Having resigned myself to the fact I will not be able to control my electric UFH I have been final testing before install. However, I have strange BDR91 switching problem that I cannot resolve.

My system is S-Plan with HTG and DHW 2-way zone valves, gas boiler and pump. I have wired exactly as per S-Plan diagram (Figure 9) in the installation guide.
I have 12 radiators in 10 zones controlled by HR92’s, the living room has a TR87RF thermostat.

The system is set up on the bench for testing, all units are within 5m of each other but not closer than 300cm.

When requesting an override increase of temperature, the HR92’s open and the heating BDR91 switches on likewise when the increase is cancelled HR92’s close and BDR91 switches off. However, when Evohome is using the ‘schedule’ times, switch on is OK but at the finish time all the HR92s close but sometimes the BDR91 remains on for a random time of between 10 minutes and an hour.

The HW works as it should.

I have factory reset the controller, removed batteries for two hours, unbound all HR92s, unbound BDR91s and then set up using the guided configuration as per Richard from Evohome Shop post, binding just one HR92. This initially solved the problem but 24 hours later the incorrect switching returned.
I have repeated the above several times, swapping BDR91’s, with the same result, checked signal strength which is maximum for all devices and changed ‘schedule times’. I don’t believe there is anything close causing interference.

Any thoughts as to what may be going on would be appreciated.