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Lighting Instructions; Setting Water Temperature; Maintenance & Service - Bosch 125B LP Installation And Operating Instructions Manual

Automatic instantaneous type water heaters for use with natural and liquefied petroleum gas
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cover of heater)
1. STOP! Read the safety information above on this plate.
2. The Gas valve must be turned off by sliding the gas
valve button to the far left under the OFF (
3. Wait five (5) minutes to clear out any gas. If you smell
gas, STOP! Follow "B" in the safety information above
on this plate. If you don't smell gas, go to next step.
4. The pilot burner is located behind the peephole in the
front center of the jacket directly below this instruction
5. Slide the gas valve button to the right, under the pilot
mark (
6. Fully depress gas valve button and light pilot by pushing
"PILOT IGNITER" button (
be repeated.
7. Observe the pilot flame through the peephole. The gas
valve button should be held down at least 15 seconds
with pilot burning. When the gas valve button is released,
the pilot should continue to burn.
- If the gas valve button does not pop up when released,
stop and immediately call your service technician or gas
- If pilot does not stay lit, repeat steps 1 through 7.
- If pilot will not stay lit after several tries, slide the gas
valve button to the left, under the OFF ( ) mark and call
service technician or gas supplier.
8. Once pilot remains lit, then slide the gas valve button to
the right, under the ON mark (
fire when water is drawn at a rate greater than the
threshold flow rate.
NOTE: If main burner should fail to ignite, make sure pilot
is burning. If not, repeat lighting steps 1 through 7.
Slide the gas valve button to the far left, under the off ( )
mark and close the gas supply to the heater.
The AquaStar 125 B LP and 125 B NG water heaters have
a gas control that modulates burner input in response to
flow. Its purpose is to ensure that the hot water temperature
will remain steady, although the water flow demand might
vary (down to 1/2 gal/minute). To adjust the temperature
on your AquaStar, turn on a hot water faucet to its
maximum flow. At the water heater, turn the large knob
located beneath the main gas controls on the front of the
heater all the way to the right (clockwise). See Fig 8. This
will produce a temperature rise of approximately 90°F at
flow rates between 0.5 and 2.0 gallons per minute. Given
that average incoming water temperatures are 50°F, this
heater will produce approximately 140°F water at these
flow rates. Turning the dial all the way to the left
(counterclockwise) will produce a temperature rise of
approximately 45°F for flow rates between 1.1 and 3.7
gallons per minute. It is safest to select a comfortable
temperature and not have to mix in cold water.
(as seen on front
) mark.
). This step may have to
). The heater will now
Fig. 8 - Water Flow Control Knob
The position you select on the temperature adjustment knob
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 adjustment knob would 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 to the maximum position,
all the way clockwise to the right.
Do not supply the AquaStar 125B with preheated water.
For this type of application, purchase a solar model 125 B
LPS or 125 B NGS.
Approximately once a year, the AquaStar 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.
Pull main cover out toward you and lift up and out. THE
Vent System: Should be checked annually. Clean and
repair as needed.
Water Valve (Part # 8707002499): The water valve on this
heater should be serviced periodically. Lubricate component
#24 on page 14 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
components #24 and #25 on page 14. 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 (#28 on page 14) is clean as well.
Pilot Flame: The pilot flame should burn with a clean sharp
blue flame and should resemble the diagram in Fig 9. If the
flame is yellow, or if the pilot knob has to remain depressed
for a long time in order to keep the pilot lighted, the pilot
burner and or the pilot burner orifice may need to be cleaned,
the orifice may need to be replaced, and or the air screen
may need cleaning. The pilot flame should envelop
approximately 10 mm (3/8") of the tip of the

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