Wiring, Flickering, etc

(Mike Bishop) #1

Most of the lights in my house are LED lamps dimmed by incandescent-only dimmers. Since I think that ought to get fixed regardless, I’ve been swapping them out for the GE Smart Motion Dimmers as I can. While three of four have gone well, there’s one that has me stymied. Hoping someone can suggest a reasonable path forward.

We have a room with LED can lights throughout, divided into two halves, each controlled by its own dimmer. (I would have done them all together, but they didn’t ask me.) First half had all the appropriate wires in the box, installed the dimmer, and they work really well. However, it’s not oriented such that the motion detector on the switch can see motion in the room, only someone entering or exiting. The second dimmer is oriented so that the motion detector on it would see the entire room. I was planning to take @mlebaugh’s suggestion to disable the auto-off on the switch and instead set a WebCoRE rule to turn both off if neither motion sensor detected activity.

Here’s where I ran into problems: The dimmer box in question has no neutral. It only has hot, load, and ground. As part of some other electrical work, I asked an electrician about putting in a neutral; his feedback was that it would hard to fix but easy to work around – since ground and neutral are tied together at the box anyway, just use ground as the dimmer’s neutral and call it good.

So I tried installing it that way, and ran into another apparently-infamous problem: The lights aren’t actually “off” – they’re very dim. And when on, they… I can’t quite see them flicker, but I have the feeling they’re doing exactly that at very high frequency.

I wondered if the neutral was in fact the issue, so I opened up an outlet a few feet away and ran a wire off of it. (Can’t leave it that way, obviously, but just to test.) Same problem when the lights were “off”, but a new problem appeared – when I turned the dimmer “on,” the lights went up to full then immediately back to the same way they were at “off”.

At that point, I just put the old dimmer back in. I’ve since installed the same unit in a different room, where it’s working just fine, so that probably rules out a bad switch. But I’m not sure what’s wrong and what to pursue next. I could just stick a motion sensor on the ceiling, I suppose, but then I can only control the lights in half the room, which kind of defeats the purpose.

Suggestions welcome.


A neutral is not a ground, and it sounds like your electrician did not understand how the networked lights are wired.

(Honestly, if it was that simple, the manufacturers would tell you you could do that in the user guide and we wouldn’t have all the threads in the forum about how to address the no neutral issue.)

@Navat604 or one of the other electrical experts in the community may have some more specific comments on your situation. I’m sure it’s very frustrating.

(Mike Bishop) #3

Fair enough. If I were convinced that’s the only issue, the back side of that wall is inaccessible enough I’m comfortable cutting a hole, running a wire off the outlet, and giving it a real neutral. The patch won’t be ugly out of proportion to the location. (Though the effort might be enough to spark another spat about why I’m doing this automation stuff, or at least some eye rolls!)

I’m more curious about the other weird behavior, even when it had the test neutral.

(Ray) #4

What’s the total wattage of the LEDs? Are they the same as other LEDs in your house? Usually a dim glow in off is caused by the LEDs not compatible with the switch.
As for light going full bright then off. Possible you have load and line reversed? Check your wiring and put in an incandescent bulb and test them again.
Don’t substitute a ground and neutral. It will definitely work but not per code and will cause other issues later. If you are going to pull a new neutral. Remember to pull one from the same circuit branch and not from another branch just in case it’s in phase and could overload your breaker.

(Eric) #5

a 4watt or 7watt nightlight with incandescent bulb on the same circuit, would probably eliminate the flicker. But as others have noted, I expect your dimmer not perfectly compatible with the low load you are putting on the dimmer.

I’d be concerned if your electrician truly believes what he told you about neutral and ground - hope he didn’t employ that concept elsewhere in the house.

(Jason) #6

@Navat604 Hello, I have a dimmer on my fan for the lights and when we turn off the lights they dim then flash at like 80% and then turn off. This switch is wired identical to all the others. The bulbs are the little tiny candle looking bulbs with a very small end to screw into the socket and they are led. Would it be the bulbs themselves that are doing this? I have not tried another bulb, but my wife is annoyed by it so trying to figure out the issue. I had these same bulbs on a non zwave dimmer and had no issues. Both dimmers do use the nutral wire, Any ideas?

(Ray) #7

Sorry but what kind of dimmer and brand? I think there are a couple of inline dimmers out there designed to work this way in order to be compatible with most LEDs.
They are dimmable LEDs?
The switch just controlling the lights and not fan/lights and within max allowable wattage?

(Jason) #8

It is a GE paddle dimmer zwave. Yes, they are dimmable LEDs, I have a separate switch for the Fan. Yes, within the watts, it is only for small leds at maybe 12 watts each. I have the same switch in my kitchen working 6 floods so def within specs.

(Mike Bishop) #9

It’s four 14W LEDs; the same as what’s on the other dimmer, oddly, which is working fine. Even the same lamp as far as I can tell.

Re: switching load/line, anything’s possible, but I checked which wire had power after I had pulled the switch and turned the power back on. I remember being surprised that the white wire was hot when I checked that.

@ero4444, I’m unsure where to put something like that hung off the load line. Any suggestions, or threads where people have attached such? I had the interesting realization last night that I don’t have any incandescent bulbs that I know of.

(Ray) #10

I don’t think it’s a dimmer issue. More like wiring or possible some fan/light brands have a current limiter to the light circuit which could cause issue. maybe drop the fan if possible and check the wiring and see if there’s a current limiter circuit to your light.

(Ray) #11

I am hoping you are using a meter to check power and not a non-contact voltage checker. Those checkers are very sensitive to voltage and will give you false reading.
you can buy cheap incandescent at homedepot. They are pretty much giving them away now.

(Jason) #12

I don’t think there is a need. I installed the fan, and I certainly did not add a limiter. Fan and light are direct wired straight to switches nothing in the middle.

(Ray) #13

One other thing to eliminate is to remove the load wire of the fan switch just in case it’s the fan is causing the issue. You could also use the fan switch to test the light to eliminate the light dimmer.

(Jason) #14

Thank you for your help.

(Mike Bishop) #15

Yes, I have a multimeter (albeit a pretty cheap one), and I’m checking for a voltage difference from ground.

(Eric) #16

as a diagnostic I’d put an incandescent bulb in place of one of the LEDs. If the flicker stops then LED load is probably too low for the dimmer. Your LEDs are max 14w, minimum unknown, when dimming you may be operating at less than a watt each, when they flicker.

The nightlight workaround is really only practical if you happened to have a receptacle on the same circuit.

(Scott Ainsworth) #17

JD is correct the ground is not a neutral. However, all neutrals are wired to ground in your electrical panel. A neutral is intended to carry current from the load to ground, thus it is insulated and will have potential proportional to the current and and resistance in the wire. A ground is intended to be a safety, and is intended to carry stray current to ground in case something goes wrong. Your electrician is correct that the ground will work. However using it is a violation of the electrical code and would not be considered safe.

I have had good success with both flickering and not shutting off by installing a FIBARO - Dimmer / switch bypass 2 FGB-002. Not sure what is in it, but I’m guessing a capacitor and resistor. The dimmers I have are linear wd500. One works perfectly with some good sylvania bulbs. The other works well (some minor flickers) it has some chinese candelabra bulbs on in. I’m sure there are situations where it does not work but its worth a try.

(Mike Bishop) #18

I think I figured it out, and if I’m right, it’s worse than I thought. Without breaking out my last module, I just opened up the existing dimmer and the existing outlet and did some measuring with my multimeter. @Navat604 had asked me to confirm load versus line. I also remember being surprised that the white wire in the dimmer was the line, so I started there. Checking for voltage gave me the same answer as before – white was hot relative to both black and ground. So I dug further.

There’s connectivity (~0 ohms) between the dimmer’s ground and the dimmer’s black wire. There’s connectivity between the dimmer’s black wire and the outlet’s white wire. So the black is neutral, not load as I had initially believed. That probably explains the dimmer freaking out and turning off immediately – “load” was being shorted to neutral.

There’s a resistive load between the dimmer’s white wire and the outlet’s black wire. And between the outlet’s black and the dimmer’s black, current flows.

The dimmer is interrupting the neutral, not the hot. Uh oh.

(Paul Haskins) #19

I’ve personally seen that before on older homes as well as been informed it’s not uncommon.

IMHO - rewire it. Depending on structure, basement, attic, etc. it may be simple or not at all.

I rewired my current home (md-50’s) before I moved in. Luckily unfinished, full basement and the luxury of time to do it before moving in.

(Mike Bishop) #20

I’m guessing not simple, but not horrific. It’s on the first floor, and there’s a second. The saving grace is that the back side of the wall in question is behind the door of the pantry, and that particular spot on the second floor is a storage area, so opening things up if we have to won’t be the end of the world. If we can find where that run breaks off and just swap the switch-return from neutral to hot, we’re in worlds better shape; if we can fish a neutral at the same time, I’m golden.