Shelly Bypass in the landing upsetting all the dimmers

Tree

So this is a hard one to find the answer to online, and I reckon it's likely to be more a feature of Irish wiring.

The house is a semi-d built in ~2000, with no neutrals at the switches, and the landing light is fed live from the downstairs circuit and neutral at the light fitting upstairs.

I've been installing Shelly relays all round the house in fits and spurts. Dimmer in the living room, dimmer in the en suite, 1L for the outside light/garage/landing/office and so on.

I installed a 1L in the landing a few weeks back, put a halogen bulb in so I didn't have to faff around with a bypass (as I was short). Everything works lovely.

Then I get another order in from Shelly, and I got an abundance of bypasses and decided to add one to the landing for in future, so I can put in an LED bulb w/o having to think about it. After a bit of a struggle (the new bypasses are chonkers), the bypass is installed in base(?) of the light. Happy days.

Then in the evening, the landing light comes on (at sunset) and the dimmer LEDs in the kitchen start freaking out (on an old fashioned dimmer switch). Turn them up full, they stop flashing. Weird, but ok, time to loaf in front of the computer for a bit (shelly 1L, no complaints).

Then it's time to watch TV with my partner (Magnum PI, levels of cheese that are probably introducing cholesterol directly into my arteries), and the living room shelly dimmer 2 absolutely refuses to behave, flashing and flickering. At 100% it's not flashing so bad, but that's too bright.

I turn off the landing light (not sure what inspired me), and the flickering stopped and we can set the living room to 30% like usual.

After Magnum saves the day, it's time for bed. The En Suite dimmer should be set low (so we're not startled in the middle of the night), and it's flashing like crazy. Turn off the landing light, and the flashing stops. But while it's set to 30% the temperature of the relay climbs and triggers a reset due to overheating. Again, leaving it at 100% overnight gets us back to a state with a working light.

Any idea why this is happening? What can I do about it long term? (I took out the landing light bypass today for the short term).

TLDR: A shelly bypass in the landing, is allowing some sort of current leakage between upstairs and downstairs lighting circuits and upsetting all the dimmer circuits in the house.

Jonathan

I'd take the Shelly bypass out of there ASAP.

The landing light likely isn't a true two way switch, but rather a borrowed/shared neutral. John Ward has a good video on the concept.

https://youtu.be/IBcw2JJsELs

Edit: missed that you already took it out.

Tree

I think it's a shared neutral alright. Two different electricians were in doing work (solar/adding sockets etc) and both were like "ugh, this is really common, it's fine, but you can't do anything useful with the circuit".

It first tripped out when the solar sparks tried to put the downstairs-only lighting on the backup circuits (an RCD is used in the backup box, so leakage made that profoundly unhappy), and now when the bypass was installed it went properly sloppy but not enough to trip anything out (as all the lighting are on the same RCD).

Tree

I've further taken the 1L out of the landing switch to see if that'll solve the problem I've had for weeks w/ the dimmer in the en suite not behaving.

Then need to find a sparks who'll unborrow the landing circuit w/o too much faff.

Tree

For anyone having similar problems.

I put a Shelly 1PM into the ceiling rose (after finding a deeper one that it'd fit in). Seems to be behaving as expected. The switched live goes to the switch input, and otherwise it's powered off the upstairs live loop.

comete

Do you have any links to the ceiling rose you used?

Tree

https://www.diy.ie/departments/klentony-matt-black-pendant-ceiling-light-dia-100mm/5059340020273_BQ.prd this in white, but I changed out the fitting and cut most of the lead away. It's pricey for what it is, but it looks not far off a regular ceiling rose.