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Bosch BGH96 Troubleshooting Manual

96% afue gas furnace 3-way multipoise condensing gas furnace.
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Bosch 96% AFUE Gas Furnace BGH96 Model
3-Way Multipoise Condensing Gas Furnace
Troubleshooting Guide

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   Summary of Contents for Bosch BGH96

  • Page 1 Bosch 96% AFUE Gas Furnace BGH96 Model 3-Way Multipoise Condensing Gas Furnace Troubleshooting Guide...
  • Page 2 2 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide Data subject to change 01.2019 | BTC 770502101 A...
  • Page 3: Table Of Contents

    Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 3 Table of Contents 1 Key to Symbols and Safety Instructions 1.1 Key to Symbols 1.2 Safety 2 Troubleshooting 2.1 Electrostatic Discharge (ESD) Precautions 2.2 Resetting From Lockout 3 Error Flash Codes 3.1 No Flash and No Fan (System Does Not Start Normally)
  • Page 4: Key To Symbols And Safety Instructions

    4 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide 1 Key to Symbols and Safety Instructions 1.2 Safety Please read all instruction in the manual and retain all manuals for future 1.1 Key to Symbols reference. Warnings WARNING:  Untrained personnel (homeowners) may only clean and replace filters and replace fuses as required  ...
  • Page 5 Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 5 WARNING: FOLLOW ALL SAFETY CODES WARNING: FIRE, EXPLOSION   Wear safety glasses, protective clothing, and work Check entire gas assembly for leaks after lighting this gloves. Have a fire extinguisher available. Read these appliance.
  • Page 6: Troubleshooting

    6 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide 2 Troubleshooting 2.2 Resetting From Lockout Furnace lockout results when a furnace is unable to achieve ignition after three attempts. Refer to the troubleshooting chart on the following pages for assistance in determining the source of unit operational problems.
  • Page 7: Error Flash Codes

    Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 7 3 Error Flash Codes 3.1 No Flash and No Fan (System Does Not Start Normally) Troubleshooting Chart Start Correct Are there any wiring loose wires or wrong according to connections? wiring diagram...
  • Page 8 8 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide No Flash and No Fan (System Does Not Start Normally) Figures & Tables 1. Check for 18-31Vac power between these 2 terminals with multi-meter. Figure 3 1. Check for 115Vac power supply between L1 and common terminal Figure 1 1.
  • Page 9 Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 9 1. Check for 18-31Vac power between “W/W1” & “C” terminals with multi-meter Figure 5 1. Check for 18-31Vac power between Hi-heat/lo-heat/hi-cool/lo-cool and COM with multi-meter 2. Check for 115Vac power supply between CIRC-H and N with...
  • Page 10: Flashes (system Lock-out Due To Failed Ignition)

    1 0 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide 3.2 7 Flashes (System Lock-Out due to Failed Ignition) 8 Flashes (System Lock-Out due to too Many Flame Dropouts) Troubleshooting Chart Start Correct wiring Are there any according to loose wires or wrong...
  • Page 11 Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 11 7 Flashes (System Lock-Out due to Failed Ignition) 8 Flashes (System Lock-Out due to too Many Flame Dropouts) Figures & Tables 1. Check for 9-17Ω between these two terminals with multi-meter.
  • Page 12: Flashes (low Fire Pressure Switch Stuck Closed)

    1 2 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide 3.3 2 Flashes (Low Fire Pressure Switch Stuck Closed) Troubleshooting Chart Start Correct wiring Are there any according to loose wires or wrong the wiring connections? diagram Does the resistance of low fire...
  • Page 13 Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 13 2 Flashes (Low Fire Pressure Switch Stuck Closed) Figures High fire pressure switch Low fire pressure switch Overflow pressure switch Figure 12 1. Check for ∞ resistance between these two terminals with multi-meter.
  • Page 14: Flashes (low Pressure Switch Stuck Open)

    1 4 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide 3.4 3 Flashes (Low Pressure Switch Stuck Open) 6 Flashes (Pressure Switch Cycle Lockout) 13 Flashes (High Pressure Switch Stuck Open) Troubleshooting Chart Start Correct wiring Are there any according to...
  • Page 15: High Fire Pressure Switch

    Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 15 3 Flashes (Low Pressure Switch Stuck Open) 6 Flashes (Pressure Switch Cycle Lockout) 13 Flashes (High Pressure Switch Stuck Open) Figures   T he pressure switch that you are checking in this step depends on the number of LED fl...
  • Page 16: Flashes (limit/rollout Switch Open Less Than 5 Mins)

    1 6 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide 3.5 4 Flashes (Limit/Rollout Switch Open Less than 5 Mins) 5 Flashes (Limit/Rollout Switch Open More than 15 Mins) 11 Flashes (Limit/Rollout Switch Open from 5 to 15 Mins) Troubleshooting Chart Start “SW2”...
  • Page 17 Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 17 4 Flashes (Limit/Rollout Switch Open Less than 5 Mins) 5 Flashes (Limit/Rollout Switch Open More than 15 Mins) 11 Flashes (Limit/Rollout Switch Open from 5 to 15 Mins) Figures & Tables 1.
  • Page 18 1 8 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide External static pressure (in. WC) Furnace Return-air Speed size inlet 1430 1390 1350 1320 1280 1240 1200 1160 1110 1065 Temp Rise-1st stage ℉ 30.7 32.2 33.6 Temp Rise-2nd stage ℉...
  • Page 19 Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 19 External static pressure (in. WC) Furnace Return-air Speed size inlet 2195 2158 2116 2072 2031 1985 1940 1896 1852 1862 Temp Rise-1st stage ℉ Temp Rise-2nd stage ℉ 40.3 41.0 41.8 42.7...
  • Page 20: Flashes (incorrect Polarity Of L1/l2)

    2 0 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide 3.6 9 Flashes (Incorrect Polarity of L1/L2) Troubleshooting Chart Start Correct the wire connection(black and white wire) according to wiring diagram. See Figure 23. Figures BLOWER DOOR SWITCH 115V FIELD-...
  • Page 21: Rapid Flashes (low Flame)

    Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 21 3.7 Rapid Flashes (Low Flame) Troubleshooting Chart Start Replace the gas Adjust the gas valve valve if the to ensure manifold pressure cannot gas pressure meets be adjusted the required values...
  • Page 22: Appendix A - Sequence Of Operation

    2 2 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide Appendix A - Sequence of Operation Two Stage Controller Logic A1. There are two heating modes: A1.1 Low Fire Heating Mode: Only W1 signal A1.2 High Fire Heating Mode: Both W1 and W2 signal  ...
  • Page 23: A1 Heating Modes

    Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 23 Heating Modes A1.1 Low Fire Heating Mode Logic (only W1 signal): Figure 24 When there is a call for heat (W1), the inducer will start on HIGH speed and the low pressure switch closes. This will last for 15s.
  • Page 24: A1.2 High Fire Heating Mode Logic (w1+w2 Signal)

    2 4 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide A1.2 High Fire Heating Mode Logic (W1+W2 Signal): Figure 25 When there is a call for heat (W1), the inducer will start on HIGH The blower motor will run at high speed for 30s for fan delay.
  • Page 25: A2 Ignition Failure And Reignition Sequence

    Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 25 Ignition Failure and Reignition Sequence If the furnace fails to ignite, there is a separate logic for the re-ignition sequence: Figure 26 When there is a call for heat (W1), the inducer will start on HIGH speed and the low pressure switch closes.
  • Page 26 2 6 | Bosch 96% AFUE Gas Furnace Troubleshooting Guide Data subject to change 01.2019 | BTC 770502101 A...
  • Page 27: Troubleshooting Guide Bosch 96% Afue Gas Furnace

    Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 27 BTC 770502101 A | 01.2019 Data subject to change...
  • Page 28 United States Bosch Thermotechnology Corp. 65 Grove Street Watertown, MA 02472 Tel: 866-642-3198 Fax: 603-965-7581 www.boschheatingandcooling.com BTC 770502101 A | 01.2019...

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