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INSTALLATION INSTRUCTIONS
G1D91BU, G1D93BC, G1D93BU, CG90CB, & CG90UB
High Efficiency 90+ Condensing Gas Furnace
Improper installation, adjustment, alteration, service, or maintenance can cause
injury or property damage. Refer to this manual. For assistance or additional informa-
tion, consult a qualified installer, service agency, or the gas supplier.
WARNING
Do not store combustible materials, including
gasoline and other flammable vapors and
liquids, near the furnace, vent pipe, or warm
air ducts. The homeowner should be cau-
tioned that the furnace area must not be
used as a broom closet or for any other
storage purposes. Such uses may result in
actions that could cause property damage,
personal injury, or death.
WARNING
This furnace is not approved for installation in
a mobile home. Do not install this furnace in a
mobile home. Installation in a mobile home
could result in actions that could cause prop-
erty damage, personal injury, or death.
®
The installation of the furnace, wiring, warm air ducts, venting, etc. must conform to the requirements of the
National Fire Protection Association; the National Fuel Gas Code, ANSI Z223.1/NFPA No. 54 (latest edition)
and the National Electrical Code, ANSI/NFPA No. 70 (latest edition) in the United States; CSA B149.1
(latest edition) Natural Gas and Propane Installation Codes and the Canadian Electrical Code Part 1, CSA
22.1 (latest edition) in Canada; and any state or provincial laws, local ordinances (including plumbing or
wastewater codes), or local gas utility requirements. Local authorities having jurisdiction should be con-
sulted before installation is made. Such applicable regulations or requirements take precedence over the
general instructions in this manual.
# 45466K003
WARNING
SAFETY ................................................. 2
INSTALLATION....................................... 3
START-UP ............................................ 19
OPERATION ........................................ 20
MAINTENANCE ................................... 23
REPAIR PARTS .................................... 24
WIRING DIAGRAMS ............................ 26
®
IMPORTANT
TABLE OF CONTENTS
Manufactured By
A.A.C.
A Lennox International Company
421 Monroe Street
Bellevue, OH 44811
Page 1
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Summary of Contents for Lennox G1D91BU
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Page 1: Table Of Contents
INSTALLATION INSTRUCTIONS G1D91BU, G1D93BC, G1D93BU, CG90CB, & CG90UB High Efficiency 90+ Condensing Gas Furnace WARNING Improper installation, adjustment, alteration, service, or maintenance can cause injury or property damage. Refer to this manual. For assistance or additional informa- tion, consult a qualified installer, service agency, or the gas supplier. -
Page 2: Safety
SAFETY WARNING The following is a list of safety rules and precautions that In the State of Massachusetts: must be followed when installing this furnace. This product must be installed by a licensed 1. Use only with the type of gas approved for this Plumber or Gas Fitter. -
Page 3: Installation
The condensate drain on this furnace is incorporated within the furnace and must be Upflow models (G1D91BU, G1D93BU, & CG90UB) may be primed before start-up. The condensate installed on wood flooring but shall not be installed directly system must not be exposed to tempera- on carpeting, tile, or any other combustible material. - Page 4 Unconfined Space Minimum Clearances to Combustibles An unconfined space is defined as “a space whose volume is more than 50 cubic feet per 1000 BTU per hour of the combined input rating of all appliances installed in " 0 that space.” When a furnace is installed in an unconfined space in a building, it can be assumed that the infiltration "...
- Page 5 10 – 13 for the type of furnace and venting being installed. Upflow models G1D91BU, G1D93BU, and CG90UB and counterflow models G1D93BC and CG90CB can be The venting system must be supported with mounting installed as either direct vent or non-direct vent units.
- Page 6 cement is recommended. Metal or plastic strapping may be In all applications where the flue pipe is run through an unconditioned space, 1/2" Armaflex or equivalent used for vent pipe hangers. must be used over the pipe. In extreme cold climates, When making ABS joints, pieces can be prepared with a 3/4"...
- Page 7 Horizontal Venting Vent Tables The vent for this appliance shall not terminate over public (numbers in inches unless specified otherwise) walkways; or near soffit vents or crawl space vents or other areas where condensate or vapor could create a Minimum Pipe Diameter nuisance or hazard or cause property damage;...
- Page 8 Sidewall Vent Terminal Clearances (Direct Vented Furnaces) Vent Terminal Air Supply Inlet Area Where Terminal Is Not Permitted a i l < a i l < a i l > a i l > < < a i l > a i l >...
- Page 9 Sidewall Vent Terminal Clearances (Non-Direct Vented Furnaces) Vent Terminal Air Supply Inlet Area Where Terminal Is Not Permitted a i l < a i l > < a i l > y l t i t r a l i t i f f h t i l a t...
- Page 10 Upflow Models G1D91BU, G1D93BU, & CG90UB Direct Vent Installation 1/4" per foot of run, to prevent accumulation of condensate. An inlet air restrictor plate (see Figure 1 on page 5) is supplied...
- Page 11 On initial start-up of the unit, some of the water used to Upflow Models G1D91BU, G1D93BU, & CG90UB Non-Direct Vent Installation prime the trap system may run down into the combustion blower and cause noise. An inlet air restrictor plate (see Figure 1 on page 5) is...
- Page 12 Counterflow Models G1D93BC & CG90CB Direct Vent Do not cement air inlet pipe. Use high temperature Installation RTV silicone sealant so inlet pipe can be removed if service is required. An inlet air restrictor plate (see Figure 1 on page 5) is supplied with this furnace and can be found in the plastic bag containing For proper operation, the vent and air intake pipe these Installation Instructions and the User’s Information...
- Page 13 G1D93BC Counterflow Non-Direct Vent 45,000 & 67,000 BTU/HR Units Vertical Venting (Models G1D93BC & CG90CB Only) STRAIGHT INLET PIPE 22.5° ELBOWS BURNER BOX Figure 12 Counterflow Models G1D93BC & CG90CB Non-Direct Vent Installation An inlet air restrictor plate (see Figure 1 on page 5) is supplied with this furnace and can be found in the plastic bag containing these Installation Instructions and the User’s Information Manual.
- Page 14 Existing Venting Systems Condensate Disposal When an existing furnace is removed or replaced, the original venting system may no longer be sized to properly vent the attached appliances. An improperly sized venting 3/4” PVC system can result in spillage of flue products into the living TEE MUST REMAIN space, the formation of condensate, leakage, etc.
- Page 15 Circulating Air Supply Combustible Floor Installation When the furnace is installed so that the supply ducts (Counterflow Models Only) carry air circulated by the furnace to areas outside the space containing the furnace, the return air shall be handled by a duct or ducts sealed to the furnace casing and terminated outside the space containing the furnace.
- Page 16 Gas supply piping should be installed in accordance with local codes and the regulations of the utility. Piping must be Gas Piping Connection of adequate size to prevent undue pressure drop. Consult the local utility or gas supplier for complete details on special requirements for sizing gas piping.
- Page 17 Bottom return filter kit AFILT529 is also available from the manufacturer. G1D91BU and G1D93BU Models A filter rack and cleanable 16" x 25" x 1/2" filter are Counterflow Models: supplied with the furnace. (Models designed for more than 1600 CFM nominal air delivery include two of each.) The...
- Page 18 Electronic Air Cleaner Minimum Filter Requirements Terminals are provided on the blower control board for connection of a 120-volt electronic air cleaner. The “EAC” terminal is energized whenever the thermostat is calling for heat, cooling, or continuous blower. Refer to the furnace wiring diagram for specific connection information.
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Page 19: Start-Up
START-UP To Start Furnace: Lighting Instructions CAUTION For Your Safety, Read Before Operating Be sure the manual gas control has been in the “OFF” position for at least 5 minutes before starting the unit. Do not attempt to WARNING manually light the burners. If you do not follow these instructions exactly, a fire or explosion may result causing prop- erty damage, personal injury, or loss of life. -
Page 20: Operation
cooling “off” delay, the control de-energizes the cooling OPERATION speed fan. At the end of the cooling “off” delay period, the control returns to the standby mode. Sequence of Operation Heating Controls During a call for heat the thermostat closes the R-W Following is a description of the operation of some of the circuit of the control board. - Page 21 Refer to the furnace wiring diagram while using the following procedure to change motor speed: Checking and Adjusting Gas Input 1. Turn off electrical power to the unit. 2. Connect the desired speed tap for cooling on the blower control board. 3.
- Page 22 Manifold Pressure vs. Altitude i t l ) . t * Consult local utility for actual heating value. Furnace Input = Input Factor x Nameplate Input Above 7500 feet, call Technical Services at 1-800- 448-5872 ext. 2610. Table 4 Page 22 # 45466K003...
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Page 23: Maintenance
MAINTENANCE Main Burners Light the burners and allow to operate for a few minutes to establish normal burning conditions. Observe the main WARNING burner flames. Compare this observation to Figure 21 to determine if proper flame adjustment is present. Flame ELECTRICAL SHOCK, FIRE, should be predominantly blue in color and strong in appear- OR EXPLOSION HAZARD... -
Page 24: Repair Parts
Burner Group Gas manifold Main burner orifices Main burners Accessories ALPKT572 Natural Gas to Propane Conversion Kit (G1D91BU and CG90UB) ALPKT574 Natural Gas to Propane Conversion Kit (G1D93BU, G1D93BC, and CG90CB) AFILTHA7 Single Side Filter Frame Kit AFILT524 Side Return Filter Kit (upflow models) -
Page 25: Control System Diagnostics
CONTROL SYSTEM DIAGNOSTICS Failure Codes Troubleshooting The following visual checks should be made before troubleshooting: t l u 1. Check to see that the power to the furnace and the blower control board is on. o i t h t i 2. -
Page 26: Wiring Diagrams
Connection Diagram P/N 45198-005 Figure 22 Page 26 # 45466K003... - Page 27 Schematic Diagram P/N 45198-005 Figure 23 # 45466K003 Page 27...
Need help?
Do you have a question about the G1D91BU and is the answer not in the manual?
Questions and answers
My furnace starts working but stop after 5 minutes. I have tried restarting the system and leaving it to cool, but that didn't work.
A Lennox furnace with part number G1D91BU could stop working after 5 minutes due to several possible issues:
1. Primary Limit Control Activation – If abnormally high circulating air temperatures occur, the normally closed primary limit control may open and shut down the furnace.
2. Auxiliary Limit Control Activation – If there is abnormal reverse airflow, the auxiliary limit control could open, stopping furnace operation.
3. Rollout Switch Activation – If the rollout switch detects excessive heat or flame rollout in the burner box, it may trip and require manual reset.
4. Fault Codes – The furnace has a self-diagnostic LED that indicates fault codes. Checking for stored fault codes may help identify the specific issue.
5. Ignition Lockout (7 Flashes) – If ignition fails multiple times, the control may enter a lockout state, shutting down the furnace.
6. Flame Dropout Issues (8 Flashes) – If the flame sensor detects too many flame dropouts, the control may enter a lockout condition.
7. Incorrect Line Voltage Phasing (9 Flashes) – If the control detects incorrect voltage phasing, it may shut down the furnace.
To diagnose the exact cause, check the LED fault codes on the control board and inspect the limit controls and rollout switch.
This answer is automatically generated