# generator newbie/THD question



## jsa307 (Oct 6, 2021)

I am a generator novice, and now interested in a portable generator. I already have an external natural gas hook-up, so I was looking into some of the tri-fuel models- specifically the FIRMAN T08071 and Champion 100416. Both of these machines seem to have very high THD ratings, however (11-14% on the Firman, < 20% on the Champion). Does anyone have experience using generators with THD ratings this high? Any concern for damage to home equipment/electronics? I read that high efficiency boiler circuits (which I have) can be particularly susceptible? It seems like the only alternatives would be 1) a tri-fuel that's 3-4x the price or 2) a generator without the natural gas option ....... thoughts?

Thank you!


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## Browse Deweb (Jan 16, 2021)

Get an inverter generator. They are more efficient, usually quieter, and provide a clean waveform. I have the Honda EU7000is and I added an MSK7000 natural gas kit to it.


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## iowagold (Jan 22, 2020)

i second the eu7000is gen set
they are the best out there right now.


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## Rene (Feb 5, 2021)

jsa307 said:


> I am a generator novice, and now interested in a portable generator. I already have an external natural gas hook-up, so I was looking into some of the tri-fuel models- specifically the FIRMAN T08071 and Champion 100416. Both of these machines seem to have very high THD ratings, however (11-14% on the Firman, < 20% on the Champion). Does anyone have experience using generators with THD ratings this high? Any concern for damage to home equipment/electronics? I read that high efficiency boiler circuits (which I have) can be particularly susceptible? It seems like the only alternatives would be 1) a tri-fuel that's 3-4x the price or 2) a generator without the natural gas option ....... thoughts?
> 
> Thank you!


I have the Firman T07571 trifuel gen. 9500/7500. Its loud but ran everything I threw at it (no 240 stuff) for 7 days straight during Ida with out a problem. I picked it up at Costco on sale for $700. I think they are now going for 900 pickup 1000/delivered.


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## LaSwamp (Mar 16, 2021)

jsa307 said:


> I am a generator novice, and now interested in a portable generator. I already have an external natural gas hook-up, so I was looking into some of the tri-fuel models- specifically the FIRMAN T08071 and Champion 100416. Both of these machines seem to have very high THD ratings, however (11-14% on the Firman, < 20% on the Champion). Does anyone have experience using generators with THD ratings this high? Any concern for damage to home equipment/electronics? I read that high efficiency boiler circuits (which I have) can be particularly susceptible? It seems like the only alternatives would be 1) a tri-fuel that's 3-4x the price or 2) a generator without the natural gas option ....... thoughts?
> 
> Thank you!


Those are nice generators, but because they are not inverters, they are going to have a higher THD output than you would see with an inverter. 

Honda makes some *very* nice inverters, although they are a bit spendy. I have had good luck with the Wen and Champion inverters. I think the Wen products are a steal, especially if you buy direct. The GN875i is now back in stock and it's only $811 out the door. It's 7 kw run-rated with a surge rating of 8.75 kw. Best of all, it's an inverter so the power is very clean. If I was looking for an inverter, that'd be the one I would get. US Carbs very likely makes a LNG kit for it. I think it warrants serious consideration.


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## jsa307 (Oct 6, 2021)

Thanks for the replies, appreciate the suggestions! As a novice, I'm a bit hesitant to modify the generator myself, though. 
Has anyone else heard about dirty power/high THD damaging home electronics? I'm tempted to stick with one of the tri-fuels I posted because of the price and natural gas option (without modification) ..


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## tabora (Sep 6, 2018)

jsa307 said:


> Has anyone else heard about dirty power/high THD damaging home electronics?


Electronic items with external power bricks or chargers do not fall into the "sensitive electrical equipment" category. Most modern electronics use chargers/batteries (like laptops and mobile phones/tablets) or AC/DC converters (TVs) that are designed for worldwide use at a wide range of voltages. There's very little out there that will be harmed by a noisy AVR or even a capacitor-regulated generator under normal conditions. 

Some UPS/APC units won't run on the power from them, though, and that's also apparently the case with some inverter refrigerators and HVAC units. Damage usually comes from severe voltage spikes from lightning or blown grid transformers, or a malfunctioning generator AVR or capacitor; I installed a GenerLink with 75KV suppression that covers input from both the generator and the grid.

I've been running my house and off-grid cottage on non-inverter generators for over 30 years and haven't fried anything yet. At my other cottage I've lost all the TVs and A/V equipment multiple times to lightning strikes. I installed an APC there and that problem has been solved.


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## macdenewf (Sep 3, 2021)

jsa307 said:


> I am a generator novice, and now interested in a portable generator. I already have an external natural gas hook-up, so I was looking into some of the tri-fuel models- specifically the FIRMAN T08071 and Champion 100416. Both of these machines seem to have very high THD ratings, however (11-14% on the Firman, < 20% on the Champion). Does anyone have experience using generators with THD ratings this high? Any concern for damage to home equipment/electronics? I read that high efficiency boiler circuits (which I have) can be particularly susceptible? It seems like the only alternatives would be 1) a tri-fuel that's 3-4x the price or 2) a generator without the natural gas option ....... thoughts?
> 
> Thank you!


I've been waiting to see some real posts about this generator in action. Costco sell this exact one for a really good price...and though I've seen many posts about its perceived poor THD...i've never actually seen any posts or feedback on one after an install.
I know dirty power can knock out arc fault breakers. I helped a neighbor install a mechanical interlock on his home and his smaller champion would kick out all the arc fault breakers every time he run the generator......after he bought a different generator....that completely stopped....so we presume it was dirty power.

Personally - i cant see costco carrying something that if it did cause problems...would have a huge return rate...or maybe its a matter of ignorance and if it works....how would you know that the power is dirty.

Perhaps buy it at a place that has a liberal return policy and if it displays problems with your electronics...simple return it.
Of course....thats just a personal opinion

firman-7500w-running--9400w-peak-tri-fuel-generator.product.100648883.html

Wow..the price has really gone up on this puppy...these were selling for 800 last year on line and 700 in the store!

On another note...ive helped several friends install a 12 KW Pulsar generator. Again don't know if the THD is high but they all seem to be happy with it.....and its a very easy conversion to try fuel.....literally 150 dollar kit ( that will of course void your warranty!) 

Cheers


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## exmar (Jun 29, 2015)

Agree with Tabora, I'd guess the majority of generators out there are of the non inverter type. The additional expense of an inverter comes into play if you have sensitive (high price) Frig or Furnace, those can be problematic. Additional consideration would be frequency and duration of outages, e.g. down south with Hurricanes, out west with "whatever" fire, etc. they've just had thrown at them. Inverters do use less fuel and in an extended outage fuel does become an issue.

I've used non inverter units for over 25 years with no issues to anything.

Perhaps a UPS ahead of your furnace for power conditioning. Make sure the UPS will run on the THD the generator you choose puts out though. That would also be useful to protect against transients, sags, surges, etc. when the power is restored. 

The greater the load, the higher the THD, just the nature of the beast. Generally, if the generator you select has a THD range of 10-25%, the lower number is for a half load as you increase that, THD goes up. For fuel consumption and longevity of the unit, half load is where you should be aiming for in a steady state scenario. The whole house units you see around (Generac, etc.) are open frame, high THD.

"You get what you pay for." A Honda will last longer, have higher resale value and be relatively trouble free for a long time. Your question is, is it worth $5,000 (whatever they cost) for an occasional outage or can you get by with a less expensive unit.

Last but not least, when you consider fuels other than gas, the Wattage of the unit is impacted. LPG subtract 10%, NG subtract 20%.


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## tabora (Sep 6, 2018)

jsa307 said:


> As a novice, I'm a bit hesitant to modify the generator myself, though. ... I'm tempted to stick with one of the tri-fuels I posted because of the price and natural gas option (without modification) ..


That should not be an issue if you can turn a wrench and screwdriver. The U.S. Carburetion snorkel kits install easily in minutes.
I have their MSK3101 kit on a PowerMate PM0126000.


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## macdenewf (Sep 3, 2021)

tabora said:


> That should not be an issue if you can turn a wrench and screwdriver. The U.S. Carburetion snorkel kits install easily in minutes.
> I have their MSK3101 kit on a PowerMate PM0126000.
> View attachment 10218


I haven't put on one of the snorkel kits but i have installed a few NG/Propane regulators on dual fuel generators 
If the generator is already set up for propane and gasoline - it's a simple matter of changing the propane regulator to a dual propane/nat gas regulator. Nash Fuels sells a propane / nat gas regulator for the pulsar i noted prior....all in took about an hour and absolutely easy to follow the instructions. The good part is no screwing around with the carb at all...and to run propane...simply need to choke back the supply or run a load block ( which can be supplied with the kit) 

Pics below are the same generator....one pic on natural gas..the other pic on Nat Gas. Did have to choke back the supply a little but dead easy to adjust on the bottle valve..else it runs too rich..but you can literally hear the difference and when i choked it back...frequency dropped right in line.

Love that generator...thats a backup tp my 13KW nat gas....never hurts to have a gasoline option but unless necessary...this backup will never see an ounce of gasoline in it!

Cheers

















.


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## speedy2019 (Jan 29, 2019)

At the end of the day, if non inverter generator damages equipment the manufactures wouldnt be alowed sell them, plus the non inverter gens has been around much longer... But if your buying a non inverter gen make sure it has AVR.


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## macdenewf (Sep 3, 2021)

speedy2019 said:


> At the end of the day, if non inverter generator damages equipment the manufactures wouldnt be alowed sell them, plus the non inverter gens has been around much longer... But if your buying a non inverter gen make sure it has AVR.


I've done a ton of searches ( as this is quote the interesting topic) and cant find any references to regulations on what the max allowable THD is on a portable power supply and as a generator is not the mains supply, doubtful the NEC would have a stipulation, I would however assert that any place that sells generators that have a liberal return policy wouldn't take a chance selling some thing that would be immediately returned due to problems. But playing the contrarian, most people use generators as backup and from what i can read, while some sensitive electronics may malfunction immediately with high THD, damage may take some time to develop ( through heat, inefficiency etc ) and as backup generators are primarily short term use....how would one know if slow damage was occurring? ...therefor would people even bring a generator back for this reason.....so how would the store selling them even know?

And after several hours searching last night....it really appears that the only multi meters capable of measuring harmonics require a signal generator.....not many reasonably priced options, and users would need more than basic electrical understanding to operate. 

No answers in this post...rather more questions. I plan on doing some more research to see how to simply measure THD...if i find a solution i'll post it.
Cheers
Mac


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## iowagold (Jan 22, 2020)

stay with the low thd gens.
would you throw sand in your bearings???
that is what high distortion is like to an electric motor.... 
causing internal vibration wear...
and over heating if it is bad enough.
now some motors are set up to handle a hf drive...
and can stand for more wave form issues...
most low cost air con and fridge freezer units will not stand for much distortion or power sag from slight brown outs.
that split second drop down to 90 volts or less is super hard on things..
that is the lights flicker...
same on the rebound of over voltage.

the little inverter units do well on the power correction.

why chance it!
on expensive electronics an extra $5k to $10 k for two eu7000i honda gens
is just cheap insurance.
good quality, and a good company ...
yea i drink the red cool aid!
GRIN!


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## Old man here (Nov 5, 2020)

macdenewf said:


> I've done a ton of searches ( as this is quote the interesting topic) and cant find any references to regulations on what the max allowable THD is on a portable power supply and as a generator is not the mains supply, doubtful the NEC would have a stipulation, I would however assert that any place that sells generators that have a liberal return policy wouldn't take a chance selling some thing that would be immediately returned due to problems. But playing the contrarian, most people use generators as backup and from what i can read, while some sensitive electronics may malfunction immediately with high THD, damage may take some time to develop ( through heat, inefficiency etc ) and as backup generators are primarily short term use....how would one know if slow damage was occurring? ...therefor would people even bring a generator back for this reason.....so how would the store selling them even know?
> 
> And after several hours searching last night....it really appears that the only multi meters capable of measuring harmonics require a signal generator.....not many reasonably priced options, and users would need more than basic electrical understanding to operate.
> 
> ...


There is a lot of information you are seeking in this thread:
Generator Oscilloscope Waveform Measurements | Power Equipment Forum


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## macdenewf (Sep 3, 2021)

Old man here said:


> There is a lot of information you are seeking in this thread:
> Generator Oscilloscope Waveform Measurements | Power Equipment Forum


I was wondering if any of those inexpensive hand held scopes can do an automatic calculation for THD. I looked at the manual for the DS 212 and it doesnt mention anything about THD as a calculation. I didn't realize there were too many options for inexpensive hand held scopes Once i searched that one on amazon- several others popped up on the 100 to two hundred range. Seeing the waveform is certainly helpful...having a calculation that doesn't rely on making a bunch of calculations would be great. if you have any recommendations or know of any that make that calculation - certainly appreciate the detail. Thanks
Mac


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## LaSwamp (Mar 16, 2021)

Scopes that perform the THD calculation are fairly expensive. Only the higher end scopes do it from what I have seen. My scope does a lot of different readings and graphs, but it does not calculate THD. If the signal is noisy, you can see it in the waveform. 

Check page 6 in the Waveform thread. There's a scope reading for the Firman 7571 there.


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## iowagold (Jan 22, 2020)

macdenewf said:


> I was wondering if any of those inexpensive hand held scopes can do an automatic calculation for THD. I looked at the manual for the DS 212 and it doesnt mention anything about THD as a calculation. I didn't realize there were too many options for inexpensive hand held scopes Once i searched that one on amazon- several others popped up on the 100 to two hundred range. Seeing the waveform is certainly helpful...having a calculation that doesn't rely on making a bunch of calculations would be great. if you have any recommendations or know of any that make that calculation - certainly appreciate the detail. Thanks
> Mac


the fluke power quality meter is the best way to look at thd..
but that is real money.


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## Rene (Feb 5, 2021)

macdenewf said:


> I've been waiting to see some real posts about this generator in action. Costco sell this exact one for a really good price...and though I've seen many posts about its perceived poor THD...i've never actually seen any posts or feedback on one after an install.
> I know dirty power can knock out arc fault breakers. I helped a neighbor install a mechanical interlock on his home and his smaller champion would kick out all the arc fault breakers every time he run the generator......after he bought a different generator....that completely stopped....so we presume it was dirty power.
> 
> Personally - i cant see costco carrying something that if it did cause problems...would have a huge return rate...or maybe its a matter of ignorance and if it works....how would you know that the power is dirty.
> ...


Just got an email .... Firman 7500w Tri-Fuel on sale, $800 delivered, $700 pick up. https://www.costco.com/.product.100648883.html?&EMID=B2C_2021_1011_HotBuysStart


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## Old man here (Nov 5, 2020)

macdenewf said:


> I was wondering if any of those inexpensive hand held scopes can do an automatic calculation for THD. I looked at the manual for the DS 212 and it doesnt mention anything about THD as a calculation. I didn't realize there were too many options for inexpensive hand held scopes Once i searched that one on amazon- several others popped up on the 100 to two hundred range. Seeing the waveform is certainly helpful...having a calculation that doesn't rely on making a bunch of calculations would be great. if you have any recommendations or know of any that make that calculation - certainly appreciate the detail. Thanks
> Mac


What you are looking for is going to be $$$$. I was lucky and found my Fluke 345 like new for $1500.
This is where I purchased mine. test_equipment_company_store on eBay


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## speedy2019 (Jan 29, 2019)

This is a vid of my gen, but mines the 6500W-E(2800watt) version, and it seems to be quite decent considering its less that £300 and Its prob ideal for occasional use. I have had mine for just under 3years and its only had exercise use so far..lol


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## tabora (Sep 6, 2018)

LaSwamp said:


> Scopes that perform the THD calculation are fairly expensive.


And this is why... 








Understanding, Calculating, and Measuring Total Harmonic Distortion (THD) - Technical Articles


Total harmonic distortion (THD) is a measurement that tells you how much of the distortion of a voltage or current is due to harmonics in the signal.




www.allaboutcircuits.com


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## LaSwamp (Mar 16, 2021)

tabora said:


> And this is why...
> 
> 
> 
> ...


Indeed. Looks like a job for the TI scientific calculator!


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## iowagold (Jan 22, 2020)

LaSwamp said:


> Indeed. Looks like a job for the TI scientific calculator!


yup on the ti 30 calc!

or just pay for the fluke power quality meter to display the number!
and snap shot the display with a smart phone so you can print off the results....
for me as a pro user i prefer to just have the readout for fast numbers as time is money when you are working on gear for clients.

retired hobby stuff.....
yea get out the old text books and get in to the math.
2 to 4 hours later you will get the number.


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## JVazquez53 (Jul 8, 2021)

jsa307 said:


> I am a generator novice, and now interested in a portable generator. I already have an external natural gas hook-up, so I was looking into some of the tri-fuel models- specifically the FIRMAN T08071 and Champion 100416. Both of these machines seem to have very high THD ratings, however (11-14% on the Firman, < 20% on the Champion). Does anyone have experience using generators with THD ratings this high? Any concern for damage to home equipment/electronics? I read that high efficiency boiler circuits (which I have) can be particularly susceptible? It seems like the only alternatives would be 1) a tri-fuel that's 3-4x the price or 2) a generator without the natural gas option ....... thoughts?
> 
> Thank you!


I would get a Honda EU7000is, is only gasoline powered, but is far more efficient than any trifuel. Very reliable, I own two.


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## LaSwamp (Mar 16, 2021)

iowagold said:


> yup on the ti 30 calc!
> 
> or just pay for the fluke power quality meter to display the number!
> and snap shot the display with a smart phone so you can print off the results....
> ...


I still have my Ti-34 from college. The Ti-30 is old school for sure.


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## iowagold (Jan 22, 2020)

i still have the slide rule!
that is old school!
lol!
yup on the eu7000i gen set.
and us carb makes a dandy tri fuel kit that works well to make the eu7000i gen set a monster for sure!


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## somedumbguy (Sep 17, 2020)

macdenewf said:


> I've done a ton of searches ( as this is quote the interesting topic) and cant find any references to regulations on what the max allowable THD is on a portable power supply and as a generator is not the mains supply, doubtful the NEC would have a stipulation,


Does the NEC even have a stipulation for mains power? As a baseline, has anyone tried to document what THD they actually get from their utility? Is this something that is routinely monitored by a regulator? Are they required to deliver a maximum THD? After doing a lot of digging, I saw that my furnace manufacturer says the THD provided should be 3% or less and its (long) list of possible fault codes includes some related to sub-par power. That's what finally pushed me over the edge to get an inverter gen. It would be great if you could buy a simple, inexpensive gizmo to monitor power and shut it off or beep if the power is sub-par. (Are such gizmos actually in inverter gens)?


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## iowagold (Jan 22, 2020)

somedumbguy said:


> Does the NEC even have a stipulation for mains power? As a baseline, has anyone tried to document what THD they actually get from their utility? Is this something that is routinely monitored by a regulator? Are they required to deliver a maximum THD? After doing a lot of digging, I saw that my furnace manufacturer says the THD provided should be 3% or less and its (long) list of possible fault codes includes some related to sub-par power. That's what finally pushed me over the edge to get an inverter gen. It would be great if you could buy a simple, inexpensive gizmo to monitor power and shut it off or beep if the power is sub-par. (Are such gizmos actually in inverter gens)?


most of the power generation of the grid power rules etc. are done by the state boards.
and weights and measures etc.
they have a board here in Iowa just for utility's. and they deal with the weights and measures on all of our utilities.
and if you as a customer have an issue with a utility you can report that issue to the utility's board.
pretty cool!

see your state .gov and search for the utility's board for your state.


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## ajnuzzi (12 mo ago)

You can relatively easily convert most gas generators to Tri Fuel. Don't let that narrow your search. If you're uncomfortable doing the conversion yourself then there are places that will do it for you. I know Green's Blue Flame in Houston will allow you to have your generator shipped directly to them for the upfit. 

I'm not knowledgeable on these boilers you speak of but I will say that ThD is way overrated. Unless you're running x ray machines or something weird like that chances are you'll be fine on a standard portable generator. If you're not planning on having it sent out immediately for a natural gas conversion I would buy the generator off amazon and after you get your electrical connections ready and try it and make sure it runs everything you need it to. If it doesn't you can exchange it pretty easily with amazon. Or if you have a friend that has a generator see if you can give a test run before purchasing.


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## kirklandlee239 (12 mo ago)

Been reading and enjoying lots of posts, especially on Sine waves, and THD etc. Being a novice in this area, the one question that still burns in my head is: How does Westinghouse offer the Wgen12000iH with 5% THD or less, but yet none of their other Non Inverter models are even close?> Short of being an inverter style, what magical part(s) is westinghouse using on the big machine? Could it be a special Voltage regualtor, or does it have fairy dust> lol?.


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## OrlyP (Oct 19, 2021)

kirklandlee239 said:


> Been reading and enjoying lots of posts, especially on Sine waves, and THD etc. Being a novice in this area, the one question that still burns in my head is: How does Westinghouse offer the Wgen12000iH with 5% THD or less, but yet none of their other Non Inverter models are even close?> Short of being an inverter style, what magical part(s) is westinghouse using on the big machine? Could it be a special Voltage regualtor, or does it have fairy dust> lol?.


I am no expert but I believe it has everything to do with how well the stator assembly was designed and made... the winding pitch, geometry, overall quality of materials and workmanship, etc. Many generators are built to a cost. I imagine that the better stator costs more money than their worth for the great majority of use cases.


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## GenKnot (Dec 20, 2021)

☝ That is exactly what I have been running across as I research the THD issue. Build quality in non-inverter generators is probably the biggest factor involved. Another factor is voltage and frequency regulation. It seems that the larger generators are the ones that are more likely to have a lower THD. There is more headroom to put more quality into a larger generator than a smaller one because people are usually not shopping price as much. A small generator is often purchased solely by price. People look at one 3KW gen vs another 3KW gen and buy based upon the price, which is just fine if you are running a saw on a jobsite or a space heater.

Another thing that seems to be a factor that favors larger non-inverter generators is that they are "stiffer" power sources than the smaller sets. In that respect, they can handle the THD that is produced within your house much better (THD can come from the generator, or your loads).

Here are three PDFs that discuss these subjects...


http://www.screenlightandgrip.com/images/Protocol_Clean_Power_%20Part1.pdf




http://www.screenlightandgrip.com/images/Protocol_Clean_Power_%20Part2.pdf




https://www.trane.com/content/dam/Trane/Commercial/global/products-systems/education-training/engineers-newsletters/control-systems-electrical-considerations/admapn019en_0106.pdf



Much of the same information from ScreenLight & Grip is available on their website here...


ScreenLight & Grip's E-Newsletter


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## LaSwamp (Mar 16, 2021)

I have a smaller non-inverter generator, a Firman P03602. It's a nice little genset, but the THD is very high. The waveform when I scoped it was ugly. It's one of the things that prompted me to get only inverters after that.


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## GenKnot (Dec 20, 2021)

I like the way Firman says the THD on the P03602 is "standard" in the manual. What the heck does that mean? LOL


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## LaSwamp (Mar 16, 2021)

GenKnot said:


> I like the way Firman says the THD on the P03602 is "standard" in the manual. What the heck does that mean? LOL


Lol, I'm not sure what that means, either. In the waveform thread, I posted a pic from the scope. It's terrible, even for a cheap generator. I was bummed when I saw it.


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## OrlyP (Oct 19, 2021)

GenKnot said:


> I like the way Firman says the THD on the P03602 is "standard" in the manual. What the heck does that mean? LOL


In the specs section, they listed this model with: "THD @ Full Load: 25%".

If that's the case, they have a very "high" standard. lol


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## kirklandlee239 (12 mo ago)

Isn't much above the Wgen9500DF, @23%, which was the unit i was set on until i did the research, joined this forum. Personally it was the perfect size for a home back up gen for power outages, not a super beast, but more than enough to run most important things, and even a water heater with timing things out. Im with with La Swamp, unless they quickly come out with a standard gen in the 9500 size range @5% or less ill go with the Duramax inverter, Like many i myself originally thought that i wanted the biggest meanest watt gen i could buy...then i realized i really dont need all that, and would have to pawn my car to buy enough propane to feed that beast...


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## GenKnot (Dec 20, 2021)

kirklandlee239 said:


> unless they quickly come out with a standard gen in the 9500 size range @5% or less ill go with the Duramax inverter


There are several non-inverter gens to choose from that have <5% THD if that is what you are wanting...








All Our 547 Generators [And Counting!] - Review Specs & Compare


Filter and compare the specifications of 547 portable generators across 26 manufacturers. Easily choose the best generator that fits your needs.




generatorbible.com


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## 50ShadesOfDirt (Oct 23, 2021)

Interesting ...

PowerLight&Grip is (for me) now a 3rd category of "heavy user" (extreme lighting/ballasted loads, non-PFC) where THD is an obvious issue.

The two others I've come across so far are Commercial buildings (hundreds of PC's and such) and Industrial sites (factories, lots of weird motors).

In all three of these extreme cases, there are EE's or electricians working to cancel out the effect of THD.

The difference between cases are the scale/scope of the power system; in PL&G's power system, it is roughly "one generator and a handful of directly connected lights", so a very small power system.

In trying to place my home into the scale/scope of THD problems, we're at the bottom with a power system of one AVR generator, a residential wiring system, and upwards of 100 or so electrical devices. Our "pond" has THD ripples from the genny _and_ from all these devices ... even so, I can't determine if that is an issue. PG&L is off to the side of us, with a _smaller_ power system, but a _larger_ THD problem due to the extreme ballasted lights in use.

My current thinking (still researching all the pieces) is that THD is a very big issue in large/extreme power systems, with big guns aimed at it (EE's and such), and a very little issue in small (non-extreme) power systems like my home ...


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## kirklandlee239 (12 mo ago)

GenKnot said:


> There are several non-inverter gens to choose from that have <5% THD if that is what you are wanting...
> 
> 
> 
> ...


just checked, and after i added the dual fuel filter, still only 1 was listed, the beast Westinghouse, 15000/12000


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## ajnuzzi (12 mo ago)

kirklandlee239 said:


> Been reading and enjoying lots of posts, especially on Sine waves, and THD etc. Being a novice in this area, the one question that still burns in my head is: How does Westinghouse offer the Wgen12000iH with 5% THD or less, but yet none of their other Non Inverter models are even close?> Short of being an inverter style, what magical part(s) is westinghouse using on the big machine? Could it be a special Voltage regualtor, or does it have fairy dust> lol?.


I've wondered this myself. I have the wgen9500df and the wgen12000df and I will say the 12000 is waaaay more stable. When hitting it with loads the hz barely fluctuates between 60.00 and 60.50 where as the 9500 will float between 59 and 62. I don't have a way of measuring THD but from what I'm seeing using it I'm not surprised that it's advertised as under 5%.


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## ajnuzzi (12 mo ago)

kirklandlee239 said:


> Been reading and enjoying lots of posts, especially on Sine waves, and THD etc. Being a novice in this area, the one question that still burns in my head is: How does Westinghouse offer the Wgen12000iH with 5% THD or less, but yet none of their other Non Inverter models are even close?> Short of being an inverter style, what magical part(s) is westinghouse using on the big machine? Could it be a special Voltage regualtor, or does it have fairy dust> lol?.


I've wondered this myself. I have the wgen9500df and the wgen12000df and I will say the 12000 is waaaay more stable. When hitting it with loads the hz barely fluctuates between 60.00 and 60.50 where as the 9500 will float between 59 and 62. I don't have a way of measuring THD but from what I'm seeing using it I'm not surprised that it's advertised as under 5%.


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## OrlyP (Oct 19, 2021)

See my my previous response here: generator newbie/THD question

It's got to do with the geometry of the windings (winding pitch, rotor or stator skew, etc). There's a TON of math involved so I won't even start to pretend I know 1% of it.

That said, the better-designed gen head costs more, or at least are sold at a slight premium.


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