Ferroli Falcon 2 - central heating constantly runs

23 Jun 2012
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United Kingdom

Recently, the central heating has started constantly running on my boiler when it is switched on, regardless of whether there is a call for heat.

I normally leave the boiler on constant, and control using a room stat.
I've ruled out the room stat as being a problem - and in fact the heating runs even when the heating is switched to the "0" position.

The hot water circuit works ok, and the heating switches off for the usual timeout period once the demand for hot water has stopped - after which the heating will fire up again.

Any ideas what the most likely cause is?

I don't have the manual.
Thanks in advance.

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primary thermistor out of calibration, this sensor also acts as a frost stat so the boiler is trying to protect its self.
Thanks for the suggestions.

The thermister has failed before (only fault I've had with the boiler), so it would make sense for it to have gone again as it has been a few years now.
When it failed previously the boiler wouldn't stay running (so indicating up to temp I guess), but the frost protection also being controlled by it explains why it would run all the time.


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Just wanted to update to say I changed the primary thermistor as suggested and boiler working perfectly again.

Thanks to picasso for the advice.

Thanks for the feedback.
Expensive thermistors those, aren't they!

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