I think I'm being a bit stupid, but I can't work out the operation of
these units.
If you have a instantaneous gas water heater do you have to keep
changing the unit's set temperature when you want to fill a kitchen sink
or have a shower?
For a kitchen sink the temp could be 50C, so you set the heater to 50C
and that should be the max you get, but the flow rate would be limited
depending upon the heater's power.
But if you want a shower, if you leave the dial at 50C then the flow
will be lower than when it's set to (say) 40C. Does this have any effect
on the shower head flow or does the shower thermostatic mixer handle it all?