Vokera Boiler problem

[kpmc14]

We are having a few problems with our boiler (Vokera 14-48 se). According to an engineer it's the pressure switch that needs replaced. The boiler pressure drops when the heating and water are both off but rises once they are switched back on. The heating and water are set on the timer. If the pressure switch is replaced will the pressure remain at a constant level when either off or on?? Also we would like to change to a combi boiler. Would we need to change the pipes? Many thanks

[gasman]

It is perfectly normal for the pressure to fluctuate, this is because the water when heated will expand thus raising the pressure and it will fall again when the water cools. It is nothing to worry about. Changing the pressure switch will not stop the pressure going up and down.

As for the combi question you could probably use the old heating pipes but they will need cleansing and flushing also the gas pipe may need to be upgraded to 22mm and more pipes will be needed to be installed aswell for the condesate drain the hot water, cold water and the blow off.