MAINTENANCE AND SERVICE
Approximately once a year, the Bosch should be checked, cleaned and serviced as necessary. To remove the front cover, first remove the incandescent particle tray, then pull off the temperature adjustment knob and unscrew and remove the plastic collar. Pull main cover out toward you and lift up and out. THE FOLLOWING OPERATIONS SHOULD BE PERFORMED BY A QUALIFIED SERVICE PERSON:
Vent System: Should be checked annually. Clean and repair as needed. See Preventative Maintenance Page 11.
Water Valve: The water valve on this heater should be serviced periodically. The frequency will depend on the mineral content of the water and conditions of use or whenever signs of corrosion appear at the gas and water valve joint. Check that the water inlet filter (#36 on Figure 18, page 20) is clean. Diaphragm should be replaced every
Pilot Flame: The pilot flame should burn with a clean, sharp, blue flame and should resemble the diagram in Fig. 12. If the flame is soft and yellow the pilot screen may be dirty or the pilot burner orifice may need to be cleaned or replaced. The pilot flame should be approximately 2 inches long, extending past the flame sensor. If the flame is too small, it will not reach the flame sensor and the burners will not come on.
3mm
Correct gap between pilot burner tip and electrode tip
Sparking plug electrode
Pilot cap orifice
Pilot tube
Flame sensor
Sparking plug electrode
Fig. 12 - Characteristic Pilot Flame
To clean the pilot burner and/or the pilot orifice: Turn off the gas to the unit. Set the On/Off switch to Off (position 
). Remove the cover of the heater. To do so, pull off the temperature adjustment knob and unscrew and remove the plastic collar. Pull main cover out toward you and lift up and
out. The pilot orifice should be cleaned or replaced.
Do not enlarge the orifice.
Do not use any wire or sharp object to clean orifices. Natural gas orifices are large enough that you can usually clean them by blowing through them. To access the pilot orifice, remove 2 screws holding pilot assembly in place. Then loosen compression fittings to expose pilot orifice.
Heat Exchanger should be visually examined once a year or more often in dusty areas. If fins at top show dust or debris accumulation, remove and clean with brush and soapy water.
Removal of the Heat Exchanger
1. Shut off the gas and water cold supply lines to the heater and remove the front cover.
2. Remove the drain screw from the bottom of the water regulator and open the hot water tap to allow the unit to drain.
3. Remove cover and unscrew metal retaining bar at the top front of the heat exchanger
4. Undo water connection nuts at
heat exchanger from both sides
5. Tilt the heating body to the front at the top and lift away from the heater.
Estimated service time is 10 minutes to re & re, plus cleaning time
Main Burner Flames: The main burner flames should be blue, with a more intense blue cone in the center core. Yellow flames could be a sign of plugged or dirty burners, or a blockage on the heat exchangers fins. If some burners have yellow flames while others have good flames, it is likely that dust, lint or spider webs have partially clogged the burner venturis. To clean the burners, contact a gas service person.
Mineral Scale
Flue gas safety device:
The flue gas safety device must not under any circumstances be switched off, simulated or replaced by any other component.
Operation and safety precautions
The flue gas safety device checks the effectiveness of flue gas extraction by the flue. If it is inadequate, the appliance switches off automatically so that the combustion fumes do not escape into the room in which the appliance has been installed. The flue gas safety device resets after a cooling- down period.
If the appliance shuts down while in operation, ventilate the room. Wait about 10 minutes then restart the appliance. If the problem recurs, call an engineer. The user must never make any modifications to the appliance.
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