Lennox International Inc. Merit Series Gas Furnace manual

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 ML180UH MERIT ® SERIES GAS FURNACE UPFLOW / HORIZONT AL AIR DISCHARGE 506816−01 06/201 1 Supersedes 506778−01 THIS MANUAL MUST BE LEFT WITH THE HOM[...]

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. Single side return air wit[...]

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 rollout switches) Combustion Air Inducer Combustion Air Inducer Pressure Switch Heat Exchanger Upper Access Panel Blower Access Panel Capacitor Primary L[...]

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. T he bottom p anel must b e removed if the unit is to b e i nstalled in a horiz[...]

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. See f igure 2. W ith a p arallel f low arrangement, a d amper (or other means to control t he flow of air) m us t adequ[...]

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.  When the furnace is inst alled in an attic or other ins[...]

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. This space also includes adjacent rooms which are not separated by a door . Though an area [...]

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. VENTILA TION LOUVERS (Eac[...]

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. The M L180UH g as furnace c an be installed as shipped in either t[...]

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. If the furnace i s installed on a platform w ith b ottom r etur n, make an a irtight s eal b etween the bottom of the furnace and the platform t o e nsur e t hat t he furnace operates pro[...]

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. Once the bottom panel has been removed, reinstall the bottom cap. See figure 1 1. Removing the Bottom Panel FIGURE 1 1 Screw Bottom Panel Bottom Cap Horizontal Application Installation Clearance[...]

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. Co mbustion and flue products must never be allowed to enter the ret [...]

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 . FIGURE 15 Mounting Screws Location Mounting Screws Flue Transition Up flow Position FIGURE 16 UPFLOW POSITION T op V ent Discharge FLOW AIR Collector B[...]

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 Z223.1) in the USA. A fan−assisted Category I fur- nace is an appliance equipped with an integral mechanical means t o either draw or force combustion product s th[...]

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. Refer to the cap[...]

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. PERMANENTL Y S[...]

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. 17 − If vent connectors are combined prior to entering the common vent, the maximum common vent capacity listed i n the c ommon venting t able[...]

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 − D (inches) 3 Inch 4 Inch 5 Inch 6 Inch Appliance Input Rating in Thousands of Btu Per Hour MIN MAX MIN MAX MIN MAX MIN MAX 6 0 38 77 59 151 85 249 1[...]

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 ent and Connector Diameter − D (inches) 3 Inch 4 Inch 5 Inch 6 Inch Appliance Input Rating in Thousands of Btu Per Hour MIN MAX MIN MAX MIN MAX MIN[...]

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 Connector Diameter − D (inches) 3 Inch 4 Inch 5 Inch 6 Inch Appliance Input Rating in Thousands of Btu Per Hour MIN MAX MIN MAX MIN MAX MIN MAX 6 1 NA NA[...]

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. Conduct t he following test while each appliance is operat- ing and t he o ther applia[...]

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. CAUTION If a flexible gas connector is required or allowed by the authority that has jurisdiction, black iron pipe shall b e inst alled at the gas valve and[...]

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. NPT Plugged T ap Shown) NOTE − BLAC[...]

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. The inst aller should proper[...]

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. Use the provided unit wiring diagram and the field wiring diagram shown i n fi[...]

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. Call for heat can continue. 3 − Integrated control (A92) energizes combustion air inducer B[...]

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 AC FUSE HEA T F AN OFF DELA Y JUMPER TERMINAL DESIGNA TIONS HUM LINE XFMR EAC COOL HEA T P ARK FLAME NEUTRALS Humidifier (120V AC) Input (120V AC) Tr[...]

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. Attempt s to use the furnace can result in fire or explosion. Immedi ately call a qualified ser- vice t echnician to i nspect the f urnace a n d t o replace all g as[...]

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. 2 − Combustion air pressure switch proves blower opera- tio[...]

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 3.5 3.2 2.8 3.5 4.5 13.0 LP/propane 10.0 10.0 10.0 10.0 1 1.0 13.0 090 Nat 3.5 3.2 2.7 3.5 4.[...]

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 90 120 180 60 Second off T ime 90 Second off T ime 120 Second off T ime 180 Second off T ime Thermost at Heat Anticipation Set the heat anticipator setting (if[...]

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 0.10 1620 663 1335 577 1 130 470 940 376 0.20 1570 619 1330 543 111 5 455 950 366 0.30[...]

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. Single Side Return Air − Air volumes in bold require eld fabricated transition [...]

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. Before servicing, disconnect all electrical power to fu[...]

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. 3 − Label the wires from gas valve, rollout switches, [...]

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. 1 1 − Backwash using steam. Begin fr om the burner opening on eac h clam. S team must n[...]

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 . Burners − Must be inspec[...]

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. SIMUL T ANEOUS F AST FLASH SIMUL T ANEOUS F AST FLASH Normal operation − [...]

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 . COMBUSTION AIR INDUCER OFF . INDOOR BLOWER DELA Y OFF . LED #1 ON LED #2 ON (RESET CONTROL B[...]

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. CAN FLAME BE PROVEN WITHIN 4 SECONDS AFTER GAS V AL VE OPENS? (0.5 microamps) FLAME PRESENT? INDOOR BLOWER ON AFTER 30−SECOND DELA Y PRIMARY AND SECONDARY LIMIT SWITCHES CL[...]

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. CONTROL WILL CONTINUE TO CALL FOR COOLING IN THIS CONDITION. POWER ON GAS V AL VE OFF .[...]

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. EAC TERMINAL IS ENERGIZED. THERMOST A T CALLS FOR HEA T (W). THERMOST A T CALL[...]