Ferroli Optimax A3 error

[Billythekidd]

Have an Optimax HE31c which is throwing an A3 error but only when the central heating has been on and you then run a bath and then go to top the bath up with hot.

Have replaced the two temp sensors for HW and CH any pionters ?

What does the diverter valve do ?

I have a list of Perameter Mode settings could it be a timing issue when switching between CH and HW where the pump is not turning after switching to HW making the CH to overheat ?

Any pointers.

 

[Hason]

Hi it could be many things with that model. The best thing to do is get ferroli out on a fixed price repair --- this will be around 200/300 mark but atleast they will change the failed part(s)
Good luck

 

[petit_pablo]

hateful boiler for overheating - it could be that the hot water heat exchanger is restricted. It could be much worse.

 

[andytw]

My experience of this is here..

//www.diynot.com/diy/threads/ferolli-optimax-he-31c.424526/#3297414

andytw

 

[ecowarrior]

Turn down DHW o/p to 90%, increase DHW pump overun to 2 minutes
Reduce DHW flow temp to 50.

Fins on the HX comer loose & cant dissipate the heat when cycling so heat backs up real quick with the bath hot water and trips the HLS. if u look in the memory codes it will have lots of 08 blocking codes to confirm this. In Information mode u can check flow temp rising when hot water switched of after a long run. Anything over 85 & your in trouble!
Very common fault