Central Heating

[Kazal]

I have an Ideal Classic gas boiler to an indirect system.The past couple of days when the system has started up, although the heating and hot water lights appear on the timer/controller and also on the heating control the boiler is not firing up for about 45 to 50 minutes. Any suggestions please?

[AlBags]

Is there a room stat .. ?
and have you checked the pump is running immediately on 'call for heat'?
Have you a motorised Mid-position valve? There is an over-ride lever on the side that can over-ride the electrical motor and spring .. switch on and go pill lever across and hook into it's retaining slot to keep open. Does boiler fire up?