Unvented Cylinder Some days Water Hot Some Warm

[RajaStyle]

I've noticed throughout the year that some days the water from our unvented cylinder is piping hot when we shower hence mix with cold, some days it is just warmish to the point we have to turn the shower setting to hot only (not a great shower feeling).

Can anyone help me understand why this might be ?

Timings & settings are consistent throughout the year.

 

[ReJect]

Might be whatever is heating the cylinder is not getting power at times, or if you have a gas or oil system, the motorised cylinder valve is failing.
Or you have a leak at tundish or elsewhere in house at times - dripping tap etc.
You need a G3 unvented qualified plumber to do any of the work at cylinder.
Should be serviced once a year