Boiler runaway (dangerous heat) under eBus control - advice please?

Hi all - I recently removed my tado wireless programmer with a switched live (relay), in favour of a tado extension kit with eBus control, so that I could benefit from modulation control of my boiler.

I have a UK s-plan system with 2 port values and to achieve the above I introduced a glow worm smart wiring centre 2 (swc2) to communicate between tado’s extension kit and my boiler (glow worm energy 18r boiler). The swc2 manages the cylinder stat and 2 port valves.

Initially when tested this worked well, however I continued to monitor and on two separate occasions I witnessed that when a heating request ends (ie. seemingly nothing in my tado app is calling for heat) the boiler enters an uncontrolled cycle of burner ON, burner OFF. Because all TRV’s are closed this rapidly causes the boiler display to reach heat in excess of 100 Celsius (as displayed on the front) and I can hear boiling inside the boiler! Manually turning off the boiler doesn’t help because when powered up again, the looping continued. Only a total reset of the tado internet bridge, extension kit etc seemed to stop the problem.

I understand when you move to eBus control, upper heat limits etc are managed by the smart device? (This seems to be the case as I could no longer use the boiler buttons to select maximum heat).

It’s possible this is a boiler issue and not a tado issue, but until I can pinpoint the cause I have reverted back to the wireless programmer with switched live (relay control) and everything works properly again (no overheating, although no modulation!).

Has anyone experienced this behaviour?


  • Jurian
    Jurian | Admin
    edited November 22

    This is not a common issue and it seems like you have too many variables.

    I would first remove the smart wiring centre 2, and then wire the tado extension kit as the traditional S-Plan

    That way, you can test if it is because of the wiring center, or because of how the Smart Radiators are calling for heating.

    Alternatively, please remove the tado smart radiators temporarily, and then test the system with tado on eBUS.

    Furthermore, we have some information indicating that the Smart Wiring Center 2 is not compatible.

  • Thank you @Jurian good suggestions, I will try these steps to troubleshoot.

    About your last comment, I read in various posts on this forum that Smart Wiring Centre 2 is something Tado is compatible with. Has something changed please?