Vokera mynute EHE not going into co mode

[johntheplumb]

I was asked to repair a Vokera Mynute 25 EHE last week. It was intermittently locking out and after being reset would operate ok anywhere from 1-5 days. Usually it would lock out at peak demand.

I went along done a visual inspection of the set up, the flue had 2 fairly long hair line cracks in it so I shut it down ordered a new one. Got my hands on the new one today, then went about re-comminishing it.

Checked and set the burner pressure at max + min. At min it was spot on. At max is was set at 4mbar when it should have been 9.40mbar. I was getting my hopes up at this stage assuming the boiler was set up wrong.

Then I carried out a combustion test . According to the MI's, take off the control switch turn fully clockwise and it should go into C0 mode for 15 mins and the LED should flash yellow. For whatever reason it would not go into CO mode.

The burner would light fine and cut in and out as normal. No led flashing yellow and the burner pressure was at 4mbar. I manually put it into hi fire just to see how it was burning,the burner pressure hit 9.4mbar,but the readings on the analyzer were way way out. At low fire I was getting the correct readings....
To summarize I have a working boiler but am unable to set it up correctly... any suggestions would be appreached

 

[GrahamM]

All controls calling for heat etc. On/off selector set to off on boiler, remove switch and press button with small driver? CO mode!
Always worked for me. If not working pcb could be playing up.

 

[johntheplumb]

Yeah all controls are good. That the way to do it for the HE, with the EHE you need to take switch off turn fully clockwise and it should be in co mode