Timer Short Circuit 3 Times in Eighteen Months

Hi there, looking for some urgent advice. I have a PulseCoil A Class APA4140 boiler installed in my flat. A serious problem has occured recently. About eighteen months after installation (April 2006) the original timer switch a Sangamo Powersaver Weekly Timeswitch, underwent a short circuit and caught fire. I called out an electrical engineer who replaced the timer. This lasted a year. Same problem. This was replaced by a third Sangamo timer, but last Friday (15th October) the timer suffered the same fate as the previous two timers. This time lasting less than four months. The problem seems to be linked to the boost button as the short circuit occurs after pressing the boost button. But not immediatley, it takes a few presses of the button to instigate the short. Any ideas would be greatly appreciated. So far I have been very fortunate as the short circuits have occured whilst I am at home. Obviously the potential fire hazard is a very serious matter. Cheers

Is the time switch a 13 amp model?
Sounds to me as if is underated.
Mike.

Checked the amp rating on the timer switch. It is 16A.

As long as there are no relays or stat stuck on causing overheating.
Then I would contact the timer maker.
Mike