Maintenance And Service - Bosch WR 400-3.K Série Mode D'emploi

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. THE FOLLOWING OPERATIONS SHOULD
BE PERFORMED BY A QUALIFIED SERVICE PERSON:
Vent System: Should be checked annually. Clean and
repair as needed.
Water Valve (Part #24): 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 (# 28 on figure
18, page 13) is clean. Diaphragm should be replaced every
7-8 years in residential applications and 3-5 years for
commercial applications. In acid water areas the venturi
should also be replaced at the same time.
Pilot Flame: The pilot flame should burn with a clean, sharp,
blue flame and should resemble the diagram in Fig. 1 3. 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 note come on.
3mm
Pilot screen
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
0). Remove the cover on the heater. To do so, pull of 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 orifice.
Correct gap between pilot
burner tip and electrode tip
Electrode
Flame sensor
Electrode
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. LP orifices, on the other
hand, are too small to clean and should be replacement. To
access the pilot orifice, remove 2 screws holding pilot
assembly in place. Then loosen compression fittings to expose
pilot orifice.
Fig. 14 - Pilot burner with pilot orifice
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 Build-up: In hard water areas the Bosch,
when operated at lower temperature settings, tend not to
accumulate mineral buildup. If however, the heater is used
at the higher temperature settings and the water has a high
mineral content, periodic descaling may be necessary. The
heating coils should be flushed with a descaling solution.
Signs of scaling are rising outlet temperature and knocking
noises when water is flowing.
TROUBLE SHOOTING
Introduction
The Bosch WR400-3.K.. burners are activated by a water
flow valve. Numerous water related problems can cause
this water valve to malfunction such as: Insufficient water
flow volume or pressure to activate the burners at its
minimum flow requirement; Dirt in the water flow valve
causing it malfunction; Sediment built-up in faucet aerators,
or shower heads; Uneven pressures between cold and hot,
(with single lever faucets) Plumbing cross over. These water
flow related problems can cause the heater to deliver less
than its full output, or to fail to ignite or to shut down
completely.
Problems are stated in upper case, bold face. Most common
causes for the problems follow in order of likelihood. The
suggested solutions require that the cover be taken off. To
do this, remove incandescent particle tray, pull off the
temperature adjustment knob and unscrew and remove the
plastic collar. Pull main cover out toward you and lift up and
out.
PILOT ORIFICE
9