Vokera Compact SE 28 Red Light

[Kasheen]

Wondering if anyone can help me troubleshoot our boiler, the symptom seems to be as follows:

• 
  
  - Central Heating will run until the cows come home but if you start to use the DHW while the heating has been on for about 30mins the boiler goes to a solid red light.
  
  - Resetting the boiler causes it to go green but if you keep drawing DHW and central heating it'll go back to red in about ten seconds. When doing this I took the cover off and looked through the little opening to see that the boiler isn't firing, it makes a kind of blowing noise and quiet high pitched kind of hum and then goes to red.
  
  - Using DHW from a cold boiler is fine for at least the duration of a shower (so 20mins say). No red light.
  
  - Turning off CH after a period of usage and then turning on DHW too quickly causes the red light. However turning off CH and giving it a few mins then using DHW seems to be fine.
  

I've tried the following: I have an old Linea 24 which has the same primary thermistor as the Compact 28 (part #8484) so I took it off the Linea and placed it on the Compact as primary thermistor. I then used the old primary thermistor of the compact in place of it's secondary thermistor (dhw) which had some corrosion (had gone green, the primary thermistor had no visible corrosion). I know this isn't ideal because none of these are new thermistors - is it worth while buying new ones just to see?

The water inlet pipe (for dhw) is fully open and there's good flow from the taps, so I don't think there's a blockage.

Any suggestions that I can use to narrow down what the problem is would be greatly appreciated. Thank you!

 

[Kasheen]

Think I may just get two new thermistors anyway since they are cheap enough to see if it makes a difference.

Anyone got any other ideas? Think I may just call the gas man after I try new parts since I'm not sure there is much else I can service without being GSR myself.

Had a read at some other threads but couldn't really find the exact same problem as mine, most seemed to occur with CH or DHW alone rather than only with both together.

Thanks again if anyone has any suggestions.

 

[Kasheen]

Still having the same issue with two brand new thermistors on the Primary and DHW.

It seems to be the same issue that triggers it, get the central heating to fire for a while then turn on the water and it locks out.

Something new I noticed last night though was that it seemed to lock out with CH only after a few hours...

Do boilers overheat, is there any way I can check that?