Table of Contents
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SERVICE
I – INTRODUCTION
G20RE and G20RXE series units are mid–efficiency
downflow gas furnaces with Duracurve
changers formed of aluminized steel. G20RE units
come in heating capacities of 50,000 to 150,000 Btuh. In
cooling applications, blowers are equipped to handle
up to 5 tons of cooling capacity. Refer to Engineering
Handbook for proper sizing.
Units are factory supplied for use with natural gas. A
conversion kit to LPG operation is available for the
G20RE only. All units are equipped with an electronic
ignition. G20RXE models meet the California Nitrogen
Oxides (NO
) Standards and California Seasonal Effi-
x
ciency requirements. All units use a redundant gas
valve to assure safety shut–off as required by A.G.A.
Featured on G20RE series is a burner box damper as-
sembly located on the intake side of the burners. A
damper door in the burner box shuts during unit off
cycles to retain heat in the unit. A damper prove switch
ensures that damper is open before gas valve is ener-
gized. Since the G20RE 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.
Model No.
Input Btuh
Output Btuh
*A.F.U.E.
California Seasonal Efficiency– "X" Models
Flue connection (in. diameter)
Temperature rise range
High static certified by A.G.A.(in wg.)
Natural
Gas piping size
I.P.S. (in.)
LPG
**
Blower wheel nominal diameter x width (in.)
Blower motor hp.
Number and Size of Filters (in.)
Tons of cooling (add–on)
Electrical characteristics
*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.
**LPG kit must be ordered extra for field changeover.
Not Available with LPG.
UNIT
INFORMATION
Corp. 9419 – L9
G20RE SERIES UNITS
heat ex-
SPECIFICATIONS
G20RQ2/3E-50
G20RQ3E–75
G20RQ2/3XE-50
G20RQ3XE–75
50,000
75,000
40,000
58,000
78.0%
78.0%
72.1%
74.8%
4 Round
4 Round
20-50
50-80
.50
1/2
1/2
10 x 8
10 x 8
1/3
(2) 20 x 10 x 1
(2) 20 x 10 x 1
2, 2–1/2 or 3
2, 2–1/2 or 3
120 volts — 60 hertz — 1 phase (less than 12 amps) — All Models
Page 1
G20RE
(continued on next page)
G20RQ4E-75
G20RQ4XE-75
75,000
59,000
78.0%
72.0%
4 Round
30-60
.50
.50
1/2
1/2
1/2
1/2
11 x 9
1/3
1/2
(2) 20 x 12 x 1
3, 3–1/2 or 4
Litho U.S.A.
G20RQ3/4E-100
G20RQ3/4XE-100
100,000
79,000
78.0%
74.5%
5 Oval
50-80
.50
1/2
1/2
11 x 9
1/2
(2) 20 x 12 x 1
3, 3–1/2 or 4
1994 Lennox Industries Inc.
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Table of Contents
Related Manuals for Lennox G20RE Series
Summary of Contents for Lennox G20RE Series
- Page 1 All units use a redundant gas valve to assure safety shut–off as required by A.G.A. Featured on G20RE series is a burner box damper as- sembly located on the intake side of the burners. A damper door in the burner box shuts during unit off cycles to retain heat in the unit.
-
Page 2: Specifications
SPECIFICATIONS (continued from previous page) G20RQ5E-100 G20RQ3E–125 G20RQ4/5E-125 Model No. G20RQ4/5E-150 G20RQ5XE-100 G20RQ3XE–125 G20RQ4/5XE-125 Input Btuh 100,000 125,000 125,000 150,000 Output Btuh 77,000 98,000 99,000 118,000 *A.F.U.E. 78.0% 78.0% 78.0% 78.0% California Seasonal Efficiency– “X” Models -–––– 74.7% 75.6% 74.4% Flue connection (in. -
Page 3: Unit Components
II – UNIT COMPONENTS 1 – Control Transformer (T1) All G20RE series units use a single line voltage G20RE unit components are shown in figure 1. The (120VAC) to 24VAC transformer. It is located inside the blower controls can be accessed by removing the up- control box providing power to the low voltage section per access panel. - Page 4 C – Blower Motors and Capacitors current to the gas valve. If the limit is tripped, BCC2-2 energizes the blower. The limit automatically resets All G20RE units use direct drive blower motors. All mo- when unit temperature drops below the reset point. tors used are 120V permanent split capacitor motors to See table 3.
- Page 5 H – Secondary Limit (S21) J – Electronic Ignition Control (Figure 7) The Robertshaw electronic ignition control (A3) is an The secondary limit switch (S21) is a high temperature limit located on the left side of the blower scroll. The intermittent ignition control module located on the vestibule panel.
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Page 6: Pilot Assembly
K – Pilot Tube, Ignition Wire and Flame Rod M – Damper Prove Switch (S64) The spring, which is held by a notch in the burner box The pilot tube from the gas valve and the flame sensor frame, activates the damper prove switch as the damp- and ignition wires from the electronic ignition control er door opens. -
Page 7: Heating System Service Checks
Gas Leak Detector is strongly recom- to guarantee no gas leak into combustion chamber. mended. It is available through Lennox under part Turn off power to unit. All access panels, covers and number 31B2001. See Corp. 8411–L10, for further de- vent caps must be in place and secured. - Page 8 E – Check Manifold Pressure G – High Altitude Derate C.G.A. certified units used in high altitude applications After line pressure has been checked and adjusted, are factory equipped with modifications that eliminate check manifold pressure. Move pressure gauge to out- the need for manifold pressure adjustment to obtain let pressure tap located on unit gas valve (GV1).
-
Page 9: Static Pressure Test
2 – Set thermostat for a heating demand and check To Measure Temperature Rise: flame signal with unit operating. For G20RE series, 1 – Place plenum thermometers in the supply and re- a reading of 1 to 5 microamps DC should occur. -
Page 10: Blower Speed Selection
D – Blower Speed Taps 9 – Depress harness connector tab to release wire ter- minal. Select connector location for new speed (re- Blower speed tap selection is accomplished by chang- fer to unit wiring diagram). Insert wire terminal un- ing the taps at the harness connector at the blower mo- tor. -
Page 11: Maintenance
270 SECOND FAN OFF TIME 1 – Check and clean blower wheel. 330 SECOND FAN OFF TIME 2 – Motors used on G20RE series units are permanent- NO JUMPER ly lubricated and need no further lubrication. C – Flue and Chimney... - Page 12 To clean heat exchanger: 10 – Attach bottom of chain to 2 ft. (600 mm) rod. 1 – Turn off both electrical and gas power supplies to 11 – Push and pull the rods back and forth and up and furnace.
- Page 13 17 – Clean inside of each burner with a bottle cleaning CAUTION brush. See figure 21. 18 – Replace burners making sure to fully engage in rear Potential for unit damage. receiving slot in heat exchanger. See figure 22. Re- Use extreme care when opening damper door to secure gas manifold and supply piping.
-
Page 14: Sequence Of Operation
SEQUENCE OF OPERATION 1– When disconnect is closed, 120V feeds to line voltage 7– Through the electronic ignition control, the pilot valve side of the blower control (A15). Door interlock switch “P” of the gas valve opens. The spark electrode ignites (S51) must be closed for A15 to receive voltage.