# How to add pure sine wave to a cheap generator



## Tambourineman

I know I am doing this all backwards and probably just threw $300 down the drain, but even if it doesn't work i won't be any worse off than I am now (generatorless).

I ordered a DuroStar DS4400EHF Elite Hybrid Portable Dual Fuel Propane/Gas RV Generator. (Some day I'll order a eu6500is with a trifuel kit and connect it to my natural gas.)

The basic specs are: 
An EPA approved (Chinese made) 196cc, 7.0 Hp with cast iron sleeved and steel bearinged, air cooled OHV with low oil lamp & shutoff, 12V battery electric key start producing 4400W max, 3500W run on a heavy duty 1-inch steel tube frame on four point isolated motor mounts with a flexible line allows for different LPG tank sizes with a solid fill wheel kit & handle. The front panel includes engine shutoff, volt meter, circuit breaker and power outlets. Noise level is 69db at 7 meters. An idle control holds RPM at a constant level. There are two 120 Volt 20 Amp 3-Prong Outlets and one 120 Volt / 240 Volt 30 Amp Twist Lock (NEMA L14-30 3 Pole 4 Wire), plus a 12V 8A DC output. 

Since it is not stated, I assume the output is modified sine wave at best and possibly just square wave.

I want this mainly to run my gas furnace and two circulating pumps, plus my fridge. I expect this would be OK for the heat, but the fridge (Kenmore Elite circa 2007) could be a problem. It would be nice to also be able to charge laptop or cellphone batteries or watch a LCD widescreen.

What's the best inexpensive way to get clean power?


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## aandpdan

I had to look up the generator as "hybrid" had me. 

It's a traditional generator, not an inverter. By default it makes a sine wave. How "clean" it is, I can't answer. It is not "modified" and it is not a square wave.

Most electronics are not that sensitive to voltage fluctuations if they use a switch mode power supply. Check your computer and you'll see they work over a fairly wide voltage range.

I run a 44 year old generator (propane too) and have never had a problem with my TV, laptop, chargers, fridge, or my boiler. 

There are "power conditioners" that you can get.


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## Tambourineman

Hmmmm. I know enough to be dangerous and what I didn't know is even more dangerous. 

I thought all generators produced DC power that had to be converted to AC. I had seen the term "inverter generator" but never thought that much about it. 

I thought "hybrid" referred to it being bi-fuel. 

I think I understand now why it has a regulator to run at the proper RPM and I guess it runs at that RPM despite the load whereas an inverter one can run at a lower speed at a lower load and thus use less fuel? At 50% load it supposedly runs 8 hours on its 4 gallon tank (and 20 on a presumably 20 lbs propane tank. This is long/efficient enough for me. 

In 30 years here we once lost power for 4 days (but during a really cold spell), and for the other infrequent power losses it's only been 8 or less hours.

Anyway, this has opened a whole new can of worms: power conditioners, transient harmonics/THD, digital automatic voltage regulators, transient-voltage-surge suppressor (TVSS or SPD)/with chokes and capacitors in addition, or instead of MOVs.

I guess my earlier statement that the hot water circulating pumps would not be a problem compared to other stuff was wrong. I guess the motor in the fridge can be problem. I thought it would have been the electronics. I was gonna replace one hot water circulating pump as it may be 80 years old and is probably a power hog and wanted to reduce my load. Now I may want to keep it, or if I replace it I will now know to check into inverter duty motors.

I gotta have an electrician come in to do the transfer switch. Mayber I can find one that has a power analyzer And can tell me if I need to do anything.


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## aandpdan

It's called a generator but it does make ac. 

Yes it needs to run at a specific RPM, usually 3600, in order to produce 60hz. Inverters can vary their RPM according to demand.

Motors should not be a problem at all. They can be with an inverter however.

I really would not worry about using it. If you are forget buying it and get a whole house generator. Very few portable generators have close frequency and voltage regulation.


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## Tambourineman

Thanks for your continued insights.

We probably don't really need a generator since unless there's too much snow we could always decamp to close by relatives. It's just that as one gets older, heat is more important. The last time the outside temps were in the teens and the final inside temp after 4 days got down to the 40's. But that was very unusual. Fortunately the cook top and hot water is on NG so we could get hot coffee or take a hot shower and warmup, plus I have ECWS modular sleeping bags good down to -30. We're looking into a chimney liner and fireplace insert, but then I saw this deal which could add another heating method.

I haven't got it yet but so far I am happy with my "bargain." I just don't want to damage anything because then it's no longer a bargain.

There's a very interesting (and for me, enlightening) thread on DSLReports about cleaning up dirty power and what's affected by it. Here: https://www.dslreports.com/forum/r27117217-Dirty-Power-Cleanup


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## grouchy-hermit

aandpdan said:


> Motors should not be a problem at all. They can be with an inverter however.


Would you kindly expound on this? Are my furnace and sump pump motors at risk when powered by my Honda inverter?

Thanks for any info that you might offer.


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## aandpdan

ambourineman, read the post by Whizkid. He's right. Switching power supplies aren't fussy at all. Your computer doesn't run on AC, it's run on DC. It's rectified and filtered. The majority of power supplies can handle a wide range of voltages and frequencies as can most phone chargers, TV's, and other electronics. 

Grouchy, It depends upon the motor but many demand a true sine wave, not a stepped approximation from an inverter. 

Heat is one issue. Insulation failures are another. 

I can't say it any better than Baldor, a major motor manufacturer.

Here: http://www.google.com/url?sa=t&rct=...zJ0MUslwwcRhQaD3QsmBNOw&bvm=bv.91665533,d.eXYhttp://http://www.google.com/url?sa...zJ0MUslwwcRhQaD3QsmBNOw&bvm=bv.91665533,d.eXY


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## Tambourineman

Yes I read the post at DSLReports by whizkid with care and interest as It was the opposite of my erroneous prior understandings. He sounds like he knows what he's talking about. 

BTW, your link to the Baldor material is messed up. 

The DSLReports thread has good info on the effect on motors.


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## aandpdan

Fixed the link.


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## Tambourineman

Thanks for fixing the link.

I have learned that the THD (harmonic distortion) for the one I bought is 10%. Better generators are only 5%,. but 10% may be useable except for sensitive electronics.

Another key is the ability to keep the voltage up and not let it or the frequency drop below 110v or 50 hz.

Here is a link to an interesting thread on THD levels produced by various types of gennys and the effect on things run off of a generator.

Total Harmonic Distortion and generator heads


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## Tambourineman

My primary two purposes for getting a generator were to run my NG hot water heating sytem in the winter, and my fridge in the summer in case of prolonged power outages.

Here is an article about generators and heating systems. My furnace is at least 25 years old and fairly low tech so hopefully I'll be Ok.

http://support.fluke.com/find-sales/Download/Asset/3497420_6112_ENG_A_W.PDF


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## aandpdan

A 25 year old boiler is likely not computerized so that's not a likely issue. Most of the problems with newer boilers are ignitor related and MOST can be solved by proper installation of a transfer switch/panel.

Good info on the Fluke site, thanks.


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## Tambourineman

Yeah, I am not concerned about the circuitry for the NG furnace/boiler. I am mildly concerned about the fridge as it has an LCD panel. My main concern is for the motors for the hot water circulating pumps and the compressor for the fridge.

I don't understand whizkids comments on how harmonics can destroy motors. I can appreciate that low voltage could destroy them as the windings would heat up and burn the insulation. For a $300 gas/LPG generator I can't complain about a 10% THD rating. I guess there's not much I can do about it. Based on the suggestion for a line conditioner, I looked at a Tripp Lite LC1800 but it does nothing for harmonics. I don't think there is any easy/cheap solution for them other than buying a generator that has low ones to begin with. I haven't done a lot of shopping, but I don't remember anyone even mentioning THD in their ads. But I suppose that's par for the course.

Is there a cheap type of instrument that checks THD?


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## aandpdan

I wouldn't worry about the LCD. It's DC, rectified and filtered.

There are THD analyzers, maybe an electrician has one. Some generators do list the spec, but most do not.

Few people would even think of asking about it.

Do you have an infrared thermometer? Measure the temp of the motor when running on POCO and then check again running on your generator.


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## MarkMannM2

Goodness Gracious! Guys, you are way all over the map on this... You need clean power, most newer electronic devices will do better with cleaner power... Your grandmother's iron is not included... ok... 1. Make sure you have adequate power (primary supply) to support additional circuitry and the device you are trying to get adequate performance from. Rule of thumb 8% to 10% overage for most applications. Consider 12v batteries that can give you back up and smoothly support "pure sine wave circuitry." Even lead-acid car batteries are wonderful at supporting clean output circuitry. 2. The Reason For My Brashness... Oh, have you guys ever considered "Proper Grounding Techniques" in your brilliance? Find a way to strap your source to good earth ground. 2a. chain link fences. 2b. Metalic water pipes... not brass faucets that connect to PVC behind the wall... Lakes, Wet Soil, 8' copper rods in the earth, you know the jazz... 3. Chassis grounding... all or nothing here grasshoppers, audio amp or motor drive using a chassis ground, get on it and use shielding throughout your system... "the complete system." You see my friends, you are only as good as your weakest link so if you have poor grounding and a misunderstanding of which components are utilizing chassis ground and you think a 1" brass water valve connected to 30' of PVC pipe is an ideal ground then you are hereby officially refrained from going near ANY generator or power tool.... FACTOID; old noisy AM RF, the best high power AM stations would use lakes or the sea/ocean as ground planes when positioning their massive antennas. Quiz: Do the vast majority of Laptop manufacturers integrate the chassis ground of the laptop and the external power supply? (find out in our next installment) Be well! MarkMannM2 Technology Tucson, AZ


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## speedy2019

What THD Anyway and what causes the bad wavelengths? I think the main things that will cause damage to stuff is high or real low voltage and the herts being wrong.

Also you say, your gen is 7hp engine and will putout 4400watts, my gen is 8hp engine and will only putout 2800watts?


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## tabora

speedy2019 said:


> Also you say, your gen is 7hp engine and will putout 4400watts, my gen is 8hp engine and will only putout 2800watts?


@speedy2019 his rating is at 120V and yours is at 230V.


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## tabora

MarkMannM2 said:


> Goodness Gracious! Guys, you are way all over the map on this...


Dude, this thread was 5 years old; the technology has changed a lot since then, as has the common level of generator knowledge... But many of us certainly agree about the importance of proper generator grounding!


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## desertratt68

you should be fine its a traditional gen so it it pure sine. the exact frequency is the only isssue. with most household systems thats no problem ( i lived the last 8 years on solar and discovered recently that my inverter was installed with the switch turned to 50 hz and had no issues). but with any gen setup you sshould have a ups for any sensitive electronics


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