Slow Hot Water

[Spooked]

Hi all.
Logic 35 Combi
Just lately the hot water has lowed right down.
I noticed it because I was filling a bath.
It took at least twice as long as usual.
There is no issue with the water pressure, cold is fine.
One other thing I've noticed.
Sometimes, when I turn the cold tap on, the exhaust fan on the boiler comes on.
Any clues?
Cheers

 

[Madrab]

If the mains hasn't changed or a valve or anything hasn't been altered into the boiler then possibly a flow turbine/limiter restriction.

The cold tap is moving the water to the boiler and nudges the turbine and ergo the hall sensor, that's triggering the fan

 

[Spooked]

Cheers.
So the fan thing just happens sometimes, not a fault?
No, nothing has changed, just the slow flow.
Any gas involved fixing the limiter or can I do it?

 

[Madrab]

So the fan thing just happens sometimes, not a fault?

Not a fault as such, more just a symptom of the way it's piped

Any gas involved fixing the limiter or can I do it?

It means opening the room sealed case, so not really DIY territory.