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Lights Flickering After Powerwall Install [info to help troubleshoot]

Hi Everyone,

I had two Powerwalls installed in early 2021 and since then have experienced quite a few flickering issues. Some happened even when I was on grid power, and some happen when I was timeshifting (powerwall supplying power with the grid up), and some only happen when I'm totally off-grid on powerwall only. I've gotten most of them resolved, but am still hunting down one of them. I wanted to share my experience and what I've learned so that it might help others who come along after me. Here's what I've learned:

Residential service in the USA is delivered as 240 volts at 60 hertz. The voltage is delivered on two 120-volt legs. For convenience, I'll call them the "A" leg and the "B" leg. In a typical electrical panel, each set of two breakers alternates between the A and B leg. In other words, the first two breakers are pulled off the A leg. The second two breakers are pulled off the B leg. And so on.

When Tesla installs your Powerwall (and Solar system), they move many (sometimes all) of your circuits to a sub-panel. When they do this, they pay no attention to which leg the circuits were on before. That is to say, if your LG washing machine was on the "A" leg and your bathroom lights were on the "B" leg on your main panel before Tesla showed up, when Tesla moves those circuits to a sub-panel, they might just put them both on the "A" leg. This means that your washing machine and your bathroom lights were previously not sharing a 120-volt feed from the power company, but they are now.

Newer LED bulbs are very sensitive to voltage fluctuations. The more efficient the bulb, the more likely it is to flicker with even a slight voltage change. Older LED bulbs had transformers in them that stepped the voltage down and which converted some of the energy to heat. They were pretty resilient to voltage fluctuations. But, the very newest bulbs appear to run directly on 120 volts. These bulbs are the most likely to experience flickering when there is even a slight voltage change. The flickering is most noticeable when the voltage fluctuates down and then back up (or up and then back down) nearly immediately.

Many devices in your home can generate momentary, but substantial energy draws that can cause the voltage to temporarily drop on the same circuit, and even on adjacent circuits on the same leg. The most common culprits I have found in my house are my LG washing machine (especially when it is on the agitate cycle), my laser printer, my Toto bidet toilet seat, and my electric space heaters.

When a large load kicks on the same circuit, this can cause a voltage drop. If the load is large enough, it can even cause a voltage drop on adjacent circuits on the same leg, though the drop will not be as large. When you're on grid power, additional power will rush in and raise the voltage back up quite quickly. If you're on Powerwall, it takes a bit longer.

And this is one of the reasons that we can experience flickering on newer, highly efficient LED bulbs once a Powerwall is installed. Even when you're on grid power, if Tesla moved a noisy device (like your LG washing machine or a laser printer) to the same **leg** as your highly efficient bathroom lights, then the bathroom lights may flicker when your washer is agitating or when your printer is printing. This can happen even when they are on different circuits. The problem can be worse when you're off-grid, but it can occur even when you're using grid power. The solution, if you care about it, is to move the circuits back to separate legs.

There can be other causes of flickering. When you're on Powerwall power and the powerwall is more than 97% charged, the powerwall starts out generating power at 66hz, and not 60 hz. It does this in order to tell your solar panels not to generate any power. It does this even if you don't have solar panels. This can cause some UPS devices to believe that the power is unreliable and to use the batteries instead of relying on the powerwall supplied power. You can call Tesla and ask them to change this to a lower frequency if you want. I changed mine to 62 hz. I have found that once the Powerwall gets below 98%, it reverts to 60 hertz. Some have reported that the Powerwall's initial tendency to produce a higher frequency power when its power level is above 97% can cause flickering, especially with older dimmer switches. I have found that certain older dimmer switches do have issues when off-grid, but didn't find that it made any difference whether the frequency was at 60hz or higher. Eventually, I just replaced the dimmer switch with a newer LED compatible switch and the problem went away.

There's also the possibility of a loose neutral (or a shared neutral) causing issues. When I first started experiencing problems, I used an Ideal 61-164 to check my house for loose neutrals and couldn't find any.

I did, however, find a shared neutral. Finding a shared neutral is a major PITA, but it is worth doing as it also causes massive EMF fields in your house (if you're worried about that sort of thing) and it can electrocute someone in very rare cases. The easiest way to find if you have a shared neutral is to shut off the main power at your main breaker, and then pull one neutral off the main panel at a time, and check that neutral for continuity against the neutral bus. If there is continuity, that neutral is tied to another neutral on the bus somewhere in your house (and it shouldn't be). Put that neutral back on the neutral bus, remove the next one, and check it. Once you find the neutrals that are shared, you have to hunt down where they are shared. It's usually in a breaker box that has multiple circuits (such as a gang of light switches that are served by different circuits).

I hope this helps someone else. If anyone else has any suggestions on addressing flickering, I welcome comments below.
 

aesculus

Still Trying to Figure This All Out
May 31, 2015
4,627
2,654
Northern California
I have found that certain older dimmer switches do have issues when off-grid, but didn't find that it made any difference whether the frequency was at 60hz or higher. Eventually, I just replaced the dimmer switch with a newer LED compatible switch and the problem went away.
^^^^ This for me. Some poor quality LED lights flicker and also you need to make sure the dimmer is high quality too.

Other than this when I am on grid power everything is fine. Off grid, even thought I have had Tesla lower the frequency to 62 Hz max, I can still run into issues with some Insteon devices. Not worth the hassle to me to make that all perfect because it's only when off grid and near full charge.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Moderator
Nov 28, 2018
12,536
14,986
Riverside Co. CA
Hi Everyone,

I had two Powerwalls installed in early 2021 and since then have experienced quite a few flickering issues. Some happened even when I was on grid power, and some happen when I was timeshifting (powerwall supplying power with the grid up), and some only happen when I'm totally off-grid on powerwall only. I've gotten most of them resolved, but am still hunting down one of them. I wanted to share my experience and what I've learned so that it might help others who come along after me. Here's what I've learned:

Residential service in the USA is delivered as 240 volts at 60 hertz. The voltage is delivered on two 120-volt legs. For convenience, I'll call them the "A" leg and the "B" leg. In a typical electrical panel, each set of two breakers alternates between the A and B leg. In other words, the first two breakers are pulled off the A leg. The second two breakers are pulled off the B leg. And so on.

When Tesla installs your Powerwall (and Solar system), they move many (sometimes all) of your circuits to a sub-panel. When they do this, they pay no attention to which leg the circuits were on before. That is to say, if your LG washing machine was on the "A" leg and your bathroom lights were on the "B" leg on your main panel before Tesla showed up, when Tesla moves those circuits to a sub-panel, they might just put them both on the "A" leg. This means that your washing machine and your bathroom lights were previously not sharing a 120-volt feed from the power company, but they are now.

Newer LED bulbs are very sensitive to voltage fluctuations. The more efficient the bulb, the more likely it is to flicker with even a slight voltage change. Older LED bulbs had transformers in them that stepped the voltage down and which converted some of the energy to heat. They were pretty resilient to voltage fluctuations. But, the very newest bulbs appear to run directly on 120 volts. These bulbs are the most likely to experience flickering when there is even a slight voltage change. The flickering is most noticeable when the voltage fluctuates down and then back up (or up and then back down) nearly immediately.

Many devices in your home can generate momentary, but substantial energy draws that can cause the voltage to temporarily drop on the same circuit, and even on adjacent circuits on the same leg. The most common culprits I have found in my house are my LG washing machine (especially when it is on the agitate cycle), my laser printer, my Toto bidet toilet seat, and my electric space heaters.

When a large load kicks on the same circuit, this can cause a voltage drop. If the load is large enough, it can even cause a voltage drop on adjacent circuits on the same leg, though the drop will not be as large. When you're on grid power, additional power will rush in and raise the voltage back up quite quickly. If you're on Powerwall, it takes a bit longer.

And this is one of the reasons that we can experience flickering on newer, highly efficient LED bulbs once a Powerwall is installed. Even when you're on grid power, if Tesla moved a noisy device (like your LG washing machine or a laser printer) to the same **leg** as your highly efficient bathroom lights, then the bathroom lights may flicker when your washer is agitating or when your printer is printing. This can happen even when they are on different circuits. The problem can be worse when you're off-grid, but it can occur even when you're using grid power. The solution, if you care about it, is to move the circuits back to separate legs.

There can be other causes of flickering. When you're on Powerwall power and the powerwall is more than 97% charged, the powerwall starts out generating power at 66hz, and not 60 hz. It does this in order to tell your solar panels not to generate any power. It does this even if you don't have solar panels. This can cause some UPS devices to believe that the power is unreliable and to use the batteries instead of relying on the powerwall supplied power. You can call Tesla and ask them to change this to a lower frequency if you want. I changed mine to 62 hz. I have found that once the Powerwall gets below 98%, it reverts to 60 hertz. Some have reported that the Powerwall's initial tendency to produce a higher frequency power when its power level is above 97% can cause flickering, especially with older dimmer switches. I have found that certain older dimmer switches do have issues when off-grid, but didn't find that it made any difference whether the frequency was at 60hz or higher. Eventually, I just replaced the dimmer switch with a newer LED compatible switch and the problem went away.

There's also the possibility of a loose neutral (or a shared neutral) causing issues. When I first started experiencing problems, I used an Ideal 61-164 to check my house for loose neutrals and couldn't find any.

I did, however, find a shared neutral. Finding a shared neutral is a major PITA, but it is worth doing as it also causes massive EMF fields in your house (if you're worried about that sort of thing) and it can electrocute someone in very rare cases. The easiest way to find if you have a shared neutral is to shut off the main power at your main breaker, and then pull one neutral off the main panel at a time, and check that neutral for continuity against the neutral bus. If there is continuity, that neutral is tied to another neutral on the bus somewhere in your house (and it shouldn't be). Put that neutral back on the neutral bus, remove the next one, and check it. Once you find the neutrals that are shared, you have to hunt down where they are shared. It's usually in a breaker box that has multiple circuits (such as a gang of light switches that are served by different circuits).

I hope this helps someone else. If anyone else has any suggestions on addressing flickering, I welcome comments below.

Welcome to TMC and the TMC energy subforum, OP. Heck of a first post! Thank you for sharing your information, it could possibly help others in this situation either know where to start troubleshooting, or what might be the cause.

Hope you choose to stick around!
 

slcasner

Active Member
Supporting Member
Feb 20, 2011
1,426
967
Sunnyvale, CA
I did, however, find a shared neutral. Finding a shared neutral is a major PITA, but it is worth doing as it also causes massive EMF fields in your house (if you're worried about that sort of thing) and it can electrocute someone in very rare cases. The easiest way to find if you have a shared neutral is to shut off the main power at your main breaker, and then pull one neutral off the main panel at a time, and check that neutral for continuity against the neutral bus. If there is continuity, that neutral is tied to another neutral on the bus somewhere in your house (and it shouldn't be). Put that neutral back on the neutral bus, remove the next one, and check it. Once you find the neutrals that are shared, you have to hunt down where they are shared. It's usually in a breaker box that has multiple circuits (such as a gang of light switches that are served by different circuits).
I have seen the term "shared neutral" used differently. An example would be where a 12/3 Romex cable is run to a room where the black wire is connected to the lights while the red wire is connected to the receptacles and they share the white neutral wire. This is called a multiwire branch circuit. I just learned that NEC 210.4(B) requires the the black and red wires be connected to a 2-pole common-throw circuit breaker even though the lights and receptacles are independent 120V devices rather than a 240V device. This is to avoid the electrocution risk that you mention.
 

gpez

Member
Apr 25, 2019
782
646
USA
I have LED lights in the master bathroom and closet that flicker pretty bad. I'm 99% sure it's because of a UPS I have in the server closet which is on the same circuit as the master: when I disconnect the UPS the flickering goes away. I have no idea why this is the case.
 
I have seen the term "shared neutral" used differently. An example would be where a 12/3 Romex cable is run to a room where the black wire is connected to the lights while the red wire is connected to the receptacles and they share the white neutral wire. This is called a multiwire branch circuit. I just learned that NEC 210.4(B) requires the the black and red wires be connected to a 2-pole common-throw circuit breaker even though the lights and receptacles are independent 120V devices rather than a 240V device. This is to avoid the electrocution risk that you mention.

That's a great point. A multi-wire branch circuit does indeed "share" a neutral wire with a single A-leg circuit and a single B-leg circuit, but that's okay. Because the A-leg and the B-leg are out of phase with one another, the neutral is only ever carrying electrons back from one of the circuits at any given moment in time.

When I wrote about shared neutrals, I was referring to the situation where two separate circuits, with two separate neutrals, have their neutrals tied together. This happens most often when a contractor installs a box with two of more devices, such as two light switches, or an outlet and a switch. If those devices are on separate circuits, the neutrals from each of the two circuits should not be tied together in the box. However, many non-electricians (and some incompetent electricians) will just twist all the neutrals in the box together (as they would with all the ground wires) and then call it a day. In that case, you'll end up with what I referred to as a "shared neutral." I know from experience that this can create massive EMF in your house (though people will debate whether that matters) and it can also cause a situation where a neutral is energized even though it shouldn't be. And in very rare cases, it could cause a neutral to overload, though that would require that both of the circuits be on the same left and that one of the two neutrals also become loose or disconnected downstream from the location where they are shared.
 
Correction: Where I wrote:

"And in very rare cases, it could cause a neutral to overload, though that would require that both of the circuits be on the same left and that one of the two neutrals also become loose or disconnected downstream from the location where they are shared."

I meant:

"And in very rare cases, it could cause a neutral to overload, though that would require that both of the circuits be on the same phase and that one of the two neutrals also become loose or disconnected downstream from the location where they are shared."
 

cali8484

Member
Jul 8, 2018
308
186
California
When Tesla installs your Powerwall (and Solar system), they move many (sometimes all) of your circuits to a sub-panel. When they do this, they pay no attention to which leg the circuits were on before. That is to say, if your LG washing machine was on the "A" leg and your bathroom lights were on the "B" leg on your main panel before Tesla showed up, when Tesla moves those circuits to a sub-panel, they might just put them both on the "A" leg. This means that your washing machine and your bathroom lights were previously not sharing a 120-volt feed from the power company, but they are now.

Does Tesla use licensed electricians to do the work? They should know better.
 

slcasner

Active Member
Supporting Member
Feb 20, 2011
1,426
967
Sunnyvale, CA
Does Tesla use licensed electricians to do the work? They should know better.
No, there's no assurance that when circuits are relocated from one panel to another that their assignments to the A or B leg will remain the same. The sizes or arrangements of the two panels may differ and there may be various reasons why the circuits would not be installed in the same order.
 

power.saver

Grid Specialist
Supporting Member
Mar 4, 2018
664
707
Arcadia, CA
No, there's no assurance that when circuits are relocated from one panel to another that their assignments to the A or B leg will remain the same. The sizes or arrangements of the two panels may differ and there may be various reasons why the circuits would not be installed in the same order.
Well there should be. When multi-wire branch circuits (MWBC) are relocated, they have to be placed on opposite legs and on adjacent common trip breakers.
 

jboy210

Well-Known Member
Supporting Member
Dec 2, 2016
5,974
4,024
Northern California
I have LED lights in the master bathroom and closet that flicker pretty bad. I'm 99% sure it's because of a UPS I have in the server closet which is on the same circuit as the master: when I disconnect the UPS the flickering goes away. I have no idea why this is the case.
How old is the battery in UPS? After about 4 years they are shot from constantly being held at a high state of charge. I replace mine about every 4-5 years when time on backup power gets short when I do my semi-annual testing.
 

Vines

Active Member
Jul 20, 2018
2,313
2,843
Silicon Valley, CA
Well there should be. When multi-wire branch circuits (MWBC) are relocated, they have to be placed on opposite legs and on adjacent common trip breakers.
Hopefully, nobody is just pulling apart common trip MWB circuits and making 2 separate circuits out of them, same with other 2-pole breakers.

On the other hand, balancing the load across the 2 legs is something that should be kept in mind while installing to keep things balanced. Practically it is pretty difficult to do without the homeowner running their life and the panel being complete and safe.
 
I have the LED flickering issue a bit with a hot water booster on the bathroom sinks that draws 30A, 240V to pre-heat cold standing water sitting in the hot water pipes before the actual hot water from the water heater. So it only runs briefly when a faucet is first opened, but the issue is when the tap is set to warm not hot, the low hot water flow causes the booster to rapidly pulse on and off to modulate the temp. The voltage fluctuations then cause the bathroom lights to momentarily flicker for maybe 10 secs!
 

gpez

Member
Apr 25, 2019
782
646
USA
I have the LED flickering issue a bit with a hot water booster on the bathroom sinks that draws 30A, 240V to pre-heat cold standing water sitting in the hot water pipes before the actual hot water from the water heater. So it only runs briefly when a faucet is first opened, but the issue is when the tap is set to warm not hot, the low hot water flow causes the booster to rapidly pulse on and off to modulate the temp. The voltage fluctuations then cause the bathroom lights to momentarily flicker for maybe 10 secs!

I haven't stuck my multimeter in the outlet yet but the UPS I have shows voltage but not very granular - just down to the volt. I tried to correlate my flickering to voltage by adding in all sorts of loads but the voltage drop down to 117v from 121v didn't seem to affect it...
 

slcasner

Active Member
Supporting Member
Feb 20, 2011
1,426
967
Sunnyvale, CA
Well there should be. When multi-wire branch circuits (MWBC) are relocated, they have to be placed on opposite legs and on adjacent common trip breakers.
Yes, and of course 240V loads need to still have a 2-pole breaker on both legs. But I was referring to independent circuits with dedicated neutrals. I read that multiwire branch circuits are discouraged, although my 1980 home has three.
 

wwhitney

Active Member
Nov 2, 2017
1,122
1,489
Berkeley, CA
Newer LED bulbs are very sensitive to voltage fluctuations. The more efficient the bulb, the more likely it is to flicker with even a slight voltage change.
I would say it is lower quality LED bulbs that flicker with AC voltage fluctuation. Any LED bulb has to incorporate a constant current DC power supply, and I would think a higher quality such power supply would be less likely to have its output fluctuate with incoming power fluctuations.

There's also the possibility of a loose neutral (or a shared neutral) causing issues.
As others have commented I wouldn't call what you describe a "shared neutral." Maybe an improperly cross-connected neutral.

Cheers, Wayne
 

wwhitney

Active Member
Nov 2, 2017
1,122
1,489
Berkeley, CA
This is called a multiwire branch circuit. I just learned that NEC 210.4(B) requires the the black and red wires be connected to a 2-pole common-throw circuit breaker even though the lights and receptacles are independent 120V devices rather than a 240V device. This is to avoid the electrocution risk that you mention.
Common throw is not a typical term, more typical would be "common trip" or independent trip". Usually 2 pole breakers are common trip, but that's not required for an MWBC that supplies only 120V loads. An independent trip 2 pole, or two 1 pole breakers that have a handle tie, is sufficient for that.

Well there should be. When multi-wire branch circuits (MWBC) are relocated, they have to be placed on opposite legs and on adjacent common trip breakers.
The two hots of a MWBC are required to be grouped within the panel for identification, which happens automatically when they are in a 12/3 or 14/3 NM cable, as they are within the same outer sheath. So while it's possible to be careless and not pay attention, it's not hard to recognize them in that way and reterminate them properly. Of course it's also possible to wire an MWBC in other ways, in which case recognizing an MWBC could be harder, which is why there is supposed to be some other explicit grouping (e.g. wire tying the conductors together).

I read that multiwire branch circuits are discouraged, although my 1980 home has three.
They are not so much discouraged as having been made more trouble to use in the last decade or two, so you see less of them. The biggest reason in residential work is that initially all single pole AFCIs incorporated some level differential current sensing between L and N (like GFCI, but that term means that the trip level is set to 4-6 ma current imbalance). That makes using single pole AFCI on MWBCs impossible. But now several brands have single pole AFCI breakers without differential current sensing (which makes them fairly useless in my estimation), so with those brands you can use a pair of single pole AFCIs for an MWBC.

Cheers, Wayne
 
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Reactions: BGbreeder

slcasner

Active Member
Supporting Member
Feb 20, 2011
1,426
967
Sunnyvale, CA
Common throw is not a typical term, more typical would be "common trip" or independent trip". Usually 2 pole breakers are common trip, but that's not required for an MWBC that supplies only 120V loads. An independent trip 2 pole, or two 1 pole breakers that have a handle tie, is sufficient for that.
Learning something new all the time: I interpreted "handle tie" to be the bar linking the handles to make them trip together. What does a handle tie that does not cause common trip look like?
They are not so much discouraged as having been made more trouble to use in the last decade or two, so you see less of them. The biggest reason in residential work is that initially all single pole AFCIs incorporated some level differential current sensing between L and N (like GFCI, but that term means that the trip level is set to 4-6 ma current imbalance). That makes using single pole AFCI on MWBCs impossible. But now several brands have single pole AFCI breakers without differential current sensing (which makes them fairly useless in my estimation), so with those brands you can use a pair of single pole AFCIs for an MWBC.
Since you have knowledge of AFCI implementation, an unrelated question: The Tesla electrician just installed a HOM115CAFI (combination series and parallel AFI) breaker for the circuit that had a GFCI breaker before the branch circuits were relocated to the new backup panel. Ignoring for a moment that an AFCI breaker does not provide ground-fault protection, my problem is that the controller for all my Insteon home automation devices is on that circuit and could no longer communicate with the other devices over the power line. Would the AFI function act as a filter for high-frequency data?
 

wwhitney

Active Member
Nov 2, 2017
1,122
1,489
Berkeley, CA
Learning something new all the time: I interpreted "handle tie" to be the bar linking the handles to make them trip together. What does a handle tie that does not cause common trip look like?
A handle tie does not cause common trip. I mean it might, but it's not intended to. It's intended to make it so that when you manually shut off one breaker, the other breaker gets shut off, too.

As to the AFCI filtering question, no idea of what's really inside the breaker. I would think that the arc fault sensing algorithm would need the unfiltered waveform to do its magic, but perhaps it then has filters on the line side to prevent tripping for upstream signals?

Cheers, Wayne
 

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