Vokera 24E - Hot water issue

Can someone help.
My daughters CH system is strange. The heating side works fine. The pressure on the gauge at the front is 1.0 bar. The hot water is the problem.
It takes her over an hour to run a reasonable size bath. The hot water seems to trickle out. Does this mean that the hot water flow rate has not been set correctly. If so, how is this done.

Any help would be much appreciated, before I rip the thing off the wall and throw it in the back yard.

The boiler requires adequate flow of gas to heat 9.5 l of water through 35 degrees temperature rise. If the gas line is undersize (like it normaly is when some people replace boilers), you will not get 9.5 l per minute. To get water at the correct temperature, the man might have throttled the cold inlet to deliver smaller flow rate at the hot tap.

Then again you could be living in Scotland where the water is coming out of the pipes at 4 degrees C. No combi can give stipulated flowrate for 55 degree hot water at the tap.

Have you thought of getting the boiler properly serviced (not the 20 minute 'look see')