# Total Harmonic Distortion filter



## jas42

I have a XG10000E generator that I use for back up power at my home. I would like to be able to run electronics on it (internet modem, TV, computer). Is there a way to filter the Total Harmonic Distortion to keep my electronics from getting fried? I have considered buying a UPS to put between the generator and my electronics but I'm not sure if this would help.


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## exmar

IMHO, "Home Electronics" can survive in a much worse electrical environment than you'd be subjecting it to. There are a lot of "Very Cost Effective" (cheap) gensets out there running same.


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## OldMasterTech

A better choice is a line conditioner as there are no batteries to maintain. Calculate your load requirements and google an appropriate device.


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## Osviur

*Harmonic distortion*

Hi jas42,

It is not a simple problem, the Generac XG series has a total harmonic distortion from 4.7 t0 25% , the XP series, less than 5%. But what is THD?.

The AC voltage supplied by the grid has a sinusoidal form (as shown in the next post) , very near to the ideal smooth curve represented by the math function sine. The main characteristic of this ideal curve is that it has not sharp changes in its trajectory. When this curve is converted in voltage, and is fed to a resistive device, such as an incandescent lamp, it impulses a current with the same wave form, a smooth variable current waveform.

Any deviation from this ideal sine waveform is called distortion. In the AC supplied by the grid, there are many big generators carefully designed to produce the best waveform and quality electrical power. In a 60 cycles per second (60 Hz) system, this frequency is named the fundamental frequency.

Due to design difficulties and costs, many portable generators produce not only a non sinusoidal waveform but more than the funamental frequency; along with the 60Hz, there are multiples of this freq., double, triple etc and they are called harmonics.

If the fundamental frequency is 60 cycles per second, at to say 120 volts, the other unwanted frequencies, especially the third harmonic (180 Hz), are present in a variable amount, to say 5volts, 12 volts etc. the fifth may be 3 volts in example. The sum up of the total amount of unwanted voltages, generated at frequencies different to 60 Hz, expressed as a percentage of the the fundamental 60 Hz 120 volts, is called Total Harmonic Distortion.

This THD, is fed mixed with the 60 Hz, deforming the smooth curve, and depending of the load, may or may not be too harmful. An incandescet lamp or a portable drill are not affected, but a sofisticated electronic control may be alterated in its functions seriously, induction motors may overheat, as power transformers. 

To filter this harmonics, there are special harmonic filters. Most common filters or economic line conditioners, merely filter out spikes or noise, regulators mantain line voltage inside safe margins, but to avoid harmonics out of your delicate electronics, you will need dedicated harmonic filters, that will control spikes too.

An UPS (uninterruptible power supply), may or not may solve the problem.
Be aware of simple UPS that will provide an horrible "square" wave full of power spikes and deformations ( see the photo) that will harm anything but an incandescent lamp. There are other that provide a "modified sine wave", similar to the produced by the common inverters, better than square . The pure sine wave inverters or UPS produce a clean, distortless voltage wave appropiate for all kind of equipment.

But, UPSs and inverters (domestic) run on low voltage DC current. UPSs have an internal battery, used only when normal AC supply is cut. Most of them (the small ones ) have a by pass relay to feed directly the protected equipment with the AC mains. The true online UPSs convert the AC supply to DC and then generates an AC sinusoidal, clean voltage wave, independent of the incomming supply. This is a solution, costly but solution.

The other solution would be exchange your generator for an XP10000.

In few words: 

Harmonic filter, true online UPS, XP10000 genset, or take the risk to damage your equipment.

Best regards.


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## Osviur

*Waveforms*

Hi,

Today I have taken some snapshots from the screen of an oscilloscope, to see real waveforms (1) from the grid, (2) a pure sine wave from a good quality UPS, (3) a square wave from a cheap UPS and (4) the equipment used, all of them feeding a 50 W incandescent lamp, which will not alter the waveform of any of the power supplies.


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## Osviur

*Pure sine wave*

Hi jas42,

Another solution would be to feed, in a separate circuit, all your "delicate electronic equipment" with an aditional inverter generator, a small one, enough to mantain running it, plus some led lights. I have seen a Generac iX800 for $ 287 in Ebay:

Generac IX800 800 Watt Portable Inverter Generator 696471057911 | eBay.

An advantage with this genset is the low noise emitted due to its size, permitting to install it near to the usage point, but of course always outdoors.

This kind of generator produce a very clean sine wave with exactly 60 Hz through all the power range, adecuate for the most sensitive electronic equipment . 

Regards


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## kishore

Harmonic distortions are one of the most common and irritating problems in industrial environment. We need to identify the source of harmonics and suppress them for a quality supply of power. If you have any queries about Total Harmonic Distortions, Please visit  Harmonic Analysis


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## simpson

jas42 said:


> I have a XG10000E generator that I use for back up power at my home. I would like to be able to run electronics on it (internet modem, TV, computer). Is there a way to filter the Total Harmonic Distortion to keep my electronics from getting fried? I have considered buying a UPS to put between the generator and my electronics but I'm not sure if this would help.


Did you ever solve this? We have a CAT 12k watt generator but the Cyberpower UPS batteries we bought won't accept the power from the generator. I'm thinking the next thing I'll try is adding a power conditioner between the generator and UPS, but I'm not sure if that will help anything


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## exmar

exmar said:


> IMHO, "Home Electronics" can survive in a much worse electrical environment than you'd be subjecting it to. There are a lot of "Very Cost Effective" (cheap) gensets out there running same.



Wow! Over five years later and I still totally agree with this and have gone though several more outages with open frame generators powering "sensitive electronics" and normal house loads, frig, freezer.

Osviur nailed the description and options for dealing with THD for those that think it's an issue. Utility power is considered the gold standard or something for "power purity." It ain't. In a steady state scenario, it is clean and the frequency is solid, when perturbations are added, switching, storms, etc. all kinds of spikes, surges, dips, etc. appear. IME more damage is caused when power is restored, particularly if the restoration isn't "solid" and dips or chatters. Please remember that THD is also a function of load, as the load varies, so does THD. So, on utility power, whatever is turning on and off and interacting in your house is ignored by the sheer...power... of the utility feed. e.g. My house has a 200Amp service, so that's 48,000Watts available at a very stiff 60 Hz. Compare that 48KW to a 5-10KW generator and its ability to "ignore" load changes as things turn on and off. Does the vast majority of things in your house care? Nope. Reports I've read here and on other forums talked about portable generators and UPS not playing together nicely. When you consider the purpose of a UPS it's to provide the ultimate in clean power to a load, It constantly monitors the incoming power and allows it to pass through to the load, at the slightest disturbance it isolates and goes on battery. Not surprising the UPS wouldn't like generator power. The UPS is doing what it's designed to do, the question is, do you need a UPS for a normal household? If you do, get an inverter generator. IMO power conditioners are a waste of money, to be effective, they have to be designed for a particular application, generic ones are generic.

I don't recall seeing any posts about inexpensive generators "frying" electronics? there have been posts about incompatibility with very upscale furnaces and frigs. Also, Generac seems to have the whole house generator market pretty much cornered with open frame generators and have yet to see THD numbers available on those?


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## 50ShadesOfDirt

Agreed ... As best I can tell, there isn't a THD problem at our level of home power requirements. I use only open-frame gennys with varying levels of thd, from 10% to 25%. Nothing in the house really complains, seems to die an early death, or exhibits any other power oddity. THD is perhaps more of a sales thing ...

Home-quality UPS's are an issue, but this may be due to varying levels of design and quality, coupled with not being intended for home generators in the first place. I've had some that wouldn't run at all on genny (cyberpower), others than ran a bit better (apc), but almost all didn't like genny power. There is also theory out there that _these and other home-class devices throw THD back out on the home wiring_, no matter what kind of power got to them in the first place.

Audiophile equipment, ham radio shacks ... these all are possible exceptions to the rule for THD doesn't matter" statement, but then, folks usually address the incoming power issue in these specialty cases anyway.

One caveat I've come to understand is that, _being off-grid_, I already have a power conditioner in place ... _for the whole house_. It's the magnum 4024 pure sine wave inverter/charger, coupled with LiFePO4 battery bank. This inverter/charger happily consumes any kind of power from any genny, and feeds it to the battery bank. Input is high THD power, output is pure sine wave power. Even here, it probably stays clean only until it hits all the crummy consumer-class equipment beyond, and goes downhill from there.

While an expensive solution, this points to one other way to solve such THD concerns; it could theoretically work on-grid. Grid-tie solar solutions (with battery bank) are also whole-house power conditoners. You wouldn't need datacenter grade ups/power conditioners (these are also very expensive). Just integrate a grid-tied or parallel inverter/charger & battery-bank, priced/sized to the load.

Another theory is that most modern consumer-class equipment defends its own turf inside (converts any kind of incoming ac to dc, then back to clean ac), but doesn't care about any other device on the house wiring (not concerned with possibly throwing THD back out). I don't have enough test points and equipment to see what's happening everywhere, although I'm trying to get there ... this is a huge ongoing effort ... oscilloscopes, breakout plugs, etc..

Multiple problems to pick from, and attempt to solve ...


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## OrlyP

Great stuff!

That's been my contention all along.... I haven't seen nor heard non-inverter generators causing havoc to "sensitive" electronics despite all the marketing propaganda against them. Though, it's not that they're lying. It's just something that's been grossly exaggerated. 

That said, if given a choice and with all else being equal, I would obviously go for an inverter generator (less noise and better fuel efficiency). However, it's not going to be a deal-breaker.


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## LaSwamp

Looks like OP never came back. 

My Firman is rated pretty high on the THD scale but I've not had any issues powering anything with it. When I used it after Ida, it was to make coffee in a percolator. It worked fine. Next time, I'll use it to power a portable hot plate to heat up food as well.


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## speedy2019

Osviur said:


> The AC voltage supplied by the grid has a sinusoidal form (as shown in the next post) , very near to the ideal smooth curve represented by the math function sine. The main characteristic of this ideal curve is that it has not sharp changes in its trajectory. When this curve is converted in voltage, and is fed to a resistive device, such as an incandescent lamp, it impulses a current with the same wave form, a smooth variable current waveform.


So thats why my halogen lamp flickers with the generator then?



simpson said:


> Did you ever solve this? We have a CAT 12k watt generator but the Cyberpower UPS batteries we bought won't accept the power from the generator. I'm thinking the next thing I'll try is adding a power conditioner between the generator and UPS, but I'm not sure if that will help anything


A UPS main purpose is to provide constant power without spikes, but a generator's power is up and down constantly, so the UPS wont accept the power and stays on battery mode..... So you need either a good "inverter generator" or a "generator friendly UPS to fix this problem, but a line conditioner might also do the job.


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## tabora

15 years ago, I ran I.T. for Konica Photo Imaging. In our photofinishing headquarters location, we had a big Cat diesel generator in case of emergencies. It fed 3phase 208V via a transfer switch into a line conditioner/converter that generated clean 120/240V and in turn into a 20KVA Toshiba UPS. That was the only way to keep it all happy.


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## drmerdp

speedy2019 said:


> So thats why my halogen lamp flickers with the generator then?


Halogen and incandescent bulbs are essentially the same except for the type of gas in the bulb. Argon for incandescent, halogen for halogen. Neither should flicker unless the power quality I’d very poor.

Led bulbs on the other hand are far more likely to flicker especially if on a dimmer switch. Pricier better quality led bulb are less prone then the cheap ones. My cheap Led bulbs will flicker on grid power on occasion but do not when powered by my eu7000s.


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## speedy2019

drmerdp said:


> Halogen and incandescent bulbs are essentially the same except for the type of gas in the bulb. Argon for incandescent, halogen for halogen. Neither should flicker unless the power quality I’d very poor.
> 
> Led bulbs on the other hand are far more likely to flicker especially if on a dimmer switch. Pricier better quality led bulb are less prone then the cheap ones. My cheap Led bulbs will flicker on grid power on occasion but do not when powered by my eu7000s.


Led bulbs seem to run fine, no flickering. I haven't tried a ones with a dimmer switch though.... I run my halogen lamp through my UPS connected to the generator and this solves the flickering.


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## iowagold

when you buy the led bulbs,,, get the ones that work with a dimmer switch for a good run.
they are made better by design.


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## macdenewf

50ShadesOfDirt said:


> Agreed ... As best I can tell, there isn't a THD problem at our level of home power requirements. I use only open-frame gennys with varying levels of thd, from 10% to 25%. Nothing in the house really complains, seems to die an early death, or exhibits any other power oddity. THD is perhaps more of a sales thing ...
> 
> Home-quality UPS's are an issue, but this may be due to varying levels of design and quality, coupled with not being intended for home generators in the first place. I've had some that wouldn't run at all on genny (cyberpower), others than ran a bit better (apc), but almost all didn't like genny power. There is also theory out there that _these and other home-class devices throw THD back out on the home wiring_, no matter what kind of power got to them in the first place.
> 
> Audiophile equipment, ham radio shacks ... these all are possible exceptions to the rule for THD doesn't matter" statement, but then, folks usually address the incoming power issue in these specialty cases anyway.
> 
> One caveat I've come to understand is that, _being off-grid_, I already have a power conditioner in place ... _for the whole house_. It's the magnum 4024 pure sine wave inverter/charger, coupled with LiFePO4 battery bank. This inverter/charger happily consumes any kind of power from any genny, and feeds it to the battery bank. Input is high THD power, output is pure sine wave power. Even here, it probably stays clean only until it hits all the crummy consumer-class equipment beyond, and goes downhill from there.
> 
> While an expensive solution, this points to one other way to solve such THD concerns; it could theoretically work on-grid. Grid-tie solar solutions (with battery bank) are also whole-house power conditoners. You wouldn't need datacenter grade ups/power conditioners (these are also very expensive). Just integrate a grid-tied or parallel inverter/charger & battery-bank, priced/sized to the load.
> 
> Another theory is that most modern consumer-class equipment defends its own turf inside (converts any kind of incoming ac to dc, then back to clean ac), but doesn't care about any other device on the house wiring (not concerned with possibly throwing THD back out). I don't have enough test points and equipment to see what's happening everywhere, although I'm trying to get there ... this is a huge ongoing effort ... oscilloscopes, breakout plugs, etc..
> 
> Multiple problems to pick from, and attempt to solve ...


That inverter is quite the solution. 
Probably not going to make that kind of investment but would you mind describing the setup? Just interested as I’d like to know what options there are for a reasonable solution to clean high THD. It looks like this is a 24v input to a 120v pure sine wave output. How do you use it with a 120 or 240 gen set. 
thanks.


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## PapaWhisky

_ "There is also theory out there that these and other home-class devices throw THD back out on the home wiring, no matter what kind of power got to them in the first place."_

This is not a theory ... this is a physical fact.


_"One caveat I've come to understand is that, being off-grid, I already have a power conditioner in place ... for the whole house. It's the magnum 4024 pure sine wave inverter/charger, coupled with LiFePO4 battery bank. This inverter/charger happily consumes any kind of power from any genny, and feeds it to the battery bank. Input is high THD power, output is pure sine wave power. Even here, it probably stays clean only until it hits all the crummy consumer-class equipment beyond, and goes downhill from there."_

This inverter charger has a DC input. I guess to run from Solar. How can this accept AC output from a generator?


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## OrlyP

PapaWhisky said:


> This inverter charger has a DC input. I guess to run from Solar. How can this accept AC output from a generator?


Good question. I would've conceded that this product is a do-all and accepts both DC from solar and AC from utility and process both into a self-generated pure sine wave. I took a peek at the specs but it just says it only accepts 18 - 33.6 VDC input.

On the THD front, I should mention that brushless generators tends to produce the dirtiest output. They're still being sold mostly on smaller (albeit, cheap) gens and in fact, sometimes even touting the "brushless" feature as a technological advantage. I'd stay clear of those unless you plan to use it exclusively for resistive loads.


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## 50ShadesOfDirt

On consumer devices throwing THD, I indicated "theory" above because I didn't have the exact whitepaper or research document found, and therefore couldn't point at that document. Good to know it isn't theory, as other docs alluded to this issue. Hope that a round of oscilloscope testing will reveal exactly what is happening inside my home, at various test points ...

On the Magnum inverter/charger, ours is a model MS-4024-PAE, which means it takes input from the 24v battery bank and turns that into 120v/240v for the house when in inverter mode; when in charger mode, it senses power from either solar or generator, and will use that to charge the battery bank, automatically. Our Duromax genny feeds into the inverter/charger.


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## PapaWhisky

50ShadesOfDirt said:


> On consumer devices throwing THD, I indicated "theory" above because I didn't have the exact whitepaper or research document found, and therefore couldn't point at that document. Good to know it isn't theory, as other docs alluded to this issue. Hope that a round of oscilloscope testing will reveal exactly what is happening inside my home, at various test points ...
> 
> On the Magnum inverter/charger, ours is a model MS-4024-PAE, which means it takes input from the 24v battery bank and turns that into 120v/240v for the house when in inverter mode; when in charger mode, it senses power from either solar or generator, and will use that to charge the battery bank, automatically. Our Duromax genny feeds into the inverter/charger.



It's my understanding that a scope alone will just give you only a qualitative idea of TDC. On a scope it's hard to tell the difference between 5% THD and 15%. You need something to calculate the THD.

I found an old Fluke 41 on eBay that should be here next week. I'll update then.


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## 50ShadesOfDirt

For more detail, we got a pre-wired assembly, with 4024, mini-mmp panel, and midnite classic 150 mppt integrated as one unit. All we had to do was feed various inputs or outputs (solar, genny, battery bank) into it ...

Again, we had to go off-grid ... too many poles to get grid power to us, at thousands per pole. Fringe benefits turned out to be clean power from the battery bank via the inverter/charger, no more grid brownouts/blackouts, and no more add-on fees in the utility bill (fuel surcharge, line fee, etc.) ...


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## 50ShadesOfDirt

That's a bummer, because I couldn't afford a fluke ... do have some inexpensive oscope stuff coming. I thought others' pics of oscope readings pointed out obvious THD problems ...

I do have the calc templates for THD, so there might be lots of calculations in my future ...

Still trying to sort out test methods, test points, breakout plugs, etc., to nail down THD throughout the entire system, from gennys, thru inverter/chargers, and then throughout the house wiring down to classes of consumer devices ...

I hope an EE cert gets sent to me in the mail, after all this ...


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## macdenewf

PapaWhisky said:


> It's my understanding that a scope alone will just give you only a qualitative idea of TDC. On a scope it's hard to tell the difference between 5% THD and 15%. You need something to calculate the THD.
> 
> I found an old Fluke 41 on eBay that should be here next week. I'll update then.


You can use a scope to calculate THD but it requires measuring voltage distortion on each of the harmonics. Then making a calculation to get the overall THD. I’d say that the average DIYer probably wouldn’t be able to make the calculation unless they were really familiar with a scope ( and I’m sure for those people it would be fairly easy ). 
it’s frustrating that there isn’t a reasonably priced device to make an automatic calculation.


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## PapaWhisky

macdenewf said:


> You can use a scope to calculate THD but it requires measuring voltage distortion on each of the harmonics. Then making a calculation to get the overall THD. I’d say that the average DIYer probably wouldn’t be able to make the calculation unless they were really familiar with a scope ( and I’m sure for those people it would be fairly easy ).
> it’s frustrating that there isn’t a reasonably priced device to make an automatic calculation.


This Fluke 41 was $210, by the way.

From my research, it's the minimum Fluke that'll do THD.


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## macdenewf

Interesting. If i could find a meter for a couple hundred I’d gladly buy one. So. That you are aware, it’s a direct measurement…not a calculation? 
thanks


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## PapaWhisky

macdenewf said:


> Interesting. If i could find a meter for a couple hundred I’d gladly buy one. So. That you are aware, it’s a direct measurement…not a calculation?
> thanks





macdenewf said:


> Interesting. If i could find a meter for a couple hundred I’d gladly buy one. So. That you are aware, it’s a direct measurement…not a calculation?
> thanks


I've found precious little information on this meter, so I can't say for sure.

But any determination of THD will involve 'some' calculation ... you have to add up the power in each harmonic.

This meter is supposed to go out to the 31st harmonic. It also computes voltage, current and power harmonics.

I'm beside myself with excitement


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## LaSwamp

PapaWhisky said:


> I've found precious little information on this meter, so I can't say for sure.
> 
> But any determination of THD will involve 'some' calculation ... you have to add up the power in each harmonic.
> 
> This meter is supposed to go out to the 31st harmonic. It also computes voltage, current and power harmonics.
> 
> I'm beside myself with excitement


Those meters new are around $700. You got a nice deal if it's in good shape.


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## bobmnh

OrlyP said:


> Good question. I would've conceded that this product is a do-all and accepts both DC from solar and AC from utility and process both into a self-generated pure sine wave. I took a peek at the specs but it just says it only accepts 18 - 33.6 VDC input.
> 
> On the THD front, I should mention that brushless generators tends to produce the dirtiest output. They're still being sold mostly on smaller (albeit, cheap) gens and in fact, sometimes even touting the "brushless" feature as a technological advantage. I'd stay clear of those unless you plan to use it exclusively for resistive loads.


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## bobmnh

bobmnh said:


> I can provide evidence of a generator with a high THD preventing a furnace from running.
> 
> Generator - Champion Tri-Fuel 8000W Model #100416
> Furnace - Lennox SLP98UHV
> 
> The furnace generates an error [126] that is displayed on the thermostat indicating the controller communication issues. Eventually we learned the Lennox installation guide calls out these requirements:
> 120 volts +- 10%
> 60 Hz (Range 57 Hz to 63 Hz)
> THD < 5%
> 
> Monitoring the output I could see the voltage and frequency were within range, which suggested the failure is due to the THD. Champion states the THD ranges from 12% to 20%.
> 
> My dishwasher also through an error condition; although, I'm not worried about washing dishes by hand during a power outage.
> 
> I'm stuck.
> 
> Sell the generator and replace it with one that generates <5% THD.
> Try to configure a line conditioner, UPS, something to save my my investment. (I saw an interesting post about a rural facility using a UPS to maintain proper operation of dialysis equipment running on generator power.)
> 
> And disappointed.
> I chose the Champion because of its ability to use natural gas. It started and ran nicely on NG and is tied it in to my electrical panel with an interlock switch.
> 
> Cheers.


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## OrlyP

If you scour the internet for furnaces failing to run properly under generator power, you will see that more often than not, it’s caused by wiring issues with regards to unbonded neutral or bad grounding.

There was just one instance where a person used a shunt capacitor across the hot and neutral leads (if I’m not mistaken) so that the furnace would operate under generator power. But whose to say he doesn’t have bad wiring to start with? Beyond that, this “dirty power” argument in this context seems mostly anecdotal.

That said, I’m not downplaying the effects of dirty power. Who wouldn’t want clean power? However, its effects are evidently limited but oftentimes exaggerated.


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## PapaWhisky

macdenewf said:


> Interesting. If i could find a meter for a couple hundred I’d gladly buy one. So. That you are aware, it’s a direct measurement…not a calculation?
> thanks



Well ... that Fluke didn't work.

I guess I was hoping too much to get a $700 meter for $200


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## Twiddles

Electrician here. Any open frame generator, read that as not a "inverter generator", will operate 99% of most home systems without any damage. This includes electronics, computers, fridges, etc. In rare cases where the generator won't work, that is not the generator but rather the device it's supplying blocking the supply because it doesn't like the supply (for whatever reason). Some UPS and battery systems do this and call it protection, typically its because they sell some form of line conditioner they want you to buy OR they are using cheap parts and any form of voltage fluctuation or THD will cause equipment to fail.
I have a smart home virtually entirely electric,, all LED lamps with only heating on propane. Everything works on occasion I have lamp flickering, which is normal on a generator.


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## motormonkey

Twiddles, Not the best way to introduce yourself. Be nice.


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## Twiddles

motormonkey said:


> Twiddles, Not the best way to introduce yourself. Be nice.


My apologies.


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## speedy2019

If non inverter open framed generators damaged devices, you wouldnt be able to buy them, as manufactures would soon go out of business.. Plus can you find anything anywhere on the net saying a generator has damaged stuff?... I found 1 instant but that was because the generator was left to run out of fuel when devices were plugged in.... But if you keep the engine running smoothly and not let it run out of fuel while devices are plugged in, a non inverter open frame generator will run you devices fine without causing damage.


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## truedatnola

Found this thread by googling "is it possible to lower the THD on a generator."

I live in New Orleans, which has periodic hours-long blackouts, but is subject to much longer outages after major storms. I can't afford a whole-house generator for my 4plex ($30K or more), so I'm trying to make do with a portable generator. I'd like to be able to at least power a couple window units, a couple fridges, separate freezer, TV, and computer in my apartment (and if possible, run extension cords to my tenants so they can at least run fridges).

The idea of keeping many gallons of gasoline or multiple propane tanks on my property is not something I'm comfortable with, so I am specifically looking for a tri-fuel model, so that I can just hook it up to my house's NG line.

I am not an electrician, but in trying to make an informed purchase, I started looking into the various options and saw that there was concern that THD of 5% or greater could harm things like computers. The problem I'm encountering is that there doesn't seem to be any tri-fuel models with THD of <5%.

This $2,500 Duromax model (13,000 Watt Tri Fuel Portable HXT Generator w/ CO Alert) claims to be the biggest tri-fuel on the market (a big plus), but also has a THD of 10-12%.

I was reading this thread hoping there would be a simple solution that someone like me who doesn't understand all the terms and jargon would be able to do – and I'm still unsure. Is there something I could buy and stick on this generator to bring the THD down below 5%?

And what supposedly happens to "sensitive" electronics with high THD? Are they unable to use the power or does it fry the circuitry and kill the devices?

Thanks for any info.


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## GenKnot

truedatnola said:


> Is there something I could buy and stick on this generator to bring the THD down below 5%?


No, not really. There are double-conversion ups units that are often used for sensitive electronics, but they are expensive.



truedatnola said:


> what supposedly happens to "sensitive" electronics with high THD? Are they unable to use the power or does it fry the circuitry and kill the devices?


Dirty power (high THD) can kill some devices...sometimes fast, and sometimes slowly. Other devices can be designed to reject dirty power (not uncommon in the solar industry) to protect themselves. Thankfully most electrical items out there will run just fine with dirty power such as space heaters, hot plates, coffee pots, and so forth because there isn't much in the way of "electronics" built into them. The older gens still run many things with no issues, but it only takes one expensive thing getting destroyed to make you regret plugging it into a dirty gen. It seems that the older "stuff" works okay with dirty gens while the new "stuff" may not like it. I had to buy a new gen because of my new furnace. My old gen (high THD) ran my old furnace just fine.

If buying a generator these days, I would stay with something <5% THD. Even if you don't currently have anything that might be harmed by dirty power, a low THD unit future-proofs you.

There is a lot of info on the web about generator THD. Here are a couple of links...





Modern Generators and Your Sensitive Electronics -


Something that concerns many individuals when they are considering a permanent standby... Read more »




www.midwestgenerators.com












Total Harmonic Distortion (THD) – What It Is & What It Does


What are harmonics and Total Harmonic Distortion (THD)? What are the causes and effects of harmonics? Portable inverter generators allow use of clean power.




generatorbible.com





And a long one...


ScreenLight & Grip's E-Newsletter


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## truedatnola

Thanks for that info. I guess if I can't modify a generator with high THD, I'll just have to keep looking for a tri-fuel with low THD.

So far, this is the only tri-fuel model I've found with THD of <5%: Winco Tri-Fuel Generator - HPS12000HE, 10800 Watt, Honda, Electric Start

It's $5,600, so I'm going to keep looking for a cheaper alternative.


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## OrlyP

TL;DR: If you can afford a low-THD generator, go for it. Otherwise, it's apparent that 10-12% is still widely acceptable unless you have equipment that specifically states that it needs <5% THD.

It's a never ending debate. If you want a black and white answer, then go for an inverter generator so you can get the coveted 3-5% THD and you no longer have to worry about whether or not it's safe for use with your appliances. A pair of either the Genmax 9000W or Predator 9500W inverter generators in parallel configuration will give you all the capacity you need.

But you have to pay the piper.

If you're like me and all you can afford to pony up is for a loud, open-frame, 3600 RPM screamer, then you're definitely not alone. They're not good at being silent or being clean (output-wise). What they are known for is that they're inexpensive. But inexpensive doesn't always mean it's cheap or bad. And "some" THD is not always going to be a deal-breaker. Here's what Champion had to say... take it with a grain of salt: Total Harmonic Distortion.



> Champion portable generators will output an *industry standard* total harmonic distortion (THD) rating of about *12%-20% depending on load applied.* They will produce a sine wave, not a modified or square wave. This is perfectly acceptable for running common commodities found in your home such as TVs, computers, your appliances, etc.
> 
> THD is a measure of the deviation of a sine wave from a "perfect" sine wave. All electricity, including line electricity, has measurable THD.
> 
> If you have a specific item that requires less than 5% THD such as a UPS style battery backup, a pellet stove, or high efficiency furnace control board, we recommend *purchasing a Champion Inverter Generator (sizes from 1600W to 3500W); Champion DH Series Open Frame Inverter (sizes from 3500W to 8750W) or a Champion Home Standby Generator (range from 8.5KW to 14KW); all units provide a less than 5% THD.
> 
> Please consult your specific appliance manufacturer to determine if the appliance requires low THD (less than 5%) to operate properly.*


So unless you have very specific equipment or electronics that require 5% or less THD, you should be fine with the 10-12% THD on the generator you were looking at for most of the appliances you will use in an emergency. It's still way lower than Champion's 12-20% THD claim. And if you read between the lines, if Champion was wrong in their stipulation and equipment started breaking left and right because of their gen's "dirty power", by claiming the above, they're opening themselves up for litigation.

To close, go with an inverter if you can afford it. They have gotten a lot cheaper in recent years but they're still at least 3-4x more expensive than conventional generators in the same wattage.. at least that's the case where I live.


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## LaSwamp

Indeed, 10-12% THD isn't really bad and most anything will run fine on it. When you get up above 20%, you're getting into some distorted waveforms. I have a performance series Firman generator, It's rated at around 25% THD. I've scoped it a few times and the waveform isn't pretty. I use it for things like a hot plate, fans, and an electric percolator, but I'm not comfortable using it for anything else. 

Inverters have come down in price pretty nicely. I'd highly recommend one if you need clean power.


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## GenKnot

LaSwamp said:


> Inverters have come down in price pretty nicely. I'd highly recommend one if you need clean power.


Agreed. But if we are responding to the @truedatnola post above, then he is wanting to supply his tenants with power. So, there would likely not be a way for him to know what they are plugging into his gen. If something failed as a result of the power he provided to them, then they might try to hold him liable. It's not uncommon for a fridge to cost $2,000-$3,000 nowadays! A landlord supplying power to a tenant can be a sticky situation.


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## LaSwamp

GenKnot said:


> Agreed. But if we are responding to the @truedatnola post above, then he is wanting to supply his tenants with power. So, there would likely not be a way for him to know what they are plugging into his gen. If something failed as a result of the power he provided to them, then they might try to hold him liable. It's not uncommon for a fridge to cost $2,000-$3,000 nowadays! A landlord supplying power to a tenant can be a sticky situation.


Yeah, it creates a bit of a conundrum. There's a need to fairly high wattage but also a need to keep THD low to reduce risk of damage to anything plugged into to it. I don't know what kind of liability he would have for power provided to his tenants during an outage. As far as I know, he has no legal obligation to provide power at all unless it's part of the lease. But I have never seen power production as a part of any lease, especially residential. It sounds like it would be provided as a courtesy. If I were him, I'd definitely find out if there is any legal exposure with that arrangement.


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## wesr228

truedatnola said:


> Thanks for that info. I guess if I can't modify a generator with high THD, I'll just have to keep looking for a tri-fuel with low THD.
> 
> So far, this is the only tri-fuel model I've found with THD of <5%: Winco Tri-Fuel Generator - HPS12000HE, 10800 Watt, Honda, Electric Start
> 
> It's $5,600, so I'm going to keep looking for a cheaper alternative.


truedat, where y'at?? and how's ya momma??

You can add on tri-fuel conversion kits to many generators. The downside though, it you'll void any warranties. That said, most warranties are not but for a year, maybe three. So if you're in it for the long haul, you'll have the generator much longer then any warranty. 

The Northern Tool in Metaire has a Powerhorse 13000es with a claimed THD under 5% in stock for $1,900, though you'ld want to add on a snorkel to run NG. Powerhorse Portable Generator 13,000 Surge Watts, 10,000 Rated Watts, Electric Start | Northern Tool

Additionally, they have what many would consider a better option, with a Honda Engine for $3,200, also with low THD. At least they offer free shipping NorthStar Portable Generator with Honda GX630 OHV Engine 13,000 Surge Watts, 10,500 Rated Watts, Electric Start, CARB Compliant | Northern Tool

Finally, if I were to have any plans on offering generator power to tenets, first, I would have some sort of Hold Harmless Agreement drafted up for them to sign that would at least be a buffer to help keep you out of trouble, and would also line out how the power gets to the tenet and what they can connect too (who is supplying the extension cord, and is the cord UL listed to run that much power for such a long run [a 10/3 cord would probably be needed to hold the 20amps] and maybe a tagging system where you put a sticker on things they can pug in).

But good luck and know there are lots of options out there!


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## truedatnola

GenKnot said:


> Agreed. But if we are responding to the @truedatnola post above, then he is wanting to supply his tenants with power.


Ideally, I'd like to supply my tenants with power during an outage as a courtesy (the one we had after Hurricane Ida lasted weeks), but that's only an option if I can afford it. Estimates on a Generac whole-house system were $24K for just my unit, and >$30K for the all 4 units. If I did have a system that could power their units, I'd first have them sign hold harmless agreements.


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## GenKnot

truedatnola said:


> Ideally, I'd like to supply my tenants with power during an outage as a courtesy (the one we had after Hurricane Ida lasted weeks), but that's only an option if I can afford it.


Got it.

Your earlier posts indicated that you are looking at 10,000W+ gens that run on NG. Maybe it would help us if we understood how much and what kind of power you would like to supply your tenants. For example, are you wanting to run 120V extension cords or 120/240V cords? And how many amps would you allow each tenant to have available for use? Then would you be on the same gen also and, if so, how much power would you like to have?

After doing the math for all of that it might narrow down which generator would be the best fit.


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## truedatnola

GenKnot said:


> Maybe it would help us if we understood how much and what kind of power you would like to supply your tenants.


Thanks for your reply.

From what I think I know, I can't expect to find any portable generator powerful enough to fully supply all 4 units of my 4plex at our normal levels of usage (and can't afford the whole-house standby systems that could).

If that's correct, then I'm hoping that I could find one that would keep me at normal usage (I don't think I have anything out of the ordinary: 2 fridges, 1 freezer, 2 window units, washer/dryer, tankless water heater, a computer and various computer equipment, average household appliances and lights), and then if there was any power beyond that, I'd want to power at least the 3 fridges in my tenants' units. 2 of my apartments have window units with heaters, another has mini-splits; I'm guessing it would be overly optimistic to think I could find a generator that could encompass their AC as well.

I am not obligated to supply power to them, but the difference between being able to stay in one's home or not during New Orleans' extended outages is whether one has _at least_ power for refrigeration and AC.

As for my concerns with THD, in theory, I suppose I could get a "dirty" energy generator for my basic usage (fridge, AC), and then get a smaller inverter specifically for my computer and other "sensitive electronics."

Someone suggested that instead of a fuel-based generator, that I instead get a solar set-up. When I asked the Generac guy (who quoted me $24K for a system that just covered my unit) if he installed solar, he said, "no. They are very expensive and will not power your AC units for very long."

I haven't been able to sift through all these variables and find any definitive answers on how I should move forward.

I hope that answers your question. I know next to nothing about any of this stuff.


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## evanah64

truedatnola said:


> I haven't been able to sift through all these variables and find any definitive answers on how I should move forward.


I'm not sure which one you have but electric tankless water heaters draw a ton of power. The general statement from google "One whole-house tankless water heater has four 7,000-watt elements, for a total electrical load of 28,000 watts. This load requires wire and a circuit breaker that will handle at least 120 amps " So if yours is electric, while likely not that large of a unit it might still be off the table. Different story if it runs on natural gas. Far as the rest of the stuff it can vary a LOT based on exactly what you have down the model of each appliance etc. But in general this could be helpful.

I'm sure folks can poke plenty of holes in this but as I said it really just depends on what exactly you have. Also how much you expect to be running at one time.


TypicalHigher EndWindow AC7501500Fridge500800Chest Freezer300600Washer6001400Electric Dryer21005000Computer400800Incandescent Lights (ea)60100LED Lights (ea)415Misc Appliances (ea)2001500


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## GenKnot

👆 Yeah, that water heater could be an issue for sure and needs to be investigated as to its power requirements. The dryers are hopefully running on natural gas. All the A/C power requirements needs to be totaled up also (don't forget the heat mode on those that have it if you plan to run it).

There are two schools of thought when it comes to generators as I see it. One method is to run everything normally as if on grid power (that would definitely need to be a big gen for 4 households). In areas where power outages are frequent and long, that is the preferred method for a lot of people, but it comes at a price.
The other method is to use load management and only run what is necessary while keeping the amperage within the limits of what is available. This is what I do since our outages are rare. I have a WEN GN625i inverter gen that I run in 120V mode only. This gives me about 40 amps of 120V power to use selectively to run things like my inverter window A/C, natural gas furnace, fridge, freezer, natural gas water heater ignitor, microwave, toaster oven, and then a few other small things like lamps, phone chargers, etc. I try not run the gen over 30 amps continuously just to extend its life. I do not use my central air unit or any other 240V appliance because the gen would simply not be big enough. The idea is to just get by using a small gen until grid power returns.

I think you really need to add up all the loads and see what you are dealing with. You can usually get the amps or watts off the labels or use a meter to actually measure the load. And which items are 240V (like possibly that water heater) because that would change things. Without knowing for sure what the loads actually are you will be shooting from the hip and more likely to make a bad decision.


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## iowagold

truedatnola said:


> Thanks for that info. I guess if I can't modify a generator with high THD, I'll just have to keep looking for a tri-fuel with low THD.
> 
> So far, this is the only tri-fuel model I've found with THD of <5%: Winco Tri-Fuel Generator - HPS12000HE, 10800 Watt, Honda, Electric Start
> 
> It's $5,600, so I'm going to keep looking for a cheaper alternative.


good solid power will cost good money.
6 k for 10 kw is a good deal if the power is super clean.
honda or an honda eu series of gen set is the gold standard.
ask lot's and lot's of questions before you buy!
you can add tri fuel to any gasoline gen set.
some are easy and are in kit form.

for me i prefer the eu7000is honda as it is inverter class and super clean and a good solid gen setup.
and you can stack them for more power as needed.


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## iowagold

oh yea if you are thinking of running a tankless electric hot water heater on a gen...
you are better off doing a cut to the chase and use an LP or NG hot water heater when on gen...
it saves all of the energy conversion loss.
you can run several hot water heaters on the same system.
i use bi fuel on hot water as a solution.
NG as primary, electric as back up in case the NG is out.


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## OrlyP

As Genknot mentioned, load management... key takeaway there. That's how I would do it. Since you're not under obligation to provide power anyway, just budget enough for them to use their lights, fridge, TV, computers, internet, a way to charge their phones and run maybe no more than a small window A/C, etc... none of the heavy stuff.

The challenge is how to impose that condition. Individual breakers and/or power meters to each apartment?

Or, would you like to take a gander at a pre-owned but unused 22kW whole-house unit? NEW Generac 22kw generator w/switch & battery, private owner. Never uncrated. $6000 FIRM CASH


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## evanah64

Curious though, typically each unit has its own panel inside so how would you ensure each tenant doesnt use more than they should? I suppose you can manage this with transfer switches limiting what's on each but this sounds far more complicated and costly than simply hooking up a generator to cover everyone's basics. I did once live in a 5 unit building that had all the breakers in the basement but still no way to prevent someone from walking down and flipping things back on without maybe putting a padlock on it.


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## OrlyP

Here's an idea of how I might approach this... Use a branch panel with an extension cord going to each home. A simple UK-style DIN consumer unit that can house individual MCBs as well as WiFi smart power meters going to each tenant. You can configure the power meters to cut power to a tenant if they go beyond the allowable wattage and/or current allotted to them. It's draconian but I don't see any other way to prevent one or more tenants from overloading the gen.

As the owner, you can monitor all four meters on your phone. It tells you how much current and power each tenant is drawing. It also measures energy consumption (kWh) so you can work out a charging scheme if you want to bill them for the power they used during the outage.























This is all 120V-only (L1-N and L2-N). Offering 120/240V (L1-N-L2) will require some changes.


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## Sly

Osviur said:


> *Harmonic distortion*
> 
> Hi jas42,
> 
> It is not a simple problem, the Generac XG series has a total harmonic distortion from 4.7 t0 25% , the XP series, less than 5%. But what is THD?.
> 
> The AC voltage supplied by the grid has a sinusoidal form (as shown in the next post) , very near to the ideal smooth curve represented by the math function sine. The main characteristic of this ideal curve is that it has not sharp changes in its trajectory. When this curve is converted in voltage, and is fed to a resistive device, such as an incandescent lamp, it impulses a current with the same wave form, a smooth variable current waveform.
> 
> Any deviation from this ideal sine waveform is called distortion. In the AC supplied by the grid, there are many big generators carefully designed to produce the best waveform and quality electrical power. In a 60 cycles per second (60 Hz) system, this frequency is named the fundamental frequency.
> 
> Due to design difficulties and costs, many portable generators produce not only a non sinusoidal waveform but more than the funamental frequency; along with the 60Hz, there are multiples of this freq., double, triple etc and they are called harmonics.
> 
> If the fundamental frequency is 60 cycles per second, at to say 120 volts, the other unwanted frequencies, especially the third harmonic (180 Hz), are present in a variable amount, to say 5volts, 12 volts etc. the fifth may be 3 volts in example. The sum up of the total amount of unwanted voltages, generated at frequencies different to 60 Hz, expressed as a percentage of the the fundamental 60 Hz 120 volts, is called Total Harmonic Distortion.
> 
> This THD, is fed mixed with the 60 Hz, deforming the smooth curve, and depending of the load, may or may not be too harmful. An incandescet lamp or a portable drill are not affected, but a sofisticated electronic control may be alterated in its functions seriously, induction motors may overheat, as power transformers.
> 
> To filter this harmonics, there are special harmonic filters. Most common filters or economic line conditioners, merely filter out spikes or noise, regulators mantain line voltage inside safe margins, but to avoid harmonics out of your delicate electronics, you will need dedicated harmonic filters, that will control spikes too.
> 
> An UPS (uninterruptible power supply), may or not may solve the problem.
> Be aware of simple UPS that will provide an horrible "square" wave full of power spikes and deformations ( see the photo) that will harm anything but an incandescent lamp. There are other that provide a "modified sine wave", similar to the produced by the common inverters, better than square . The pure sine wave inverters or UPS produce a clean, distortless voltage wave appropiate for all kind of equipment.
> 
> But, UPSs and inverters (domestic) run on low voltage DC current. UPSs have an internal battery, used only when normal AC supply is cut. Most of them (the small ones ) have a by pass relay to feed directly the protected equipment with the AC mains. The true online UPSs convert the AC supply to DC and then generates an AC sinusoidal, clean voltage wave, independent of the incomming supply. This is a solution, costly but solution.
> 
> The other solution would be exchange your generator for an XP10000.
> 
> In few words:
> 
> Harmonic filter, true online UPS, XP10000 genset, or take the risk to damage your equipment.
> 
> Best regards.


Has anyone been provided with, or found, any documentation from their Power Supplier that indicates what quality of power they provide? Including THD?
My home is fed from Ontario Hydro (Canada). Getting THD numbers from them, or the local distributor, is like pulling teeth. The range of "allowable" amounts of THD in the documents I've found includes 3%, 5%, 8%, 11% and 12% and refer to both short term and long term as well as full load and partial load conditions. I get that there are several factors that influence THD, but it seems to me that there should be a worst case scenario. E.g. stable state goal of <5%. Worst case = 12%.
I'm curious as to whether anyone has ever tested the power supply to their home to see what kind of THD they are getting. I'd like to do this with my own home, but a good clamp meters, with THD measuring capabilities, run from about $500-$1,600 USD. Kinda steep for a one time use and I can't find anyone nearby who rents them.
My goal in all of this is to find out what I'm being supplied and try and match this in the genny that I buy. I have alot of sensitive electronics and none have been affected by the power that I have been provided by our utility provider for 20+ years.
Thx


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## OrlyP

Sly said:


> Has anyone been provided with, or found, any documentation from their Power Supplier that indicates what quality of power they provide? Including THD?
> My home is fed from Ontario Hydro (Canada). Getting THD numbers from them, or the local distributor, is like pulling teeth. The range of "allowable" amounts of THD in the documents I've found includes 3%, 5%, 8%, 11% and 12% and refer to both short term and long term as well as full load and partial load conditions. I get that there are several factors that influence THD, but it seems to me that there should be a worst case scenario. E.g. stable state goal of <5%. Worst case = 12%.
> I'm curious as to whether anyone has ever tested the power supply to their home to see what kind of THD they are getting. I'd like to do this with my own home, but a good clamp meters, with THD measuring capabilities, run from about $500-$1,600 USD. Kinda steep for a one time use and I can't find anyone nearby who rents them.
> My goal in all of this is to find out what I'm being supplied and try and match this in the genny that I buy. I have alot of sensitive electronics and none have been affected by the power that I have been provided by our utility provider for 20+ years.
> Thx


Two words: Inverter Generator.

If I may be so blunt, you seem to be overthinking it. If nothing has been damaged in the last two plus decades, I wouldn't worry about the quality of the AC your utility company provides. 

But if power quality is paramount, get a dual-conversion UPS to power your sensitive electronics. For longer outages, an inverter generator would be your best bet. It will provide even better AC power quality compared to utility power.

Out of curiosity, what sort of "sensitive electronics" do you have?


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## GenKnot

Sly said:


> My goal in all of this is to find out what I'm being supplied and try and match this in the genny that I buy. I have alot of sensitive electronics and none have been affected by the power that I have been provided by our utility provider for 20+ years.


I have been told that our grid runs up to about 3-4% THD worst case, but I have no way to measure it. I have looked at it with my scope and I can see some distortion in the waveform. My WEN GN625i inverter has a much better looking waveform than my grid power.

On grid power I worry more about surges and spikes than THD.


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## OrlyP

Where I live, the max allowable TDD and THD is 5%. 



> 3.2.4 Harmonics
> 
> 3.2.4.1 For the purpose of this Section, Harmonics shall be defined as sinusoidal voltages and currents having Frequencies that are integral multiples of the fundamental Frequency.
> 
> 3.2.4.2 The Total Harmonic Distortion (THD) shall be defined as the ratio of the RMS value of the harmonic content to the RMS value of the fundamental quantity, expressed in percent.
> 
> 3.2.4.3 The Total Demand Distortion (TDD) shall be defined as the ratio of the RMS value of the harmonic content to the RMS value of the rated or maximum fundamental quantity, expressed in percent.
> 
> *3.2.4.4 At any User System, the THD of the voltage shall not exceed five percent (5%) during normal operating conditions.
> 
> 3.2.4.5 At any User System, the TDD of the current shall not exceed five percent (5%) during normal operating conditions.*


Like Genknot, I'm also worried more about voltage surges and spikes from things like nearby lightning strikes.


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## tabora

Our grid power vs PM0126000 generator...

Grid - Kind of flat on top right now...








Generator


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## speedy2019

Osviur said:


> *Harmonic distortion*
> 
> Hi jas42,
> 
> It is not a simple problem, the Generac XG series has a total harmonic distortion from 4.7 t0 25% , the XP series, less than 5%. But what is THD?.
> 
> The AC voltage supplied by the grid has a sinusoidal form (as shown in the next post) , very near to the ideal smooth curve represented by the math function sine. The main characteristic of this ideal curve is that it has not sharp changes in its trajectory. When this curve is converted in voltage, and is fed to a resistive device, such as an incandescent lamp, it impulses a current with the same wave form, a smooth variable current waveform.
> 
> Any deviation from this ideal sine waveform is called distortion. In the AC supplied by the grid, there are many big generators carefully designed to produce the best waveform and quality electrical power. In a 60 cycles per second (60 Hz) system, this frequency is named the fundamental frequency.
> 
> Due to design difficulties and costs, many portable generators produce not only a non sinusoidal waveform but more than the funamental frequency; along with the 60Hz, there are multiples of this freq., double, triple etc and they are called harmonics.
> 
> If the fundamental frequency is 60 cycles per second, at to say 120 volts, the other unwanted frequencies, especially the third harmonic (180 Hz), are present in a variable amount, to say 5volts, 12 volts etc. the fifth may be 3 volts in example. The sum up of the total amount of unwanted voltages, generated at frequencies different to 60 Hz, expressed as a percentage of the the fundamental 60 Hz 120 volts, is called Total Harmonic Distortion.
> 
> This THD, is fed mixed with the 60 Hz, deforming the smooth curve, and depending of the load, may or may not be too harmful. An incandescet lamp or a portable drill are not affected, but a sofisticated electronic control may be alterated in its functions seriously, induction motors may overheat, as power transformers.
> 
> To filter this harmonics, there are special harmonic filters. Most common filters or economic line conditioners, merely filter out spikes or noise, regulators mantain line voltage inside safe margins, but to avoid harmonics out of your delicate electronics, you will need dedicated harmonic filters, that will control spikes too.
> 
> An UPS (uninterruptible power supply), may or not may solve the problem.
> Be aware of simple UPS that will provide an horrible "square" wave full of power spikes and deformations ( see the photo) that will harm anything but an incandescent lamp. There are other that provide a "modified sine wave", similar to the produced by the common inverters, better than square . The pure sine wave inverters or UPS produce a clean, distortless voltage wave appropiate for all kind of equipment.
> 
> But, UPSs and inverters (domestic) run on low voltage DC current. UPSs have an internal battery, used only when normal AC supply is cut. Most of them (the small ones ) have a by pass relay to feed directly the protected equipment with the AC mains. The true online UPSs convert the AC supply to DC and then generates an AC sinusoidal, clean voltage wave, independent of the incomming supply. This is a solution, costly but solution.
> 
> The other solution would be exchange your generator for an XP10000.
> 
> In few words:
> 
> Harmonic filter, true online UPS, XP10000 genset, or take the risk to damage your equipment.
> 
> Best regards.


My Online UPS keeps the voltage at a rock solid 240v when connected to my non-inverter gen as the volts jumps around all over the place especally with a light load,, but I havent seen the gen ever go over 250v, as it stays within 215-245v and its quite steady at 230v with or over a load of about 20%


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## pipe

truedatnola said:


> ..and then get a smaller inverter specifically for my computer and other "sensitive electronics."


Or get a Sinewave UPS that acts as a "shield" for your sensitive items(both AVR and PFC), on utility power and/or generator power


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## speedy2019

pipe said:


> Or get a Sinewave UPS that acts as a "shield" for your sensitive items(both AVR and PFC), on utility power and/or generator power


But remember you need a generator friendly UPS for non inverter gens, as most UPS will remain on battery mode as the the power from the generator wont be steady enough for a normal UPS to get out of battery mode... I have no idea how my UPS that is a generator friendly UPS can smooth out the voltage without going to battery mode. The UPS does click over to battery mode though, when theres a sudden demand for power from the generator and the voltage drops for a second.


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## pipe

All our CyberPower units (see link) do not react discriminatively toward "dirty source" and self-correct/adjust the output to any connected devices.


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## Sly

GenKnot said:


> I have been told that our grid runs up to about 3-4% THD worst case, but I have no way to measure it. I have looked at it with my scope and I can see some distortion in the waveform. My WEN GN625i inverter has a much better looking waveform than my grid power.
> 
> On grid power I worry more about surges and spikes than THD.


Thanks for the info. Much appreciated. I agree. Surges / spikes are cause for concern. 
I have found a lot of info on THD. Some seems reliable, but most is anecdotal. My goal is to confirm its level of risk (probability & impact). The only ways I can think of doing this is to either measure it directly (best way in my opinion) or get confirmation from the group at my local power distributor. If I can eliminate THD as a low probablility / low impact risk, my home backup solution will change. 
Cheers


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## GenKnot

Sly said:


> If I can eliminate THD as a low probablility / low impact risk, my home backup solution will change.


If you go with a gen that is <5% THD you will likely be fine now and into the future. I had to change out my old gen (20%+ THD) for a cleaner waveform because of my new furnace. But, I wanted more power (old gen was only 3KW) anyway, so it worked out fine for me.


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## Sly

OrlyP said:


> Two words: Inverter Generator.
> 
> If I may be so blunt, you seem to be overthinking it. If nothing has been damaged in the last two plus decades, I wouldn't worry about the quality of the AC your utility company provides.
> 
> But if power quality is paramount, get a dual-conversion UPS to power your sensitive electronics. For longer outages, an inverter generator would be your best bet. It will provide even better AC power quality compared to utility power.
> 
> Out of curiosity, what sort of "sensitive electronics" do you have?


I agree about not worrying about my grid supply. If I can replicate it, via my backup generator, I'm golden. 
If I need an inverter generator, that's what I'll get. I'm just trying to confirm as many facts as I can before I go shopping for a $1.00/Watt generator vs a $0.10/Watt generator.


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## Sly

tabora said:


> Our grid power vs PM0126000 generator...
> 
> Grid - Kind of flat on top right now...
> View attachment 12730
> 
> Generator
> View attachment 12729


Thanks Tabora.
Would you have taken any screenshots of the harmonics report on your PP1?
Cheers


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## tabora

Sly said:


> Thanks Tabora.
> Would you have taken any screenshots of the harmonics report on your PP1?
> Cheers


Here you go... Grid L1 & L2:


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## Sly

tabora said:


> Here you go... Grid L1 & L2:
> View attachment 12733
> 
> View attachment 12734


Awesome. Thanks.
Pretty clean.


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