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Trouble Shooting - 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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thermocouple. If it is too small, the pilot burner must be
cleaned. To obtain a spark, the position of the Piezo igniter
electrode should be approximately 3 mm (1/8") from the
pilot burner tip.
Fig. 9 - Characteristic Pilot Flame
To clean the pilot burner and/ or the pilot orifice : Turn
off the gas at the unit. Remove the cover of the heater. To
do so, pull off the temperature adjustment knob and
unscrew and remove the plastic collar and unscrew the
central screw located at the bottom of the front cover. Pull
main cover out toward you and lift up and out . Pull the air
screen off, wash it and blow any lint off (See Fig 10). The
pilot orifices should also 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.
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 compression fittings to
expose pilot orifice.
Fig. 10 - Pilot burner with air screen/ pilot orifice
Correct gap between pilot
burner tip and electrode tip
Piezo Electrode
Air screen filter
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 wrong size gas orifices 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: The AquaStar heater, when
operated at lower temperatures settings, do not accumulate
mineral build-up. 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. Consult
your dealer or Controlled Energy for instructions.


The AquaStar 125B 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 to activate the burners at its minimum flow
requirement; Dirt in the water flow valve causing it to
malfunction; Sediment build-up in faucet aerators, or
shower heads; Uneven pressures between cold and hot.
(with single lever faucets) Plumbing cross overs. 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
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 and unscrew the central screw
located at the bottom of the front cover. Pull main cover
out toward you and lift up and out.
1. No gas to the AquaStar
A. Gas cock on gas line may not be open.
B. Gas valve button has not been moved to "PILOT"
position (
). Slide button to right to PILOT.
C. Gas regulator may be shut or damaged.
2. In-line AquaStar gas regulator jammed (usually on
LP gas)
Replace or unlock the regulator. Note: The regulator
furnished with the heater is designed for low gas pressure.
Excessive pressure will lock it up (propane only). Locking
usually happens if the gas pressure between the gas tank
(propane) and the water heater's gas regulator has not been
reduced. See page 2 for recommended correct gas
pressure. To unlock a regulator, consult your gas supplier.
3. Pilot orifice clogged and/or air screen dirty, or pilot
gas filter is dirty.
Clogging of the pilot burner can be caused by dust and
any suspended matter contained in the ambient air.
(see maintenance table)

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