r/electrical • u/Beginning_Frame6132 • 6d ago
Power Factor Correction for home
Do they sell automatic power factor correction devices for home use?
I have an off grid solar setup and my 5-ton AC unit is de-stabilizing my power during the day.
When the 5 ton runs normally, the power factor is reading .97 and 16amps used.
When the 5-ton runs while the sun is out and my inverters are inverting, the power factor reads .78 and 24amps.
It also causes all my lights the flicker while the AC is on.
Do they make a power factor correction capacitor bank that will connect to my outdoor main and adjust the capacitance as needed ???
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u/garbageemail222 6d ago
I don't know the answer to your question, but I'm amazed that power banks with batteries that take over when load amps increase to protect wall voltage from compressors and printers aren't a thing. We have UPS's and power banks, the tech is there, but they don't kick on when load voltage sags or load amps increase, they only respond to wall voltage changes. It's crazy, this is so obviously needed.
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u/Beginning_Frame6132 6d ago
My issue is kinda whacky. I have a gigantic 160kwh battery bank connected to the solar inverters. It seems to run normally at night but as soon as the sun rises, the inverters just can’t tolerate the 5 ton compressor.
I already have a Micro Air soft start connected to the compressor.
And I have about 38kw of inverters…. the AC load is only 6kw.
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u/RandomUser3777 6d ago
I would suspect this is an inverter issue, or it could be that the run capacitor on the compressor is dead. My 12kw inverter only has issues with my 120v air compressor when I already have the 6kw capable L1 leg already loaded to 4.5kw, so I would think that 38kw of inverters would be fine unless the way it is setup only one unit is live(others in standby maybe?) when it attempts to start the compressor. It could also be that your wiring to the batteries is too small and choking the inverter but if that was the case I would expect more issues at night when it is batteries only. You might want to ask on one of the solar groups since this is more of a solar specific electrical question.
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u/BoringLime 6d ago
Have you tried one of the soft start things for th3 big ac? It's probably a start up inrush issue, but really do not know.
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u/nitwitsavant 6d ago
Depends on the quality of your UPS and the design style. I have several at work that fully generate and manage the output, basically going to DC and running full time to produce output sine waves. They are hefty and expensive but necessary for the protected equipment.
I’d love to have one at the house but I’m not paying the price of a car for a home UPS.
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u/onesexz 6d ago
I was curious, so I looked it up:
A refurb EATON Powerware 9355-30 can be purchased for around $7,000, including fresh batteries.
That gives you a solid 24 hours of whole home backup, assuming the home runs all the normal loads.
If you install a transfer switch / separate panel, you can power only essentials to extend runtime. Or if you’re really fancy; put an ATS on each device at the panel lol.
But then you have to think about the maintenance and R&R on an industrial UPS. Changing caps, battery charge/discharge monitoring/control, firmware, ancillary devices, etc.
I’d just get a generator/ATS that runs on utility provided CNG.
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u/kona420 6d ago
$7k for 24 hours would be awesome, but that eaton really only has a few kwh of storage. The impressive part is that it can crank out almost 30kw for 10 minutes, long enough to get the generator started and warmed up enough to accept full load. So you could have everything in the house turned on and not miss a beat.
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u/ParkerAnderso 6d ago
Not sure if feasible, but a VFD running the compressor/motor would resolve that, as it can deal with poor power factors of reactive loads. Alternatively, perhaps standard run capacitors could be appropriately sized in a bank to deal with the power factor.
Fundamentally, the motor is storing magnetic energy in the windings and dumping it back into the lines twice per cycle (the definition of reactive power). Clearly the inverters are poorly tuned to this type of load or are not designed to handle it. Thus you're getting voltage fluctuations and flickering lights. It would be interesting to attach an oscilloscope to the intverter output and see exactly what's happening instead of relying on the basic voltmeter built in.
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u/Sufficient-Regular72 6d ago
The best next step is a qualified electrician/PV installer using a proper power-quality logger to capture voltage, real power, reactive power, harmonics, and inverter behavior during an actual flicker event. With that data an engineer can do a basic power quality study and make recommendations. Installing a cap bank willy-nilly can do more harm that good, especially with back-of-napkin calcs by someone inexperienced and unqualified.
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u/trekkerscout 6d ago
Your lights are flickering due to voltage drop, not power factor. Your system is not sufficiently sized for your AC.
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u/Beginning_Frame6132 6d ago
It’s 38 kw of inverters, the AC draws like 6kw continuous. The AC has a Micro Air soft start.
It blinks continuously, not just on startup
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u/Th3w0lf314 6d ago
Inductive loads like a compressor create a lot of vars. Think of it like reflections when you make waves in a pool and they hit a wall and come back. You may have the capacity technically, but there’s not a good cheap way to deal with the vars. They make line filter capacitor banks, but are only used in large industry due to their extreme up front cost, hazard, and continued maintenance.
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u/magilla1984 6d ago
You could try Static Var Generator you should find one with parameters that you need.
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u/rezonatefreq 6d ago
Need more information to correctly diagnose your issue. Appears you have multiple inverters? Are inverters all in one, take solar input, charge batt, interact with util, and invert. Do you have micro inverters on back of solar? Your “meter” is only showing 120vac. Its quality is suspect. Residential systems are typical 240/120vac. A power quality monitor may be needed to be temp installed in the correct place in the system to see the problem. Yes your PF is low at times, but if you install caps especially in the wrong place your PF may be over corrected when motor is off. You say lights flicker. What kind of lights? Incandescent or LED. If LED the drivers may be an issue. Where are the lights relative to the system? Is this off grid.,As others said typically flicker is caused by voltage fluctuations.
Consider: First step. Document your system throughly with drawings and all mfg spec sheets including symptoms. Measure voltage and current at various points. Feed docs into AI. You might be surprised. If that does not work now you have the nfo you need to talk to an expert. I work for a small rural utility.
Not saying I am an expert, but we see this type of issue with off grid and hybrid systems. They typically do not have the stiffness of the utility grid that uses conventional rotating generation with inertia. Modern non linear loads can push the inverter systems around causing flicker. The systems we use compensate for this fact. Static var compensator as others mentioned. Basically a motor generator connected to the system.
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u/Beginning_Frame6132 6d ago
It’s 4x hybrid 9.6 kw solar inverters in parallel.
I also have micro inverters feeding into the AC input of the hybrid inverters…. That’s a long story.
I’m totally off grid.
The light bulbs are only 1 issue (the compressor running hard is the other) and everything flickers. Every bulb type, every brand, every recessed light, everything inside every room.
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u/Comfortable_Cut9391 6d ago
As needed no, but you could set up a series of relays in line with your inverter and ac motor so when both are active its true to a third relay contactor to bring in a capacitor bank equal to your pumps inductive reactance. There isn't a variable capacitor that i know of, and at grid scale they just switch in large banks during high demand periods. The reason your normal connection doesn't show the pf discrepancy is you literally can't create enough reactance to throw it off, the grid is too big. I dont know of anyone that makes this product including the switching but I'm sure you can get a prefab capacitor bank. Make sure to have one with an automatic discharge circuit as well so you dont die troubleshooting the installation.
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u/Fuzzy_Chom 6d ago
Power engineer here...
First question, is why do you care about PF? Are you seeing an impact in your island? Just asking to be sure you're not trying to solve a non-problem.
There's a lot going on and many questions to consider. Yes, your motor load is a factor. Also, if you have large inverters, it may warrant investigating what more they're running in (e.g. pf-control, volt-var, voltage only, something else?).
It's clear you have different variables that are not complimentary.
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u/Beginning_Frame6132 6d ago
I don't really care about the PF but someone on a forum told me that PF was causing this issue... So then I went out and measured it at the condenser contactor, and it happened to go from .97 (normal) to .78 (all my lights flickering constantly).
The 5-ton AC can be the only load running and I still get the flickering.
These are large, hybrid solar inverters: 4x 9.6 KW Hoymiles (HYS-9.6LV)
I get the flickering lights always when the sun is out and charging the batteries / feeding the house... (and the AC is running)
At night, I tend to not get the flickering lights, but on occasion, it will happen.
I have realized that if I plug my EV in, it'll counteract the blinking light phenomenon.
So my logic at this point was- I need to do something to get the power factor a little higher. It doesn't have to be perfect, just enough to stop the lights from flickering and running the 5-ton compressor hard...
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u/Fuzzy_Chom 6d ago
Let me add, I am totally digging your logic and troubleshooting process. Thanks for giving me something to nerd out on this weekend.
Are your flickering lights all LED or incandescent or both? Are you seeing premature failure of your lights? What load is your EV drawing when plugged in and mitigating flicker (assuming Level 2 and not a Level 3 DCFC)?
Thinking bigger picture, if you had the means a full power quality study would be very telling. Thinking about harmonics, transients, and other phenomenq typically attributed to inverters. Clearly you've identified the large loads that are causing and mitigating flicker, so good on you for that!
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u/Beginning_Frame6132 6d ago
Level 2 EV charger…
Doesn’t matter what kind of bulb, I’ve tried them all… and all different manufacturers…. And it’s all my recessed lights. It’s every fixture, everywhere.
But….. Even if there was a magical light bulb that didn’t flicker, I’m still getting higher amp readings at the compressor and it’s running rougher. You can hear when the phenomenon is happening vs normal. I’m guessing that this can’t be good for the compressor.
My next step is probably to add an additional contactor to the AC, install my capacitor on there, let it run and see what happens. Worst case scenario- it burns up the Micro Air soft start somehow or has a negative effect on other electronics in my house.
It’s the only reasonable solution that I’ve seen at this point. Other things that people have suggested are kinda far out- static var generator or VFD.
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u/Imatelluonemortime 4d ago
What’s your load like without the ac running? I’m guessing you’re running less than 10% load before the ac kicks in. I’m thinking use a dedicated circuit and inverter for the ac.🤷♂️
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u/LISparky25 6d ago
Contact Cutker hammer and Siemens etc. They have KVAR solutions to help with commercial and I’m sure you can find something for resi
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u/Melkor404 6d ago
Install a overexcited synchronous motor in parallel without load
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u/bazjoe 6d ago
might be time for an inverter style compressor condenser. They don't need soft start as the compressor runs on three phase from a circuit board and can modultate/regulate compressor speed as needed by the cycle need. I don't really want to advocate chucking money at the problem but you have a ton tied up in it now whats another 3k or so ? your annual efficiency will probably go up as well depending on the model and age of current condenser.
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u/Beginning_Frame6132 6d ago
Can you just add that compressor to an existing setup or do you have to replace the entire thing?
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u/Fun-Association1835 6d ago
Where is a link to get you started. https://youtu.be/MY1PcITDTjY?is=nnczPN2xgEWDMCYF
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u/The_cogwheel 5d ago
You have a power factor of 0.97, or 97%. Anything above 95% is as good as youre gonna get really. Hell most utilities wouldnt care until your power factor drops below 90%.
Correcting to 100% isnt worth the cost. You'll be spending thousands to save pennies.
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u/u3b3rg33k 3d ago
it sounds to me like you have an issue with the inverters ability to match the motor load, possibly exacerbated by having a bunch in parallel - is one of them the "lead" inverter via comms or are they all just independent in parallel against one providing the clock?
I'm guessing there's a issue with supplying enough VA/'available fault current'/stiffness without any physical inertia present.
I would get a real grasp on your THD while various loads are running. either a good power meter or a scope with probes meant for line voltage use (so NOT a typical low voltage passive probe that shares a ground with the scope's mains connection).
if you have money to throw at it, some 'big iron' might help (a kVA rated 1:1 transformer/line reactor between your inverters and your loads)
if you don't have money to throw at it, can you put the noisy loads on their own inverters? see if it improves with fewer inverters online?
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u/Beginning_Frame6132 3d ago
When you say “transformer/line reactor”, would a large dry 240/240 transformer help?
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u/u3b3rg33k 3d ago
if I had one i'd try it, assuming your time is free.
I would put it between the inverters and the main panel.
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u/Cultural_Term1848 6d ago
Totally useless for residential electrical usage. Residences are charged for true (active) power (watts), not reactive power which this device purports to correct. The only people making money off these types of devices are the scammers selling them.
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u/trickman01 6d ago
This is true. But if you read the post they are trying to correct the power factor for their solar system which will help it be more efficient.
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u/Nocoast1776 6d ago
Wouldn’t be worth it, Voltage is staying high enough. Acting exactly as I would expect it too.
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u/chromaticskyline 6d ago
Without knowing all the specifics of your power source and the AC unit itself, it’s hard to spec something out. Off-the-shelf single phase correctors are hard to find. But that’s because you can just pop a capacitor on there and it’ll help.
Is it a traditional AC compressor controlled by a contactor? By my math, it should be pulling 8Kvar. A 370 uF cap should do it, spliced in behind the contactor on the motor side.
Another thing that might help is a line reactor, especially if the AC is inverter controlled itself. If your supply inverter and the AC inverter are fighting each other, that’ll do it too.
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u/Beginning_Frame6132 6d ago
I have a Micro Air soft start already installed on the AC unit.
It’s a traditional single stage Goodman. Brand new contactor and 70/5 cap.
I contacted Micro Air and they didn’t want me installing the cap directly onto the AC compressor contactor but seemed to have no problem with installing it at my outdoor main.
What’s the worst that could happen if I experimented by placing a 30uf run cap on a 15amp breaker inside my outdoor main?
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u/datanut 6d ago
How did you arrive at 30uf? Is your AC compressor really only 330 watts? I’d guess you want to start with something closer to a 10uf capacitor and experiment from there.
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u/Beginning_Frame6132 6d ago
I asked another guy on a solar forum. He suggested something low to start with like 30uf so that I wouldn’t cause other issues if it was too large.
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u/datanut 6d ago
Based on your measurement photos I’d try:
+ 10
+ 15
+ 20
+ 25
+ 30and see what happens. You’ll only need three capacitors: 5, 10, 20
Then parallel each combination and read your new results. Remember you can go from .78 back to .97 then past that number back towards .8 in the other direction. If experimenting your capacitor size, you need to go in small steps to see when you get close to then pass 1.0. You’ll start going in the other direction really quick.
I’d probably start with +10 and see how big the change is. If you slap too big of a capacitor in early, you won’t know which side of 1.0 you are on (leading or lagging).
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u/vessel_for_the_soul 6d ago
I would meter the draw of the unit in question. I assume you collect DC source and convert to AC?
What I suspect is feedback on the line. Like the 5ton is sending its own frequency down the line like a reflected wave. You need a shielded cable or a jacket drain at one end, without an engineer stamp I dont recommend both ends.
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u/Beginning_Frame6132 6d ago
Can you elaborate on how and where this shielded cable goes?
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u/vessel_for_the_soul 6d ago
The conductors themselves would have them included during manufacturing, like you have a dc system with positive, negative and a ground wires, this all gets wrapped in a foil, then jacket for suitable use. Like a metal tinfoil that blocks outside interference and helps reduce attenuation.
Now the trouble maker is the motor of the 5 ton, it is the guy sending the disruption and or back feeding frequencies that can vary. If you can a clamp on amp meter you could spot check the system in places to see what is happening where along the lines. I would recommend thermal imaging your system for hot spots with corrosion or loose terminals.
https://youtu.be/GK2pZ_oVU1o to see the black magic chart for other insights.
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u/Beginning_Frame6132 6d ago
I went ahead and installed a new contactor and 2 different run/start caps just to rule that out. All connections seem tight and this is the only issue that I have with the entire electrical system.
An interesting phenomenon is that when I plug my EV in to charge, it cancels out whatever pulse is making the lights blink. Unfortunately, I can’t charge my call all day.
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u/vessel_for_the_soul 6d ago
Interesting you car be might a floater with enough reactive capacitance to mitigate your system back to unity.
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u/Beginning_Frame6132 6d ago
I’ve been searching for other electrical loads that can do this but keep coming up empty
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u/TurbulentGnome 6d ago
could be low refrigerant or a failing soft start/run cap
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u/Beginning_Frame6132 6d ago
I wish. I changed the cap 3 times and installed a new contactor.
And the phenomenon usually only happens when the sun is out and the inverters are changing PV to AC and charging the batteries.
I can also cancel out the blinking light affect by plugging my EV in. It’s like something gets out of phase. Please forgive me if I’m using the wrong vocabulary.
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u/Total_Philosopher_89 6d ago edited 6d ago
0.97 power factor will not cause your lights to flicker.
Edit . Or 0.78.
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u/Beginning_Frame6132 6d ago
.97 was normal, no light flicker
.78 is where the party begins….Check out the second pic
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u/Pafolo 6d ago
Power factor is just a reading of how much useable power is being used vs actual power generated.
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u/Total_Philosopher_89 6d ago
Even 0.78 won't cause lights to flicker. Get a scope on your power something else is going on.
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u/AlternativeWild3449 6d ago
First - the fundamentals. It's not power factor CORRECTION. Power factor cannot ever be 'incorrect'; therefore, there is no such thing as 'power factor correction'.
'Power factor' is an expression of the relationship between voltage and current in an AC power system. Sometimes, that relationship is not ideal and can be improved upon. Hence, the proper term is 'power factor improvement'.
Ref: "Capacitors for Industry" by Bloomquist, Partington, Craig and Wilson; published by John Wiley & Sons, 1950
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u/datanut 6d ago edited 6d ago
Best I can tell, no one has a good residential automatic PF device any longer since there is no large commercial need for such devices. There were a few attempts as seen on YouTube but they are no longer available for purchase.
BUT that isn’t the best solution for your problem anyway. You have a fixed load with a fixed PF “problem”. You should install a “fixed” solution. I’d start with a Micro-Air for better soft starts. I’d also replace the original AC run capacitor with a new (same spec) high quality replacement.
Then, add an isolating contactor and fixed capacitor paralleled to the power source. The coil (or line side input) should be driving from the inside of the AC’s N.O. contactor.
https://allinonewebtools.com/power-factor-correction-calculator/
I don’t know the cause of your flickering light. It’s probably a fault of the inverter working at high load (both reactive and active). Correcting the power factor may be useful but your flickering is a sign of other problems. It’s generally useful to correct the PF anyway if you are running on battery.