Water pressure pump

[geordysurfer]

Once again, many thanks buildersmate and gasman. The full scenario is that we live in Spain, our water is fed directly into the house (no water storage possible) and feeds straight into the Vaillant 11litre HG Mini. The gas comes in bottles and is stored outside. The system was set up by a corgi registered friend. The igniter is automatically driven by the water feed. Early morning and in the evening the system works well and the water is hot, but during the middle of the day the temperature falls and I am at a loss to know what to do (apart from re-installing the electric heater!!!!)

[gasman]

It may be that there is too much water going through the heat exchanger at certain parts of the day and so the heater cannot heat it up as fast as it does at other times. It could well be an inadequate sized water heater for you're requirements. Try turning down the mains water isolation valve to the boiler to reduce the flow speed abit and see if this makes any difference to its performance. Try getting it serviced aswell this often helps to retain the best efficiency.