Maintenance & Service - Bosch GWH-425-EF-N Manual

140° and 95°F at various flow rates between 2.0 and 4.0
gallons per minute. The position you select on the
temperature selector dial will depend on the temperature of
the incoming water (50°F is average in the U.S.). In warm
weather regions where the incoming cold water is generally
warmer, or during the hot weather months in some other
areas a midway setting on the temperature selector knob
will produce a temperature rise of about 70°F, giving an
output of approximately 120°F. At this setting, if it is still
necessary, one could mix a small amount of cold water in a
shower and have a comfortable shower at about 3 gallons/
minute. During the colder months, or in cold climate areas,
it might be necessary to set the control all the way clockwise
to the right for maximum temperature rise.
Do not supply the 425 EF with preheated water. For this
type of application, purchase a solar model 125 B LPS or
125 B NGS.
If the inlet water temperature to the water heater is very
warm the heater can produce temperatures that may be
found to be too hot. A temperature balance shower valve
can automatically mix in cold water to reduce such hot water
temperature, in the event of any temperature instability with
the use of a temperature balance shower valve, refer to
shower valve manufactures instructions for internal
adjustment setting. Adjustments should be made to the
hottest setting in the shower valve. Additionally the
temperature control of the heater can be adjusted to produce
a more comfortable hot water temperature.
Fig. 11 - Temperature Adjustment Knob
MAINTENANCE AND SERVICE
REVIEW MAINTENANCE TABLE ON
THE BACK OF THIS MANUAL
Approximately once a year, the 425 EF should be checked
and cleaned. 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.
Unscrew the central screw located at the bottom of the
front cover. 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.
16
Water Valve (Part # 8707002802): The water valve on
this heater should be serviced periodically. Lubricate
component #36 on page 21 with a small amount of silicon,
faucet or lithium grease every two years to keep its o rings
fresh and pushrod sliding smoothly. Every 3-5 years replace
component #36 on page 21. 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. Periodically check that the water inlet filter (#27
on page 21) is clean as well.
NOTE: If water valve is removed, be sure to also inspect the
o ring seal on the end of the right hand side water pipe
before re-installing. Lubricating the o ring with lithium or
faucet and valve grease is recommended.
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 burner orifice may
need to be cleaned or serviced. 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
Fig. 12 - Characteristic Pilot Flame
To clean the pilot burner and/or the pilot orifice: Turn off
the gas at the unit (Position '
heater. To do so, pull off the temperature knob and unscrew
and remove the temperature knob collar. Pull main cover
out toward you and lift up and out. The pilot orifices should
also be cleaned or replaced. Do not enlarge the orifice
(see fig. 13). 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 replaced.
See #3 in Trouble Shooting Section. To access the pilot
orifice, remove 2 screws holding pilot assembly in place.
Then loosen the compression fitting and lift up pilot burner
to expose pilot orifice.
Correct gap between pilot
burner tip and electrode tip
Piezo Electrode
Flame sensor
Piezo
Electrode
'). Remove the cover of the
6 720 607 017