Instruction/ maintenance manual of the product Merit Series Gas Furnace Lennox International Inc.
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Page 1 06/1 1 *2P0611* 506816−01 *P506816-01* 201 1 Lennox Industries Inc. Dallas, T exas, USA AIR FLOW UPFLOW AIR FLOW AIR FLOW HORIZONT AL RIGHT HORIZONT AL LEFT INST ALLA TION INSTRUCTIONS ML.
Page 2 Unit Dimensions − inches (mm) 2 Flue outlet may be horizontal but furnace must be vented vertically 3 Optional external side return air filter kit cannot be used with the optional RAB Return Air Base. 1 NOTE − 60C and 60D unit s that require air volumes over 1800 cfm (850 L/s) must have one of the following: 1.
Page 3 Part s Arrangement FIGURE 1 Secondary Limits Blower Assembly Control Box (includes integrated control, interlock switch and transformer) Gas V alve Burner Box (includes sensor , ignitor and rol.
Page 4 ML180UH Gas Furnace The ML180UH unit is shipped ready for installation in the upflow o r horizontal right position (for horizontal left posi- tion the combus tion air pr essur e switch m us t be moved). The f ur nace is s hipped with t he bottom p anel i n place.
Page 5 Installed in Combination with a Cooling Coil When this furnace is used wi th cooling units, it shall be installed in parallel with, or on the upstream side of, cooling units to avoid condensation in the heating compartment.
Page 6 Do not install the furnace where drafts might blow direct- ly into it. This could cause improper combustion and un- safe operation. Do not block the furnace combustion air openings with clothing, boxes, doors, etc. Air is needed for proper combustion and safe unit operation.
Page 7 Unconfined Sp ace An unconfined space is an area such as a basement or large equipment room with a volume greater than 50 cubic feet (1.42 m 3 ) per 1,000 Btu (.29 kW) per hour of the com- bined input rating of all appliances inst alled in that space.
Page 8 EQUIPMENT IN CONFINED SP ACE ALL AIR FROM OUTSIDE (Inlet Air from Crawlspace and Outlet Air to V entilated Attic) NOTE−The inlet and outlet air openings shall each have a free area of at least one square inch (645 mm 2 ) per 4,000 Btu (1.17 kW) per hour of the tot al input rating of all equipment in the enclosure.
Page 9 Setting Equipment W ARNING Do not install the furnace on it s front or it s back. Do no t connect the return air duct s to the back of the fur- nace. Doing so w ill adversely affect the operation of the safety control devices, which could result in per- sonal injury or death.
Page 10 Return Air −− Upflow Applications Return air can be brought in through the bottom or either side o f the furnace installed in an upflow a pplic ation.
Page 1 1 Removing the Bottom Panel Remov e the two screws that secure the bottom cap to the furnace. Pivot the bottom cap down to release the bottom panel.
Page 12 Horizontal Application Unit Inst alled on Platform FIGURE 14 clearances. GAS ENTRY VENT PIPE See the unit nameplate for Line contact is permissible but not preferred SERVICE PLA TFORM W ARNING Improper inst allation of the furnace can result in per- sonal injury or death.
Page 13 V enting A 4−inch diameter flue transition is factory-installed on the combustion air inducer outlet of all models. Figure 16 shows the combustion air inducer as shipped from the factory .
Page 14 HORIZONT AL LEFT POSITION T op V ent Discharge FIGURE 19 Disconnect pressure switch hose from barbed fitting on the pressure switch assembly . Remove pressure switch assembly (1 screw) and cut wire tie to free pressure switch wires. Re− install pressure switch on the other side of orifice plate and re− connect pressure switch hose.
Page 15 The ML180UH series unit s are classified as fan−assisted Category I furnaces when vertically vented according to the latest edition of National Fuel Gas Code (NFP A 54 / ANSI Z223.
Page 16 FIGURE 24 Common V enting Using Metal−Lined Masonry Chimney 4 in. (102 mm) minimum MIN. LENGTH −− AS SHORT AS PRACTICAL MAX. LENGTH −− SEE NOTE 1 BELOW . SEALED PERMANENTL Y SEALED FIREPLACE OPENING EXTERIOR CHIMNEY WITH MET AL LINER VENT CONNECTOR NOTE 1 − Refer to the provided venting tables for installations.
Page 17 FIGURE 25 Common V enting Using Tile−Lined Interior Masonry Chimney and Combined V ent Connector MINIMUM LENGTH = AS SHORT AS PRACTICAL. FOR MAXIMUM LENGTH SEE NOTE TO LEFT INTERIOR TILE−LINED MASONR Y CHIMNEY NOTE − the chimney must be properly sized per provided venting tables or lined with listed metal lining system.
Page 18 16 − V ent connectors serving Category I appliances shall not be connected to any portion of mechanical draft systems operating under positive pressure such as Category III or IV venting systems.
Page 19 T ABLE 4 Cap acity of T ype B Double−W all V ent s with Single−Wall Met al Connectors Serving a Single Category I Appliance Height H (feet) Lateral L (feet) V ent and Connector Diameter .
Page 20 T ABLE 5 V ent Connector Capacity T ype B Double−Wall V ents with T ype B Double−W all Connectors Serving T wo or More Category I Appliances V ent Height H (feet) Connector Rise R (feet) V.
Page 21 T ABLE 7 V ent Connector Capacity T ype B Double−Wall V ents with Single−W all Met al Connectors Serving T wo or More Category I Appliances Height H (feet) Lateral L (feet) V ent and Conne.
Page 22 Removal of the Furnace from Common V ent In the event that an existing furnace is removed from a venting system commonly ru n with separate gas ap - pliances, the venting system is likely to be too large to properly vent the remaining attached appliances.
Page 23 Gas Piping Gas s upply p iping s hould not allow more t han 0 .5" W .C. d rop in press ure between gas meter and unit. Supply gas pipe must not be smaller than unit gas connection.
Page 24 GROUND JOINT UNION AUTOMA TIC GAS V AL VE FIELD PROVIDED AND INST ALLED GROUND JOINT UNION Left Side Piping (St andard) Right Side Piping (Alternate) AUTOMA TIC GAS V AL VE DRIP LEG DRIP LEG MANUAL MAIN SHUT−OFF VA LV E (With 1/8 in. NPT Plugged T ap Shown) MANUAL MAIN SHUT−OFF VA LV E (With 1/8 in.
Page 25 Leak Check After gas piping is completed, carefully check all piping connections (factory− and field−installed) for gas leaks. Use a leak detecting solution or other preferred means. NOTE − I f emergency shutoff is necessary , shut off the main manual gas valve and disconnect the main power to the furnace.
Page 26 Before connecting the thermost at, check to make sure the wires will be long enough for servicing at a later date. Make sure that thermost at wire is long enough to facilitate future removal of blower for service. Complete the wiring connections to the equipment.
Page 27 1 − When there is a call for heat, W1 of the thermost at energizes W of the furnace control with 24V AC. 2 − Integrated control runs a self−check. S10 primary limit, S47 rollout switch and S21 secondary limit cont acts are found to be closed.
Page 28 TYPICAL ML180UH FIELD WIRING DIAGRAM FIGURE 33 IGNITOR *R *NOTE − R" REQUIRED ON SOME OUTDOOR UNITS FIGURE 34 INTEGRA TED CONTROL (Automatic Hot Surface Ignition System) 3 AMP , 32 V.
Page 29 Unit S t art−Up FOR YOUR SAFETY READ BEFORE LIGHTING W ARNING Do not use this furnace if any part has been under- water . A flood−damaged fu rnace is extremely dan- gerous.
Page 30 1 1 − Are flame rollout switches tripped? If flame rollout switches are tripped, call the service technician for in- spection. Heating Sequence Of Operation (follow steps below or see Figure 32 for more detail) 1 − When thermostat calls for heat, combustion air blower starts.
Page 31 T ABLE 12 Manifold Pressure Settings at all Altitudes Model Input Size Gas 0−2000 ft 2105−4500 ft. 4501−7500 ft 7501 − 10,000 ft Line Pressure in.wg. Min Max 045 Nat 3.5 3.2 3.0 3.5 4.5 13.0 LP/propane 10.0 10.0 10.0 10.0 1 1.0 13.0 070 Nat 3.
Page 32 HEA T F AN-OFF TIME IN SECONDS T o adjust fan−off timing, reposition jumper across pins to achieve desired setting. NO JUMPER FIGURE 36 60 90 120 180 60 90 120 180 60 90 120 180 60 90 120 18.
Page 33 BLO WER D A T A ML180UH045P36A PERFORMANCE (Less Filter) External Static Pressure in. w .g. Air V olume / Watts at V arious Blower Speeds High Medium- High Medium- Low Low cfm W atts cfm Watts cfm W atts cfm Watts 0.00 1670 7 11 1335 614 1 140 485 925 388 0.
Page 34 ML180UH1 10P60C PERFORMANCE (Less Filter) External Static Pressure in. w .g. Air V olume / Watts at Different Blower Speeds Bottom Return Air , Side Return Air with Optional Return Air Base, Return Air from Both Sides or Return Air from Bottom and One Side.
Page 35 Service W ARNING ELECTRICAL SHOCK, FIRE, OR EXPLOSION HAZARD. Failure t o follow safety warnings exactly could result in dangerous operation, serious injury , death or property damage. Improper servicing could result in dangerous opera- tion, serious injury , death, or property damage.
Page 36 Cleaning the Heat Exchanger and Burners NOTE − Use p apers or protective covering in front of the fur- nace during cleaning. 1 − T urn off both electrical and gas power supplies to fur- nace. 2 − Remove flue pipe and top cap (some applications top cap can remain ) from the unit.
Page 37 9 − Remove screws from bo th sides, top and bottom of vestibule panel. 10 − Remove heat exchanger . It may be necessary to spread cabinet side to allow more room. If so, remove five screws from the left side or right side of cabinet. See figure 39.
Page 38 Planned Service Th e following items should be checked during an annual inspection. Power to the unit must be shut off for the service techni- cian’s safety . Fresh air grilles and louvers (on the unit and in the room where the furnace is installed) − Must be open and unob- structed to provide combustion air .
Page 39 Integrated Control Diagnostic Codes DIAGNOSTIC CODES Make sure to Identify LED’S Correctly . LED #1 (Red) LED #2 (Green) DESCRIPTION SIMUL T ANEOUS SLOW FLASH SIMUL T ANEOUS SLOW FLASH Power on − Normal operation. Also signaled during cooling and continuous fan.
Page 40 T roubleshooting: Heating Sequence of Operation HEA TING SEQUENCE OF OPERA TION NORMAL HEA TING MODE ABNORMAL HEA TING MODE CONTROL SELF−CHECK OKA Y? NORMAL OPERA TION: LED #1 −− SLOW FLASH LED #2 −− SLOW FLASH NO YES YES GAS V AL VE OFF .
Page 41 T roubleshooting: Heating Sequence of Operation (Continued) HEA TING SEQUENCE CONTINUED NORMAL HEA TING MODE ABNORMAL HEA TING MODE FLAME RECTIFICA TION CURRENT CHECK.
Page 42 T roubleshooting: Cooling Sequence of Operation COOLING SEQUENCE OF OPERA TION NORMAL COOLING MODE ABNORMAL COOLING MODE IGNITION CONTROL MAIN POWER ON. CONTROL SELF DIAGNOSTIC CHECK. IS CONTROL OPERA TING NORMALL Y? YES SIGNAL POLARITY REVERSED A T LED.
Page 43 T roubleshooting: Continuous Fan Sequence of Operation CONTINUOUS HEA T SPEED F AN SEQUENCE OF OPERA TION LED: SLOW FLASH RA TE REMAINS UNCHANGED THROUGHOUT SEQUENCE. MANUAL F AN SELECTION MADE A T THERMOST A T . CONTROL (G) ENERGIZES SYSTEM F AN A T HEA T SPEED.
An important point after buying a device Lennox International Inc. Merit Series Gas Furnace (or even before the purchase) is to read its user manual. We should do this for several simple reasons:
If you have not bought Lennox International Inc. Merit Series Gas Furnace yet, this is a good time to familiarize yourself with the basic data on the product. First of all view first pages of the manual, you can find above. You should find there the most important technical data Lennox International Inc. Merit Series Gas Furnace - thus you can check whether the hardware meets your expectations. When delving into next pages of the user manual, Lennox International Inc. Merit Series Gas Furnace you will learn all the available features of the product, as well as information on its operation. The information that you get Lennox International Inc. Merit Series Gas Furnace will certainly help you make a decision on the purchase.
If you already are a holder of Lennox International Inc. Merit Series Gas Furnace, but have not read the manual yet, you should do it for the reasons described above. You will learn then if you properly used the available features, and whether you have not made any mistakes, which can shorten the lifetime Lennox International Inc. Merit Series Gas Furnace.
However, one of the most important roles played by the user manual is to help in solving problems with Lennox International Inc. Merit Series Gas Furnace. Almost always you will find there Troubleshooting, which are the most frequently occurring failures and malfunctions of the device Lennox International Inc. Merit Series Gas Furnace along with tips on how to solve them. Even if you fail to solve the problem, the manual will show you a further procedure – contact to the customer service center or the nearest service center
