Safety Devices - A.O. Smith TWI 35-200 Installation, User And Service Manual

6.3
0313279_TWISTER II_UKUK_V1.1, 18-02-2019

Safety devices

Fig. Safety devices
Safety devices of the water heater:
Temperature
sensor (1)
Gas control
valve (2)
Air proving
switch (3)
Flame probe (4)
The water heater controls the water temperature
using a temperature sensor:
- T > 90 ºC (blocking error), max.
temperature.
- T > 95 ºC (lock out error), for safety.
The gas control valve controls the gas supply to
the burner.
The air proving switch checks the air pressure
differential during post- and pre-purging. This
guarantees that there is sufficient air supply.
The flame probe detects if there is a flame.
1. Temperature sensor
2. Air proving switch
3. Gas control valve
4. Flame probe
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