas, Texas USA
WARNING
This furnace is equipped with an ignition control
factory enabled for use with Lennox A2L refrigerant
systems.
Disabling
functionality on A2L system is prohibited by safety
codes. Refer to furnace installation instructions for
non-A2L and non-Lennox refrigerant system setup.
Contents
Unit Dimensions - inches (mm) ......................................2
ML193UHEKGas 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 Specifications...........................................14
Joint Cementing Procedure ..........................................15
Venting Practices ..........................................................16
the
refrigerant
detection
INSTALLATION
INSTRUCTIONS
ML193UHEK
MERIT
SERIES GAS FURNACE
®
UPFLOW / HORIZONTAL AIR DISCHARGE
508565-01
11/2024
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.
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.
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.
Gas Piping ....................................................................33
Electrical .......................................................................36
Ignition Control .............................................................38
Twinning .......................................................................43
Low GWP Application ...................................................44
Unit Start-Up .................................................................47
Gas Pressure Measurement.........................................48
Proper Combustion.......................................................49
High Altitude .................................................................49
Testing For Combustion Air Non-Direct Vents ..............50
Other Unit Adjustments.................................................51
Service..........................................................................52
Repair Parts List ...........................................................53
Start Up Checklist .........................................................54
Blower Data ..................................................................58
Page 1
CAUTION
WARNING
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Summary of Contents for Lennox MERIT ML193UHEK
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Page 1: Table Of Contents
Installation and service must be WARNING performed by a licensed professional HVAC installer (or equivalent), service agency, or the gas supplier. This furnace is equipped with an ignition control factory enabled for use with Lennox A2L refrigerant systems. Disabling refrigerant detection functionality on A2L system is prohibited by safety codes. -
Page 2: Unit Dimensions - Inches (Mm)
Unit Dimensions - inches (mm) NOTE - 60C size units that require air volumes over 1800 cfm must have one of the following: 1. Single side return air and Optional Return Air Base EXHAUST AIR 3-3/8 OUTLET with transition that must accommodate required (86) 20 x 25 x 1 inch (508 x 635 x 25 mm) air filter to maintain proper velocity. -
Page 3: Ml193Uhekgas Furnace
ML193UHEK Gas Furnace Shipping and Packing List The ML193UHEK Category IV gas furnace is shipped Package 1 of 1 contains ready for installation in the upflow or horizontal position. 1 - Assembled ML193UHEK unit The furnace is shipped with the bottom panel in place. The bottom panel must be removed if the unit is to be installed 1 - Bag assembly containing the following: in horizontal or upflow applications with bottom return air. -
Page 4: Use Of Furnace As A Construction Heater
The National Fuel Gas Code is available from the follow- In Canada, all electrical wiring and grounding for the unit must be installed according to the current regulations of ing address: the Canadian Electrical Code Part I (CSA Standard C22.1) American National Standards Institute, Inc. -
Page 5: General
Water softening chemicals FAILURE TO FOLLOW THE ABOVE INSTALLATION IN- STRUCTIONS VOIDS THE MANUFACTURER’S EQUIP- De-icing salts or chemicals MENT LIMITED WARRANTY. LENNOX DISCLAIMS Carbon tetrachloride ALL LIABILITY IN CONNECTION WITH INSTALLER’S Halogen type refrigerants FAILURE TO FOLLOW THE ABOVE INSTALLATION IN- Cleaning solvents (such as perchloroethylene) STRUCTIONS. -
Page 6: Unconfined Space
This reprinted material is not the complete and official po- When the furnace is installed so that supply ducts carry sition of the ANSI on the referenced subject, which is rep- air circulated by the furnace to areas outside the space resented only by the standard in its entirety. - Page 7 Air from Outside EQUIPMENT IN CONFINED SPACE (Inlet Air from Ventilated Crawlspace and Outlet Air to Outside) If air from outside is brought in for combustion and ventila- tion, the confined space shall be provided with two perma- nent openings. One opening shall be within 12” (305mm) Roof Terminated of the top of the enclosure and one within 12”...
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Page 8: Installation - Setting Equipment
flexible mounting leg). See FIGURE 10. The bolt and EQUIPMENT IN CONFINED SPACE - ALL AIR FROM OUTSIDE washer must be removed before the furnace is placed (All Air Through Ventilated Attic) into operation. After the bolt and washer have been re- moved, the rigid leg will not touch the blower housing. -
Page 9: Setting Equipment
SETTING EQUIPMENT UPFLOW APPLICATION Place level on blower Place level on the front blower deck screws to check deck to check side to side forward tilt UNIT FRONT AIR FLOW 1/2” max. SIDE VIEW HORIZONTAL APPLICATION UNIT FRONT AIR FLOW 1/2”... - Page 10 Return Air Guidelines WARNING Return air can be brought in through the bottom or either Improper installation of the furnace can result in personal side of the furnace installed in an upflow application. If the injury or death. Combustion and flue products must furnace is installed on a platform with bottom return, make never be allowed to enter the return air system or air an airtight seal between the bottom of the furnace and the...
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Page 11: Front View
Optional Return Air Base CONDENSATE (Upflow Applications Only) TRAP FURNACE FRONT 23 (584) 3−1/4 IF BASE Overall (83) IS USED (Maximum) Minimum WITHOUT 11 (279) IAQ CABINET, Maximum 22−7/16 INDOOR AIR A SINGLE Unit side return air 14 (356) (570) QUALITY RETURN AIR Opening... - Page 12 5 - If necessary, run the condensate line into a condensate on a platform, as shown in FIGURE 19. A horizontal sus- pump to meet drain line slope requirements. The pension kit (51W10) may be ordered from Lennox or use pump must be rated for use with condensing equivalent furnaces.
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Page 13: Filters
If a gas appliance is operating in the data given in the appropriate Lennox Product a room with negative pressure, the flue products can be Specifications bulletin. Additional information is provided pulled back down the vent pipe and into the room. -
Page 14: Pipe Fittings Specifications
CAUTION Pipe & Fittings Specifications All pipe, fittings, primer and solvent cement must conform Solvent cements for plastic pipe are flammable liquids with American National Standard Institute and the Ameri- and should be kept away from all sources of ignition. can Society for Testing and Materials (ANSI/ASTM) stan- dards. -
Page 15: Joint Cementing Procedure
TABLE 3 OUTDOOR TERMINATION USAGE* STANDARD CONCENTRIC Wall Kit 1-1.2 inch 2 inch 3 inch Flush Mount Kit 2 inch 3 inch Vent Pipe 71M80 69M29 Input Size Field 60L46 (US) 51W11 22G44 Dia. in. (US) (US) 44J40 (US) Fabricated 44W93 (US) (US) -
Page 16: Venting Practices
Vent Piping Guidelines NOTE - Lennox has approved the use of DuraVent® and Centrotherm manufactured vent pipe and terminations as an option to PVC. When using the PolyPro... - Page 17 Doing so will cause freeze-ups and FIGURE 23 may block the terminations. NOTE - Lennox offers a glueless vent adapter kit 17H92 TABLE 4 as an option for exhaust exiting at the furnace top cap coupling. If the kit is not used then the exhaust pipe MUST MINIMUM VENT PIPE LENGTHS be glued to the furnace exhaust fitting.
- Page 18 TABLE 5 Maximum Allowable Intake or Exhaust Vent Length in Feet NOTE - Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total. Both Intake and Exhaust must be same pipe size NOTE - Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length calculation.
- Page 19 TYPICAL EXHAUST AND INTAKE PIPE CONNECTIONS IN UPFLOW DIRECT OR NON-DIRECT VENT APPLICATIONS 2” EXHAUST 2” EXHAUST INTAKE INTAKE 2” 2” 2” 2” 3” 3” 030/045/070 Only 1−1/2” TRANSITION Exhaust 2” 6” Min Exhaust DO NOT transition from larger to smaller DO NOT transition pipe in horizontal runs from smaller to larger...
- Page 20 Intake Piping TYPICAL AIR INTAKE PIPE CONNECTIONS HORIZONTAL NON−DIRECT VENT APPLICATIONS The ML193UHEK furnace may be installed in either direct (Horizontal Right−Hand Air Discharge Application Shown) vent or non-direct vent applications. In non-direct vent ap- plications, when intake air will be drawn into the furnace from the surrounding space, the indoor air quality must be considered and guidelines listed in Combustion, Dilution and Ventilation Air section must be followed.
- Page 21 General Guidelines for Vent Terminations CAUTION In Non-Direct Vent applications, combustion air is taken If this unit is being installed in an application with from indoors and the flue gases are discharged to the out- combustion air coming in from a space serviced by an doors.
- Page 22 TABLE 7 Maximum Allowable Exhaust Vent Pipe Length (in ft.) Without Insulation In Unconditioned Space For Winter Design Temperatures Single - Stage High Efficiency Furnace Winter Design Unit Input Size Vent Pipe Temperatures1 °F Diameter (°C) 1-1/2” 32 to 21 2 in (0 to -6) 2-1/2 in...
- Page 23 ‡ Permitted only if veranda, porch, deck or balcony is fully open NOTE - This figure is intended to illustrate clearance on a minimum of two sides beneath the floor. Lennox recommends requirement and does not serve as a substitute for locally adopted installation codes.
- Page 24 ‡ Permitted only if veranda, porch, deck or balcony is fully open on a minimum of locally adopted installation codes. two sides beneath the floor. Lennox recommends avoiding this location if possible. FIGURE 33 Page 24...
- Page 25 Details of Intake and Exhaust Piping Terminations for TABLE 8 Direct Vent Installations Exhaust Pipe Termination Size Reduction NOTE - In Direct Vent installations, combustion air is taken ML193UHEK Model Termination Pipe Size from outdoors and flue gases are discharged to outdoors. *030, *045, *070 1-1/2”...
- Page 26 7 - If intake and exhaust piping must be run up a side wall to position above snow accumulation or other obstructions, piping must be supported. At least one bracket must be used within 6” from the top of EXHAUST 12”...
- Page 27 FIELD FABRICATED WALL TERMINATION NOTE − FIELD−PROVIDED REDUCER MAY BE 2” (51mm) 3” (76mm) REQUIRED TO ADAPT Vent Pipe Vent Pipe LARGER VENT PIPE SIZE TO TERMINATION A− Minimum clearance above grade or average 12” (305 mm) 12” (305 mm) snow accumulation B−...
- Page 28 Lennox provides kit 51W18 (USA) kit 15Z70 (Canada) to 2 - On field supplied terminations for side wall exit, install 2” or 3” PVC exhaust piping through the floor joists exhaust piping may extend a maximum of 12 inches and into the crawl space.
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Page 29: Condensate Piping
NOTE - In upflow applications where side return trap and line. Heating cable kit is available from Lennox in various lengths; 6 ft. (1.8m) - kit no. 26K68 and 24 ft. - Page 30 CONDENSATE TRAP LOCATIONS Condensate Trap With Optional Overflow Switch (Unit shown in upflow position with remote trap) From Evaporator Coil HorizontalFurnace4” Min. to 5” Max.above FieldProvidedVent condensatedrain connection) Min. 1” Above Condensate Drain Connection 1” Min. 2” Max. FurnaceCondensate DrainConnection *5’...
- Page 31 Furnace with Evaporator Coil Using a Separate Drain (Unit shown in horizontal left-hand discharge position) Field Provided Vent Evaporator (4” min. to 5” max. above Coil condensate connection) 4”min 5”max 5’ max. PVC Pipe Only Condensate Drain Connection (Trap at coil is optional) Drain Pan Piping from furnace and evaporator coil must slope down a minimum 1/4”...
- Page 32 TRAP / DRAIN ASSEMBLY USING 1/2” PVC OR 3/4” PVC Optional Condensate Drain Connection Adapter 3/4 inch slip X 3/4 inch mpt (not furnished) 90° Street Elbow 3/4 inch PVC (not furnished) Adapter 3/4 inch slip X 3/4 inch mpt (not furnished) Condensate Drain Connection In Unit 1 (25 mm) Min.
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Page 33: Gas Piping
3 - Gas piping must not run in or through air ducts, Gas Piping clothes chutes, chimneys or gas vents, dumb waiters or elevator shafts. Center gas line through piping CAUTION hole. Gas line should not touch side of unit. See FIGURE 56 and FIGURE 57. -
Page 34: Fire Or Explosion Hazard
WARNING FIRE OR EXPLOSION HAZARD Failure to follow the safety warnings exactly could result in serious injury, death, or property damage. Never use an open flame to test for gas leaks. Check all connections using a commercially available soap solution made specifically for leak detection. - Page 35 TABLE 9 Gas Pipe Capacity - ft3/hr (m3/hr) Nominal Internal Length of Pipe - feet (m) Iron Pipe Diameter Size Inches inches (3.048) (6.096) (9,144) (12,192) (15.240) (18.288) (21.336) (24.384) (27.432) (30,480) (mm) (mm) .622 (12.7) (17.799) (4.87) (3.34) (2.69) (2.29) (2.03) (1.84)
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Page 36: Electrical
The power supply wiring must meet Class I restrictions. Electrical Protected by either a fuse or circuit breaker, select circuit protection and wire size according to unit nameplate. IMPORTANT CAUTION When matching this gas furnace with zoning, defrost tempering stat or other 24V accessories, Failure to use properly sized wiring and circuit breaker It is recommended to replace the factory installed may result in property damage. - Page 37 BLOWER SPEED CHART (ML193UH) FACTORY CONNECTED SPEED TAPS UNIT COOL HEAT PARK PARK BURNERS 030XE36BK BLACK YELLOW BROWN BLUE 045XE36BK BLACK YELLOW BLUE BROWN 070XE36BK BLACK BLUE BROWN YELLOW FLAME ROLLOUT FLAME FLAME ROLLOUT IGNITER BROWN 090XE36CK BLACK YELLOW BLUE SENSOR SWITCH SWITCH...
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Page 38: Ignition Control
Indoor Blower Operation DIP Switch Setting The heat Integrated Control fan-on time of 30 seconds is not adjustable The heat fan- Integrated Control DIP Switch Settings off delay (amount of time that the blower operates after the heat demand has been satisfied) may be adjusted ML193UHEK units are equipped with a single-stage inte- by changing the two position dip switch on the integrated grated control. -
Page 39: Wiring Connections
On Board Links Must NOT Be Cut To Select Thermostat Wiring Connections AC ON System Options Heat / Cool FURNACE OUTDOOR T'STAT TERM. STRIP UNIT DO NOT CUT ANY ON-BOARD LINKS FIGURE 60 Wiring Connections On Board Links Must Be Cut To Select Thermostat Heat Pump Options FURNACE... - Page 40 Single Stage, Constant Torque, Non-Communicating 107792-01 FIGURE 62 TABLE 10 TABLE 11 1/4” QUICK CONNECT TERMINALS THERMOSTAT INPUT TERMINALS HEAT 120V HUM POWER FOR HUMIDIFIER (120 VAC COMMON GROUND LINE INCOMING POWER LINE (120 VAC) 24V AC XFMR TRANSFORMER PRIMARY (120 VAC) CIRC INDOOR BLOWER MOTOR (120 VAC) COOL...
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Page 41: Ignition Control Diagnostic Codes
IGNITION CONTROL DIAGNOSTIC CODES DIAGNOSTIC CODES / STATUS OF FURNACE CODE IDLE MODE (DECIMAL BLINKS AT 1 HERTZ -- 0.5 SECONDS ON, 0.5 SECONDS OFF INDOOR BLOWER OPERATION: CONTINUOUS FAN MODE (CONSTANT TORQUE ONLY) INDOOR BLOWER OPERATION: FOLLOWED BY CFM SETTING FOR INDOOR BLOWER (1 SECOND ON, 0.5 SECOND OFF) / CFM SETTING FOR MODE DISPLAYED (VARIABLE SPEED ONLY) COOLING STAGE (1 SECOND ON, 0.5 SECOND OFF) 1 OR 2 DISPLAYED / PAUSE / REPEAT CODES. -
Page 42: Performance Warning
IGNITION CONTROL DIAGNOSTIC CODES (CONTINUED) SOFT LOCKOUT FAULTS (60 MINUTES) SOFT LOCKOUT-FLAME FAILURE ON IGNITION, IGNITION RETRY>MAX, LAST FAILED RETRY DUE E270 TO FLAME FAILURE SOFT LOCKOUT-PRESSURE SWITCH OPEN, IGNITION RETRY>MAX, LAST FAILED RETRY DUE TO E271 LPSW OPEN SOFT LOCKOUT-PRESSURE SWITCH OPEN, IN RUN MODE HEATING RECYCLES>MAX, LAST FAILED E272 RETRY DUE TO LPSW OPEN SOFT LOCKOUT-FLAME FAILURE IN RUN MODE,HEATING RECYCLES>MAX, LAST FAILED RETRY... -
Page 43: Twinning
The 24 VAC secondary of the two systems must be in Twinning Two ML193UHEK Furnaces phase. All thermostat connections are made to one control The control board in this furnace is equipped with a provi- only. See diagram below. sion to ”twin” (interconnect) two(2) adjacent furnaces with The twinned furnace without thermostat connections is a common plenum such that they operate as one (1) large to have the call for heat supplied by an external 24VAC... -
Page 44: Low Gwp Application
Low GWP Application WARNING For use with Lennox approved evaporator coil and LGWP sensors only. Use original manufacturer recommended LGWP sensors if using non Lennox approved evaporator coil. CONNECTING THE FURNACE CONTROL BOARD SENSOR. See FIGURE 65 and follow steps below: FIGURE 64 1 - Route sensor wire #1 through provided grommet. - Page 45 FURNACE CONTROL BOARD LOW GWP MODES OF 2. The furnace control board activates the blower (high OPERATION speed). The blower purges refrigerant from the cabinet, plenum, and ductwork. The modes of operation for the furnace control board are Initializing, Normal, Leak Detected, and Fault. 3.
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Page 46: Start-Up Procedure
LGWP TEST BUTTON FUNCTIONALITY External Alarm (For applications with external alarms wired directly to the The furnace control board is equipped with a Test/Reset furnace control board) push button. The Test button can be used to perform sev- The furnace control board triggers the external alarm sys- eral functions, depending on the mode of operation of the tem when it enters Leak Detected mode. -
Page 47: Unit Start-Up
6 - Adjust the thermostat to deactivate the heating Unit Start-Up demand and wait for the combustion air inducer to FOR YOUR SAFETY READ BEFORE OPERATING stop. At this point, the trap should be primed with sufficient water to ensure proper condensate drain WARNING operation. -
Page 48: Gas Pressure Measurement
4 - Move gas valve switch to OFF. Furnace should operate at least 5 minutes before check- ing gas flow. Determine time in seconds for two revolu- 5 - Replace the upper access panel. tions of gas through the meter. (Two revolutions assures Failure To Operate a more accurate time.) Divide by two and compare to time in TABLE 16. -
Page 49: Proper Combustion
Proper Combustion High Altitude Information Furnace should operate minimum 15 minutes with correct NOTE - In Canada, certification for installations at eleva- manifold pressure and gas flow rate before checking com- tions over 4500 feet (1372 m) is the jurisdiction of local bustion. -
Page 50: Testing For Combustion Air Non-Direct Vents
Testing for Proper Venting and Sufficient Combustion Air for Non-Direct Vent Applications 3 - To the extent that it is practical, close all building WARNING doors and windows and all doors between the space in which the appliances connected to the venting . -
Page 51: Other Unit Adjustments
Blower Speeds Other Unit Adjustments Follow the steps below to change the blower speeds. Primary Limit. 1 - Turn off electrical power to furnace. The primary limit is located on the heating compartment 2 - Remove blower access panel. vestibule panel. This limit is factory set and requires no adjustment. -
Page 52: Service
Perform a general system test. Turn on the furnace to At the beginning of each heating season, and to comply check operating functions such as the start-up and shut- with the Lennox Limited Warranty, your system should off operation. be checked as follows:... -
Page 53: Repair Parts List
Winterizing and Condensate Trap Care Repair Parts List 1 - Turn off power to the furnace. The following repair parts are available through Lennox 2 - Have a shallow pan ready to empty condensate dealers. When ordering parts, include the complete fur- water. -
Page 54: Unit Setup
Start-Up & Performance Check List UNIT SET UP (typical) Furnace: Model Number_______________ Serial Number_________________ SUPPLY Line Voltage GAS SUPPLY LP Propane Gas Natural Gas Piping Connections Tight Leak Tested Flter Supply Line Pressure “W.C.________ RETURN AIR Gas Supply Pressure DUCT SYSTEM SUPPLY AIR DUCT Sealed INTAKE / EXHAUST PIPE... -
Page 55: Unit Operation
UNIT OPERATION HEATING MODE COOLING MODE GAS MANIFOLD PRESSURE “W.C._____ INDOOR BLOWER AMPS______ COMBUSTION SAMPLE CO CO PPM_______ TEMPERATURE DROP ______ Return Duct Temperature _________ INDOOR BLOWER AMPS______ Supply Duct Temperature _______ Temperature Drop = _________ TEMPERATURE RISE TOTAL EXTERNAL STATIC (dry coil) Supply Duct Temperature ________ Supply External Static _______ Return Duct Temperature... - Page 56 4 - INSPECTION. The state or local gas inspector of the Requirements for Commonwealth of Massachusetts side wall, horizontally vented, gas-fueled equipment Modifications to NFPA-54, Chapter 10 shall not approve the installation unless, upon Revise NFPA-54 section 10.8.3 to add the following inspection, the inspector observes carbon monoxide requirements: detectors and signage installed in accordance with the...
- Page 57 FOR THE PROVINCE OF ONTARIO, HORIZONTAL ADDENDUM FOR ALL PROVINCES OF CANADA SIDEWALL VENT APPLICATIONS ONLY See below for venting in all provinces of Canada. Lennox For exterior horizontal venting applications, the 2” X 1.5” approves the following termination for use in all provinces reducer for 2”...
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Page 58: Blower Data
Blower Data ML193UH030XE36BK PERFORMANCE (Less Filter) Air Volume / Watts at Various Blower Speeds External High Medium-High Medium Medium-Low Static (Black) (Brown) (Blue) (Yellow) (Red) Pressure in. w.g. Watts Watts Watts Watts Watts 0.00 - - - - - - - - - - - - - - -... - Page 59 Blower Data ML193UH090XE36CK PERFORMANCE (Less Filter) Air Volume / Watts at Various Blower Speeds External Static High Medium-High Medium Medium-Low (Black) (Brown) (Blue) (Yellow) (Red) Pressure in. w.g. Watts Watts Watts Watts Watts 0.00 1478 1358 1211 0.10 1447 1326 1177 0.20 1416...
- Page 60 Blower Data ML193UH110XE48CK PERFORMANCE (Less Filter) Air Volume / Watts at Various Blower Speeds External Static High Medium-High Medium Medium-Low (Black) (Brown) (Blue) (Yellow) (Red) Pressure in. w.g. Watts Watts Watts Watts Watts 0.00 1783 1579 1445 1328 1232 0.10 1736 1519 1386...
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