While you wait for answers, we may have found some information which could help you.
Success
Message
DHW Run's hot and then goes cold?
what part do ineed?
ferolli modena 102?
c/h hotwater?
falling presher?
how can i fix this ?
High pressure on my Optima Ferolli 901 central heating?
Can't get hot water but central heating is working fine, any ideas??
DHW running hot then cold?
Ferroli Boiler Optimax HE 31C?
2 amp fuse blown?
shower in bathroom keeps going hot then cold then hot etc?