Devireg 550 underfloor heating control box fix

we are dealing with high voltage here! so please only attempt if you have some experience and a multimeter otherwise get a electrician to help out even if its just replacing the whole control panel and your not sure about that – better to get someone who knows then cook yourself to a cinder  via the mains!

Surprising to see so many forums posting dead ,or sporadic  behaviour in the devireg550 after 3-5 years of use. Seems to be a bad choice of components in the power board…

so to fix this, first things first is to remove the dead capacitor….


diff model but the 550 model has similar way of releasing the front square cover  like this picture shows

Symptoms I’ve read on theses forums correlate with my own experiences these are things like ‘display blanks out when relay eventually switches on’, or ‘no error codes displayed yet no heating’?
Also another tell tell sign is no heating even when sensor readings shows 7k-24k ohms (working sensor resistance) or heater ring wires show good values on multimeter readings yet no heating…also if the bacon/heat icon is not showing then its not heating and by measuring the load outputs it normally would show 240 v but  doesn’t. Output in this case is a big fat zero reading, so to fix this, first things first is to remove the dead capacitor.(and possibly relay unit but thats an optional second step)

so you need to remove the square box like in the picture ,followed by two tiny screws on either side of the clock dial..this will release the cpu/display unit which will allow you to access the wall screws to the frame.

found image at awesome -I labeled it so you can see exactly what we need to remove

heres the culprit ! On removing the capacitor above it showed a reading of 0.33 uf not good ,should be 1 ,so go down to your local component store like maplins or farnell and get this exact replacement ,or like me you may have something lying around from a broken  device ,(so I used an  old component i found from a broken dvd player power board)  although it was higher rated at 400v which is no bad thing I guess.

On removing the capacitor above it showed a reading of 0.33 uf not good ,should be 1 


click here to see the exact replacement item,even if you can only find a smaller version just solder some wire in place to fit in the board ,works fine.


thats all you should need to do -within a 1min of reconnecting to the mains etc you should see the bacon symbol :) and connecting the multimeter to the load pins should now show 240 v output ,if not ,next thing would be to repeat the process and replace the relay too,but in my case the capacitor was enough for tiles and no expense(or very little) other than your time.


resources :

manual for re-setup of clock temps etc



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