is this a sime format 25he? if so there should be a clock face surrounded by alot of little dials these can be pushed in and out to turn the boiler off and on (you will quickly find out which is which). There should also be a tiny snicket next to the clockface when pushed to the top the timer is off when pushed to the middle it is on the clock times and when it is pushed to the bottom it is on constant (24hrs)
