Bosch Therm C 1210 ES Installation And Operating Instructions Manual page 62
Indoor residential and commercial models
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Also See for Therm C 1210 ES:
- Applications manual (40 pages) ,
- Technical service bulletin (2 pages) ,
- Installation manual (72 pages)
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Problem solving
Display
Cause
Overheat sensor (ECO) open
circuit (resets when cooler
temperatures are detected 220°F/
104 °C).
No flame ionization detected with
water flow.
Ionization failure during operation. 1. Check gas type, fig. 2, page 12.
Internal hardware/software
failure.
62
Solution
1. Disconnect power supply cord and check wire connections on the overheat
sensor (fig. 74, page 69) and the two connectors on the control board.
2. Check white wire connections at the overheat sensor. Clean terminals with
an eraser. If badly corroded, replace sensor and wire harness.
3. Check that venting specifications are met. Long vent lengths, venting with
more than three elbows, blocked vent or combination venting may cause this
failure.
4. In areas where water has a high mineral content, periodic descaling may
necessary, see chapter 7.3, page 51.
5. Unplug power supply cord to the water heater. Open a hot water tap for
several minutes to allow cold water to pass through heat exchanger. Close hot
water tap and disconnect lead wires to overheat sensor. Using a multimeter,
check continuity through overheat sensor contacts. Replace sensor if open.
1. Verify that all manual gas shut off valves are open.
2. Check gas type. See fig. 2, page 12.
3. Reset error code and open a water tap to cycle the heater in an effort to purge
air. Cycling hot water tap on and off multiple times may be necessary. If heater
still faults with EA error code, have a licensed gas technician properly purge air
out of the gas line leading to the water heater.
4. Check three wire connections on the lower front of the heat exchanger are
secure.
5. Check gas pressure. See chapter 4.14, page 44.
6. Check venting specifications are met. Improper venting may cause
premature failure of the flame sensor rod. See chapter 4.3, page 15.
7. Check that the minimum power fan speed has been adjusted to the proper
value. See page 29.
8. Observe inside the viewing window of the heat exchanger when a hot water
tap is opened. Sparking should be followed by a steady blue flame. If flame is
unstable/yellow with proper gas pressure, confirm CO
chapter 7.5, page 53.
2. Check three wire connections to ignition group on the lower front of the heat
exchanger are secure.
3. Verify that venting specifications are met. Improper venting may cause
premature failure of the flame sensor rod. See chapter 4.3, page 15.
4. Check gas pressure. See chapter 4.14, page 44.
5. Check and adjust CO2 readings. See chapter 7.5, page 53.
6. Check that the minimum power fan speed has been adjusted to the proper
value. See page 29.
1. Disconnect power supply cord and check the two wire and ground
connections on control board as well as ground connection on heater chassis.
2. Pressing the wrong combination of buttons on the control unit can create
confusion among the microprocessors inside. In this case, the error code
should not happen more than once or twice. Turn off the water heater. Turn
water heater back on and try resetting error code. Use the reset button (
to reset any error codes.
3. Possible defective control unit call Bosch Water Heating for further
instructions.
readings per
2
C 1210ES/ESC – 6 720 644 887 (2022/04)
)
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