when opening hot water tap boiler delays in firing up when it starts the water temperature goes to 60c the suppose (to go from high to low flame it works sometimes )but it cut out the flame until the temp goes to below 40c when flowing water cools it down and fires up again to reach the temp again.central heating works perfect

nat, May 2007

Google 'vokera flue venturi' , , 'temperature cycling' etc.
The flue venturi has to be quite clean for proper air pressure switch operation. You can download the manual from www.vokera.co.uk. Check APS switch operation with a multimeter, the fan heat exchanger and flue all need cleaning if this is the trouble. If you are unsure you would be best getting it done as part of the standard maintenance by a by a vokera trained professional.

c, May 2007