Lennox Merit ML296UH090XV48C Unit Information Download Page 51

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Page 51

Heating

On a call for heat from the room thermostat, the control

board performs a 1 second self check. Upon confirma

tion that the pressure switch contacts are in an open posi

tion, the control energizes the combustion blower on high

speed. The control then checks for adequate combustion

air by making sure the low-fire pressure switch contacts

are closed.
The igniter energizes and is allowed to warm up for 20

seconds before the gas valve energizes on 1st stage and

burners ignite. 30 seconds after ignition the circulating

blower is energized. 45 seconds after the control confirms

ignition has occurred, the control drops the combustion

blower to low speed.
The circulating blower operates at full 1st stage heat speed
until either the heat call is satisfied or the thermostat initi

ates a call for 2nd stage heat. On a call for 2nd stage heat,

the control energizes the circulating air blower on full CFM

2nd stage heat.
If the automatic heat staging option is being used the fur

nace does not switch to 2nd stage heat in response to a

call from the thermostat but instead operates at 1st stage

heat for the duration of the selected time before automati

cally switching to 2nd stage heat.
When the call for heat is satisfied, the gas valve and com

bustion air blower shut down. The control board shuts off

the gas valve and runs the combustion blower for an addi

tional 15 seconds. The circulating air blower continues to

run the selected heat blower off delay time. before ramp

ing down. In the event the unit loses ignition, the control

will attempt to recycle up to five times before it goes into

a 1 hour lockout.
Lockout may be manually reset by removing power from

the control for more than 1 second or removing the ther

mostat call for heat for more than 3 seconds.
If during a heating cycle the limit control senses an ab

normally high temperature and opens, the control board

deenergizes the gas valve and the combustion blower

while the circulating blower ramps up to 2nd stage heat

speed. The circulating blower remains energized until the

limits are closed.

Fan On

When the thermostat is set for continuous fan operation

and there is no demand for heating or cooling, a call for

fan closes the R to G circuit energizing the the circulating

blower. For -55 units the motor runs at 50% of the selected

cooling CFM and for -56 units the motor runs at 38% of the

selected cooling CFM, until switched off. When the call for

fan is turned off, the control de-energizes the circulating

blower.

Cooling

The unit is set up at the factory for single stage cooling.

For two stage cooling operation, clip the jumper wire lo

cated between the Y to Y2 terminals on the integrated ig

nition/ blower control board. If the active dehumidification

feature is enabled, the circulating blower runs at 70% of

the selected cooling speed as long as there is a call for

dehumidification.

IMPORTANT

The system MUST NOT be in either the passive

OR active dehumidification mode when charging a

cooling system.

Single Stage Cooling

A call for cooling from the thermostat closes the R to Y

circuit on the integrated ignition/blower control board. The

control waits for a 1-second delay before energizing the

circulating blower to 82% of the selected cooling CFM

(passive dehumidification mode). After 7.5 minutes, the

circulating blower automatically ramps up to 100% of the

selected cooling airflow. When the call for cooling is satis

fied, the circulating blower ramps back down to 82% of the

selected cooling airflow for 1 minute, then shuts off.

Two-Stage Cooling

A call for 1st stage cooling from the thermostat closes the

R to Y circuit on the control board. The control waits for a

1- second delay before energizing the circulating blower.

The blower motor runs at 57% of the selected air flow for

the first 7.5 minutes of the 1st stage cooling demand (pas

sive dehumidification mode). After 7.5 minutes, the blower

motor runs at 70% of the selected cooling air flow until 1st

stage cooling demand is satisfied.
A call for 2nd stage cooling from the thermostat closes

the R to Y2 circuit on the control board. The blower motor

ramps up to 100% of the selected cooling air flow. When

the demand for cooling is met, the blower ramps down to

Y1 until satisfied, then ramps down to 57% for 1 minute,

then turns off.

Heat Pump

For heat pump operation, clip the jumper wire located bel

low the O terminal on the integrated ignition/blower control

board. In heat pump mode, a call for heat will result in the

circulating air blower operating at the selected cooling air

flow after a brief ramp-up period.

Summary of Contents for Merit ML296UH090XV48C

Page 1: ...ations up to 5 tons Refer to Engineering Handbook for proper sizing Units are factory equipped for use with natural gas Kits are available for conversion to LPG operation ML296U HV X unit meets the California Nitrogen Oxides NOx Standards and California Seasonal Efficiency require ments All units use a redundant gas valve to assure safe ty shut off as required by C S A All specifications in this m...

Page 2: ... according to FTC labeling regulations Isolated combustion system rating for non weatherized furnaces SPECIFICATIONS Gas Heating Performance Model No ML296UH090XV48C ML296UH110XV60C 1 AFUE 96 96 High Fire Input Btuh 88 000 110 000 Output Btuh 84 000 106 000 Temperature rise range F 45 75 45 75 Gas Manifold Pressure in w g Nat Gas LPG Propane 3 5 10 0 3 5 10 0 Low Fire Input Btuh 57 000 72 000 Outp...

Page 3: ...Single 44J22 44J22 Ten Pack 66K63 66K63 Size of filter in 16 x 25 x 1 16 x 25 x 1 TERMINATION KITS See Installation Instructions for specific venting information Direct Vent Concentric US 2 in 71M80 69M29 3 in 60L46 Canada 2 in 44W92 44W92 3 in 44W93 Flush Mount US 2 2 1 2 or 3 in 51W11 51W11 Canada 2 2 1 2 or 3 in 51W12 51W12 Wall Close Couple US 2 in 22G44 3 in 44J40 44J40 Wall Close Couple WTK ...

Page 4: ...ML296UH045XV36B BLOWER MOTOR WATTS COOLING Jumper Speed Positions Motor Watts Various External Static Pressures in wg First Stage Second Stage 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 0 Plus SETTING Adjust Jumper at Setting COOL Speed Tap D 20 35 58 79 99 125 148 168 197 63 89 112 140 171 193 222 247 267 295 321 Tap C 49 73 98 120 141 169 187 212 242 123 147 181 20...

Page 5: ...296UH070XV36B BLOWER MOTOR WATTS COOLING Jumper Speed Positions Motor Watts Various External Static Pressures in wg First Stage Second Stage 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 0 Plus SETTING Adjust Jumper at Setting COOL Speed Tap D 35 56 79 101 124 146 164 192 214 86 110 139 167 190 223 249 268 297 321 347 Tap C 50 72 103 126 151 174 199 222 243 134 163 196 ...

Page 6: ... ML296UH090XV48C BLOWER MOTOR WATTS COOLING Jumper Speed Positions Motor Watts Various External Static Pressures in wg First Stage Second Stage 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 0 Plus SETTING Adjust Jumper at Setting COOL Speed Tap D 48 71 94 117 144 164 186 207 234 110 135 165 194 219 243 274 299 330 351 378 Tap C 71 94 121 146 169 193 214 245 266 179 208 ...

Page 7: ...y speed is approximately 38 of the same second stage COOL speed position Lennox Harmony III Zoning System Applications Minimum blower speed is 460 cfm ML296UH110XV60C BLOWER MOTOR WATTS COOLING Jumper Speed Positions Motor Watts Various External Static Pressures in wg First Stage Second Stage 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 0 Plus SETTING Adjust Jumper at ...

Page 8: ...Valve Heat Exchanger Combustion Air Inducer Pressure Switch Assembly Primary Limit Variable Speed Motor Two Stage Integrated Control Access Panel Bag Assemblies shipping location Field Make Up Box Door Interlock Switch 16X4W Box some models Access Panel FIGURE 1 ...

Page 9: ... to various system inputs such as thermostat signal pressure and limit switch signal and flame signal The furnace has a built in self diagnostic capability If a system problem occurs a fault code is shown by a red LED on the control The control continuously monitors its own operation and the operation of the system If a failure occurs the LED will indicate the failure code The flash codes are pres...

Page 10: ...delay on ML296 55 and earlier units is factory set at 120 seconds and NON ADJUSTABLE TABLE 4 12 Pin Terminal Designation Pin Function 1 Gas Valve Second Stage 2 Second Stage Prove Switch 3 Rollout Switch In 4 Ground 5 24V Hot 6 Primary Limit In 7 Gas Valve First Stage 8 Gas Valve Common 9 24V Neutral 10 Ground 11 Rollout Switch Out 12 First Stage Prove Switch Heating Mode These units are factory s...

Page 11: ...Input 120VAC XFMR Transformer 120VAC EAC Indoor Air Accessory 120VAC Cool Cool Speed 120VAC Park 1 Dead terminal for alternate speed tap Park 2 Dead terminal for alternate speed tap Heat Stage Jumper single stage shown Heat Taps Cool Taps Air Flow Jumper Fan Off Delay FIGURE 3 ...

Page 12: ...l with three LED s PW RX and TX located on the face for trou bleshooting FIGURE 7 shows the location of the 16X4W and TABLE 5 the LED codes The 16X4W may be located on the indoor blower housing on some models FIGURE 8 BLOWER MOTOR COMPONENTS STATOR WINDINGS OUTPUT SHAFT BEARING ROTOR FIGURE 5 GenTeq BLOWER MOTOR B3 MOTOR CONTROLLER J49 J48 FIGURE 6 NIDEC BLOWER MOTOR B3 MOTOR CONTROLLER 16X4W May ...

Page 13: ...nect switch is bounced when the disconnect is closed the disconnect contacts may become welded Try not to bounce the disconnect switch when applying power to the unit Motor Start Up When B3 begins start up the motor gently vibrates back and forth for a moment This is normal During this time the electronic controller is determining the exact position of the rotor Once the motor begins turning the c...

Page 14: ...is used on 5 ton 1 hp units The choke is located on the blower housing and is used to suppress transient current spikes Precautions If the furnace or its electronically controlled blower mo tor is improperly or inadequately grounded it may cause television interference commonly known as RFI or radio frequency interference This interference is caused by internal switching frequen cies of the motor ...

Page 15: ...C O volts 325VDC WINDING 1 WINDING 2 WINDING 3 O volts 325VDC O volts 325VDC O volts 325VDC WINDING 1 WINDING 2 WINDING 3 O volts 325VDC O volts 325VDC O volts 325VDC Motor speed is determined by the size of the electrical pulse sent to the motor windings The longer the pulse the faster the motor One Pulse ON PULSE OFF PULSE WINDINGS TURNED OFF The frequency of the pulses to the windings is 20KHz ...

Page 16: ...ox Kits in clude burner orifices and a gas valve 4 Flame Rollout Switches S47 Flame rollout switch is a high temperature limit located on top of the burner box one on each side See FIGURE 12 The limit is a N C SPST manual reset limit When S47 senses rollout the circuit breaks and the ignition con trol immediately stops ignition and closes the gas valve Rollout can be caused by a blocked heat excha...

Page 17: ...Page 17 HEATING COMPONENTS Intake Air Top Cap Sensor Rollout Switch Rollout Switch Burner Assembly Ignitor Manifold And Gas Orifices Two Stage Gas Valve Burner Box Cover FIGURE 12 ...

Page 18: ... the plug Reading should be between 39 and 70 ohms If the reading is correct then the problem is with the wiring between the jack plug and the control If reading is not correct the issue is the ignitor Test 3 Check ignitor for correct voltage Insert meter probes into terminals 1 and 5 use small diameter probes in order not to damage plug Check voltage during 20 second ignitor warm up period Voltag...

Page 19: ...700 070 0 920 090 1 100 110 1 155 8 Combustion Air Inducer Pressure Switch S18 Units are equipped with a dual combustion air pressure switch first and second stage located on the combustion air inducer orifice bracket See FIGURE 14 The switch is connected to the combustion air inducer housing by means of a flexible silicone hose It monitors negative air pressure in the combustion air inducer housi...

Page 20: ...ubing and tee into the tubing from the negative side of the cold end header box and the other side of the 2 square tubing Connect the other end of the 10 square tubing the the negative side of the measuring device 5 Operate unit and observe manometer reading Readings will change as heat exchanger warms a Take one reading immediately after start up b Take a second reading after unit has reached ste...

Page 21: ...pe from the furnace flue collar must be accessible for inspection IMPORTANT Exhaust and intake connections are made of PVC Use PVC primer and solvent cement when using PVC vent pipe When using ABS vent pipe use transitional solvent cement to make connections to the PVC fittings in the unit Use PVC primer and solvent cement or ABS solvent ce ment meeting ASTM specifications refer to TABLE 11 As an ...

Page 22: ...o ULC S636 for use in Canada only 5 See TABLE 17 for vent accelerator requirements 6 2 in pipe to 1 1 2 in reducer required and must be field provided Joint Cementing Procedure DANGER DANGER OF EXPLOSION Fumes from PVC glue may ignite during system check Allow fumes to dissipate for at least 5 minutes before placing unit into operation 1 Measure and cut vent pipe to desired length 2 Debur and cham...

Page 23: ...OXIDE POISONING HAZARD Failure to follow the steps outlined below for each appliance connected to the venting system being placed into operation could result in carbon monoxide poisoning or death The following steps shall be followed for each appliance connected to the venting system being placed into operation while all other appliances connected to the venting system are not in operation 1 Seal ...

Page 24: ...ximum vent lengths termination clearances etc apply and must be followed Follow the instructions provided with PoyPro by DuraVent and Inno Flue by Centrotherm venting system for assembly or if re quirements are more restrictive The PolyPro by Duravent and InnoFlue by Centrotherm venting system must also follow the uninsulated and unconditioned space criteria listed in TABLE 16 The ML296UHV can be ...

Page 25: ...VENT PIPE LENGTHS ML296UHV MODEL MIN VENT LENGTH 045 070 090 110 15 ft or 5 ft plus 2 elbows or 10 ft plus 1 elbow Anyapprovedterminationmaybeaddedtotheminimumlength listed Two 45 degree elbows are the equivalent to one 90 de gree elbow IMPORTANT Do not use screens or perforated metal in exhaust or intake terminations Doing so will cause freeze ups and may block the terminations Use the following ...

Page 26: ...5 95 73 38 118 117 98 98 6 56 41 19 90 90 68 33 113 112 93 93 7 51 36 14 85 85 63 28 108 107 88 88 8 46 31 n a 80 80 58 23 103 102 83 83 9 41 26 75 75 53 18 98 97 78 78 10 36 21 70 70 48 13 93 92 73 73 Standard Termination Elevation 4500 10 000 ft No Of 90 Elbows Usedl 1 1 2 Pipe 2 Pipe 2 1 2 Pipe 3 Pipe Model Model Model Model 045 070 090 110 045 070 090 110 045 070 090 110 045 070 090 110 1 25 2...

Page 27: ...39 106 106 99 99 5 53 38 22 85 85 69 34 101 101 94 94 6 48 33 17 80 80 64 29 96 96 89 89 7 43 28 12 75 75 59 24 91 91 84 84 8 38 23 n a 70 70 54 19 86 86 79 79 9 33 18 65 65 49 14 81 81 74 74 10 28 13 60 60 44 n a 76 76 69 69 Concentric Termination Elevation 4500 10 000 ft No Of 90 Elbows Used 1 1 2 Pipe 2 Pipe 2 1 2 Pipe 3 Pipe Model Model Model Model 045 070 090 110 045 070 090 110 045 070 090 1...

Page 28: ... 15 10 66 51 29 9 95 95 73 38 113 112 93 93 3 10 n a 61 46 24 4 90 90 68 33 108 107 88 88 4 n a 56 41 19 n a 85 85 63 28 103 102 83 83 5 51 36 14 80 80 58 23 98 97 78 78 6 46 31 9 75 75 53 18 93 92 73 73 7 41 26 4 70 70 48 13 88 87 68 68 8 36 21 n a 65 65 43 8 83 82 63 63 9 31 16 60 60 38 3 78 77 58 58 10 26 11 55 55 33 n a 73 72 53 53 Standard Termination Elevation 4500 10 000 ft No Of 90 Elbows ...

Page 29: ...er pipe in horizontal runs of exhaust pipe Exhaust 6 Min FIGURE 20 SIDE VIEW 2 2 2 or TYPICAL EXHAUST AND INTAKE PIPE CONNECTIONS IN HORIZONTAL DIRECT OR NON DIRECT VENT APPLICATIONS RIGHT HAND DISCHARGE SHOWN 3 2 45 MAX 45 MAX DO NOT transition from smaller to larger pipe in horizontal runs of exhaust pipe EXHAUST 12 max 2 2 When transitioning up in pipe size use the shortest length of 2 PVC pipe...

Page 30: ...n installing the unit in Non Direct Vent applications where combustion air is taken from indoors or ventilated attic or crawlspace and flue gases are discharged outdoors 1 Use field provided materials and the factory provided air intake screen to route the intake piping as shown in FIGURE 22 and FIGURE 23 Maintain a minimum clearance of 3 76mm around the air intake opening The air intake opening w...

Page 31: ...from outdoors and the flue gases are discharged to the out doors The ML296UHV is then classified as a direct vent Cate gory IV gas furnace In both Non Direct Vent and Direct Vent applications the vent termination is limited by local building codes In the absence of local codes refer to the current National Fuel Gas Code ANSI Z223 1 NFPA 54 in U S A and current CSA B149 Natural Gas and Propane Inst...

Page 32: ...n a 13 n a 12 n a 3 in 1 1 2 2 8 8 7 7 1Refer to 99 Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook 2 Poly Propylene vent pipe PP by Duravent and Centrotherm 3 Vent length in table is equivalent length Consider each elbow as 5ft of linear length NOTE Concentric terminations are the equivalent of 5 and should be considered when measuring pipe len...

Page 33: ...n public property Clearance under veranda porch deck or balcony 12 Equal to or greater than soffit depth 3 feet 9m 12 3 feet 9m within a height 15 feet 4 5m above the meter regulator assembly 3 feet 9m 6 inches 152mm for appliances 10 000 Btuh 3kw 12 inches 305mm for appliances 10 000 Btuh 3kw and 100 000 Btuh 30kw 36 inches 9m for appliances 100 000 Btuh 30kw 3 feet 9m above if within 10 feet 3m ...

Page 34: ...randa porch deck or balcony 12 7 feet 2 1m 3 feet 9m within a height 15 feet 4 5m above the meter regulator assembly 3 feet 9m 6 inches 152mm for appliances 10 000 pliances 10 000 Btuh 3kw and 50 000 pliances 50 000 Btuh 15kw 6 inches 152mm for appliances 10 000 Btuh 3kw 12 inches 305mm for appliances 10 000 Btuh 3kw and 100 000 Btuh 30kw 36 inches 9m for appliances 100 000 Btuh 30kw 3 feet 9m abo...

Page 35: ...paration requirement of intake and exhaust pipe DOES NOT apply 3 On roof terminations the intake piping should terminate straight down using two 90 elbows See FIGURE 29 4 Exhaust piping must terminate straight out or up as shown A reducer may be required on the exhaust piping at the point where it exits the structure to improve the velocity of exhaust away from the intake piping See TABLE 17 5 On ...

Page 36: ...PROVIDED REDUCER MAY BE REQUIRED TO ADAPT DIFFERENT VENT PIPE SIZE TO TERMINATION INTAKE Accelerator not required for 3 concentric 12 305mm FIGURE 33 12 305mm Min above grade or average snow ac cumulation DIRECT VENT CONCENTRIC WALL TERMINATION 71M80 69M29 or 60L46 US 44W92 or 44W93 Canada INTAKE AIR EXHAUST AIR INTAKE AIR INTAKE AIR EXHAUST AIR OUTSIDE WALL GRADE CLAMP Not Furnished FIELD PROVIDE...

Page 37: ...12 305 mm Min 16 405 mm Max 6 152 mm Max 6 152 mm Min 24 610 mm Max 9 227 mm Min 12 305 mm Min 20 508 mm Max 6 152 mm Max Intake Elbow WALL SUPPORT B A D E B D E A ALTERNATE TERMINATIONS TEE FORTY FIVE DEGREE ELBOWS ONLY D C 12 1 2 E B A 1 The exhaust termination tee should be connected to the 2 or 3 PVC flue pipe as shown in the illustration Do not use an accelerator in applications that include ...

Page 38: ...or other obstructions piping must be supported every 24 inches 610MM When exhaust piping must be run up an outside wall any reduction in exhaust pipe size must be done after the final elbow 4 Distance between exhaust pipe terminations on multiple furnaces must meet local codes Crawl Space and Extended Horizontal Venting Lennox provides kit 51W18 to install 2 or 3 PVC exhaust piping through the flo...

Page 39: ...urnace to the drain 5 FIGURE 44 and FIGURE 45 show the furnace and evaporator coil using a separate drain If necessary the condensate line from the furnace and evaporator coil can drain together See FIGURE 46 FIGURE 47 and FIGURE 48 Upflow furnace FIGURE 47 In upflow furnace applications the field provided vent must be a minimum 1 to a maximum 2 length above the condensate drain outlet connection ...

Page 40: ...ible a heat cable kit may be used on the condensate trap and line Heating cable kit is avail able from Lennox in various lengths 6 ft 1 8m kit no 26K68 24 ft 7 3m kit no 26K69 and 50 ft 15 2m kit no 26K70 Furnace With Evaporator Coil Using A Separate Drain Condensate DrainConnection Field Provided Vent 1 min 2 max above condensate connection Evaporator drain line required Trap at coil is optional ...

Page 41: ...low Switch FIGURE 46 Furnace with Evaporator Coil Using a Common Drain 1 min to 2 Max above condensatedrain connection Condensate DrainConnection Evaporator drain line required Trap at coil is optional FIGURE 47 Furnace with Evaporator Coil Using a Common Drain Unit shown in horizontal left hand discharge position Condensat e Drain Connection 4 min to 5 Max above condensatedrain connection 5 max P...

Page 42: ...ection In Unit Condensate Drain Connection In Unit Vent To Drain Condensate Drain Connection In Unit Optional Condensate Drain Connection OptionalDrainPipingFromTrap DrainTrapAssembly Furnished DrainTrap Assembly with 1 2 inch Piping DrainTrap Assembly with 3 4 inch Piping 1 2 inch 3 4 inch 1 25 mm Min 2 50 mm Max Above Top Of Condensate Drain Connection In Unit 1 25 mm Min 2 50 mm Max Above Top O...

Page 43: ...primed with sufficient water to ensure proper condensate drain operation WARNING If you do not follow these instructions exactly a fire or explosion may result causing property damage personal injury or death Gas Valve Operation FIGURE 50 1 STOP Read the safety information at the beginning of this section 2 Set the thermostat to the lowest setting 3 Turn off all electrical power to the unit 4 This...

Page 44: ...ocated on the gas valve provides access to the supply pressure See FIGURE 50 Back out the 3 32 hex screw one turn connect a piece of 5 16 tub ing and connect to a manometer to measure supply pres sure See table 21 for supply line pressure E Check Manifold Pressure NOTE Pressure test adapter kit 10L34 is available from Lennox to facilitate manifold pressure measurement A manifold pressure post loca...

Page 45: ...eplacement to ensure prop er operation at higher altitudes See TABLE 20 for gas conversion and pressure switch kits See TABLE 21 for manifold pressures TABLE 20 LP Propane Conversion Kit and Pressure Switch Requirements at Varying Altitudes Unit Natural to LP Propane High Altitude Natural Burner Orifice Kit High Altitude LP Propane Burner Orifice Kit High Altitude Pressure Switch 0 7500 ft 7501 10...

Page 46: ...r or partial ground Compare the readings to the table below If the readings exceed the maximum shown in TABLE 22 make repairs before operating the furnace 2 In addition measure the AC voltage from Line Hot to Line Neutral spade terminals on the integrated control See FIGURE 52 This voltage should be in the range of 97 to 132 Vac TABLE 22 Furnace Status Measurement VAC Expected Maximum Power On Fur...

Page 47: ...only the blower motor running and the evaporator coil dry observe the manometer reading Adjust blower motor speed to deliver the air desired according to the job requirements For heating speed second stage heat speed external static pressure drop must not be more than 0 8 W C For cooling speed second stage cool speed external static pressure drop must not be more than 1 0 W C 4 Seal the hole when ...

Page 48: ...tall the clean out cap Condensate Hose Screen FIGURE 55 Check the condensate hose screen for blockage and clean if necessary 1 Turn off power to the unit 2 Remove hose from cold end header box Twist and pull screen to remove 3 Inspect screen and rinse with tap water if needed 4 Reinstall screen and turn on power to unit Condensate Hose Screens Hose Hose FIGURE 55 Cleaning Heat Exchanger If cleanin...

Page 49: ... ports 38 Reconnect flame roll out switch wires 39 Reconnect sensor wire and reconnect 2 pin plug from ignitor 40 Reinstall gas valve manifold assembly Reconnect gas supply line to gas valve 41 Reconnect the combustion air intake pipe 42 Reinstall burner box cover 43 Reconnect wires to gas valve 44 Replace the blower compartment access panel 45 Reconnect gas supply piping Turn on power and gas sup...

Page 50: ...Page 50 VII Wiring and Sequence of Operation ML296UHV Schematic Wiring Diagram ...

Page 51: ...ooling a call for fan closes the R to G circuit energizing the the circulating blower For 55 units the motor runs at 50 of the selected cooling CFM and for 56 units the motor runs at 38 of the selected cooling CFM until switched off When the call for fan is turned off the control de energizes the circulating blower Cooling The unit is set up at the factory for single stage cooling For two stage co...

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