Bosch Appliances Model GWH 425 manual Burners do not operate cleanly yellow flames when operating

Troubleshooting

the way clockwise, the flow rate should be close to 2gpm, filling the jug in 15 seconds. With the temperature adjustment knob set all the way counterclockwise, the flow rate should be close to 4gpm, filling the jug in 7 seconds. If the flow rate is not adequate, inspect and clean the inlet filter screen (see chapter 5.2).

2.Inspect the water path outside of the heater for obstructions. Make sure all outlets (i.e. showerheads, faucet aerators and whole house filters are clear of debris. Restrictions in the water path can slow water flow through the heat exchanger causing it to boil and make noise.

3.If the water has a high mineral content, the heat exchanger may be scaled internally. This restricts the water path, causing the water to boil resulting in noise and overheating. Instructions for descaling the heat exchanger are available at www.boschpro.com.

6.12Burners do not operate cleanly; yellow flames when operating

1.Verify gas type indicated in rating sticker located on right-hand side of cover, coincides with the gas type you are using. NG is a natural gas unit and LP is for liquid propane.

2.Gas pressure may be inadequate resulting in improper combustion. Ensure gas pressure is in accordance with manufacturer's specifications (see chapter 3.6). A gas pressure reading is needed to proceed further. Contact your original installer or a licensed gas technician to obtain this reading.

3.For proper combustion at high elevations the inlet gas pressure should be set at installation to the value shown in table 3 (while operating at maximum BTU). A gas pressure reading is needed to proceed further. Contact your original installer or a licensed gas technician to obtain this reading.

4.Ventilation is not adequate. Ensure adequate combustion air is being supplied to the unit in accordance with manufacturer's specifications (see chapter 3.6).

5.Make sure the water heater is vented properly. Check for proper draft and ensure venting is in accordance with manufacturer's specifications (see chapter 3.7).

6.The water heater has burners much like a furnace. It is essential that they remain clean and are supplied with adequate air for combustion. If the flames burn yellow or orange, it is strongly recommended that the burners be removed from the unit and cleaned. Once the burners are removed, the fins in the top of the heat exchanger can be accessed and brushed or vacuumed clean. Instructions to remove burners are available at www.boschpro.com.

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