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Operation Instructions; Lighting Instructions - Bosch Pro Tankless GWH-425-HNO-N Instructions For Use Manual

Gwh 425 hno outdoor model for exterior use only
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Operation instructions

4
Operation instructions
4.1
For
your
operating your water heater
Warning: If you do not follow these
instructions exactly, a fire or explosion
may result causing property damage,
personal injury or loss of life.
A. This appliance is equipped with electronic ignition for
lighting the main burners. When turning the heater on,
follow these instructions exactly.
B. What to do if you smell gas.
WHAT TO DO IF YOU SMELL GAS
B Do not try to light any appliance.
B Do not touch any electric switch; do not use any
phone in your building.
B Immediately call your gas supplier from a neighbors
phone. Follow the gas supplier's instructions.
B If you cannot reach your gas supplier, call the fire
department.
C. Use only your hand to turn the on/off control switch.
Never use tools. Follow these instructions exactly. If
control switch is jammed, close the gas supply and call
a qualified service technician. Attempted forceful repair
may result in a fire or explosion.
D. Do not use this appliance if any part has been under
water. Immediately call a qualified service technician to
inspect the appliance and to replace any part of the
control system and any gas control which has been
under water.
4.2

Lighting instructions

B 1. STOP! Read the previous safety information.
B 2. Turn off power supply to heater.
B 3. Open the cold water inlet supply to the heater fully.
B 4. Open a hot water faucet to permit the water to fill
the heater and the piping and to eliminate the air
trapped in the system.
B 5. Close the hot water faucet after the water flows
freely and all the air has escaped from the system.
The water heater is now ready to operate.
B 6. Open gas isolation valve. Wait five (5) minutes. If
you smell gas, STOP! Follow "B" in the safety infor-
mation above. If you do not smell gas, go to the next
step.
B 7. Set the switch (located behind the sliding viewer
window on the front panel strip) to the "ON" position.
In this position, the water heater is ready to use.
Note: On first time initial installation, existence of air in
the gas supply line and in the water line may cause
14
safety
read
before
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.
B 8. 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.
B 9. 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.
B 10. For maximum power, slide gas valve button all the
way to the right.
4.3
To turn off appliance
B Turn off the manual gas shut off valve on the supply
line to the heater. See Fig. 11.
B Turn power switch to the off (O) position.
B Drain water lines if unit will sit for a long period of
time.
4.4
Setting the water temperature
The 425 HNO has 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. The output
temperature
can
be
temperature adjustment knob or the gas control slide.
GAS CONTROL
SLIDE
TEMPERATURE
ADJUSTMENT KNOB
Fig. 10 Temperature Adjustment Controls
Temperature adjustment knob
The temperature adjustment knob on the front bottom of
the heater (see Fig. 10) adjusts temperature by
adjusting flow capacity. See table 4 for details.
adjusted
with
either
8 716 473 148
the

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