Bosch WTD 15-3 AME 31 - Working Principle and Operation; Water Flow Detection and Solar Mode

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When in solar mode, the unit remains in stand-by mode, because the expected outlet
water temperature is within an acceptable value when compared to the setpoint value. The
water heater must be able to go into solar mode, when water flow is detected if:
- inlet water temperature is higher than [Setpoint -1ºC];
or
- expected outlet temperature, calculated with minimum power, is higher than
[Setpoint +10ºC] or 60ºC (whichever is higher)
When the conditions disappear, the unit must be able to start-up the burner and run in
normal operation mode without the symbol in the display.
Operation
Action
Connection to
the control
unit
Result
Standby
(Inputs Signals
must be within
expected limits)
Main Switch in control unit
Input
ON
Electrical plug connected
Input
230 V
AC
Thermostat (temperature limiter)
and Thermal fuse with continuity
Input
Contact closed
Ionization reading
Input
0 µA
Temperature sensors OK
Input
Ohm Value inside
range
Hot Water Demand
(tap opening)
Turbine detects water flow
Input
Frequency value
to control unit
Spark to ignition electrodes
Output
Gas valve solenoid activation
Output
V
DC
Flame on main
burner
Ionization detection (spark stops)
Input
I > 8 µA
Hot Water Delivery
Safety devices monitor operation
Input
Table 9 – Operation conditions