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Preventive Maintenance; Pilot And Main Burner; Pressure Relief Valve - Bosch WR400-1K Series Installation Operation & Maintenance

Instantaneous gas water heater
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Check pilot and main burners at least every 12 months for
proper flame characteristics.
The pilot flame should envelop approximately 10 mm (3/8
inch) of tip of thermocouple.
Figure 11
If the pilot flame is too small, then the pilot burner must be
cleaned. The position of the igniter electrode should also
be checked to assure that electrode is approximately 3 mm
(1/8 inch) from pilot. See Figure 11.
The main burner should exhibit the following characteristics:
Provide complete combustion of gas.
Cause rapid ignition and carryover of flame across
Operate quickly during ignition, burning, and extinction.
Burner flames should be blue and there should be no
lifting of flames from burner ports. See figure 12.
Figure 12
If the main burners fail to exhibit they must be cleaned,
either by blowing them off with compressed air or by washing
them in soap and water and rinsing.
If it proves necessary to wash the main burner assembly the
following procedure should be used:
1. Turn off the gas supply to the water heater by closing
the heaters individual shutoff valve.
2. Disconnect pilot gas tube at the gas valve and unscrew
the gas manifold assembly unit nut, where the gas
manifold inlet pipe connects to the gas valve, and remove
the gas burner assembly.
3. Wash the gas burner assembly in soap and water and
then rinse.
4. Dry thoroughly.
5. Reassemble. – Check for gas leaks after reassembly
and correct as required.
6. Refer to LIGHTING INSTRUCTIONS to relight the
The vent piping and finned heat exchanger should be checked
at least once a year for dust and carbon deposits, and
cleaned as necessary.


At least once a year the pressure relief valve should be
checked to insure that it is in operating condition. Before
testing the relief valve take necessary precautions to prevent
water damage. Lift the lever on the valve several times until
the valve seats properly and operates freely. Do not check
the relief valve when hot water is being drawn and the main
burner is on. Water exiting the valve under these conditions
would be hot.
If the pressure relief valve on the appliance discharges this
is an indication of water pressure above the pressure rating
of the relief valve. If the pressure relief valve continually
discharges on a periodic basis, contact the water supplier
or local plumbing inspector on how to correct the situation.
Do not plug the pressure relief valve.
After 12 or 24 months of service, depending on frequency
of use and water hardness, the heater should be checked
for accumulation of calcium carbonate (lime) and delimed,
if necessary. Thereafter a regular schedule, based on initial
inspection findings, should be set- up to delime the heater.

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Wr400-1 k p