Lennox G23Q3-50 User Manual

Page 1
ã 1998 Lennox Industries Inc.
L
i
t
h
o
U
.
S
.
A
.
Corp. 9814-L8
G23(X)
Service Literature
Revised 08-2001
G23(X) SERIES UNITS
G23(X) series units are mid-efficiency upflow gas fur-
naces manufactured with Duralokt aluminized steel
clamshell type heat exchangers. G23(X) units are avail-
able in heating capacities of 50,000 to 150,000 Btuh and
cooling applications up to 6 tons. Refer to Engineering
Handbook for proper sizing.
Units are factory equipped for use with natural gas. A kit is
available for conversion to LPG operation. G23(X)-1, -2, -3
and-4modelunitsuseelectronic (intermittentpilot)ignition.
G23(X)-5 and -6 model units feature the Lennox Sur-
eLightT silicon nitride ignition system. All units meet the
California Nitrogen Oxides (NO
x
) Standards and California
Seasonal Efficiency requirements with the installation of
flame baffles. 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 outlined in this manual are
presented as a recommendation only and do not super-
sede or replace local or state codes. In the absence of lo-
cal or state codes, the guidelines and procedures outlined
in this manual (except where noted) are recommended
only.
SPECIFICATIONS
Model No. G23Q2(X)-50 G23Q3(X)-50 G23Q2/3(X)-75 G23Q4/5(X)-75 G23Q3(X)-100
Input Btuh (kW) 50,000 (14.7) 75,000 (22.0) 100,000 (29.3)
Output Btuh (kW) 40,000 (11.7) 61,000 (17.8) 80,000 (23.4)
lA.F.U.E. 80.7% 80.8% 80.4% 80.1%
California Seasonal Efficiency 75.5% 75.6% 76.9% 74.2% 76.6%
Flue size connection diameter— in. (mm) round 3 (76) 4 (102)
Temperature rise range — _F (_C) 30-60 (17-33) 35-65 (19-36) 20-50 (11-28) 45-75 (25-42)
High static certified by A.G.A. — in wg. (Pa) .50 (125)
G
a
s
P
i
p
i
n
g
S
i
z
e
I
.
P
.
S
.
in. 1/2
G
a
s
P
i
p
i
n
g
S
i
z
e
I
.
P
.
S
.
Natural or LPG/propane
mm 12.7
B
l
o
w
e
r
w
h
e
e
l
n
o
m
i
n
a
l
in. 10 x 7 10 x 8 11-1/2 x 9 10 x 8
B
l
o
w
e
r
w
h
e
e
l
n
o
m
i
n
a
l
diameter x width
mm 254 x 178 254 x 203 292 x 229 254 x 203
Blower motor output — hp (W) 1/5 (149) 1/3 (249) 3/4 (560) 1/3 (249)
N
o
m
i
n
a
l
c
o
o
l
i
n
g
Tons 1 to 2 1 to 3 3-1/2 to 5 1 to 3
N
o
m
i
n
a
l
c
o
o
l
i
n
g
that can be added
kW 3.5 to 7.0 3.5 to 10.6 12.3 to 17.6 3.5 to 10.6
Shipping weight — lbs. (kg) 1 package 135 (61) 140 (64) 146 (66) 186 (84) 159 (72)
Electrical characteristics 120 volts — 60 hertz — 1 phase (all models) (less than 12 amps)
lAnnual Fuel Utilization Efficiency based on U.S. DOE test procedures and FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.
}Cleanable polyurethane frame type filter.

Lennox G23Q3-50 Specifications

General

Brand	Lennox
Model	G23Q3-50
Category	Furnace
Language	English

Summary

UNIT INFORMATION

G23(X) SERIES UNITS

Overview of the G23(X) series furnaces, including heating and cooling capacities.

SPECIFICATIONS AND BLOWER PERFORMANCE

G23Q2(X)-50 Blower Performance

Air volume and motor watts at specific blower taps for the G23Q2(X)-50 model.

BLOWER PERFORMANCE DATA

G23Q2/3(X)-75 Blower Performance

Air volume and motor watts at specific blower taps for the G23Q2/3(X)-75 model.

BLOWER PERFORMANCE DATA

G23Q3/4(X)-100 Blower Performance

Air volume and motor watts at specific blower taps for the G23Q3/4(X)-100 model.

BLOWER PERFORMANCE DATA

G23Q5/6(X)-150 Blower Performance

Air volume and motor watts at specific blower taps for the G23Q5/6(X)-150 model.

FILTER AIR RESISTANCE

Table showing air resistance (in. w.g.) for various CFM (L/S) values.

OPTIONAL ACCESSORIES AND HIGH ALTITUDE

Optional Accessories

List of optional accessories available for G23(X) furnaces.

UNIT ORIENTATION

General Parts Orientation

Diagram illustrating the general parts layout of the G23(X) furnace.

HEAT EXCHANGE ASSEMBLY

Control Box Components

Diagram of control box for -5 and -6 G23X models.

UNIT COMPONENTS

Control Box Components

Details of control box components including transformer and circuit breaker.

Make-Up Box Installation

Instructions for installing the make-up box for electrical connections.

UNIT COMPONENTS

BCC Blower Control

Description of the BCC blower control used in -1 through -4 models.

ESD Precautions and Procedures

Safety precautions for handling electronic components to prevent electrostatic discharge.

UNIT OPERATION AND IGNITION CONTROL

Unit Operation

Explanation of the furnace's normal heating operation sequence.

Ignition Control (-1 Through -4 Models)

Details on the intermittent pilot ignition control for specific models.

IGNITION CONTROL OPERATION

Diagnostic LED

Explanation of the diagnostic LED functions for troubleshooting the ignition control.

BLOWER MOTORS AND LIMIT CONTROLS

Blower Motors and Capacitors

Table of blower motor horsepower and capacitor ratings for G23(X) units.

BURNER ASSEMBLY AND COMPONENTS

Pilot, Spark Electrode, Flame Sensor and Burners

Arrangement and function of pilot, spark electrode, flame sensor and burners.

SURELIGHT IGNITION SYSTEM

SureLight Ignition System (-5 and -6 models)

Description of the SureLight ignition system for specific G23(X) models.

SURELIGHT CONTROL TERMINAL DESIGNATIONS

Electronic Ignition

Details on the electronic ignition sequence and control logic.

GAS VALVE AND COMBUSTION AIR SWITCH

Gas Valve

Information on the gas valve, its types, and replacement procedures.

PLACEMENT AND INSTALLATION

Fresh Air Requirements

Guidelines for ensuring adequate fresh air for combustion and ventilation.

CONFINED SPACE INSTALLATION

Air from Inside

Requirements for bringing combustion air from an unconfined space into a confined one.

VENTING REQUIREMENTS

Flue Venting Requirements

Guidelines for proper flue venting and compliance with codes.

GENERAL VENTING REQUIREMENTS

Venting Tables and Connector Sizing

Information on vent diameter, capacity, and connector sizing.

START-UP PROCEDURES

Preliminary and Seasonal Checks

Checks to perform before unit start-up, including wiring and voltage.

HEATING SYSTEM SERVICE CHECKS

Gas Piping and Testing

Procedures for checking gas supply pressure and piping.

GAS PIPING AND PRESSURE CHECKS

Check Manifold Pressure

Procedure to check and adjust manifold pressure for proper unit operation.

TYPICAL OPERATING CHARACTERISTICS

Blower Operation and External Static Pressure

Guidelines for blower operation and measurement of external static pressure.

BLOWER REMOVAL AND SPEED ADJUSTMENT

Blower Speed Taps

Instructions for changing blower speed taps on leadless and leaded motors.

MAINTENANCE

Filters

Instructions for inspecting, cleaning, and replacing furnace filters.

OPERATION SEQUENCE

Models -1 to -4

Operation sequence for G23(X) models -1, -2, -3, and -4.

TROUBLESHOOTING FLOWCHARTS

BCC Troubleshooting Flowchart

Flowchart for diagnosing issues with the BCC blower control.

G776 IGNITION CONTROL TROUBLESHOOTING

Spark Present, Pilot Not Lighting

Troubleshooting steps when spark is present but the pilot does not light.

G776 IGNITION CONTROL TROUBLESHOOTING

No Spark, System Not Working

Troubleshooting steps when there is no spark and the system does not work.

G776 IGNITION CONTROL TROUBLESHOOTING

Pilot Lights, Main Valve Not Opening

Troubleshooting steps when pilot lights but the main valve does not open.

SURELIGHT CONTROL HEATING SEQUENCE

Normal Heating Mode

Sequence of operation for the SureLight control during normal heating.

SURELIGHT CONTROL HEATING SEQUENCE CONTINUED

Abnormal Heating Mode

Sequence of operation for the SureLight control during abnormal heating.

SURELIGHT CONTROL COOLING SEQUENCE

Normal Cooling Mode

Sequence of operation for the SureLight control during normal cooling.

CONTINUOUS LOW SPEED FAN SEQUENCE

Fan Operation Sequence

Sequence of operation for continuous low speed fan mode.

SURELIGHT TROUBLESHOOTING GUIDE

Unit Fails to Operate

Troubleshooting guide for unit failure to operate in cooling, heating, or fan modes.

TROUBLESHOOTING: UNIT FAILS TO OPERATE

Problem 1: Unit Fails to Operate

Diagnosing issues when the unit fails to operate in cooling, heating, or fan modes.

TROUBLESHOOTING: UNIT FAILS TO FIRE

Problem 3: Unit Fails to Fire (No Combustion Air Blower)

Diagnosing failure to fire when combustion air blower does not energize.

TROUBLESHOOTING: BURNERS LIGHT, SHUT DOWN PREMATURELY

Problem 6: Burners Light, Unit Shuts Down

Diagnosing issues when burners light but unit shuts down prematurely.