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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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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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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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Discussion Starter · #6 ·
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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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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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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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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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.
Gas Automotive exterior Automotive tire Auto part Electric motor
 

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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



Automotive tire Motor vehicle Automotive exterior Asphalt Gas
Automotive lighting Automotive tire Motor vehicle Bumper Automotive exterior
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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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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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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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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
There is a lot of information you are seeking in this thread:
Generator Oscilloscope Waveform Measurements | Power Equipment Forum
 

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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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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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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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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
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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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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