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INSTALLATION 
INSTRUCTIONS

CAUTION: READ ALL SAFETY GUIDES 

BEFORE YOU START TO INSTALL 
YOUR FURNACE.

SAVE THIS MANUAL

ALL POSITION 

AUTOMATIC IGNITION FURNACES

G8C / FG8 SERIES MODELS

50 - 125 MBH INPUT

UPFLOW / HORIZONTAL

AUTOMATIC IGNITION FURNACES

G8C / FG8 SERIES MODELS

150 MBH INPUT

035-15241-003 Rev. A (201)

TABLE OF CONTENTS

GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . .  2

FURNACE SPECIFICATIONS   . . . . . . . . . . . . . . . . . . . .  3

PRE-INSTALLATION INSPECTION . . . . . . . . . . . . . . . .  4

CODE COMPLIANCE  . . . . . . . . . . . . . . . . . . . . . . . . . . .  4

INSTALLATION POSITION 
(50-125 MBH Models) . . . . . . . . . . . . . . . . . . . . . . . . . . .  4

INSTALLATION POSITION 
(150 MBH Models)  . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  4

CONVERSION INFORMATION
(50-125 MBH Models) . . . . . . . . . . . . . . . . . . . . . . . . . . .  4

TO CONVERT FROM DOWNFLOW TO UPFLOW 
CONFIGURATION (50-125 MBH Models)  . . . . . . . . . . .  4

TO CONVERT FROM UPFLOW TO DOWNFLOW 
CONFIGURATION (50-125 MBH Models)  . . . . . . . . . . .  5

FURNACE LOCATION  . . . . . . . . . . . . . . . . . . . . . . . . . .  6

COMBUSTION AND VENTILATION AIR  . . . . . . . . . . . .  7

FURNACE SIZING AND DUCT 
SYSTEM DESIGN  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  8

RETURN AIR AND FILTERS  . . . . . . . . . . . . . . . . . . . . .  9

GAS PIPING  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  10

VENTING (CATEGORY I)  . . . . . . . . . . . . . . . . . . . . . . .  13

SIDEWALL VENTING  . . . . . . . . . . . . . . . . . . . . . . . . . .  15

ELECTRICAL WIRING  . . . . . . . . . . . . . . . . . . . . . . . . .  15

WIRING DIAGRAM  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  19

PRE-OPERATIONAL CHECKS  . . . . . . . . . . . . . . . . . .  19

SEQUENCE OF OPERATION   . . . . . . . . . . . . . . . . . . .  19

FURNACE OPERATION . . . . . . . . . . . . . . . . . . . . . . . .  20

INSTALLATION CHECKS   . . . . . . . . . . . . . . . . . . . . . .  21

SERVICE INSTRUCTIONS  . . . . . . . . . . . . . . . . . . . . . .  22

REPLACEMENT PARTS   . . . . . . . . . . . . . . . . . . . . . . .  22

EFFICIENCY

RATING

CERTIFIED

Summary of Contents for FG8 SERIES

Page 1: ...POSITION 50 125 MBH Models 4 INSTALLATION POSITION 150 MBH Models 4 CONVERSION INFORMATION 50 125 MBH Models 4 TO CONVERT FROM DOWNFLOW TO UPFLOW CONFIGURATION 50 125 MBH Models 4 TO CONVERT FROM UPFLOW TO DOWNFLOW CONFIGURATION 50 125 MBH Models 5 FURNACE LOCATION 6 COMBUSTION AND VENTILATION AIR 7 FURNACE SIZING AND DUCT SYSTEM DESIGN 8 RETURN AIR AND FILTERS 9 GAS PIPING 10 VENTING CATEGORY I 1...

Page 2: ...eaning compounds plastic items or con tainers gasoline kerosene cigarette lighter fluid dry cleaning fluids or other volatile fluid 3 Paint thinners and other painting com pounds 4 Paper bags boxes or other paper products Never operate the furnace with the blower door removed To do so could result in serious person al injury and or equipment damage GENERAL INFORMATION IMPORTANT These instructions ...

Page 3: ...5 000 60 000 1200 17 1 2 10 x 8 35 65 165 1 3 4 1FB0318 75 000 60 000 1600 21 10 x 10 30 60 160 1 2 4 1FB0319 100 000 80 000 1600 21 10 x 10 40 70 170 1 2 4 1FB0319 100 000 80 000 2000 24 1 2 2 10 x 6 35 65 165 3 4 4 1FB0320 125 000 100 000 2000 24 1 2 2 10 x 6 40 70 170 3 4 5 1FB0320 150 000 120 000 2000 24 1 2 2 10 x 6 40 70 170 3 4 5 NA MODEL A B C D E F G H J 50 40 1200 75 60 1200 17 1 2 16 1 ...

Page 4: ...e conversion instructions starting on Page 5 and Page 6 INSTALLATION POSITION 150 MBH Models This furnace may be installed in an upflow or horizontal poi sion No conversion is necessary CONVERSION INFORMATION 50 125 MBH Models This furnace may be shipped in either the upflow or the downflow configuration To convert from upflow to downflow or vice versa it is necessary only to exchange the top and ...

Page 5: ...ion on the vent blower using the three screws supplied on the vent blower See Figure 4 10 Rotate the vent blower 180º so that its outlet points toward the inlet air end of the furnace See Figure 3 11 Line up the vent blower mounting holes with the holes in the vent pan and screw it into place Use the same machine screws that held the vent blower in place previ ously 12 Install the two extra machin...

Page 6: ... to any combustible mate rials must be maintained These required minimum clear ances are shown below and on a label in the furnace Minimum Clearances Upflow Front 2 inches Back 0 inches Sides 0 inches Top 1 inch B 1 Vent 1 inch Single wall Vent 6 inches Floor combustible Minimum Clearances Downflow Front 2 inches Back 0 inches Sides 0 inches Top 1 inch B 1 Vent 1 inch Single wall Vent 6 inches Flo...

Page 7: ...n the furnace If all air is from inside building the total free area of each opening must be at least one square inch for each 1 000 BTUH of furnace input but not less than 100 square inches If all air is from outdoors when communicating directly with the outdoors through vertical ducts the total free area of each opening must be at least one square inch for each 4 000 BTUH of furnace input When c...

Page 8: ...pply air duct attached to the furnace be provided with a removable access panel The opening should be accessible when the furnace is installed in service and should be large enough that smoke or reflected light may be observed inside the casing to indicate the presence of leaks in the heat exchanger The cover panel for this opening should be attached in such a manner as to prevent leaks A C USAGE ...

Page 9: ...quired depending on the capacity of the air conditioner and the air flow required The return air opening in the top of the furnace is large enough for the largest capacity air conditioner for which the furnace blower is rated RETURN AIR CONNECTION HORIZONTAL The return air duct must be connected to the inlet end of the furnace It is not permissible to cut out the side of the furnace casing for sid...

Page 10: ...pecifics It is recommended that a gas cock shutoff valve be installed in the gas supply line outside the casing where it is readily accessible as close to the furnace as is practicable as shown in Figures 9 10 and 11 An 1 8 in NPT plugged pressure tap for test gauge connec tion must be installed in the gas supply line immediately upstream from the furnace if local authorities do not allow use of t...

Page 11: ...VALVE PRESSURE SWITCH VENT VENT PIPE TRANSITION GAS PIPE 3 DIAMETER VENT PIPE GAS SHUT OFF VALVE ROLL OUT SWITCH DIRT LEG VENT BLOWER FURNACE CONTROL FIGURE 10 UPFLOW CONFIGURATION 50 125 MBH MODELS ONLY BLOWER DOOR SWITCH ROLL OUT SWITCHES BURNERS HOT SURFACE IGNITOR GAS VALVE PRESSURE SWITCH GAS PIPE GAS SHUT OFF VALVE ROLL OUT SWITCH DIRT LEG VENT BLOWER FURNACE CONTROL ...

Page 12: ...in the limits shown FIGURE 11 UPFLOW HORIZONTAL 150 MBH MODEL ONLY BLOWER DOOR SWITCH ROLL OUT SWITCHES BURNERS HOT SURFACE IGNITOR GAS VALVE PRESSURE SWITCH GAS PIPE GAS SHUT OFF VALVE ROLL OUT SWITCH DIRT LEG VENT BLOWER FURNACE CONTROL During pressure testing of the gas supply piping system observe the following to avoid fire explo sion asphyxiation or damage to the appliance a If test pressure...

Page 13: ...and fastened to the furnace flue collar using screws where required 9 Joints in the vent pipe must be securely made and any horizontal run of the vent pipe must be supported less than one support every three feet to prevent sagging 10 This furnace may be common vented with a water heater or other gas fired naturally vented appliance VENT SYSTEM SIZING Refer to the venting tables in the NATIONAL FU...

Page 14: ...ertical portion of the chimney or vent above the connector A vent connector must not pass through any ceiling floor firewall or fire partition A single wall metal pipe vent connec tor must not pass through any interior wall CONDENSATION These furnaces are not intended to have condensation occur in the furnace or in the venting system Such condensation can cause corrosion and premature failure of t...

Page 15: ...s a device that keeps the power venter in operation for a short period at the end of each burner cycle in order to clear out all flue gases from the vent Manufacturers of power ven ters also can supply post purge timers ELECTRICAL WIRING All internal wiring has been made at the factory Field wiring requires only the connection of line voltage supply wiring and low voltage thermostat wiring Service...

Page 16: ...the furnace The furnace control board has a ter minal marked TWIN which can be used to cause two furnace blowers to operate together If two furnaces are to be twinned using a single wall thermo stat connect an isolation relay as shown in Figure 12 below BLOWER MOTOR SPEED SELECTION These furnaces are equipped with blowers which have multi speed direct drive motors The blower speed selected is depe...

Page 17: ... TAP EXTERNAL STATIC PRESSURE INCHES W C 0 10 0 20 0 30 0 40 0 50 0 60 0 70 0 80 50 40 1200 75 60 1200 HIGH 1407 1367 1315 1279 1211 1138 1053 961 MED 1141 1130 1092 1059 1009 945 876 782 LOW 885 894 881 863 811 782 719 649 75 60 1600 100 80 1600 HIGH 1776 1736 1717 1664 1608 1536 1445 1347 MED HI 1588 1558 1515 1459 1403 1298 1203 1082 MED LOW 1357 1357 1335 1317 1266 1193 1099 990 LOW 1151 1146 ...

Page 18: ...or shorted wires bad pressure switch Three flashes Pressure switch failed to close Check vent blower pressure switch vent blockage disconnected pres sure hose Four flashes Limit switch open Check for open limit switch loose connections in limit circuit Five flashes Rollout switch open Check for open rollout switches loose connections in rollout switch circuit Six flashes One hour pressure switch l...

Page 19: ...mally open pressure switch contacts 3 As the vent blower increases in speed the contacts of the pressure switch will close and complete the electrical circuit to the ignitor 4 During the next 30 seconds the vent blower will bring fresh air into the heat exchanger and the ignitor will begin to glow At the end of this period the gas valve will open and the burners will light 5 After the burners ligh...

Page 20: ...n not reach your gas supplier call the fire department 3 USE ONLY YOUR HAND TO MOVE THE GAS CON TROL LEVER OR SWITCH NEVER USE TOOLS IF THE LEVER OR SWITCH WILL NOT MOVE BY HAND DON T TRY TO REPAIR IT CALL A QUALIFIED SER VICE TECHNICIAN FORCE OR ATTEMPTED REPAIR MAY RESULT IN A FIRE OR EXPLOSION 4 DO NOT USE THIS APPLIANCE IF ANY PART HAS BEEN UNDER WATER IMMEDIATELY CALL A QUALI FIED SERVICE TEC...

Page 21: ...at is necessary to achieve the correct input rate use the following formula GAS VALUE X 3600 DESIRED INPUT SECONDS NEEDED Example 1000 BTU gas furnace input 100 000 BTUH Seconds for one cubic foot 1000 X 3600 100 000 36 seconds When clocking the meter if the one cubic foot dial makes a complete revolution in less time than was calculated that it should the furnace is overfired and should be derate...

Page 22: ...ng of the heat exchanger and flue gas pas sageways is not necessary and is not recommended under normal circumstances REPLACEMENT PARTS Should it be necessary to replace any component parts these may be obtained through an authorized dealer who is experienced and can be of assistance Information on the nearest Distributor may be obtained directly from the com pany shown on the furnace rating plate...

Page 23: ... Ignitor Bracket 15 Gas Orifice 16 Door Switch 17 Capacitor 18 Blower Wheel 19 Blower Motor 20 Sensor Rod 21 Blower Motor Clamp 22 Rubber Motor Mounts 23 Transition 24 Rollout Switch Bracket 25 Door Latch 26 Pressure Hose 27 Casing Bottom Cap Gasket Package not shown Wire Harness not shown FIGURE 16 REPAIR PARTS VIEW UPFLOW CONFIGURATION SHOWN 23 23 12 12 13 13 11 11 10 10 17 21 22 18 19 15 13 20 ...

Page 24: ...thout notice Printed in U S A 035 15241 003 Rev A 201 Copyright by York International Corp 2001 All rights reserved Supersedes 035 15241 002 Rev A 800 Unitary 5005 Norman Products York OK Group Drive 73069 SERVICE RECORDS ...

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