Dual fuel portable generators question

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Tozguy

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My 20 some year old gas generator is too noisy. I want to replace it with dual fuel one (gas/propane) that is a bit more powerful and more QUIET! Been doing lots of research but there is one answer that still eludes me.

Since the continuous run watts is derated when run on propane, would you expect that it would also be more quiet when running on propane than when running on gasoline?

If anyone who has run a dual fuel generator wants to share their thoughts in general on owning one it would be much appreciated.
 
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Car engines run on LPG are no less noisy than on petrol, so I don't think you're going to gain much there.
 
Awh shucks! Was wishing mine was not just wishful thinking.:)
Thanks for the replies.
 
You can buy a generator from harbor freight that will be a loud rattle box, or buy a Honda of similar size that will be relatively quiet. I think it has more to do with muffler design, build quality, and exterior shrouding than fuel type.
 
I would agree with Barncat's assessment. We're currently having a lawn service doing our yard work since I'm temporarily unable.. For mowing the lawn they use a 20+ hp propane powered mower. While it probably burns a little cleaner than my 22 hp John Deere it makes just as much noise.

As for generators we've had 3 over the years. One is and older (circa 1980) Pincor 3,000 watt I originally bought when building a couple houses. It runs fine, but is an annoying screamer. The muffler is nothing more than something you'd expect to find on a Briggs & Stratton lawn mower engine. Our newest one is a 2013 Cummins/Onan 5500 watt. Mechanically it's much more quiet than the Pincor, and it has a muffler similar in size to the one on my JD. You can stand within 3 feet of it and carry on a conversation in a normal tone of voice.

The one I wish I still had is a Kohler 3,000 watt. It was the same vintage as the Pincor, but looking back was much better built, and far more quiet. The only downside was that it was unbelievably heavy. While it was supposed to be "portable" it was on it's own self contained skid, and took at least 2 strong men to move it. After moving it around from site to site for a couple years I got so tired of the weight I traded it off for the Pincor. That was a mistake. Not only was the Kohler much more quiet it had a "demand cycle". The engine would idle down when there was no load. Just a low rumble in the background. As soon as the "demand circuit" sensed a power draw it would come up to speed and remain at speed until there was no longer a demand.

I would look for something powered either by a Honda, Cummins/Onan, Suzuki, or Kohler. Over the years I've had over 50 pieces of portable equipment powered by just about every make of gasoline engine on the market. The longest lasting, quietist, lowest maintenance, most dependable were powered by these brand engines.

I'm not sure if Suzuki ever entered the generator market, but I have 2 small tractors powered by their 22 hp, twin cylinder, water cooled engines. They're both about 20 years old and as dependable as they come. They both start easily in temperatures ranging from -20F to 90+F and run all day long with minimal fuel consumption, plenty of power, and minimal maintenance. Small engines have come a long way in the last 30 years. The quality ones are still more expensive, but well worth the money in the long run.
 
I have had a Generac 17,000 watt unit for 11 years as an emergency backup. It uses a Generac 2 cylinder engine that runs on natural gas (can be run on LP with adjustments). It automatically runs once a week for exercise and oiling. It's about the same noise level as a quality large engined riding mower running against the governor but not driving the blades. It has run during power outages (at least four times a year, once for four days straight) during the time I've owned it without any troubles what so ever.
 
I have identical equipment that is powered by gas and propane. Their is no difference in engine noises. Muffler is still the same so noise will not change. A propane engine will burn more fuel than a gas engine. It will burn cleaner and servicing the oil will be cleaner. Oil will look just like when put in. No carbon great thing is you won’t have to worry about bad gas. Propane doesn’t degrade like gas. One could always add a better muffler. IMO Honda makes the quietest gens.
 
You didn't say how many watts you need. I have a Honda EU3000is, it is one of the quietest generators on the market (49 db).

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They went to great lengths to soundproof the enclosure etc. It is also extremely fuel efficient, but I don't believe that Honda is making dual-fuel generators.
 
I don't have a "multi-fuel" gen set, so can be ignored if you want. I do have a 6.5 KW Honda (ex professional) for my residence and shop. And as an electrician, I have worked with many gen sets over the years. And always recommend that a generator be derated up front even for gasoline fueled machines.

50% is a good, albeit conservative, rating. My 6.5 KW plant actually runs around 60% worst case full load. That's with a 220 Amp welder, the kitchen range, and a cloths dryer all running. If you have a worst case full load of 2 KW, it is a good move to use a 3 or 3.5 KW, or higher, gen set. They should never be tasked with a full 100% load. That excludes the "surge" rating which is for motor starting and the like. Derating even further for alternative fuel.

Noise is a whole different "ball of wax". Propane or natural gas, while cleaner, isn't really a factor in noise. There is the mechanical noise of "explosions" as the fuel is ignited in the cylinder(s) and from vibration of the engine and frame. A good exhaust system and muffler will do more to reduce noise levels than changing fuels. There is also the "drumming" of sheet metal panels on the frame.

Using even a motorcycle muffler will make a world of difference in noise levels. And a random crease or bracing for flat sheet panels. Most "low end" gen sets are low end because of cost saving measures when they are assembled. That includes the "muffler" that is often no better than a cheap lawn mower damper to reduce the "bark" of the exhaust to a more tolerable level. Look for external noise suppression and full load capacity as the cause of noise.

Most generators run as 2 pole machines. Hence, the engine needs to run at 3600 RPM. That is fixed to get 60 cycles. I have an old riding lawnmower, a JD 216, that has a retrofit 2 pole generator running off the PTO. By using a belt "reduction". actually increasing speed, allows the Kohler engine to run slower than 3600 RPM. Lower W&T on the engine, lower noise, &c. Though with a direct drive plant, such is not an option. The JD is experimental and I allow for 10% variation of frequency. I may use a freq. meter to get a finer adjustment later. When I get a "round tuit".

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