ZL7431US Issue driving LED lights

I’m using a ZL7431US to drive 12 LED lights that run up my entrance stairs.
These are wired through a pair of 3 way switches and transformer that lowers the voltage to something that the LEDs like.

From time to time, the wall switches will just become unresponsive and are unable to turn the lights off… When this happen the mobile app acts really weird and it reports that the lights are cycling on and off REALLY fast. (the icon basically flashes blue/white… on/off)

This is very intermittent, I wired this all a few weeks ago and this has happened only three since then any thoughts?

Do you get power for the relay before or after transformer?


If it helps -> Line -> ZL7431 -> Transformer -> 12 LEDs

Do you need specs on the transformer? It is under the stairs.

Edit back from under the stairs…
The transformer is one of these:

Oh and thanks again for helping me with the other 3 way issue…

Do you think that swamping the blue and red wires would work again?

This 3 way is wired different than the garage light

This one is one of those

switch -> Power and light -> switch.

I’m confused. Where are the 3 way switches wired in here? You say line to transformer to LEDs but no where to do mention how the switches are worked in.

There are (at least) 5 different ways to wire a 3 way switch.
In this case is it wired:
Switch -> power and light -> switch. Like this:

At the box with the power and the light(aka load) is a transformer that drives the LEDs.

So the ZL7431 is getting full line voltage, a good neutral, a load (the LED transformer) and a signal from the wall switches.

The system works. But it works intermittently . It seems that after a while the ZL7431 can no longer sense that the lights are on, or the relay is cycling really fast or there isn’t enough load to “latch” or register the state of the LEDs.

Sometime it works… Sometimes the mobile app will show the switch cycling on and off rapidly and the switch is unresponsive to the mobile app… sometime the mobile app is fine and the wall switches will just stop working.

See, what I am asking is, how is your system wired? How are you controlling the relay from both the ST and from the wall switches? That is the part that I’m not understanding. I know what are many ways you can do this, I’m asking how you did it. If you don’t want to give an answer to the questions asked, then don’t expect help with your issue.
How many watts is your transformer drawing? This relay isn’t rated for loads below 20.

Sorry about that, your wiring question was not clear to me. Let me try again.

The system is wired as per the image above.
The ZL7431 is spliced into the middle box:
Black and Blue to the line wire (black wire with the yellow wire nut)
White to the neutral (spliced into the wire by the light/tranfsormer)
Red goes to the load (in the photo that is the light in my case it is the LED transformer) and
Green is attached to the switch signal… Black common wire from the left switch…

Of course in my case you can replace the light with an electronic transformer. The specs of that transformer was posted a couple of post above.

In this case the wires are all easily accessible in a 4"x4" box under the stars… It would be easy to “clip” them and see what kind of draw the transformer takes… I’m betting is it miliAmps. there are 12 lights but they are small and not very bright. I’ll clip it and post back, but lets say hypothetically the draw is less than 20 watts can I add a resistor to the circuit to get the relay to sense a load? What size/rating of resistor would you recommend? And should it be installed in parallel with the transformer or some other way?

Thanks again, sorry again my previous response was not what you needed.

It’s not a transformer. It’s AC/DC power supply.

It does not sense anything. It’s a dumb relay controlled on z-wave. Relay will cycle only if power fluctuates or z-wave tells it to go on/off. It might also happen if your switch controlling it is flimsy.

So does the relay need a 20 Watt load as per Ryan’s post? Or could it support a miliamp load?

Have you ever read the manual for the relay?

Do NOT do it.

Yes I read the manual… the schematic you posted is for a different relay,

Mine is the one relay switch the ZL7431 The schematic you posted is for a ZL7432 (dual relays)

Do you know if there is a minimum load for this relay? Or is that not the issue here?

Only a maximum. That minimum only applies to OLD dimmers and solid state relays.
This is contact output (like a switch). Also works with no load at all.

Same relay. Only use Load1/Switch1 for yours.

Here with 2 configurations (single switch and 3-way)

Correct… the relay is the same but the wiring diagrams are different.

Mine is wired as per the second schematic.
I’ve installed a few of these now… Only this one acts weird…

In the garage you helped me by recommending that I wire it different than the manual… you recommended that I swap the Blue and the red wires… do you think that might help?

Should I try that?

Nothing to lose.
I think that manual has improper colors. Use the same as garage

No luck…

I removed the ZL7431 and will do some bench testing… This little guy is very confused (both me and the ZL7431) LOL.

On the bench (with a simple two way switch) it works fine…

Back to the 3 way… it still acts weird…

In desperation with the circuit hot I started to measure the voltages of the various legs of the 3ways to ground. On my 3 way, like the diagram the commons are black and the travelers are Red and White.
With the lights “on” one of the travelers would be open… zero volts… and I verified that both with the white leg and the red leg (with the switches both the other ways… both up and both down… if that makes sense)

But with the lights off the “off” leg is now attached to the NO relay in the ZL7431… (switches up/down and down/up) in theory it should still be open or zero volts. It is not, and gets even weirder… with the light off and the white leg on the relay I get 8.1 volts to ground and the system works, the lights are off. (again flipping both switches the other way) the Red leg is now on the relay and there is 10.2V and now there is enough voltage to trigger the lights! But when I measure the voltage to ground the voltage drop through the meter is enough to turn off the lights.

I’m back to the question "Resistor? " I think I need something to drain off a couple of volts when there are 10ish volts on that leg but not burn down the house when that leg has 110V… Does that make sense?

Maybe that is the wrong question… maybe a better question is where are the 8-10V coming from?

Or maybe i’ll just give up and use this gizmo to turn on and off the driveway lights…

Oh and Daniel, thanks again for your help, it is always informative.

Per NEC code black is power and red is switched power. The White you see should’ve been marked with black tape as it also carries power - it is NOT neutral.

To make things simpler for you

  1. At that location identify POWER coming from breaker (one cable with black, white and ground). In 3-way configuration neutral is not used on the switches. It might come into the box and then go to Load, or it might be capped in the box in a bundle.
  2. Leave your 3-way in place, wired as is
  3. Connect Black and white relay wires to black and white from POWER , respectively.
  4. Disconnect wire that goes from 3-way to transformer and connect it to GREEN on the relay and connect it to the BLUE wire on the relay
  5. Connect RED wire on the relay to BLACK wire from POWER.
  6. Verify functionality. It should work both from the 3-way as well as from z-wave control.

Safety hazard. Do NOT do it.

Induction, bad ground, etc.

Correct, they are labeled, easy to see, not the neutrals.

Yes, in my case this is very easy to figure out… there is one black/white pair from the panel, there is one black/white pair to the Ac/DC power adapter and there are two three wire sets that go to the switches… the reds are connected with a wire nut as are the two whites… and they are labeled with black tape. just like the diagram.


Yup that is how it is wired

The Zwave on off works. The right switch (call it the “source” switch) will turn the lights on but not off and the right switch (call it the signal switch) will work, but only if the source switch is “off”…
Of the four possible states three work
Up Up = On (correct)
Down Down = On (correct)
Up Down = Off (correct)
Down Up = On (which is wrong… should be off)

In other words the “ghost” voltage on the “white” traveler is low enough for this to work… the ghost voltage on the Red traveler is just high enough to trip the relay.

I’m going to spend the weekend trying to source the 8-10 mystery volts on the traveler legs…It has to be coming from the ZL7431, there is no voltage on the travelers without it…

And I agree… no resistor!..
Oh and thanks again for you input and advice, it is really helpful and welcomed!

One thing you can try is to swap position of the red wires with the black wires at both switch boxes and the Z-Wave relay box. Sometime that’s enough to bring down the ghost voltage.

This is quite concerning. I would disconnect the load of the Z-Wave relay and check to see if this is caused by the transformer.
Possible you have a loose neutral as well. Anyone of the above will cause the relay to cycle.

So the Smartest House got back to me… Their comment on this:

“If the lights are driven by the dimable electronic power supply you identified , you won’t be able to use the Vision module here because of the electronics in the Vision module. The device will fail soon and it will never work correctly. Z-Wave switches need to control all loads “directly” with nothing in between so transformers, power supplies or motion sensors hard wired to the lights will always prevent regular z-wave switches from working correctly”

So I’m giving up…


I find this very curious…since you would think the power supply is just another “load” and should work just like a ballast in a fluorescent light.

So under the category of “Don’t try this at home”…

At work we have a large supply of “big” 5W barrel resistors ranging from “Next to Zilch” Ohms to “Uber” Ohms. So knowing that my multimeter probe to ground was sometimes enough of a current sink to make this work (~10M Ohm) … I brought home a 33K Ohm resistor and I used that to “short” the green switch signal to Neutral. (before anyone asks… 33K Ohm was not a guess and was not calculated it was simply the largest “surplus” 5W rated resistor that I could find)

In the circuit The voltage drop across the resistor is 2.6 volts (or a 0.0002 Watt draw) The “mystery” voltage on the “off” traveler legs of the 3 way switches dropped below 10Volts and the system started to work perfectly.

I played with it for a few minutes, did a halfhearted victory dance, and then took it all apart. The ZL7431 (Resistor free) is now driving a simple on off switch to drive the light outside of the garage.

Thanks all again… This was a great learning experience.