I'm hoping these symptoms will be obvious to someone who knows better:

I'm adding smart dimmers in a fairly new (2013) house in Canada. Two are replacing regular dimmers in a four-gang box which controls four separate light fixtures with no other switches. There's five wires coming into the box - the four lights plus the supply. All the existing switches just use the live but I do have neutrals which are all bound together. It all seems pretty modern and simple and I've installed smart switches in similar boxes with the same config.

Here's the problem - when I replace the two dimmers with the smart dimmers both work but one switches on both fixtures instead of just the one it handles the load for. The other just switches on its own load, as I'd expect. I've checked, double-checked and re-done all connections, swapped the two switches, tried them on their own and always end up with the same results. Probably also relevant is the fact that when both sets of lights come on in response to one switch, they're clearly under-powered (flickering) and turning on the second switch adds more juice and both run as normal, so it seems like somehow the live from switch one is being shared to both sets of lights?

The smart dimmers have four connections which I'm connecting as follows:

  • Load (red) to the fixture black wire
  • Live (black) to the common live (blacks) coming into the box
  • Neutral (white) to the common neutrals/whites coming into the box
  • Ground to a ground on the box
  • The neutral from the fixture wires goes to the common neutrals

I'm guessing there's a mixup somewhere and I'm doing something dumb. Any ideas? Many thanks in advance... :-)

EDIT: Adding some pictures. Thanks in advance. This is with just one smart switch - this setup works fine. If I replace the manual dimmer (spot #3) with another smart dimmer we get the issue.

First two switches are irrelevant I think - removed for visibility

I believe middle cable of the five is supply

Zoomed into the back of the smart switch - Treatlife Smart Dimmer - https://www.amazon.ca/dp/B07YKFSWJN

  • @ThreePhaseEel to be clear, the setup in these pics works - the smart dimmer only controls the expected light. I get the problem if I replace the regular dimmer in spot #3 with another smart dimmer - then #4 switches on both #3 and #4. Make sense? Dec 6, 2020 at 23:58
  • Can you get us an actual make/model number for your smartswitch please? Dec 6, 2020 at 23:59
  • It's this one - amazon.ca/dp/B07YKFSWJN. Treatlife DS02S. Dec 7, 2020 at 0:00
  • @user3019595 -- are you attached to that particular smart dimmer, or would getting something else be OK by you? Dec 7, 2020 at 0:06
  • I would suggest that either there is a limit on how many you can have on a network or their "programming/setup" is incorrect. Jan 11 at 2:17

1 Answer 1


I'd junk those smart-dimmers and get ones that are less...cheesy

The first problem you have to address is that you have Cheesy smart dimmers that never went through the gauntlet of testing required by CSA/UL/... and thus can't be reasonably guaranteed to not do untoward things to you, like try to light your house on fire. Since your wiring configuration looks utterly conventional here, I'd try with a better (i.e. not so Cheesy) set of smart dimmers and see if you're still getting the misbehavior described.

  • What others would you recommend? It still seems an odd issue that would be more to do with my wiring but OK. Dec 7, 2020 at 0:13
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    @user3019595 -- my starting point would be to shop at your local electrical supply house instead of Amazon/Ebay/... If you want a brand name, my inclination would be to go with the Leviton stuff if WiFi was important to you, and with either Insteon or Lutron gear otherwise Dec 7, 2020 at 0:18
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    @user3019595 -- UL's gotta pay their bills too... Dec 7, 2020 at 0:38
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    @user3019595 Well, it's illegal to install non-approved equipment, NEC 110.2, so I would say to stick to UL approved units. I think these units are interfering with each other anyway. That's what happens when amateurs design stuff blind into a foreign market, pinching pennies as they go. (US design houses "eat their own dogfood" i.e. install their prototypes in their own offices and homes. Chinese can't since their power is incompatible.) Dec 7, 2020 at 2:04
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    @user3019595 it's likely that your options are pay 4x the cost to make it work, or pay 1x the cost, live without the 2nd smart switch and a higher risk of a failure that could potentially burn down your house. Like everything in life, there is a cost to quality - Lutron, et al, are expensive because being UL approved is a more expensive process.
    – FreeMan
    Dec 7, 2020 at 13:19

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