All condensing system boilers only have one water temperature setting ! Independent control of domestic hot water comes from a thermostat affixed to the hot water storage tank. This thermostat controls the 'motorised' 3 way valve. When the temperature set on the hot water storage tank thermostat is 'satisfied' the water flow thru the tank is cut off. This allows high temperature water settings on your boiler stat without dangerously hot water from your hot water taps.
All of them? Do no systems still have the boiler loop passing through coils in the hot water tank and the central heating tank, enabling both hot water and central heating to heat simultaneously, the temperatures to be wildly different and independent from the boiler loop temperature, and both central heating and boiler loop to contain performance chemicals?
Your earlier comment about 40 degree temp water from your taps ! Your domestic hot water needs to be set at a minimum of 60 degrees
or you are at risk from Legionnaires' disease
Suggest you read this:-
Legionnaires' disease
An old chestnut based on half-understood outdated advice for a different situation. 40 degrees at-tap will mean a higher temperature in the tank, even with pipe insulation. In the high-40s, legionella does not multiply.
That HSE advice to store hot water at 60 degrees contradicts NHS advice for 46 degree maximum at-tap water temperature to avoid scalding people, especially people with reduced skin sensation. HSE seem to think 50 degrees at-tap is acceptable, which IIRC is about 90-second scalding! And even that is only achieved by kludging expensive thermostatic valves in, which can't be used on many gravity-fed systems, which means you need an even more expensive electric pump. It is unrealistic and wasteful old advice from HSE which should be updated in the face of the climate and energy crises.
HSE's mainly about workplaces and I doubt many homes comply with most risking scalding by omitting the valves, or risking legionella if someone's turned the tank down to fix scalding hot tap water. Do you actually follow that HSE advice for your home? For example, when did you last drain your hot water cylinder and check it?
The latest advice is that home water tanks should be heated to 60 degrees for an hour every 1-2 weeks (legionella dies in about half that time at 60 degrees) and that it's far more important that the hot water system should contain no dead legs where legionella can grow, even with a 60 degree tank. Modern heating controllers have a legionella cycle on them to manage the tank, plus a thermometer so they can avoid it sitting lukewarm. Much better than the old brainless thermostats with almost no gap between off and on temperatures that then got linked to a timer to stop it reheating too often, with the end result of water held in the 32-42° ideal growth range.
Heat your tank to 60 every time any water is taken out of it if you want, and install expensive valves and pumps to cool it to safe use temperature, but please don't try to scare everyone into spending all that.
which suggests you probably do need to read that. However I understand your irritation.
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