Bosch AQUA STAR 2400E LP - Manual (Page 38)

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Troubleshooting
E1 Over-temperature detected by temperature
sensor on hot water pipe.
(part# 8700400015) 1. This water heater must be supplied with cold
water for domestic hot water only. Do not
recirculate water through this heater or supply with
preheated water.
2. Check that the hot water temperature sensor is
firmly attached to the horizontal section of the hot
water pipe.
3. Check red wire connections at hot water
temperature sensor. Clean terminals with an eraser.
If badly corroded, replace sensor and wire harness.
4. Swap hot water temperature sensor with the cold
water temperature sensor. If the heater produces
an E2 error, replace hot water temperaure sensor.
5. Clean inlet filter screen per chapter
5.2 and clear
any debris out of shower heads, faucet aerators and
whole house filters.
6. In areas where water has a high mineral content,
periodic descaling may necessary. See chapter
5.3
E2 Cold water temperature sensor fault.
(part# 8700400015) 1. Check blue wire connections at cold water
temperature sensor. Clean terminals with an eraser.
If badly corroded, replace sensor and wire harness.
2. Verify that the sensor is firmly attached to the
horizontal section of the cold water pipe.
3. Sensor will trip if it detects temperatures at or
below 36°F. Protect heater from freezing conditions
as any damage resulting from freezing is not
covered under warranty.
4. Swap cold water temperature sensor with the hot
water temperature sensor. If the heater produces an
A7 error, replace cold water temperature sensor.
E9 Temperature limiter (ECO) open circuit
(should reset when cooler temperatures are
detected).
(part# 8707206204) 1. This water heater must be supplied with cold
water for domestic hot water only. Do not
recirculate water through this heater or supply with
preheated water.
2. Disconnect power supply cord and check white
wire connections on ECO (top right of heat
exchanger). Clean terminals with an eraser. If badly
corroded, replace sensor and wire harness.
3. Verify that venting meets specifications outlined
in chapter
3.6 . Long vent lengths, venting with more
than three elbows, blocked vent or combination
venting may cause this failure. Verify backdraft
flapper inside flue gas collector is not stuck shut.
4. Clean inlet filter screen per chapter
5.1 and clear
any debris out of shower heads, faucet aerators and
whole house filters.
5. In areas where water has a high mineral content,
periodic descaling may necessary. See chapter
5.3
for directions.
6. 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 ECO.
Using a multimeter, check continuity through ECO
Display Cause Solution
Table 12
* By installer or service technician only.