Shelly 1 PM Plus ‘over voltage detected’


Distinguished Member
Recently I had a new electric towel rail fitted to a bathroom by an electrician. I got him to install a Shelly 1PM Plus at the same time. The Shelly is basically acting a smart isolating switch.

I don’t really use the Shelly much, it’s usually left on, and the heater is manually controlled using its own simple on/off/2hr boost panel. However I wanted the Shelly for the occasional times when wanted a timer or remote control, so that I could control it on cold winter mornings when I get up at 5am.

Anyway it’s been fine for the last few months. But it’s just suddenly started giving a ‘over voltage warning’ notification. The heater inst in use, hadn’t been used for weeks, so isn’t drawing any power.

What could be issue be? Is it faulty? Anything I can check in the app? Do I need to get the electrician in urgently?


Seb Briggs

Distinguished Member
Is the firmware up to date on the Shelly module ?

Over voltage normally means that the power to the module (230v) is going over that . The tolerance is listed as 10% so possibly you are getting a spike. This could occur regardless of the towel rail being on or not as it a "constant" 230v feed to the module.


Distinguished Member
Hi Seb, yeah it’s the latest version. After a reboot it seems ok so I’m hoping it’s just a glitch.


Distinguished Member
Turned out it was a bug the firmware giving false reading. Shelly have released a firmware update for it now which fixes the issue.


Distinguished Member
Mains voltage in the UK can go up to 253V and still be within spec.

Mine is often around 248V depending on time of day…

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