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Page 6

K – Pilot Tube, Ignition Wire and Flame Rod

The pilot tube from the gas valve and the flame sensor
and ignition wires from the electronic ignition control
enter through the top of the burner box to the pilot
burner assembly.

Figure 8 shows the clearance between top of the pilot
burner head and the top of the main burner surface.

IGNITION

WIRE

FLAME SENSOR

WIRE

PILOT ASSEMBLY

5/16”

PILOT
HEAD

FIGURE 8

BURNER

SURFACE

L – Burner Box/Damper Door

The damper motor is located on the right side of the
burner box. On the left side of the burner box, behind a
protective plate is the damper prove switch. Refer to
figure 9. The burner box top is removable on all units.

When there is a call for heat, the damper motor is ener-
gized and damper door opens as the damper motor
axle begins to rotate.

REMOVEABLE

TOP

DAMPER MOTOR/GEAR

PATCH PLATE

PATCH PLATE

SPRING

DAMPER

PROVE SWITCH

PROVE

SWITCH COVER

OBSERVATION PORT

COVER

DAMPER

PILOT PATCH

PLATE

DAMPER

BOX

DAMPER BOX PARTS ARRANGEMENT

(G20RE Units Shown)

DAMPER OPENING

FIGURE 9

ROLL–OUT

SWITCH

M – Damper Prove Switch (S64)

The spring, which is held by a notch in the burner 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 damper door.

After service is complete, the spring must rest snugly
in notch for damper prove switch to function properly.
Do not force door open, damage to the spring and mo-
tor may occur. Take care to open damper door slowly.

Axle rotates
and  opens the
door, slot in left
end of axle
pulls spring
back to activate
damper prove
switch.

DAMPER

PROVE

SWITCH

SPRING

SPRING FITS

SNUGLY IN NOTCH

FIGURE 10

AXLE

DAMPER

DOOR

DAMPER PROVE SWITCH ASSEMBLY

MANIFOLD

III – PLACEMENT AND INSTALLATION

Make sure the unit is installed in accordance with
installation instructions and all applicable codes.

IV – START-UP

A – Preliminary and Seasonal Checks

1 – Inspect electrical wiring, both field and factory

installed for loose connections. Tighten as re-
quired.

2 –  Check voltage at disconnect switch. Voltage must

be within range listed on the nameplate. If not, con-
sult the power company and have voltage condi-
tion corrected before starting unit.

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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