Viessmann FB2B Installation And Service Instructions Manual page 123

Repairs
(cont.)
6. Check the connections on the heat-
ing water and DHW side for contam-
ination and scaling; if required,
replace the plate heat exchanger.
Checking the temperature limiter
If the burner control unit cannot be reset after a fault shutdown, although the boiler
water temperature is below approx. 75 °C, check the following:
A
7. Install in reverse order with new gas-
kets.
1. Pull the leads from temperature lim-
iter A.
2. Check the continuity of the tempera-
ture limiter with a multimeter.
3. Remove the faulty temperature lim-
iter.
4. Coat the replacement temperature
limiter with heat conducting paste
and install it.
5. After commissioning, press reset but-
ton R on the control unit.
Troubleshooting
123