Putting in a larger boiler does not give you a better flow rate. All it will give you is the same flow rate, but at a higher temperature.
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This was your original statement which is is simply not true.
If you had a incoming supply 20 l/min and you installed a 24kw combi boiler, you would be getting 9-10 l/min at the hot tap at a 35 dergrees rise.
If you fitted a a 35kw combi on the same supply, you would get around 14 l/min at the hot tap at a 35 degrees rise, you would not get 14 l/min out of the 24kw boiler, the water temperature would be too low for use.
So putting in a larger boiler does give you a better flow rate.
[/quote]
This was your original statement which is is simply not true.
If you had a incoming supply 20 l/min and you installed a 24kw combi boiler, you would be getting 9-10 l/min at the hot tap at a 35 dergrees rise.
If you fitted a a 35kw combi on the same supply, you would get around 14 l/min at the hot tap at a 35 degrees rise, you would not get 14 l/min out of the 24kw boiler, the water temperature would be too low for use.
So putting in a larger boiler does give you a better flow rate.