Why does my central heating come on by itself?

Wood_V

I have a Baxi boiler in my garage. We had a new pump fitted as the old one died and the boiler kept turning itself off as it was overheating. Now the heating turns itself on at random times during the day and night, with a lot of banging noises. It will turn on for a significant amount of time(hours rather than minutes). We have had the two port valve replaced as this was sticking. There is a frost stat next to the boiler which is set to 10 degrees (this hasn’t been touched since we moved in 7 years ago). The problem appears to have kicked in since we had the pump replaced but this may just be a coincidence.  Can anyone shed light on what might be going on as our engineer is at a loss. TIA

jennifernil

A frost stat set to 10degrees, in a garage, in winter, is going to make the boiler come on quite frequently.  You could cut that down by also fitting a pipe stat on the return to turn the boiler off when the return water reaches the set temperature.

However, you say nothing has changed other than the new pump and the 2 port valve, neither of which should affect how the system operates if wired correctly.

Were the replacements identical?  And the wiring identical?

 Could  there be a mouse somewhere that has been munching on the wiring?

Le_Kirk

Would echo the post above.  Regarding the banging noises; does that also happen when you turn the heating on with the time switch?

Wood_V

Le_Kirk said:

Would echo the post above.  Regarding the banging noises; does that also happen when you turn the heating on with the time switch?

Yes it also happens when you turn the heating or hot water  on with the time switch. 

southcoastrgi

Is the pump the right way round ?

Is the zone valve the right way round ?
Is there a bypass ?
Frost stat should be set to 5° & really in line with a low limit pipe stat 

Wood_V

southcoastrgi said:

Is the pump the right way round ?

Is the zone valve the right way round ?
Is there a bypass ?
Frost stat should be set to 5° & really in line with a low limit pipe stat 

I would like to think it is (pump) as it was fitted by a gas safe engineer. Frost stat is set to 5 degrees but still the same problem. Presuming you mean the 2 poet valve when you say zone valve? If so, yep on the right way by the looks of things.  Not sure about a bypass?  This is a recent problem. Been fine before