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Lennox G20RQ3E-75 User Manual

Lennox G20RQ3E-75
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SERVICE
G20RE
UNIT
INFORMATION
Page 1
1994 Lennox Industries Inc.
Corp. 9419 – L9
Litho U.S.A.
G20RE SERIES UNITS
I – INTRODUCTION
G20RE and G20RXE series units are mid–efficiency
downflow gas furnaces with Duracurve heat ex-
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
x
) Standards and California Seasonal Effi-
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.
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 (in.)
Blower motor hp.
Electrical characteristics
Natural
**LPG
G20RQ2/3E-50 G20RQ3E–75 G20RQ4E-75 G20RQ3/4E-100
50,000
40,000
78.0%
4 Round
20-50
.50
1/2
1/2
10 x 8
1/3
2, 2–1/2 or 3Tons of cooling (add–on)
58,000
78.0% 78.0% 78.0%
75,000
59,000
75,000
79,000
4 Round 4 Round 5 Oval
50-80 30-60 50-80
.50 .50 .50
1/2
1/2
1/2
1/2
1/2
1/2
10 x 8 11 x 9 11 x 9
1/3 1/2 1/2
*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.
G20RQ2/3XE-50 G20RQ3XE–75 G20RQ4XE-75 G20RQ3/4XE-100
100,000
California Seasonal Efficiency– “X” Models
72.1% 74.8% 72.0% 74.5%
Number and Size of Filters (in.) (2) 20 x 10 x 1 (2) 20 x 10 x 1 (2) 20 x 12 x 1 (2) 20 x 12 x 1
2, 2–1/2 or 3 3, 3–1/2 or 4 3, 3–1/2 or 4
Not Available with LPG.
**LPG kit must be ordered extra for field changeover.
120 volts — 60 hertz — 1 phase (less than 12 amps) — All Models
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Lennox G20RQ3E-75 Specifications

General IconGeneral
BrandLennox
ModelG20RQ3E-75
CategoryFurnace
LanguageEnglish

Summary

Parts Identification

G20RE Component Locations

Visual identification of key components: burner box, blower, control panel, gas manifold, and safety switches.

Unit Components

Control Box Components

Location and function of the control box, housing the transformer and grounding lug.

BCC2-2 Blower Control

Details the BCC2-2 blower control board, its functions for blower and gas valve operation.

Gas Valve

Information on the redundant Robertshaw gas valve, its safety features, and replacement.

Electronic Ignition Control

Details the intermittent ignition control module, spark generation, and flame sensing.

Heating System Service Checks

Testing Gas Piping

Procedure for testing gas piping connections for leaks using leak detection solutions.

Testing Gas Supply Pressure

Method for testing supply gas pressure and acceptable ranges for natural and LP gas.

Manifold Pressure Check

Procedure to check manifold pressure and acceptable operating ranges for burner performance.

Blower Operation and Adjustment

Blower Speed Taps

Instructions on changing blower speed by selecting different tap connections on the motor.

Sequence of Operation

Heating Cycle Steps

Step-by-step explanation of the unit's operational sequence during a call for heat.

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