Lennox G50UHX Series Unit Information
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Lennox G50UHX Series Unit Information

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See also: User's Information Manual , Instruction and Installation Manual
Service Literature
G50UH(X) series units are mid−efficiency gas furnaces
used for upflow or horizontal applications only, manufac-
tured with Lennox Duralok Plus heat exchangers formed of
aluminized steel. G50UH(X) units are available in heating
capacities of 44,000 to 154,000 Btuh and cooling applica-
tions up to 5 tons. Refer to Engineering Handbook for prop-
er sizing.
Units are factory equipped for use with natural gas. Kits are
available for conversion to LPG operation. G50UH(X) mod-
el units are equipped with the Lennox SureLight silicon ni-
tride ignition system. The G50UH(X) unit meets the Califor-
nia Nitrogen Oxides (NO
x
sonal Efficiency requirements. All units use a redundant gas
valve to assure safety shut−off as required by C.S.A.
All specifications in this manual are subject to change. Pro-
cedures outlined in this manual are presented as a recom-
mendation only and do not supersede or replace local or
state codes. In the absence of local or state codes, the
guidelines and procedures outlined in this manual (except
where noted) are recommended only and do not constitute
code.

TABLE OF CONTENTS

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Corp. 0005−L3
Revised 09−2006
) Standards and California Sea-
Page 2
Page 6
Page 15
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Page 18
Page 27
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Page 38
Improper installation, adjustment, alteration, ser-
vice or maintenance can cause property damage,
personal injury or loss of life. Installation and service
must be performed by a qualified installer, service
agency or the gas supplier.
Electric shock hazard. Can cause injury
or death. Before attempting to perform
any service or maintenance, turn the
electrical power to unit OFF at discon-
nect switch(es). Unit may have multiple
power supplies.
Sharp edges.
Be careful when servicing unit to avoid sharp edges
which may result in personal injury.
Page 1
G50UH(X)
IMPORTANT
WARNING
WARNING
© 2000 Lennox Industries Inc.

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Summary of Contents for Lennox G50UHX Series

  • Page 1: Table Of Contents

    Units are factory equipped for use with natural gas. Kits are available for conversion to LPG operation. G50UH(X) mod- el units are equipped with the Lennox SureLight silicon ni- tride ignition system. The G50UH(X) unit meets the Califor- nia Nitrogen Oxides (NO ) Standards and California Sea- sonal Efficiency requirements.

  • Page 2: Specifications

    SPECIFICATIONS G50UH−24A−070 Model No. G50UH−24A−045 G50UH−36A−070 G50UH−48B−070 Heating Heating Performance Low NOx Model No. G50UH−24A−045X − − − − G50UH−36A−070X − − − − Input − Btuh (kW) 44,000 (12.9) 66,000 (19.3) 66,000 (19.3) 66,000 (19.3) Output − Btuh (kW) 36,000 (10.5) 54,100 (15.8) 54,100 (15.8)
  • Page 3 SPECIFICATIONS G50UH−36C−110 Model No. G50UH−36B−090 G50UH−48B−090 G50UH−48C−110 Heating Heating Performance Low NOx Model No. − − − − G50UH−48B−090X − − − − − − − − Input − Btuh (kW) 88,000 (25.8) 88,000 (25.8) 110,000 (32.2) 110,000 (32.2) Output − Btuh (kW) 72,100 (21.1) 72,100 (21.1) 90,200 (26.4)
  • Page 4 SPECIFICATIONS Model No. G50UH−60C−110 G50UH−48C−135 G50UH−60D−135 G50UH−60D−155 Input − Btuh (kW) 110,000 (32.2) 132,000 (38.7) 132,000 (38.7) 154,000 (45.1) Heating Heating Performance Output − Btuh (kW) 90,200 (26.4) 106,900 (31.3) 106,900 (31.3) 124,700 (36.5) lAFUE 80.0% 80.0% 80.0% 80.0% California Seasonal Efficiency 75.7% 76.0% 75.0%...
  • Page 5 SPECIFICATIONS Model No. G50UH−60C−110−4 G50UH−60D−135−4 G50UH−60D−155−4 Heating Heating Performance Input − Btuh (kW) 110,000 (32.2) 132,000 (38.7) 154,000 (45.1) Output − Btuh (kW) 89,400 (26.2) 106,900 (31.3) 124,700 (36.5) lAFUE 80.0% 80.0% 80.0% California Seasonal Efficiency 73.9% 75.0% 75.6% High static (AGA/CGA) − in. w.g. (Pa) .50 (124) .50 (124) .50 (124)

  • Page 6: Blower Data

    BLOWER DATA G50UH−24A−045 PERFORMANCE Air Volume / Watts at Various Blower Speeds External Static External Static Pressure High Medium in. w.g. Watts Watts Watts 0.00 1090 0.05 1080 0.10 1065 0.15 1050 0.20 1030 0.25 1015 0.30 0.40 0.50 0.60 0.70 0.80 0.90...
  • Page 7 BLOWER DATA G50UH−36A−070 PERFORMANCE Air Volume / Watts at Various Blower Speeds External Static External Static Pressure High Medium−High Medium−Low in. w.g. Watts Watts Watts Watts 0.00 1500 1290 0.05 1475 1275 0.10 1450 1255 0.15 1425 1240 0.20 1400 1225 0.25 1370...
  • Page 8 BLOWER DATA G50UH−36C−110 PERFORMANCE Air Volume / Watts at Various Blower Speeds External Static External Static Pressure High Medium−High Medium−Low in. w.g. Watts Watts Watts Watts 0.00 1555 1335 1085 0.05 1540 1330 1080 0.10 1525 1320 1075 0.15 1510 1310 1070 0.20...
  • Page 9 BLOWER DATA G50UH−48C−110 PERFORMANCE Air Volume / Watts at Various Blower Speeds External Static External Static Pressure High Medium−High Medium−Low in. w.g. Watts Watts Watts Watts 0.00 2015 1620 1340 1150 0.05 1990 1615 1340 1150 0.10 1965 1610 1340 1150 0.15 1930...
  • Page 10 BLOWER DATA G50UH−60C−110−1, −2, −3 PERFORMANCE − Bottom Return Air, Side Return Air with Optional RAB Return Air Base, Return Air from Both Sides or Return Air from Bottom and One Side. Air Volume / Watts at Various Blower Speeds External Static External Static Pressure...
  • Page 11 BLOWER DATA G50UH−60C−110 PERFORMANCE − Bottom Return Air, Side Return Air with Optional RAB Return Air Base, Return Air from Both Sides or Return Air from Bottom and One Side. Air Volume / Watts at Different Blower Speeds External Static External Static Pressure High...
  • Page 12 BLOWER DATA G50UH−60D−135−1, −2, −3 PERFORMANCE − Single Side Return Air − Air volumes in bold require field fabricated transition to accommodate 20 x 25 x 1 in. (508 x 635 x25 mm) cleanable air filter in order to maintain proper air velocity. Air Volume / Watts at Various Blower Speeds External Static External Static...
  • Page 13 BLOWER DATA G50UH−60D−155−1, −2, −3 PERFORMANCE − Bottom Return Air, Side Return Air with Optional RAB Return Air Base, Return Air from Both Sides or Return Air from Bottom and One Side. Air Volume / Watts at Various Blower Speeds External Static External Static Pressure...
  • Page 14 BLOWER DATA G50UH−60D−155 PERFORMANCE − Bottom Return Air, Side Return Air with Optional RAB Return Air Base, Return Air from Both Sides or Return Air from Bottom and One Side. Air Volume / Watts at Different Blower Speeds External Static External Static Pressure High...

  • Page 15: High Altitude

    HIGH ALTITUDE All −1 to −14 models − Pressure regulator adjustment may be required depending on altitude. See below for proper pressure regulator setting. Manifold Pressure (Outlet) in. w.g. (kPa) ALTITUDE ft. (m) FUEL 0−4500 4501−5500 5501−6500 6501−7500 (0−1372) (1373−1676) (1677−1981) (1982−2286) Natural Gas...
  • Page 16 Air Deflector G50UH(X) PARTS ARRANGEMENT ALL G50UH−48C−135, (UP FLOW POSITION) ALL G50UH−36C−110. ALL G50UH−60D−155 & G50UH−60C−110−1, −2, −3 Units Only Flue Box Gasket Heat Exchanger Pressure Port Location for −1 to −14 units Gasket Flue Collector Box Flue Transition Combustion Air Orifice Combustion Air Prove Switch Pressure Port...

  • Page 17: Parts Identification

    G50UH(X) PARTS IDENTIFICATION (HORIZONTAL POSITION) BLOWER ASSEMBLY BLOWER ACCESS PANEL HEAT EXCHANGER ASSEMBLY PROVE CONTROL SWITCH BOARD BURNER ASSEMBLY COMBUSTION AIR BURNER INDUCER ACCESS PANEL PRIMARY LIMIT GAS VALVE FIGURE 2 G50UH (X) HEATING COMPONENTS Air Deflector ALL G50UH−48C−135, ALL G50UH−36C−110. ALL G50UH−60D−155 &...

  • Page 18: I Unit Components

    (A92) 56L83 & 97L48 the low voltage section of the unit. Transformers on all models are rated 40VA with a 120V primary and a 24V sec- The Lennox SureLight ignition system consists of ignition ondary. control board (figure 6 with control terminal designations 2.
  • Page 19 After the 15−second pre−purge period, the SureLight igni- SURELIGHT INTEGRATED CONTROL BOARD tor warms up for 20 seconds during which the gas valve opens at 19 seconds for a 4−second trial for ignition. Units with control 56L83: ignitor stays energized for the first sec- ond of the 4−second trial.
  • Page 20 Ground 5. SureLight Integrated Ignition Control (A92) 69M15 The Lennox SureLight ignition system consists of ignition control (figure 8), sensor (figure 10) and ignitor (figure 12). The ignition control and ignitor work in combination to ensure furnace ignition and ignitor durability. The igni- tion control, controls all major furnace operations.
  • Page 21 TABLE 6 d−Fan Time Control Heating The heating fan on time of 45 seconds is not adjustable. SURELIGHT BOARD 69M15 TERMINAL Fan off time (time that the blower operates after the heat DESIGNATIONS demand has been satisfied) can be adjusted by setting the PIN # FUNCTION S1 dip switches l0ocated on the SureLight integrated con-...
  • Page 22 The SureLight board is equipped with two LED lights for troubleshooting. The diagnostic codes are listed below in table 8. TABLE 8 DIAGNOSTIC CODES Make sure to Identify LED’S Correctl.. LED #1 LED #2 56L83, 97L48 −DIAG1 Green 56L83, 97L48 − DIAG2 Green DESCRIPTION 69M15 −...

  • Page 23: Flame Sensor

    6. Flame Sensor 8. Blower Motors and Capacitors A flame sensor is located on the left side of the burner sup- All G50UH(X) units use direct drive blower motors. All mo- port. See figure 10. The sensor is mounted on the flame tors are 120V permanent split capacitor motors to ensure rollout plate and the tip protrudes into the flame envelope maximum efficiency.
  • Page 24 9. Combustion Air Inducer (B6) motor to prevent damage to the wires. Use sheet metal shears to remove the cut out from the side of the cabinet. All G50UH(X) units use a combustion air inducer to move air through the burners and heat exchanger during heating See figure 14.
  • Page 25 SureLight board will go into Watch guard for one hour. The switch is factory set and cannot be adjusted. The switch may have a different setpoint for each unit model number. If limit switch must be replaced, see Lennox Repair Parts handbook. Page 25...

  • Page 26: Combustion Air Inducer

    LPG changeover kits are available from Lennox. Kit s include burner orifices and a gas valve regulator conversion kit. On start-up, the switch senses that the combustion air in- ducer is operating.

  • Page 27: Installation

    II−PLACEMENT AND INSTALLATION D−Extended Period Shutdown Turn off thermostat or set to UNOCCUPIED" mode. Close Make sure unit is installed in accordance with installation all gas valves (both internal and external to unit) to guaran- instructions and applicable codes. tee no gas leak into combustion chamber. Turn off power to III−START-UP unit.
  • Page 28 Gas Leak Detector is strongly recommended. It is available F− Proper Gas Flow (Approximate) through Lennox under part number 31B2001. See Corp. & Combustion 8411−L10, for further details. Furnace should operate at least 5 minutes before check- Do not use matches, candles, flame or any other source of ing gas flow.

  • Page 29: Typical Operating Characteristics

    (Part TRANSDUCER V−TYPICAL OPERATING CHARACTERISTICS #78H5401 available from (PART #78H5401) Lennox Repair Parts) is A−Blower Operation and Adjustment required measure flame signal if meter used 1 − Blower operation is dependent on thermostat control will not read a low micro system.

  • Page 30: Maintenance

    C−External Static Pressure VI−MAINTENANCE At the beginning of each heating season, the system 1 − Tap locations shown in figure 21. should be checked as follows: 2 − Punch a 1/4" diameter hole A−Filters STATIC PRESSURE TEST in supply and return air ple- All G50UH(X) filters are installed external to the unit.
  • Page 31 1 − Check and clean blower wheel. place brush end of cable snake into the bottom openings 2 − Motors used on the Lennox G50UH(X) series units of each of the heat exchanger sections. Clean the bottom are permanently lubricated and need no further lu- opening as described in step 7.

  • Page 32: Wiring And Sequence Of Operation

    VII− Wiring and Sequence of Operation G50UH−1 through −7 Units 5 − Gas valve opens for a 4−second trial for ignition. 1 − When there is a call for heat, W1 of the thermostat energizes 6 − Flame is sensed, gas valve remains open for the heat call. W of the furnace control with 24VAC.
  • Page 33 G50UH−8 Units 5 − Gas valve opens for a 4−second trial for ignition. 1 − When there is a call for heat, W1 of the thermostat energizes 6 − Flame is sensed, gas valve remains open for the heat call. W of the furnace control with 24VAC.
  • Page 34 SURELIGHT CONTROL HEATING SEQUENCE OF OPERATION NORMAL HEATING MODE ABNORMAL HEATING MODE POWER ON GAS VALVE OFF. COMBUSTION AIR INDUCER ON. INDOOR BLOWER ON. LED #1 ALTERNATING FAST FLASH CONTROL SELF−CHECK OKAY? LED#2 ALTERNATING FAST FLASH CHECK FOR BROKEN IGNITOR OR COMBUSTION AIR INDUCER ON FOR 1 SECOND.
  • Page 35 NORMAL HEATING MODE ABNORMAL HEATING MODE 15-SECOND COMBUSTION AIR INDUCER PREPURGE INITIATED BY CLOSED PRESSURE SWITCH. IS VOLTAGE ABOVE 75 VOLTS? LEDS SIGNAL IGNITOR WARM-UP −− 20 SECONDS. ALTERNATING IS THERE A PROPER GROUND? FAST FLASH IS IGNITOR INTACT AND CONNECTED? 4-SECOND TRIAL FOR IGNITION.
  • Page 36 SURELIGHT CONTROL COOLING SEQUENCE OF OPERATION NORMAL COOLING MODE ABNORMAL COOLING MODE POWER ON IGNITION CONTROL MAIN POWER ON. GAS VALVE OFF. COMBUSTION AIR INDUCER OFF. INDOOR BLOWER OFF WITH NORMAL DELAY. CONTROL SELF DIAGNOSTIC CHECK. SIGNAL CIRCUIT BOARD FAILURE AT LED. IS CONTROL OPERATING NORMALLY? INTERRUPT MAIN POWER TO RESET CONTROL.
  • Page 37 SURELIGHT CONTROL CONTINUOUS FAN SEQUENCE OF OPERATION LED: SLOW FLASH RATE REMAINS UNCHANGED THROUGHOUT SEQUENCE. MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL (G) ENERGIZES INDOOR BLOWER ON CONTINUOUS BLOWER SPEED. ELECTRONIC AIR CLEANER TERMINAL IS ENERGIZED. HEATING ACCESSORY TERMINAL THERMOSTAT CALLS FOR HEAT (W). ENERGIZES WITH COMB.

  • Page 38: Surelight Troubleshooting Guide

    SURELIGHT − TROUBLE SHOOTING GUIDE UPON INITIAL POWER UP, REMOVE ALL THERMOSTAT DEMANDS TO THE UNIT PROBLEM: 1 UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE Condition Possible Cause Corrective Action / Comments 1.1.1 ACTION 1 − Check 120V main voltage. −...
  • Page 39 PROBLEM 1: UNIT FAILS TO OPERATE IN THE COOLING, HEATING, OR CONTINUOUS FAN MODE Condition Possible Cause Corrective Action / Comments ACTION 1 − Check that the unit is properly 1.5.1 ground. − On initial power−up the combustion ACTION 2 − Install a proper main ground to the Improper ground to the unit.
  • Page 40 PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR INDUCER DOES NOT ENERGIZE (CONT.). Condition Possible Cause Corrective Action/Comments − Unit operates with a cooling and con- 3.3.1 ACTION 1 − Check for correct wiring and loose tinuous fan demand.
  • Page 41 PROBLEM 5: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER ENERGIZES, IGNITOR IS ENERGIZED. Condition Possible Cause Corrective Action/Comments ACTION 1 − Check line pressure at the gas valve. 5.1.1 Pressure should not exceed 13" WC for both nat- −...
  • Page 42 PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY (CONT.) Condition Possible Cause Corrective Action/Comments ACTION 1 − Check that the manifold pressure matches value listed on nameplate. See installa- − Combustion air inducer energizes 6.3.1 tion instructions for proper procedure. with a heating demand.
  • Page 43 PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY (CONT.) ACTION 1 − Check that the sensor is properly lo- 6.5.1 cated. − Combustion air inducer energizes ACTION 2 − Check that the sense wire is proper- Loose sensor wire connection causes with a heating demand.

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