Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4

Observation:

Inspect the bypass valve for correct adjustment.
Using a flat bladed screwdriver, the bypass can be adjusted to its minimum position (anti-clockwise) or
to its maximum position (Clockwise).
The correct position is fully anti-clockwise.
If already correctly adjusted, discharge and drain the boiler and remove and inspect the bypass valve.