I am not a boiler engineer - I just guess...
Boilers I think have a pump-overrun feature - the circulation pump continues to run after the gas has shut off so as to remove residual heat from the heat exchanger - I suspect that your trip is detecting an overheat condition because of a defective or inadequate pump overrun.
You might consider calling in a boiler engineer- or turning down the boiler's heat setting or adjusting the speed of the circulation pump to make it run faster.
The trip feature seems to be working properly - detecting an overheat condition.
But I only guess...
Good Luck...
November 2016
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