Ariston Eurocombi, DHW maximium setting, low temperature

[simon07]

Our Ariston Eurocombi A/23 MFFI has a problem on the DHW side.
Boiler fires up, microswitch for DHW is working.
The temp setting on control panel is at max indicator lights working going up to 80 degrees but water coming from tap is only around 35 degrees.
Have removed DHW heat exchanger and this is clear of scale etc.
Boiler is 7 years old.
Central heating working fine.

 

[ChrisR]

Try measuring/changing the temp sensor. Probably should be about 10k ohms cold, but I'm not certain. "We" have various ways for checking them... You can ususally try swapping them for the CH one, but you'll get wet I think.

Also you could do with the gas valve checking - not something you'll be able to do, corgi job.

 

[Rob]

If the primary side really is getting to and staying at around 80 degrees then the heat loss must be somewhere. The diverter isnt passing to the radiators?

 

[bengasman]

What happens when you run the tap at 5 litres per minute?

 

[simon07]

Have tried isolating the central heating side ( turning to DHW only and shutting rad supply by ball valve under boiler)
Turning on hot tap, boiler lights, very hot primary side but only tepid at tap. Not sure where the heat is going but only ran for a little while not wanting to do more damage.
Control also has option for flue test. On this option we get hot water from tap, again only ran for a short while.

Seems we can get hot water under certain conditions but not others.

Could this be a diverter valve issue?

thanks for the suggestions so far.

Simon.