CH fires up when set to off...

[Jimothy]

Hi all,

having a problem with our baxi 80 eco boiler.

The CH has been coming on in the last few days, despite all possible settings (room stat, timer settings, even main boiler function knob) being set to stop it. Only way to stop the heating coming on is to turn the boiler off entirely.

Had a plumber round to look at it, and he reckons a dodgy frost stat may be the answer, but I just found the manual online and there's no mention of an integral frost stat (or am I missing something)?: http://www.acwilgar.co.uk/pdf/combi-80-eco.pdf

Any ideas would be greatly appreciated,
Thanks,
Jim

 

[heatserve]

Page 12 section 7.4.2 refers to it.

 

[Jimothy]

Thanks for taking the time to help with this.

I see it mentions frost protection, but says that the function switch should be left in the HW+CH position, whereas this fault is happening even if the switch is on HW only.

Also, there's no frost stat on any of the schematics, or is the main temp sensor used for this "frost protection" as well?

 

[peterbaxi]

yes the thermistor acts as a frost stat,
the problem is your hot water microswitch front left hand side on front of pressure differential valve. push in microswitch i bet it is springy and does not have a click on and off.