RVelectricity – What’s all the noise about generators?

22

By Mike Sokol

Dear Mike,
Are the so called RV-Ready generators any quieter than the contractor generators you’re always talking about? The salesman at the store says they are, but I’m a little leery of spending my hard-earned money on something that’s going to be too loud to use while boondocking. I’ve already added solar panels, but I might need to run a generator for an hour a day to charge my batteries if the sun doesn’t shine. I invested in solar for the quiet, so I can’t imagine listening to a loud generator even for an hour or two every day. I camp to enjoy the peace and quiet, not to hear motors running. Any suggestions on what to look for in a generator? —Sam & Alice

Dear Sam & Alice,
With many of our favorite campgrounds shut down due to COVID-19, lots of you are turning to boondocking for your camping adventures this season. And as you can imagine, that doesn’t mean you’ll be the only one in that neck of the woods. So I think it’s great that you’re thinking about preserving the quiet for everyone else to enjoy as well.

And you’re in luck because I’ve just begun testing several types of generators for noise level. In a few weeks I’ll create a video showing how I test generators for noise pollution and comparing the calibrated noise levels for your own judgment. Note that I am an audio engineer (in addition to a few other things) and teach all about SPL (sound pressure level) and decibel (dB) levels at college level, so I’m well-equipped to measure and discuss them. For a previous article I wrote that includes the extended math of how SPLs are measured, read more HERE.

I break portable generators down into four basic classes, which I’ll discuss briefly here. Note that standard measurement practice is to use a calibrated decibel meter set to the A-weighted scale and slow response, positioned 23 feet (7 meters) away from the generator in an open space.

Contractor generators: These are the cheapest and least desirable class of generator for camping since they generally have no sound insulating panels, and use pretty cheap mufflers. Hey, if you have a bunch of other machinery running at a construction site, what’s a few more dBs of noise in the big picture? However, you can hear these running in the woods from hundreds of yards away, so they’re generally shunned from camping areas. Here’s what the noise specs are for a typical contractor grade generator. I’m showing a Generac 249344 GP Series 3600W for example which is listed as 69 dBA from 23 feet.

“RV Ready” open-frame generators: These so-called RV Ready generators are basically contractor open-frame generators dressed up a bit. They will include a TT-30 outlet, meaning you don’t need a twist-lock adapter to connect it to your shore power cord. And many will include some sort of over-voltage spike protection, which is essentially a surge protector built into their outlets. This one from Champion also has better voltage and frequency regulation than your garden variety contractor genny, as well as an electric start via a remote control, which makes it easy to start from inside your RV when you want to crank up your coffee maker. All are good ideas, but none of them make the generator any quieter to run while boondocking. For example, here’s the info on a Champion 3,500 watt generator with the following noise specifications: From 23 ft., the noise level is 68 dBA.

Inverter generators: While the first two generators are actually dynamos (an AC generator that’s spun at a constant RPM by a gas engine with a speed governor to keep the frequency stead at 60 Hz), inverter generators are actually 3-phase DC alternators which produce around 12 volts DC, then use a built-in pure-sine wave inverter to make 120 volts AC at 60 Hertz. The beauty of this type of technology is that the engine doesn’t have to run at a constant speed. Unlike a dynamo generator that needs to run at 3,600 RPM just to make 60 Hz AC for even at a small load, an inverter generator can be set to an “eco-throttle” mode, which lets the engine idle when not much power is needed, but then rapidly comes up to full speed when more output wattage is required. I’m using the Honda EU3000-I as an example here. It’s rated at 50 dBA noise level with a 1/4 load at 23 feet. But when you get up to 1/2 load the engine speed does increase with a corresponding increase in noise level to around 56 dBA. While the difference between a 68dB SPL contractor generator and a 50dB SPL inverter generator on idle doesn’t look like much on paper, that 18 dB difference is huge, around 63 times as much acoustic noise. And that sounds at least 3 to 4 times louder to the human ear.

CarGenerator™: While not technically a portable generator at all, it’s basically the final part of an inverter generator that makes really clean (less than 3% distortion) pure sine waves. It works by first installing a heavy-duty connector onto the battery of your tow vehicle, and then when you need AC power for an hour or so to charge your RV batteries, you hang the CarGenerator on the front of your car, plug it in, start up your car engine and let it idle. CarGenerator does the rest, making 1,000 to 1,500 watts (depending on the model) of pure sine wave 120 volt AC, which will charge your RV house batteries just as quickly as they can from a typical pedestal power source. That means the CarGenerator isn’t any louder than your tow vehicle while running on idle. Now if you’ve modified your truck’s exhaust system to go vroom, this could be a little louder. But I just measured my Nissan Frontier with a 4.0 Liter V6 engine, and the noise level at 23 ft. is an almost imperceptible 48 dB SPL (for comparison, with the engine off the residual outside noise was just under 46 dB SPL A/Slow). That’s all the louder it will get while powering a CarGenerator. And that’s one of the things I’ll be testing next week. For more information on the CarGenerator please click HERE.

I’ll be doing a calibrated video shoot-out of these types of portable generators in a few weeks, so watch (listen?) for them on my RVelectricity YouTube channel. But in the meantime, here’s a calibrated video I made comparing the noise levels of a Honda EU3000i generator with a typical 3,500-watt contractor generator. Yes, the sound levels between a contractor and inverter generator are really that much different. Stand beside a running inverter generator and you can converse normally. Stand beside a running open-frame contractor generator and you’ll need to shout.

For my tech groupies out there (yes, they do exist), here’s what I’m going to be using to load test these generators in the next few weeks, an Avtron K490 10kW load bank. While I don’t take selfies with too many people, I do take them with my cats and test gear. Ain’t she pretty?

Let’s play safe out there….

(Professor of Sound)

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

For information on how to support RVelectricity and No~Shock~Zone articles, seminars and videos, please click the I Like Mike Campaign.

##RVT945

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Harry
5 months ago

Mike, you should know that small Diesel engines like in the Mercedes Sprinter do not do well idling. They can clog up with soot in as short as 15 minutes. They do best at higher rpms and hot temperatures.
The delivery vans usually have a fast idle option, since they do idle at most stops.
The car generator may not be a good option for this type of vehicles.

Jim Langley
5 months ago
Reply to  Harry

Interesting. We had a Roadtrek Agile SS with a Mercedes diesel Sprinter. Everybody told us it was fine to let it idle. We let it idle all the time, sometimes as long as an hour. We had 3 dogs at the time so we would run the AC from the engine and just let it idle. We never had any problems with the motor.

Benny H Smith
5 months ago

Mike. Enjoyed the comparisons. Feb 2019 we camped in a NavyRV park where they had noise limits at 10 feet of 70db. The generators over 3KW mostly failed including Hondas. The Prediter 3500 from Harbor freight were all over the park because they are quite. And at under $700 the lowest price of any 3.5KW. It starts every time, unlike my Champion duel fuel, which is noticeably louder. I recommend you test this one as well as the better advertise Hondas and Champions.

Sherry L
5 months ago

So most of this is greek to me. Can someone tell me how to run my air conditioner without the all the heat and noise from the rv’s generator? There is so much heat blasting on the ground that it literally turns the grass brown. Can one of these inverter generators work?

Steve
5 months ago
Reply to  Sherry L

Sherry – you have a couple options, but the simplest is a 3000 -3500 watt inverter generator. Honda is a good choice but top dollar. Champion and Yamaha make good units and many like the Harbor Freight Predator 3400 (much less money). The HF Predator is much lower cost. You will need to buy an adapter to match the generator to the trailer plug. I am sure the place you buy the unit from can help you find a small stand to lift the unit off of the ground to eliminate the “brown” grass issue. I don’t think most of the inverter units would not have this problem. Good luck!

Benny H Smith
5 months ago
Reply to  Sherry L

I recommend you buy an up pipe to send the exhaust up and above your rig. That brown grass is a fire hazard. Your RV dealer can help you find one to fit your RV.

K. Martin
5 months ago

Dear Mike,
We have a new cargo trailer ( Traditional 7-prong connector) and a Briggs & Stratton Inverter generator and would like to connect the two in order to run lights already installed in trailer… Is this possible?…Is there a converter that would assist?
It works great when we connect to our SUV from the trailer but would like to incorporate the generator.

Thanks a million for any advice,
Kenneth & Kim

Beverley Lynne Harris
6 months ago

Hi, Mike. Thanks for this article – I’m saving it.
FYI I have recently bought a dual-fuel ( gas/propane) inverter-generator – Firman WH3200IE 0model WH02942 – and so far running it only on propane. Decibel level stated as 58.
Starting watts: 3200 gas/2900 LPG
Running watts: 2900 gas/2600 LPG

Pleased with it. No more jerry cans.
Any experience or or observations you would share about this make/model??

Steve S.
6 months ago

Beverley, is this sufficient to start and run an A/C unit in your rig? TIA.

Max
6 months ago

If you want quiet and dependable electric power, stay away from any unit run by a lawnmower engine. There is little you can do to quiet an engine screaming away at 3600 rpm. At full load it is similar to driving 100 mph. Up hill. Pulling a trailer. These little aluminum engines only hold a quart of oil (or less). A small engine working that hard is simply not going to last.
Better generators (Onan, Kohler) are made to run at 1800 rpm. They generally hold several quarts of oil. You will pay considerably more for one of those, but you won’t have to buy a new one every few years. Running at half the speed of a typical (cheap) unit, they are considerably quieter.
Inverter units have limited output. True RV units are available up to 10 KW.
Their lack of inclusion in this article leaves me wondering how much the author really knows about generators.

Mike Sokol
6 months ago
Reply to  Max

This article was about selecting portable generators for boondocking, not about the 10-12 kilowatt generators already installed in coaches. What more do you think I should have included on this topic? BTW I often spec and connect large 3-phase generators in excess of 50,000 watts for large concerts and shows. And I’ve supervised a few large industrial backup generator installations.

Steve S.
6 months ago
Reply to  Max

Max, as he indicated at the very top of the article: “In a few weeks I’ll create a video showing how I test generators for noise pollution and comparing the calibrated noise levels for your own judgment.” This was never intended as an all-inclusive article.

He also provided a link to previous articles that provide detailed information about generators. Did you bother to click on the link to find out the additional information?

Your lack of observation leaves me wondering how much you are interested in learning about generators vs. how much all you want to do is denigrate the author.

Tommy Molnar
6 months ago

I’ve got 700 watts of solar on our trailer roof and they handle all we need. But, from some rough experiences, I never leave home without my trusty Champion 2000 watter between October and May.

Ernie
6 months ago

Will you also cover the noise that two smaller generators produce? I had the option to buy 2 2000 watt units that could be coupled to double their output, but went with a single 4500 watt Westinghouse unit that is very quiet. The only problem is that it weighs 100lbs and is tough to lug around. So, now I wonder if two smaller, lighter units would have been a better decision.

Wayne
6 months ago
Reply to  Ernie

I was camped next to a set of paired 2000w Honda’s running an air conditioner and the exhaust fumes were bad enough that I decided to move my camp farther away. It seemed to me the exhaust was much worse than my Honda 3000 but I have no way to measure that.

Steve
5 months ago
Reply to  Wayne

Wayne, That is an interesting consideration. I am putting a carrier on my 5th wheel and will be carrying a Predator 3400 inverter. I am going to be looking at a way to add a “exhaust” pipe going vertical to get the exhaust higher and hopefully being quieter.

But your exhaust question / comment is something that needs to be considered.

Dan
6 months ago

Now if someone will just offer an inverter style generator to replace that nasty green belch fire Onan boat anchor in our little RV, the world would be a better place for everyone. Quieter too. In all fairness the Onan does do a good job, about three fourth’s of the time, but when it does run, everyone nearby can hear it. Oh, and is it time to change the spark plug and oil and filter? Dont plan anything else that day. I have to wonder why the RV manufacturers put such junk in an expensive toy like that. We’ve owned three of them, all conspicuously loud, and not totally reliable. Same for that cheap Dometic refrigerator that is soon to be replaced by a small Fridgedaire from a big box store. At least if it fails I can pull it out and put in a new one in a couple hours for less than $250.00.

Max
6 months ago
Reply to  Dan

Sounds like your Onan needs a tuneup and a new muffler. Unless it’s one of their cheaper ones that runs at 3600 rpm. Once Onan was bought out by Cummins, they went down hill from the quality brand they once were.

tom
6 months ago

contractor gensets are cheap for a reason. When we have a hurricane event, you can hear them from the next neighborhood.
Love my inverter set.