Incandescent bulb stops LED flicker

Thread Starter

twobbs

Joined May 11, 2024
5
I have two lighting circuits in my rented apartment which flicker like crazy when I use all LEDs in the multiple sockets. However, the (visible) flickering stops if I replace one of the LEDs (in each circuit) with an incandescent bulb. Any idea what is happening? Anyone willing to hazard a guess for the most probable cause of the flickering? (Both these circuits are multi-pole switched with 30-yo hardware.)

Ted in Italy
 

Ian0

Joined Aug 7, 2020
10,005
I have two lighting circuits in my rented apartment which flicker like crazy when I use all LEDs in the multiple sockets. However, the (visible) flickering stops if I replace one of the LEDs (in each circuit) with an incandescent bulb. Any idea what is happening? Anyone willing to hazard a guess for the most probable cause of the flickering? (Both these circuits are multi-pole switched with 30-yo hardware.)

Ted in Italy
Do they have dimmers?
 

MisterBill2

Joined Jan 23, 2018
18,941
I have observed the same thing, and in those cases it was because of a dimmer circuit that used some sort of scheme that is incompatible with the LED light internal circuit. This also happens with some CFL (compact florescent light) devices, except that they are destroyed by either a dimmer or the switch in a motion sensor.
One way around the issue is to only use LED bulbs identified as "dim-able". At least that has been my experience. The exact cause of the flickering is not clear to me, because the internal circuits of the guilty bulbs are not available.
 

MisterBill2

Joined Jan 23, 2018
18,941
OK, no dimmer but at some point there is a waveform distortion that is disrupting the internal circuits in the LED devices.
Are you able to measure the mains voltage in these two branch circuits?? Are there any outlets on these two branch circuits?
It may be that there is a dimmer hidden someplace in series with each of the circuits/ Are both lighting circuits fed from a single fuse or breaker?
 

Thread Starter

twobbs

Joined May 11, 2024
5
OK, no dimmer but at some point there is a waveform distortion that is disrupting the internal circuits in the LED devices.
Are you able to measure the mains voltage in these two branch circuits?? Are there any outlets on these two branch circuits?
It may be that there is a dimmer hidden someplace in series with each of the circuits/ Are both lighting circuits fed from a single fuse or breaker?
Thanks for the reply.

There are exactly two breakers in the apartment and all lighting circuits run off of one. However, multiple other LED bulbs run without a problem on the same breaker. I have not yet tried to measure voltages but am pretty certain that something is not right with the segments in question. I note that in another part of the apartment, there is a floor plug with two outlets, one switched and the other not. An LED bulb runs fine on the unswitched outlet, but flickers uncontrollably on the switched one. So, this apartment is full of things like that.

I suspect an electrician is called for, as well as hoping that the problem is with a switch and not the wires in the wall (which are approximately unreplaceable).

However, I am interested in understanding why adding an incandescent bulb "magically" causes all the LEDs in these circuit not to flicker, even presumably in the presence of flaky voltages. Just curious.
 

Tonyr1084

Joined Sep 24, 2015
7,945
Do they have dimmers?
Even if they don't have dimmers, I've seen SOME "Occupancy light switches" that do the same thing. The switch (or dimmer) does not have sufficient loading on it to completely shut it down when it should be off. They can even flicker when they're supposed to be on.
Hi
those LEDs flickers when the switch is OFF?
• I'm betting they do
• I'm also betting they flicker even when the switch is ON.

If either is the case I'm betting it's solid state switching controlled. I have replaced my Occupancy switches with the type that have a relay inside them. No flickering ON or OFF.

The REASON why an incandescent stops the issue is because it provides sufficient loading which prevents flickering and prevents them from failing to turn OFF.

Just for informational sake; I still have an incandescent lamp in circuit with my occupancy switch.
 

MisterBill2

Joined Jan 23, 2018
18,941
So now we have some additional information, which is that some of the LED lights on the same breaker function correctly. THat points more directly at a wall switch that is actually a toggle style dimmer switch.
So now here is another check that requires no tools, just good eyes: Examine very closely the control switch for the lights that flicker. I have a friend and in her house there are what look like regular light on/off switches, BUT along side the toggle lever is a small slider that dims the lights. It is next to the toggle lever and passes thru the same opening. as the toggle lever. The button may even be broken off.
OR, the slider may be hidden by a replacement cover plate. You can remove that plate safely even with the power ON, just do not poke your fingers inside the electrical box. (I AM AWARE that some folks will panic at the very though of this act).
If there is a dimmer function, such as a slider visible the suspicion is confirmed. If there is no slider BUT most of the box opening is filled with an aluminum plate so that it is difficult to see into the box, then it would be a toggle operated dimmer. Replacing it with a normal ON/OFF switch will solve the problem. Since you have access to the circuit breaker it will be simple to replace the dimmer with a plain switch. Total price, less than $10 for the replacement. Orhire an electrician to do it, total price over $100, at least.
 

Tonyr1084

Joined Sep 24, 2015
7,945
Do the lights flicker when the switch is off?
With mine, they never went fully off.

So is it going to be a problem to leave a single incandescent type lamp in the circuits? If not - I'd not worry about it. In my laundry room is where I had the issue. Several LED Can lights. Maybe 5. They'd never fully turn off until I put an incandescent bulb in circuit. I've sense changed the Occupancy Switch and haven't had any flickering issues even when the incy bulb burned out.

So DO you have a dimmer or occupancy switch?
 

Tonyr1084

Joined Sep 24, 2015
7,945
I am interested in understanding why adding an incandescent bulb "magically" causes all the LEDs in these circuit not to flicker, even presumably in the presence of flaky voltages. Just curious
There is a chance you have some faulty wiring. I had an apartment a long time ago. The electric stove was powered with 240VAC while the regular outlets were 120VAC split phase. One evening half the lights went out. Then came back. This started happening more and more frequently. When I plugged a Halogen Lamp - the kind you can't buy anymore because of all the fires they started - when plugged in and switched on ALL the outlets would go live again. I also discovered that when half the circuit was out, turning the stove on brought everything back on. It took a long time to find the trouble, but eventually it was discovered that one of the two incoming lines was loose under the power meter. Once that was re-greased and tightened that was the end of the trouble.

So I'm wondering if maybe the presence of the incy bulb there's enough current to make the connection better. There could be a loose neutral on either of those circuits or a common neutral is loose. Or you have a couple old switches that just need to be replaced. In my home now - I had an outlet that stopped working. When testing for voltage - it was there. But you couldn't power anything from that outlet. Recently I did some remodeling which required making a new connection in that J-box. It was there I discovered a loose wire nut. The whole reason why that outlet would not work. YOUR loose connection could be anywhere. It may take some time tracking it down. You DID say your switches are 30 years old. They don't last forever.
 

MrAl

Joined Jun 17, 2014
11,565
Thanks for the reply.

There are exactly two breakers in the apartment and all lighting circuits run off of one. However, multiple other LED bulbs run without a problem on the same breaker. I have not yet tried to measure voltages but am pretty certain that something is not right with the segments in question. I note that in another part of the apartment, there is a floor plug with two outlets, one switched and the other not. An LED bulb runs fine on the unswitched outlet, but flickers uncontrollably on the switched one. So, this apartment is full of things like that.

I suspect an electrician is called for, as well as hoping that the problem is with a switch and not the wires in the wall (which are approximately unreplaceable).

However, I am interested in understanding why adding an incandescent bulb "magically" causes all the LEDs in these circuit not to flicker, even presumably in the presence of flaky voltages. Just curious.
Hi,

The LED "bulb" (note the quotes) draws current differently than an incandescent bulb, and that causes some electronic circuits to go unstable. There is most likely some electronic circuit somewhere inline with the sockets. There is almost no other explanation except that there could just be something wrong with the power line itself such as low voltage or maybe even over voltage. The limits in the USA are plus and minus 15 percent, but I don't know what they are in Italy, and I do not know how stable the power is in either country now with the questionable grid these days. It could be something with the grid even.

To find out for sure you'd probably have to get an oscilloscope or at least a fast acting analog AC voltmeter. You can watch for quick dips in voltage.

I have seen the very same problem where a neighbor had an RF switched socket (a screw in device that allows the bulb to turn on and off with a remote control that works on RF not IR). With the LED bulb and the socket turned off with the remote, the bulb would flicker. Using a two way bulb adapter and an additional incandescent bulb, that meant that there was the LED bulb and the added bulb in the same switched socket. That stopped the flickering.

Some sockets that are electronically controlled operate on current not voltage (when turned 'off'). The current (very low level) keeps the circuit alive when the bulb is turned off. If the "bulb" in question does not draw a continuous current when it's turned off (remember the electronic circuit does not turn all the way off but allows a tiny current to flow so it can stay alive when the bulb is not glowing) then the circuit could go unstable due to an unstable power source. That causes flickering when the 'bulb' is turned 'off', but a non-continuous current could be a problem even when it is 'on'.

Problems like this come up with electronic circuits that control bulbs and things like that rather than a regular old on/off toggle switch which was the standard for a long time. The triacs inside can genrerate RF noise and they would intefere with radios and TV's and people would not know why. It's the unusual way the current behaves that causes the problems, and that is caused by the triac because it has to turn on and off repeatedly when you turn it 'on'. In the USA it could turn on and off 120 times a second, and with a 50Hz line (Europe) it could turn on and off 100 times a second. That's a lot lot lot more than just once for a regular old wall switch.

As Tony said, sometimes the wall switches get bad over time and they have to be replaced. That could be the thing that solves this problem. You'd have to buy a new switch and replace the old one.

So you'd need to troubleshoot this problem and that requires some test equipment.
 

marcf

Joined Dec 29, 2014
294
You do not specify the voltage of your LED bulbs.

I had the same issue when I replaced my incandescent 12V bulbs with 12v LED bulbs. I discovered because the incandescent bulbs draw about 10X the amperage that the LED bulbs do, the power supply meant to power the AC incandescent bulbs was not loaded enough to power the LED ones and they flickered. I replaced the power supply with one rated for LEDs and the problem was solved.
 

MisterBill2

Joined Jan 23, 2018
18,941
The positions work as intended with an incandescent bulb in one position. So now I suggest noting the brightness of that incandescent bulb in that circuit versus a different circuit that does not have the problem.

And I suggest that the problem circuit functions correctly with non-LED bulbs. THAT tends to indicate that it is not a wiring issue or a failing switch that has become old. It points very directly to a solid state control element that has not been found yet.
 

jeffkrol

Joined Dec 8, 2015
56
I have two lighting circuits in my rented apartment which flicker like crazy when I use all LEDs in the multiple sockets. However, the (visible) flickering stops if I replace one of the LEDs (in each circuit) with an incandescent bulb. Any idea what is happening? Anyone willing to hazard a guess for the most probable cause of the flickering? (Both these circuits are multi-pole switched with 30-yo hardware.)

Ted in Italy
This is what makes leds not shut off all the way. Your flicker could be related though I'm not seeing exactly how atm.

This could be caused by capacitance of the wiring. Although it is very low, the longer the cables in the system are, the more capacitance it will have. With an AC supply, this means there's always a very small amount of current flowing, even if nothing is connected.

In some LED lights, this current can be enough to make the LEDs glow.

It is entirely safe, the same happens in other appliances, but you don't notice it because the current is too low.

If you can install an incandescent bulb in parallel to the LED light, and that makes the glow stop, then you know that's what causing it.

I would say having a switch to disconnect both the live and neutral entirely will fix the issue, as that will disconnect it completely from the supply.
 

marcf

Joined Dec 29, 2014
294
  • This is a note from the Amazon website regarding 12V Leds.
    • ✔Warm Tips: Not dimmable,can't work with any dimmer. You may need to leave 1 or 2 halogen bulbs in fixture. Otherwise there's not enough load for your transformer or power supply and the led bulbs would flicker and buzz.
 

MrAl

Joined Jun 17, 2014
11,565
I don't think my last reply was clear enough on the power source issue for an electronic circuit like a dimmer switch. I'll explain a bit more here using a dimmer switch as an example of a circuit.

Some dimmer switches require 3 wires while some require only 2.
The ones that have 3 wires require a hot AND a neutral wire, meaning they have (in the US) 120vac supplied to them at all times, whether the bulb is turned on or turned off.
Since it is more rare to see 120vac supplied in the light switch electrical box itself (because regular mechanical switches do not need that) dimmers that only require 2 wires came about. These do not work on voltage they work on current for their power source. They have to have at least some current (even if very low like 1ma or even 100ua) flowing or else they do not work right and can cause flickering. Now a regular filament bulb (which they were originally designed for) allows this because the filament never breaks the current completely. When the filament is hot, a large current flows and the bulb lights up brightly. When the filament is cold, a small current can still flow but it's so small that the bulb will not light up or even come close to lighting up. That small current though is enough to keep the dimmer circuit working properly because the dimmer converts that small current into a voltage that can drive the circuitry. With an LED bulb however, the on/off current profile can be very different. With the LED bulb 'off' it may not supply enough current, which can charge the dimmer circuit to the point of normal operation, but then as soon as the dimmer circuit starts up again, it loads its own voltage down again and thus the LED flickers.

It would be interesting to see how much resistance it would take to get the dimmer circuit to work under these conditions. I have never tried this except with a separate filament bulb of normal size like 60 watts. Could a 10 watt bulb do it, or even a small night light bulb (I think they are 6 watts). That would be interesting to find out. Or, how about just a resistor like 120k, or 12k, of something like that. Not sure if I'd want to use a 10 watt power resistor, but that might be needed.
Would be interesting to see what value would work in a real life situation. I guess each dimmer could be a little different though probably depending on when they were manufactured (modern or old style).
 

MisterBill2

Joined Jan 23, 2018
18,941
I don't think my last reply was clear enough on the power source issue for an electronic circuit like a dimmer switch. I'll explain a bit more here using a dimmer switch as an example of a circuit.

Some dimmer switches require 3 wires while some require only 2.
The ones that have 3 wires require a hot AND a neutral wire, meaning they have (in the US) 120vac supplied to them at all times, whether the bulb is turned on or turned off.
Since it is more rare to see 120vac supplied in the light switch electrical box itself (because regular mechanical switches do not need that) dimmers that only require 2 wires came about. These do not work on voltage they work on current for their power source. They have to have at least some current (even if very low like 1ma or even 100ua) flowing or else they do not work right and can cause flickering. Now a regular filament bulb (which they were originally designed for) allows this because the filament never breaks the current completely. When the filament is hot, a large current flows and the bulb lights up brightly. When the filament is cold, a small current can still flow but it's so small that the bulb will not light up or even come close to lighting up. That small current though is enough to keep the dimmer circuit working properly because the dimmer converts that small current into a voltage that can drive the circuitry. With an LED bulb however, the on/off current profile can be very different. With the LED bulb 'off' it may not supply enough current, which can charge the dimmer circuit to the point of normal operation, but then as soon as the dimmer circuit starts up again, it loads its own voltage down again and thus the LED flickers.

It would be interesting to see how much resistance it would take to get the dimmer circuit to work under these conditions. I have never tried this except with a separate filament bulb of normal size like 60 watts. Could a 10 watt bulb do it, or even a small night light bulb (I think they are 6 watts). That would be interesting to find out. Or, how about just a resistor like 120k, or 12k, of something like that. Not sure if I'd want to use a 10 watt power resistor, but that might be needed.
Would be interesting to see what value would work in a real life situation. I guess each dimmer could be a little different though probably depending on when they were manufactured (modern or old style).
THANK YOU for a brilliant idea!! I did a custom two LED light fixture for a client, the first dimmer produced an interesting strobe light effect that she did not like at all. The second dimmer I installed, an expensive one from a decent hardware store, promised to dim every LED perfectly, dimmed a third LED lamp on the same circuit but did not dim the two I installed one bit. My lan now is to go back to the first dimmer , BUT to add an additional 60 watt incandescent light in her basement,storage area. It will be totally done to code and if that solves the problem then I can invoice the project.
 

MrChips

Joined Oct 2, 2009
30,931
Here is a possible answer.
If the LEDs are powered by half-wave rectification of 50Hz line voltage, they will flicker at 50Hz.
Incandescent lamps do not show flicker at line frequency. With the incandescent lit at the same time, it reduces the visual effect of the flicker from the LEDs.
 
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