Bosch Appliances GWH 2400 ES LP, GWH 2400 ES NG manual Over-temperature detected by

Problem solving

Display	Cause	Solution
	Over-temperature detected by	1. Check that the sensor is firmly attached to the vertical section of
	outlet temperature sensor on hot	the hot water pipe (see Fig. 69, page 52).
	water pipe.	2. Check red wire connections at outlet temperature sensor.
	Temperature > 185°F	Clean terminals with an eraser. If badly corroded, replace sensor
		and wire harness. Check sensor resistance (see Fig. 59, page
		43.

3.Clean inlet filter screen per chapter 6.2, page 27 and clear any debris out of shower heads, faucet aerators and whole house filters.

4.In areas where water has a high mineral content, periodic descaling may be necessary. See chapter 6.3, page 27 for directions.

Cold water temperature	sensor	1. Check connector on wires coming from top of watervalve for a
fault.		secure connection. See Fig. 63, page 46.
		2.	Sensor may trip if water temperature drops below freezing to
		protect heater from freezing conditions Any damage due to
		freezing conditions is not covered under warranty.
Backflow temperature sensor over		1.	Check combustion air and backflow vent piping for blockage.
309°F.		2.	Check if secondary fan connections are disconnected.
The appliance will close the burner		3.	Check venting specifications are met. Long vent lengths,
and lock.		venting with more than three elbows, blocked vent or combination
		venting may cause this failure.
		4.	Check sensor resistance (see Fig. 61, page 44).
Overheat sensor (ECO)	open	1. Disconnect power supply cord and check wire connections on
circuit (should reset when cooler		overheat sensor (top right of heat exchanger) and the two
temperatures are detected).		connectors on the control board. See Fig. 63, page 46.
		2.	Check white wire connections at overheat sensor. Clean
		terminals with an eraser. If badly corroded, replace sensor and
		wire harness.
		3.	Check venting specifications are met. Long vent lengths,
		venting with more than three elbows, blocked vent or combination
		venting may cause this failure.
		4.	Clean inlet filter screen 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 6.3.
		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
		overheat sensor. Using a multimeter, check continuity through
		overheat sensor contacts. Replace sensor if open.

Table 20

* By installer or service technician only.

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