Question about Ariston Combi Boiler

[dominot5]

We have just brought a new house with the above boiler. I have noticed the thermostat is not calibrated correctly. If the Thermostat is set to 20 degrees it actually switches the boiler off at 17 degrees.

My question however relates to the running of the boiler. I have noticed the following.

The boiler comes and and runs for 30 minutes until the thermostat indicates the correct temperature has been reached it then switches off. It then seems to switch back on 4 - 5 minutes later and it runs for 3 - 4 minutes then switches off, it then comes on again 4 - 5 minutes later and runs for 3 - 4 minutes again, this keep repeating for an hour.. is this normal or do I have a problem.. could this be related to the mis calibrated thermostat ?

 

[meldrew's_mate]

Nothing to do with your thermostats, which seem to be working properly; don't expect a £15 'stat to be accurate, just expect it to be repeatable.

Have a competant gas fitter adjust the burner output to match your heating load, you can adjust it's maximum output internally, and check the minimum burner pressure is as per the manufacturer's data.