Viessmann Vitotwin 300-W Installation And Service Instructions For Contractors page 148

Troubleshooting
Repairs
(cont.)
Checking the temperature limiter
If the burner control unit cannot be reset
after a fault shutdown even though the
boiler water temperature is below
approx. 75 °C, check the following:
1. Pull the cables from thermal circuit
breaker A.
2. Check the continuity of the thermal
circuit breaker with a multimeter.
148
A
3. Remove the faulty thermal circuit
breaker.
4. Fit a new thermal circuit breaker and
connect cables.