Bosch BGH96M060B3A Installation, Operation And Maintenance Manual

Also see for BGH96 Series: Troubleshooting guide Installation instructions User's information manual

Contents

4 8 | Bosch 96% AFUE Gas Furnace Installation, Operation & Maintenance04.2019 | Bosch Thermotechnology Corp.Data subject to change12 Operational ChecksDANGER: FIRE, EXPLOSION, ELECTRICAL SHOCK, ANDCARBON MONOXIDE POISONING HAZARD To avoid personal injury or death. Do not remove anyinternal component covers or attempt any adjustment.Electrical compartments are contained in bothcompartments. Contact a qualified service agent at once ifan abnormal flame appearance should develop.Burner FlameThe burner fl ames should be inspected with the burner access panel installed.Flames should be stable, quiet, soft, and blue (dust may cause orange tips butthey must not be yellow). Flames should extend directly outward from the burnerswithout curling, fl oating,or lifting off , and should enter heat-exchanger tube.Flames must not impinge on the sides of the heat exchanger fi ring tubes.Figure 40Check the burner flames for:1. Stable, soft and blue2. Not curling, floating, or lifting offBurner Flame13 Safety Circuit Description13.1 GeneralA number of safety circuits are employed to ensure safe and proper furnaceoperation. These circuits serve to control any potential safety hazards and serveas inputs in the monitoring and diagnosis of abnormal function. These circuits arecontinuously monitored during furnace operation by the integrated control module.13.2 Integrated Control ModuleThe integrated control module is an electronic device which controls all furnaceoperations. Responding to the thermostat, the module initiates and controlsnormal furnace operation, and monitors and addresses all safety circuits. Ifa potential safety concern is detected, the module will take the necessaryprecautions and provide diagnostic information through an LED.13.3 Chamber Limit Switch - FixedThe chamber limit switch - fi xed control is located on the partition panel andmonitors heat exchanger compartment temperature (it is an automatic resettemperature sensor). The limit guards against the overheating resulting frominsufficient air passing over the heat exchanger.13.4 Fan Mounted Limit SwitchThe fan mounted limit switches are located beside the blower housing. They aretemperature sensors which are automatically reset. They are used to preventoverheating by hot air when the furnace is installed horizontally.13.5 Rollout Switch - ResettableThe rollout switch - resettable controls are mounted on the burner/manifoldassembly and monitor the burner fl ame. They are manual-reset temperaturesensors. This limit guards against burner fl ames not being properly drawn into theheat exchanger.13.6 Overflow Protection Pressure Switch (Overflow Switch)Overfl ow switch is a diff erential pressure switch. The shape and dimension of theoverfl ow switch is similar to the two other pressure switches except it has twopressure ports, one in gray color (negative) and the other in black color (positive).The overfl ow switch is normally closed. When condensate hoses/trap is blockedand condensate is stopped fl owing to drain system, the level of condensate insidethe condensate collector box will rise. When the condensate reaches too highof a level in condensate collector box, the overfl ow switch will open and shutoff the furnace. Make sure that black port (positive) is conn- ected to the lowerposition tap on the condensate collector box and gray port (negative) to highertap of condensate box. [add the following in warning box]: The manufacturer’sdefault setting is for upfl ow and horiz- ontal right installations only. For horizontalleft installation, hoses for overfl ow switch are required to switch (see horizontalleft installation). Conn- ecting hoses incorrectly will result in failure to protectcondensate overfl ow.13.7 Pressure SwitchesThe pressure switches are normally open, negative air pressure activated switches.They monitor the airflow (combustion air and fl ue products) through the heatexchanger via pressure taps located on the induced draft blower. These switchesguard against insufficient airfl ow (combustion air and fl ue products) through theheat exchanger.13.8 Flame SensorThe fl ame sensor is a probe mounted to the burner/manifold assembly which usesthe principle of flame rectifi cation to determine the presence or absence of fl ame.WARNING: FIRE, EXPLOSION, OR CARBON MONOXIDEPOISONING HAZARD Replace ONLY with the same model number or as specifi edby the manufacturer.