Bosch Appliances GWH 425 HN Water Heater User Manual


 
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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 425 HN, 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.
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. 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 425 HN LP and 425 HN 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
425 HN, 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.