A.O. Smith Theta T Series Installation, User And Service Manual page 95

Indication Cause
F20 (blocking error)
3-way mixing valve not
(2/2) functioning.
Temperature of heating
system is to high.
Sensor S
5
positioned.
Sensor S
5
connected.
S10 (blocking error) Sensor S
5
connected.
Open circuit of sensor S .
5
Damaged cable and/or
defective sensor
S20 (blocking error) Short circuit of sensor circuit.
Short circuit of sensor S .
5
Installation-, User- and Service Manual
Measure
1. Check whether the 3-way mixing valve is connected
correctly.
2. Check whether the cable of the 3-way mixing valve
(correctly) connected to the controller.
3. Check whether the 3-way mixing valve is correctly
configurated (11.5 "Configuration 3-way mixing valve").
not correctly Check whether the sensor is correctly positioned in the heating
system.
not (correctly) Check whether the sensor is connected correctly
not (correctly) Connect sensor S
Replace cable and/or sensor.
Replace cable and/or sensor.
correctly.
5
Remark
See electrical diagram (11 "Appendices").
-
- To replace the necessary parts, you must contact
your installation engineer.
See electrical diagram (11 "Appendices").
-
- To replace the necessary parts, you must contact
your installation engineer.
- To replace the necessary parts, you must contact
your installation engineer.
95