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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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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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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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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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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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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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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
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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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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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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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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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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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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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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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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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.

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...

And a long one...
 
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