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Troubleshooting
35
7Troubleshooting
7.1 Introduction
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).
7.2 Burner 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 23 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. 28,
page 20.
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 27.
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 46 for
location of these parts.
7.3 Water is too hot
1. Selected temperature on the unit is set too high. To
lower output temperature, see chapter 5.4, page 25.
2. Clean inlet filter screen per chapter 6.1, page 27.
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 5 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 28 for directions.
7. Ensure the outlet temperature sensor is making
contact and firmly mounted on the hot water pipe.
7.4 Water is not hot enough
1. Selected temperature on the unit is too low. To raise
output temperature, see chapter 5.4, page 25.
2. Clean inlet filter screen. See chapter 6.1, page 27.
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 5 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 22. 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
heater. Then open all of the hot water taps served by
Warning: If you are unable to perform
the tasks listed below, or need
additional assistance please contact
your original installer or licensed gas
technician.