TKB TZ78 unresponsive

Bought ten of these recently and four are now unresponsive. Can’t be detected and no led light. Is it possible they have all failed? Does anyone know how to do a hard reset on them? Have tried the 3 x power on/off and then hold button, 3 x press button then hold button. Frustrating.

Not used these particular relays myself.

If the LED indicator is not lighting up at all the user manual in the troubleshooting section suggest they are faulty.

Personally Id do some testing with a multi meter to see what’s going on with the supply voltage. Are they all on the same mains ring wiring?

Did they all fail at the same time?

User manual

Not sure if they failed at the same time but two were definitely on same ring, one may have been on this ring and the other was on a completely separate circuit. As it is, I have managed to replace two like for like and they seem to be working ok. The two that definitely failed on the same ring I have not replaced yet.

An electrician recently completed the 5 yearly inspection and didn’t flag any problems with the circuits.

did the electrician do a insulation resistance test on the affected circuit/s? and did they remove your devices before testing, and what country are you in?

Yes he did - looks like ‘live/live’ is limited (test has not been done/couldn’t be?) - ‘Live/Earth’ >200 MΩ Test voltage DC 250 V. Don’t believe devices were removed and am in UK.

OK it looks like he reduced the voltage to 250v for the test so the likelyhood he caused the devices to break is low. If he had done test at the normal 500v , i would suspect that he might of damaged devices. To be sure in future remove devices or turn off at socket if switches are double pole. He sould have discussed with you any limitations for testing, ie electronics in circuit -transformers, dimmers, smart devices. I would have join live and neutral and tested them both to earth, same result less likely to break something.

May i ask why you had a test after 5 years as its normally 10 or change of occupancy.

Thanks for the input! - It’s a holiday cottage.

Still stumped. Is there any way to do a hard reset on them?

I have no idea how to reset, try contacting the manufacturer

Are they still in warranty

Just a thought, did the electrician disconnect them to test and forgot to reconnect, or may be a wire came lose and they have no power to the devices.

Doubt it - he would have come across a fair few before these ones. I have tested them in wall/out of the wall and there is definitely no light coming on.