Article reference KA-02059
This may simply be due to the cylinders hygiene cycle. Periodically the cylinder will heat the water to 60-65oC in order to kill off bacteria such as legionella. On the Quantum cylinder this can be set to occur daily, weekly, or monthly.
The settings for this cycle can be found in the service menu by pressing and holding Menu+Back+Dial
Applicable models
QWCd125-580, QWCd125-580RF, QWCd135-480, QWCd135-480RF, QWCd150-580, QWCd150-580RF, QWCd180-480, QWCd180-480RF, QWCd210-580, QWCd210-580RF, QWCd250-580, QWCd250-580RF, QWCd300-580, QWCd300-580RF