Troubleshooting
7Troubleshooting
Warning: If you are unable to perform the tasks listed below, or need additional assistance please contact your original installer or licensed gas technician.
7.1Introduction
Many of the questions customers ask regarding operation of this unit can be answered by following the troubleshooting steps as outlined below. Visit our web site at www.boschhotwater.com for more detailed troubleshooting and service bulletins. For best results, perform each step before proceeding to the next. The suggested solutions may require that the cover be taken off. (See Page 6. Fig. 3).
7.2Burner do not ignite when hot water is turned ON
1.If the display is blank, verify power to outlet. (120VAC/60Hz properly grounded circuit required). Verify that the heater ON/OFF button is turned ON.
2.Verify the fuses in the control board are good. See Section 4.2, page 28 of the installation manual for fuse locations.
3.Make sure cold water inlet connection is plumbed to the right side of heater when facing unit. See Fig. 30, page 25.
4.A minimum of 0.65 gallons per minute (GPM) (2.5 l/
m)is required to activate the heater. A quart container should fill in 25 seconds or less to activate heater. In areas of warm inlet water temperatures, the heater may increase activation rate to as high as 1.6 gallons per minute (GPM) to prevent overshooting of set temperature.
5.Clean inlet filter screen per chapter 6.2, page 32.
6.Inspect the water path for obstructions. Make sure all showerheads, faucet aerators and whole house filters are clear of debris.
7.The heater activates when the water flow through the unit is at or above the required minimum of 0.65 GPM (2.5 l/m). A crossover in the plumbing creates back pressure on the water flowing through the heater. Therefore, a higher flow rate than normal is needed to force the heater to activate. To check for a plumbing crossover, shut off the cold water supply to the water heater. Then open all of the hot water taps served by the heater. Wait 10 minutes and check for water flow at taps. There should be no water flowing. Any continuous flow of water, small or large, indicates a crossover is present and must be corrected. Consult a professional plumber for help in correcting a crossover. Failing single lever faucets
and mixing valves are common causes of plumbing crossovers.
8.With the ON/OFF switch turned to OFF (O) position and the power supply cord unplugged, remove the unit's front cover (See Page 6. Fig 3). Check wire connections between the water valve, control unit and electrode set. See chapter 12.1, page 49 for location of these parts.
7.3Water is too hot
1.Selected temperature on the unit is set too high. To lower output temperature, see chapter 5.4, page 30.
2.Clean inlet filter screen per chapter 6.1, page 32.
3.Inspect the water path for obstructions. Make sure all showerheads, faucet aerators and whole house filters are clear of debris.
4.Confirm the heater's gas type coincides with the type of gas being supplied. See Fig. 2, page 6 for location of rating plate.
5.Avoid restrictive outlets. Clean all showerheads and faucet aerators. It may be necessary to upgrade to higher flow rate shower heads if allowable by local code.
6.In areas where the water has a high mineral content, periodic descaling may necessary. See chapter 6.3, page 33 for directions.
7.Ensure the outlet temperature sensor is making contact and firmly mounted on the hot water pipe.
7.4Water is not hot enough
1.Selected temperature on the unit is too low. To raise output temperature, see chapter 5.4, page 30.
2.Clean inlet filter screen. See chapter 6.1, page 32.
3.Inspect the water path for obstructions. Make sure all showerheads, faucet aerators and whole house filters are clear of debris.
4.Confirm the heater's gas type coincides with the type of gas being supplied. See Fig. 2, page 6 for location of rating plate.
5.Check inlet gas particle screen for blockage at gas inlet connection on bottom of unit.
6.Verify gas pressure is in accordance with specifications in chapter 3.12, page 27. A gas pressure reading is needed to proceed further. Contact your original installer or a local certified gas technician to obtain this reading.
7.Cold water is mixing into the hot water lines (plumbing crossover). A plumbing crossover can unintentionally mix cold water with the hot water leaving the heater. The end result is a cooler water temperature than desired. To check for a plumbing crossover, shut off the cold water supply to the water
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