VZM31-SN No-Neutral Instability Challenges

[UnsoughtNine]

I am looking for guidance on VZM31-SN installs in switch boxes with no neutral (NN). In boxes where neutral is present, the dimmer is always stable. In NN locations (neutral available at the fixture), the dimmer appears marginal on power (LED bar flicker, occasional reboot/drop-off) and the load flickers as well (sometimes only at low levels, sometimes even at higher output). I have tried a range of settings and mitigation steps; some changes may marginally affect symptoms, but the device is not usable in its current state.

I have three separate instances of this issue in my home. In all three cases the wiring is single-pole and neutral is available at the fixture. The fixtures contain either two A19 White Ambiance Hue bulbs (two locations) or a single A19 White Ambiance Hue bulb (one location). The behavior is essentially the same across all three, possibly slightly worse with the single-bulb fixture. I understand the low effective load / power draw is likely the underlying issue. The bulbs are set to Smart Bulb Mode. I have tried switching dimming modes (leading vs trailing), increasing the no-neutral output setting (low → high), and installing a LUT-MLC at the fixture (including briefly testing multiple LUT-MLC in parallel - not rated, I know). In any event, no combination tested these seemed to produce a meaningful improvement in stability.

Is there a known solution that reliably stabilizes VZM31-SN in NN installs under low-load conditions like this, or is the correct conclusion that these locations require a neutral and/or additional load? The manual suggests NN operation can be stabilized, but I have not been able to achieve that. If you have a stable configuration, what specific settings and/or bypass model worked, and what kind of fixture does your switch control?

[Bry]

As you properly surmised, power to the switch with a non-neutral can be an issue. The power delivery is a factor of the load. Using the SBM, as required for smart bulbs, seems to increase the issues.

The first solution that you’ve already tried is to use a bypass, or multiple bypasses. But that didn’t solve your issue.

For testing, I’d try to temporarily swap the bulbs in the 2-fixture luminaire for a larger wattage, non-smart, if you have them. If it works properly then, you’ve confirmed a power delivery issue.

I only know of one other solution when the bypass thing doesn’t work, rewiring to to send a hot and neutral to the switch. (This doesn’t require additional wiring, just a changing of connections . . . just noting this as it tends to confuse some people . . )

At the light box, re-wire to connect the hot and neutral to the light, so that the light is powered full time and unswitched. Connect the 2-wire going to the switch in parallel to those connections so that the switch now has a hot and neutral.

The downside to this is that the only way to cut power to the light is to throw the breaker. However, you can augment this installation with a smart relay in the light box to cut power to the light when required for maintenance.

[UnsoughtNine]

Incredible. Yes, it was a power delivery issue, and yes, rewiring to to send a hot and neutral to the switch is a largely functional fix. Thank you, @Bry