Lennox G26 series User Manual
  1. Manuals
  2. Brands
  3. Lennox Manuals
  4. Furnace
  5. G26 Series
  6. User manual

Lennox G26 series User Manual

Hide thumbs Also See for G26 series:
Table of Contents

Advertisement

Quick Links

See also: User's Information Manual , Instruction and Installation Manual

Service Literature

G26 series units are high−efficiency upflow gas furnaces manufactured with
DuralokPlust aluminized steel clamshell-type heat exchangers. G26 units
are available in heating capacities of 50,000 to 125,000 Btuh and cooling
applications up to 5 tons. Refer to Engineering Handbook for proper sizing.
Units are factory equipped for use with natural gas. A kit is available for con-
version to LPG operation. G26−1 and −2 model units use electronic (intermit-
tent pilot) ignition. G26−3, −4, −5 and −6 model units feature the Lennox Sur-
eLightT silicon nitride ignition system. Each unit meets the California Nitro-
gen Oxides (NO
) Standards and California Seasonal Efficiency require-
x
ments without modification. All units use a redundant gas valve to assure
safety shut−off as required by A.G.A. or C.G.A.
Information contained in this manual is intended for use by qualified service
technicians only. All specifications are subject to change. Procedures out-
lined in this manual are presented as a recommendation only and do not su-
persede 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.
2
7
1
6

G26 SERIES UNITS

3
FIGURE 1
AG26 HEAT EXCHANGE ASSEMBLY
4

Combustion Process:

1. A call for heat starts the combustion air blower.
2. Outdoor air is drawn through pipe into the burner
compartment where it mixes with gas in a con-
ventional style inshot burner.
3. The SureLight ignition system lights the burners.
4. Combustion products are drawn downward
through the heat exchanger. Heat is extracted
as indoor air passes across the outside surface
of the metal.
5. Latent heat is removed from the combustion
5
products as air passes through the coil. Conden-
sate (water) is formed as the combustion prod-
ucts cool.
6. As the combustion products exit the coil, con-
densate is collected and drained away.
7. Combustion products are pulled from the heat
exchanger and forced into the flue.
Page 1
G26
Corp. 9721−L11
Revised 08−2004
G26 FURNACEY
© 1997 Lennox Industries Inc.
Litho U.S.A.

Advertisement

Table of Contents
loading

Related Manuals for Lennox G26 series

Summary of Contents for Lennox G26 series

  • Page 1: Service Literature

    Units are factory equipped for use with natural gas. A kit is available for con- version to LPG operation. G26−1 and −2 model units use electronic (intermit- tent pilot) ignition. G26−3, −4, −5 and −6 model units feature the Lennox Sur- eLightT silicon nitride ignition system. Each unit meets the California Nitro-...
  • Page 2 SPECIFICATIONS Model No. G26Q2-50 G26Q3-50 G26Q3-75 G26Q4/5-75 Input Btuh (kW) 50,000 (14.7) 75,000 (22.0) Output Btuh (kW) 46,000 (13.5) 47,000 (13.8) 70,000 (20.5) 69,000 (20.2) lA.F.U.E. 92.4% 92.0% 92.0% California Seasonal Efficiency 85.9% 86.5% 86.3% 83.8% Exhaust pipe connection (PVC) diameter in.
  • Page 3 SPECIFICATIONS Model No. G26Q3/4-100 G26Q4/5-100 G26Q3/4-125 G26Q4/5-125 Input Btuh (kW) 100,000 (29.3) 125,000 (36.6) Output Btuh (kW) 91,000 (26.7) 93,000 (27.2) 115,000 (33.7) 116,000 (34.0) lA.F.U.E. 92.0% 92.0% 91.0% 92.0% California Seasonal Efficiency 86.6% 85.8% 87.5% 87.0% Exhaust pipe connection (PVC) diameter in.
  • Page 4 BLOWER PERFORMANCE DATA FILTER AIR RESISTANCE cfm (L/s) in. w.g. (Pa) 0 (0) 0.00 (0) 200 (95) 0.01 (0) 400 (190) 0.03 (5) 600 (285) 0.04 (10) 800 (380) 0.06 (15) 1000 (470) 0.09 (20) 1200 (565) 0.12 (30) 1400 (660) 0.15 (35) 1600 (755) 0.19 (45)
  • Page 5 BLOWER PERFORMANCE DATA G26Q2-50 BLOWER PERFORMANCE Air Volume and Motor Watts at Specific Blower Taps External Static External Static Pressure High Medium in. w.g. Watts Watts Watts 1115 1095 1065 1035 - - - - - - - - - - - - NOTE All air data is measured external to unit with 1 in.
  • Page 6 BLOWER PERFORMANCE DATA G26Q3/4-100 BLOWER PERFORMANCE Air Volume and Motor Watts at Specific Blower Taps External Static External Static Pressure High Medium-High Medium-Low in. w.g. Watts Watts Watts Watts 2065 1760 1570 1245 2000 1730 1550 1240 1925 1685 1515 1225 1840 1625...
  • Page 7 INTAKE and EXHAUST PIPE VENTING TABLE Vent Pipe Minimum Vent Pipe Diameter Required Maximum Maximum 50,000 Btuh (14.7 kW) 75,000 Btuh (22.0 kW) 100,000 Btuh (29.3 kW) 125,000 Btuh (36.6 kW) Equivalent Length Feet Meters 1-1/2 12.2 15.2 16.8 18.3 21.3 24.4 27.4...
  • Page 8 G26−3 THROUGH −6 COMPONENTS GLASS FIBER GASKET FLUE COLLAR FRESH AIR TOP CAP INTAKE FITTING WARM HEADER (COLLECTOR) BURNER BOX ASSEMBLY CABINET PATCH PLATE WITH BARBED FITTING AND FLAME PATCH ROLL−OUT SWITCH PLATE FLUE DuralokPlus TRANSITION HEAT EXCHANGER ASSEMBLY COMBUSTION AIR FLAME SIGHT PROVE (PRESSURE) GLASS...
  • Page 9 G26 HEAT EXCHANGER FRESH AIR INTAKE SURELIGHT IGNITOR LENNOX DURALOKPLUST FITTING CORBEL ORIFICE HEAT EXCHANGER AS- BURNER BURNER BOX CUPS SEMBLY ACCESS COVER MANIFOLD GAS VALVE WARM HEAD COMBUSTION AIR (COLLECTOR) BLOWER MOTOR COMBUSTION COLD HEADER AIR BLOWER (COLLECTOR )
  • Page 10 MAKE-UP BOX INSTALLATION OUTSIDE INSTALLATION Box may be installed inside or outside cabinet and may INSIDE INSTALLATION be installed on left side or right side of cabinet MAKE-UP BOX STAR WASHERS MAKE-UP BOX MUST BREAK PAINT ON UNIT CABINET FOR PROPER GROUND.
  • Page 11 Each orifice and burner are sized spe- 2− Circuit Breaker (CB8) cifically to the unit. Refer to Lennox Repair Parts Listing for correct sizing information. A flame retention ring in the end of A 24V circuit breaker is also located in the control box. The...

  • Page 12: Diagnostic Codes

    SURELIGHT CONTROL BOARD TABLE 1 SURELIGHT CONTROL TERMINAL DESIGNATIONS ACB COOL Blower − Cooling Speed (Line Volt) ACB HEAT Blower − Heating Speed (Line Volt) PARK Alternate Blower Speeds (Dead) ACB LOW Continuous Low Speed Blower Accessory Terminal (Line Volt) 120VAC Hot to Transformer 120VAC Hot Input HTG ACC...
  • Page 13 TABLE 3 pressure switch closes and a 15−second pre−purge be- gins. If the pressure switch is not proven within 2−1/2 min- SureLight BOARD J156 (J2) TERMINAL DESIGNATIONS utes, the control goes into Watchguard−Pressure Switch mode for a 5−minute re−set period. PIN # FUNCTION After the 15−second pre−purge period, the SureLight igni-...
  • Page 14 LIMIT CONTROL (S10) FOR The fan off" timing is initiated after a heating demand but not G26 SERIES UNITS AND ALTERNATE STYLE Units may be equipped with either style limit. after a blower or cooling demand (that is, when indoor ther-...
  • Page 15 G26 BLOWER CONTROL - BCC2-3 (A15) ATable 8 shows terminal designations. DETACHABLE STRIP ON EARLY BOARDS ONLY Table 8 shows" terminal designations. FIGURE 16 12−Ignition Control (−1 and −2 models) IGNITION CONTROL A3 G26 −1 and −2 model units use an intermittent pilot ignition manufactured by Johnson Controls.
  • Page 16 Diagnostic LED Johnson G776 Ignition Control Operation The information in this section is protected by a copyright issued by The furnace control is equipped with a diagnostic LED Johnson Controls, Inc., and is reproduced with permission. used for troubleshooting the unit and the control. LED On a call for heat from indoor thermostat, the ignition control functions are shown in table 7.
  • Page 17 place when reading manifold pressure. TYPICAL BURNER PILOT/ELECTRODE ORIENTATION An LPG changeover kit is available. The kit includes main and view looking at side of burners pilot burner orifices (pilot orifice for −1 and −2 units only) and a FRESH AIR INTAKE regulator conversion kit.
  • Page 18 (Combustion Air Prove Switch) AOPERATION AT THIS EXTREME MAY INDICATE A BLOCKED G26 series units are equipped with a differential pressure OUTLET OR OTHER PROBLEM switch located on the vestibule panel. The switch is con- nected to the combustion air blower housing by means of a flexible silicon hose.
  • Page 19 CHART REPESENTS NORMAL OPERATING CHARACTERISTICS OF THE PRESSURE SWITCH ONLY AND SHOULD NOT BE USED FOR TROUBLSHOOTING −1.2 DIFFERENTIAL SWITCH CLOSED −1.0 −0.8 −0.6 DIFFERENTIAL SWITCH OPEN (Furnace will not operate) −0.4 −0.2 −0.2 −0.4 −0.6 −0.8 −1.0 −1.2 BURNER BOX STATIC PRESSURE FIGURE 24 Temporarily jumpering the pressure switch when trouble- Measuring pressure differential...
  • Page 20 9 − Operate unit and observe draft gauge reading. Read- 6 − Promptly apply solvent cement to end of pipe and in- side socket surface of fitting. Cement should be ap- ings will change as heat exchanger warms. plied lightly but uniformly to inside of socket. Take a.
  • Page 21 Intake Piping 1 − Seal any unused openings in the common venting sys- tem. 1 − Cement intake piping in slip connector located at top of unit. 2 − Visually inspect the venting system from proper size and horizontal pitch and determine there is no block- 2 −...
  • Page 22 Heating cable installation kit is 5 − Exhaust piping must terminate straight out or up as available from Lennox. See Condensate Piping section for shown. In rooftop applications, a 2" X 1−1/2" reducer for part numbers.
  • Page 23 8 − If intake and exhaust piping must be run up a side wall EXHAUST to position above snow accumulation or other ob- TERMINATION structions, piping must be supported every 3 ft. (.91m) EXHAUST as shown in figure 33. Refer to figures 31 and 32 for proper piping method.
  • Page 24 When horizontally vented, minimum clearance for ter- 10− Suspend piping using hangers at a minimum of every mination from electric meters, gas meters, regulators 5 feet (1.52m) for schedule 40 PVC and every 3 feet and relief equipment is 4 ft. (1.2m) for US installa- (.91m) for ABS−DWV, PVC−DWV, SPR−21 PVC, and tions.
  • Page 25 Front View EXHAUST (229) VENT Front View (127) EXHAUST VENT (305) NOTE−Enclosed exhaust pipe 5−1/2 INTAKE VENT is insulated with 1/2" (13mm) (140) INTAKE foam insulation. If intake and exhaust pipes are reversed, slit VENT and remove foam insulation (864) and reapply to other vent.
  • Page 26 Condensate Piping 3 − Use the provided adapter (1/2" PVC x 1/2" MPT) and This unit is designed for either right- or left-side exit of con- the nipple (1/2" PVC) to carry drainage outside the densate piping. Condensate drain line should be routed cabinet.
  • Page 27 Heating sate line must be sloped downward away from drip cable kit is available from Lennox in various lengths; leg to drain. If drain level is above drip leg, conden- 6ft. (1.8m) − kit no. 18K48; 24ft. (7.3m) − kit no. 18K49;...
  • Page 28 How To Operate Gas Valve (Figure 43) III−START-UP A−Preliminary and Seasonal Checks WARNING 1 − Inspect electrical wiring, both field and factory installed for loose connections. Tighten as required. 2 − Check voltage at disconnect switch. Voltage must be If you do not follow these instructions exactly, a within range listed on the nameplate.
  • Page 29 NOTE−On initial start−ups and when condensate trap is Testing for abnormally high CO and CO. dry, unit may turn itself off and on to allow condensate One method for testing the CO /CO content is the Bachar- trap to fill. This is normal operation. ach CO test with the Fyrite CO indicator.
  • Page 30 Leave hose barb on valve open to at- Gas Leak Detector is strongly recommended. It is available mosphere. See figure 46. through Lennox under part number 31B2001. See Corp. 3 − Start unit and allow 5 minutes for unit to reach steady 8411−L10, for further details.
  • Page 31 NOTE−During this test procedure, the unit will be a flame signal transducer (part number 78H5401) available overfiring: from Lennox to measure the flame signal. D Operate unit only long enough to obtain accurate read- Flame (microamp) signal is an electrical current which ing to prevent overheating heat exchanger.
  • Page 32 4 − Connect (+) lead of transducer to ignition control sen- 2 − Set thermostat to highest setting. sor connection. See figure 47. 3 − After plenum thermometers have reached their high- 5 − Connect (−) lead of the transducer to sensor wire. See est and steadiest readings, subtract the two readings.
  • Page 33 To Remove Blower: 1− Turn off line voltage power. Unplug J69 from P69 located on blower deck. 2− Disconnect thermostat wiring con- nections by removing low voltage terminal strip. 3− Disconnect J58/P58 located on blow- er deck. 4− Disconnect J43/P43 from blower motor.
  • Page 34 Filter handicoater is RP Products coating and blower assembly from cabinet. Take care not to no. 418 and is available as Lennox part no. P-8-5069. lose the combustion air orifice. 3 − If replacement is necessary, order Lennox part no.
  • Page 35 BURNER ACCESS/REMOVAL BURNER MOUNTING PATCH PLATE BRACKET Simplified Burner Removal: 1− Remove cover by loosening bottom screws (2) and re- moving cover front screws (5). 2− Remove pilot tube, spark wire and sensor wire. Re- move gas valve and manifold assembly.
  • Page 36 11− While supporting pilot, ignitor and sensor wires (−1,−2 to the vestibule panel. units) or ignitor and sensor lines (−3 units) at the grom- 20− Re-install the electrical connections to the gas valve. met, grasp burners and simultaneously pull burners Orange wire to M1 and yellow wire to C2.
  • Page 37 VII−WIRING DIAGRAM, SEQUENCE OF OPERATION &TROUBLESHOOTING A−Field Wiring, Thermostat Connections TYPICAL G26−3 through −6 MODELS FIELD WIRING DIAGRAM FLAME IGNITION ROLLOUT LIMIT CONTROL SWITCH COMBUSTION FIELD AIR PROVE SWITCH MAKE−UP BLACK WHITE COMBUSTION THERMOSTAT VALVE BROWN AIR BLOWER W R Y TRANSFORMER CONTROL TO ACCESSORY IF USED.
  • Page 38 B−Wiring Diagram G26 (−3 & −4 Shown) Page 38...
  • Page 39 HEATING SEQUENCE OF OPERATION SURELIGHT CONTROL NORMAL HEATING MODE ABNORMAL HEATING MODE POWER ON GAS VALVE OFF. COMBUSTION AIR BLOWER ON. INDOOR BLOWER ON. LED #1 ALTERNATING FAST FLASH CONTROL SELF−CHECK OKAY? LED#2 ALTERNATING FAST FLASH CHECK FOR BROKEN IGNITOR OR OPEN IGNITOR CIRCUIT COMBUSTION AIR BLOWER ON FOR 1 SECOND.
  • Page 40 HEATING SEQUENCE CONTINUED NORMAL HEATING MODE ABNORMAL HEATING MODE 15-SECOND COMBUSTION AIR BLOWER PREPURGE INITIATED BY CLOSED PRESSURE SWITCH. IGNITOR WARM-UP −− 20 SECONDS. GAS VALVE OFF. COMBUSTION AIR BLOWER ON. INDOOR BLOWER OFF. HAS CONTROL FAILED TO SENSE FLAME FOR 4-SECOND TRIAL FOR IGNITION.
  • Page 41 COOLING SEQUENCE OF OPERATION SURELIGHT CONTROL NORMAL COOLING MODE ABNORMAL COOLING MODE POWER ON IGNITION CONTROL MAIN POWER ON. GAS VALVE OFF. COMBUSTION AIR BLOWER 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 42 CONTINUOUS LOW SPEED FAN SEQUENCE OF OPERATION SURELIGHT CONTROL LED: SLOW FLASH RATE REMAINS UNCHANGED THROUGHOUT SEQUENCE. MANUAL FAN SELECTION MADE AT THERMOSTAT. CONTROL (G) ENERGIZES SYSTEM FAN AT ACB LOW SPEED. ACC. TERMINAL IS ENERGIZED. HTG ACC. TERM. ENERGIZES THERMOSTAT CALLS FOR HEAT (W).
  • Page 43 D− SureLight Control 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 44 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 45 PROBLEM 3: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER 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 46 PROBLEM 5: UNIT FAILS TO FIRE IN THE HEATING MODE, COMBUSTION AIR BLOWER ENERGIZES, IGNITOR IS ENERGIZED. (CONT.) Condition Possible Cause Corrective Action/Comments ACTION 1 − Check line pressure at the gas 5.1.1 valve. Pressure should not exceed 13" WC for −...
  • Page 47 Lennox personnel. ACTION 1 − Check for sooting deposits or other restrictions in the heat exchanger assembly. Clean assembly as outlined in instruction manu- 6.3.4...
  • Page 48 PROBLEM 6: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN PREMATURELY (CONT.) − Combustion air blower energizes with a heating demand. − Burners light. − Diagnostic lights flash watch guard 6.5.1 ACTION 1 − Check that the sensor is properly lo- flame failure.
  • Page 49 E− G26 −1 and −2 Models 5- When S18 closes, assuming primary limit (S10) is closed, the ignition control opens the pilot valve and 1- When disconnect is closed, 120V is routed through begins spark. door interlock switch (S51) to feed the line voltage 6- When flame is sensed, spark stops and main valve side of the blower control (A3) and transformer T1 pri- opens to light main burners.

  • Page 50: Troubleshooting

    F−BCC2 Blower Control −1 and −2 Models START BCC2 TROUBLESHOOTING FLOWCHART DOES UNIT OPERATE? CHECK CIRCUIT BREAKER. RESET IF NECESSARY. CHECK: 1−UNIT POWER 24VAC ACROSS 2−INTERLOCK SWITCH R & T? 3−TRANSFORMER 4−LIMIT SWITCH JUMPER ACROSS SCREWS R & G BLOWER REPLACE REPLACE 120VAC ACROSS...
  • Page 51 G−G77 Ignition Control −1 and −2 Models G776 IGNITION CONTROL TROUBLESHOOTING Spark is present but pilot will not light 1993 Johnson Controls, Inc. Reprinted with permission. Are pilot valve Securely connect at START connections correct terminal 1 and and secure? ground.
  • Page 52 G776 IGNITION CONTROL TROUBLESHOOTING −1 and −2 MODELS No spark and system will not work 1993 Johnson Controls, Inc. Reprinted with permission. Check the following: Is 24VAC 1) 120VAC Supply between THS 2 START 2) Transformer and ground? 3) Thermostat Open thermostat contacts for 30 seconds.
  • Page 53 G776 IGNITION CONTROL TROUBLESHOOTING −1 and −2 MODELS Pilot lights but main valve will not come on 1993 Johnson Controls, Inc. Reprinted with permission. Does spark Is 24VAC stay on for more than Replace START between terminals 5 seconds after pilot control.

Table of Contents