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Troubleshooting; Introduction; Water Is Turned On; Water Is Too Hot - Bosch C 1210 ES Installation Manual

Bosch indoor residential and commercial models tankless water heaters temperature modulated with electronic ignition suitable for heating potable water and space heating, natural & liquefied petroleum (lp) gas
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7

Troubleshooting

Warning: If you are unable to perform
the tasks listed below, or need
additional assistance please contact
your original installer or a licensed gas
technician.
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.boschpro.com
troubleshooting. For best results, perform each step
before proceeding to the next. The suggested solutions
may require that the cover be taken off. (See Page 7.
Fig. 3).
7.2
Burner does not ignite when hot

water is turned on

It is recommended to use "Control board diagnostics"
page 46, chapter 6.7 as a tool for problem solving.
1. If the display is blank, verify power to outlet.
(120VAC/60Hz properly grounded circuit required).
Verify that the heater power button is pressed ON.
2. Verify the fuses in the control board are good. To
access fuses, the control board must be removed.
See chapter 4.2, page 36.
3. Make sure cold water inlet connection is plumbed to
the right side of heater when facing unit. See Fig. 32,
page 29.
4. A minimum of 0.5 gallons per minute (GPM) (1,9 l/m)
is required to activate the heater. A quart container
should fill in 23 seconds or less, from hot water tap
only, to activate heater. Refer to 3d in diagnostics
(Table 26).
5. Clean inlet filter screen, see chapter 3.9, page 29.
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 0.5 GPM
(1,9 l/m). A crossover in the hot and cold plumbing
pipes 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 each tap. 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
6 720 644 887
for
more
detailed
faucet mixing valves are common causes of plumbing
crossovers.
8. With the power button pressed to OFF and the
power supply cord unplugged, remove the unit's
front cover (See Page 7. Fig 3). Check wire
connections between the water valve, control unit
and electrode set. See chapter 12.2, page 60 for
location of these parts.
9. Water heater in solar mode. If inlet water
temperatures exceed the water heater's set
temperature, the burners will not ignite and the solar
mode indicator will show on the display. See Fig. 54,
page 37.
7.3

Water is too hot

1. Selected temperature on the unit is too high. To
lower output temperature, see chapter 5.4, page 38.
2. Clean inlet filter screen, see chapter 6.1, page 40 to
increase flow through the heater.
3. Inspect the water path for obstructions. Make sure all
showerheads, faucet aerators and whole house
filters are clear of debris.
4. Confirm that 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 41 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 38.
2. Clean inlet filter screen. See chapter 6.1, page 40 to
increase flow through the heater.
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
specifications in chapter 3.14, page 35. A gas
pressure reading is needed to proceed further.
Troubleshooting
is
in
accordance
with
47

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