Push the over heat re-set button in (up) can be found under the boiler (left hand side), then to reset the appliance and initiate a further ignition attempt it is necessary to turn the main switch through to the Reset position(spring returns to setting).
If the red safety lockout LED illuminates again after another ignition attempt, another fault may exist.
If the fault persist, consult your installer or service enginer.
Paul68
November 2008
I can answer this question...
The locked out light has come on on my Halstead Ace high combi boiler?