Lennox G20RE Series Service Manual Download Page 2

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Page 2

Model No.

Input Btuh
Output Btuh
*A.F.U.E.

Flue connection (in. diameter)

Temperature rise range
High static certified by A.G.A.(in wg.)

Gas piping size

I.P.S. (in.)

Blower wheel nominal diameter x width (in.)

Blower motor hp.

Electrical characteristics

Natural

LPG

G20RQ5E-100

G20RQ3E–125

G20RQ4/5E-125

G20RQ4/5E-150

100,000

77,000

78.0%

5 Oval

40-70

.50
1/2

1/2

12 x 12

3/4

120 volts — 60 hertz — 1 phase (less than 12 amps) — All Models

4, 4–1/2 or 5

Tons of cooling (add–on)

98,000

78.0%

125,000

99,000

125,000

118,000

5 Oval

6 Oval

70-100

50-80

55-85

.50

1/2

10 x 8

12 x 12

1/3

3/4

*Annual Fuel Utilization Efficiency based on D.O.E. test procedures and according to F.T.C. labeling requirements.
Isolated combustion system rating for non–weatherized furnaces.

•

G20RQ5XE-100

•

G20RQ3XE–125

•

G20RQ4/5XE-125

150,000

California Seasonal Efficiency– “X” Models

74.7%

75.6%

74.4%

-––––

Number and Size of Filters (in.)

(2) 20 x 14 x 1

(2) 20 x 16 x 1

2, 2–1/2 or 3

4, 4–1/2 or 5

•

Not Available with LPG.

**LPG kit must be ordered extra for field changeover.

SPECIFICATIONS

(continued from previous page)

PILOT/ELECTRODE

ASSEMBLY

PARTS IDENTIFICATION (G20RE)

HEAT

EXCHANGER

DRAFT

HOOD

UPPER ACCESS PANEL

BURNERS

BURNER

BOX

IGNITION

CONTROL

GAS

MANIFOLD

BURNER BOX DAMPER ASSEMBLY

PRIMARY

LIMIT

CONTROL

CABINET

ROLL–OUT

SWITCH

VENT SAFETY

SHUT–OFF

SWITCH

GAS
VALVE

FLUE TRANSITION

LOWER

ACCESS

PANEL

FILTER ACCESS

DOOR

INTERLOCK

SWITCH

BCC2

CONTROL

REMOVABLE

STRIP

. .

LEFT SIDE VIEW

BURNER BOX

FIGURE 1

DAMPER PROVE

SWITCH (S64)

RETURN

SPRING

DOOR

PATCH
PLATE

AXLE

FILTERS

Summary of Contents for G20RE Series

Page 1: ...0RE furnaces have atmospheric burners there is no induced draft motor All G20RE units have a draft diverter which allows the use of stan dard single wall vent connectors SPECIFICATIONS continued on next page Model No Input Btuh Output Btuh A F U E Flue connection in diameter Temperature rise range High static certified by A G A in wg Gas piping size I P S in Blower wheel nominal diameter x width i...

Page 2: ...F T C labeling requirements Isolated combustion system rating for non weatherized furnaces G20RQ5XE 100 G20RQ3XE 125 G20RQ4 5XE 125 150 000 California Seasonal Efficiency X Models 74 7 75 6 74 4 Number and Size of Filters in 2 20 x 14 x 1 2 20 x 14 x 1 2 20 x 14 x 1 2 20 x 16 x 1 2 2 1 2 or 3 4 4 1 2 or 5 4 4 1 2 or 5 Not Available with LPG LPG kit must be ordered extra for field changeover SPECIF...

Page 3: ...g Fan off timings are adjustable The board is divided into two sections 120VAC and 24VAC CAB and XFMR send 120VAC to the damper mo tor and transformer respectively Active cooling and heating blower speed terminals and three dummy D terminals are located on the 120VAC side of the BCC2 2 The CF terminal is used for wiring in the op tional continuous fan kit Also located on this side of the control a...

Page 4: ...ITCH SETPOINTS HEATING INPUT KBTUH SETPOINT 50 75 100 125 150 260 F 12 F 300 F 12 F G Primary Limit Control S10 The primary limit switch S10 on all units is located in the middle of the heating vestibule wall G20RQ2 3 X E 50 Q3 X E 75 Q4 X E 75 Q3 4 X E 100 and Q3 X E 125 units use a SPST self resetting limit See figure 4 When excess heat is sensed in the heat ex changer the limit switch will open...

Page 5: ...P C M PRESSURE REGULATOR ADJUSTMENT SCREW TOP VIEW FRONT VIEW PILOT ADJUSTMENT SCREW VALVE INLET VALVE OUTLET OUTLET PRESSURE TAP J Electronic Ignition Control Figure 7 The Robertshaw electronic ignition control A3 is an intermittent ignition control module located on the vestibule panel See figure 1 When there is a call for heat the control generates a spark to ignite the pilot after which the co...

Page 6: ...box frame activates the damper prove switch as the damp er door opens See figure 10 The axle rotates the damper door to open position As the axle turns the spring winds backward to make contact with the damp er prove switch The protective cover plate is remov able one screw and the spring may be unclipped for service to the damper door or burner box Spring must be removed in order to remove the da...

Page 7: ...emergency shutdown is required turn off the main shut off valve and disconnect the main power to unit These controls should be properly labeled by the installer When pressure testing gas lines the gas valve must be disconnected and isolated Gas valves can be dam aged if subjected to more than 0 5psig 14 W C See figure 11 If the pressure is equal to or less than 0 5psig 14 W C use the manual shut o...

Page 8: ...er G High Altitude Derate C G A certified units used in high altitude applications are factory equipped with modifications that eliminate the need for manifold pressure adjustment to obtain proper heat input Check the unit rating plate to make sure unit is a high altitude unit A G A certified units must be derated when installed at an elevation of 2 000 ft 610 m or more above sea lev el Tables 6 a...

Page 9: ...eed and static pressure of the unit setup Blower speed must be set for unit operation within range of AIR TEMP RISE F listed on the unit rating plate To Measure Temperature Rise 1 Place plenum thermometers in the supply and re turn air plenums Locate thermometers in the first horizontal run of the warm air plenum where it will not pick up radiant heat from the heat exchanger 2 Set thermostat to hi...

Page 10: ... 5 X E 150 G20RQ4 X E 75 UNIT Factory Con nected Speed Taps Motor Speeds Available Cool Heat 2 4 4 2 5 4 2 4 4 2 4 4 2 4 4 3 6 5 3 6 5 3 6 5 DO NOT USE LOW SPEED TAP ON Q2 3 50 BLOWER SPEED SELECTION HI LOW 2 3 4 5 2 3 4 5 6 SPEED TAPS 4 5 TABLE 8 MOTOR PLUG SPEED TAP DESIGNATION 9 Depress harness connector tab to release wire ter minal Select connector location for new speed re fer to unit wiring...

Page 11: ... Turn off electric power to furnace 2 Remove upper access panel and filter access door See figure 1 3 Lift left side filter over left support angle For easy handling hold filter at center bottom 4 Rotate filter sideways and pull it through the blow er access panel opening 5 Pull the second filter out the same way as the first 6 Wash filters with warm water and mild detergent When dry filters shoul...

Page 12: ...eel rod with a 20 in length of chain attached to one end into top opening of heat exchanger Refer to figure 18 9 Shake rod to drop chain through clamshell into burner cavity in bottom of heat exchanger 10 Attach bottom of chain to 2 ft 600 mm rod 11 Push and pull the rods back and forth and up and down with a vigorous motion The chain will dis lodge the soot and scale deposits inside the heat ex c...

Page 13: ...ent damage to the damper door Can cause damage to damper motor resulting in improper furnace operation 20 Install flue restrictor 50E models only 21 Before replacing draft hood flue pipe and access panels inspect draft hood gasket Replace gasket if necessary 22 Carefully check all piping connections factory and field for gas leaks Use a leak detecting solution or other preferred means CAUTION Pote...

Page 14: ... that the gas valve is energized and initiates a 45 second time delay At the end of the 45 seconds the blower B3 is energized 8 When flame is sensed the main gas valve opens and supplies the burners with gas 7 Through the electronic ignition control the pilot valve P of the gas valve opens The spark electrode ignites the pilot and the flame sensor senses the pilot 6 When S64 closes assuming flame ...

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Lennox G20RE Series, Service Manual

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