Lighting and operating instructions, Setting the water temperature – Bosch 125HX NG User Manual

Page 10

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6 720 606 804 (02.10)

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.
If you supply the AquaStar 125HX, with preheated water
(i.e.) in a solar installation the unit could overheat.
It will
then shut off on safety when the outlet temperature reaches
194°F. For this type of application, purchase a solar model
125B LPS or 125B NGS.

Fig. 8 - Temperature Adjustment Knob

LIGHTING AND OPERATING INSTRUCTIONS

1. STOP! Read the safety information above on this label.
2. The gas valve must be shut off by putting the ON/OFF

switch to position “

”. Wait five (5) minutes to clear

out any gas. If you smell gas, STOP! Follow “B” in the
safety information above. If you do not smell gas, go to
the next step.

3. This water heater is equipped with a safety pilot burner

and an automatic ignition control system.

4. Set the ON/OFF switch (flip down cover plate on front

panel strip) to the

position. In this position, the

water heater is ready to use.

5. If the red LED indicator light is flashing, this is a warning

that the water pressure is not enough to ignite the main
burner.

6. Turn the hot water faucet on to the minimum flow rate

required to activate the heater. The automatic ignition
system first ignites the safety pilot burner which then
ignites the main burner in about 4 seconds.

7. The green LED indicator is on when the main burner is

on.

8. The pilot flame will extinguish 10-30 seconds after the

burners come on. The burners will remain on until the
hot water tap is turned off.

NOTE: On a first time initial installation, existence of air in
the gas supply line and in the water line may cause some
ignition delay. In that case, repeatedly open and close the
hot water tap in order to restart the ignition process until
all the air has been purged.

TO TURN OFF GAS TO APPLIANCE

Turn off the manual lever on the gas supply line to the
heater and set the ON/OFF switch to the OFF (

)

position. See Fig 9.

SETTING THE WATER TEMPERATURE

The AquaStar 125 HX LP and 125 HX 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 control 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.

Temperature Adjustment Knob

To start and to shut down
the appliance press the
button “ ”.
The switch is located
behind the flip down
cover plate on the front
panel strip.

G661_004

Decrease
temperature and
increase flow

Increases temperature

and decreases flow

Fig. 9 - Principles of Operation

- on

- off

Green light on = main
burner on.

Green light off = main
burner off.

If the red light is flashing,
that means the water
flow is not enough to
ignite the burner.

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