Generators, nat gas: Noise?

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. I thought natural gas-powered standby generators would purr.... apparently not.
Two smaller Generacs:
http://www.youtube.com/watch?v=_cJX8M2VvKk

http://www.youtube.com/watch?NR=1&v
1e3I1eoNU&feature=endscreen Guy yaks until 0:50
Here's a quiet one, but much larger (an Onan, apparently):
http://www.youtube.com/watch?feature=endscreen&v=KHN3sZe9xGo&NR=1

The Generac I'm looking at is their smallest. A few brands of the approx 7 kW size are here: http://www.electricgeneratorsdirect.com/quick_search.php
The Generac CorePower 5837 is the cheapest, lightest of the bunch. It uses a single cylinder approx 400c engine, at 3600 rpm.
The Briggs/Stratton is TWO cylinder, but apparently noisier, from the specs (81 db vs. 62 db -- if those db are accurate), and from a cupla reviews -- if you can trust reviews. I'm wondering how much of the noise is exhaust noise, how much is just "unit noise" -- engine clanking, fans, etc.
I'm thinking of keeping mine inside (theft, consideration of neighbors) -- is it generally straightforward to hose-clamp a metal flex hose to a tailpipe? IS there a tailpipe on the small units to clamp to?
Any experience with these types of units, brands? Recommendations?
--
EA



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Existential Angst wrote:

They are as loud as any typical small air cooled engine. If you want quiet you have to move up to a commercial grade liquid cooled model.

Most noise from a small air cooled engine is from other than the exhaust, thus a good muffler does little to quiet them.

Inside is a bad idea unless you build it into a sealed externally vented space with CO detectors adjacent.

Go look at the display unit in any 'Depot or Lowe's. I believe there is a stub of tailpipe sticking out of the housing.

The home standby units are intended for just that, home standby. They are not remotely close in construction to the commercial grade units even in the sizes where the residential and commercial models overlap in rated capacity. They will do the job, but will not last through very many long outages, especially if loaded near capacity. If they are sized to run perhaps half load, are well maintained and typical outages are only a few hours duration they are fine. If you are in a rural area and days long outages are common invest in a commercial grade unit.
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They are as loud as any typical small air cooled engine. If you want quiet you have to move up to a commercial grade liquid cooled model.
CY: Neat, didn't know that.

Most noise from a small air cooled engine is from other than the exhaust, thus a good muffler does little to quiet them.
CY: Years ago, I read of a Tecumseh "lo tone" muffler that helped a lot.

Inside is a bad idea unless you build it into a sealed externally vented space with CO detectors adjacent.
CY: I've heard of people killed by running a generator indoors, even "in the cellar with the door open".

Go look at the display unit in any 'Depot or Lowe's. I believe there is a stub of tailpipe sticking out of the housing.
CY: Years ago, BS engines used to thread to the muffler via 1/2 inch pipe thread.

The home standby units are intended for just that, home standby. They are not remotely close in construction to the commercial grade units even in the sizes where the residential and commercial models overlap in rated capacity. They will do the job, but will not last through very many long outages, especially if loaded near capacity. If they are sized to run perhaps half load, are well maintained and typical outages are only a few hours duration they are fine. If you are in a rural area and days long outages are common invest in a commercial grade unit.
CY: I just had a virus, and lost hard drive, and a lot of emails. So, I can't quote my source. I did read one time from a woman who used generator for power, for well and such on her farm. The consumer model Coleman only lasted a few hundred hours. Typical consumer with a couple hours a year, a machine designed for 200 hours is plenty. She finally bought a Honda, which lasted a lot longer.
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On Dec 20, 10:49 am, "Stormin Mormon"

1800 RPM is far quieter than 3600 RPM..
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Air cooled versus liquid cooled has naught to do with what kind of fuel it takes.
Christopher A. Young Learn more about Jesus www.lds.org .

I wouldn't expect the same engine to have any significant difference in noise based on what fuel you put in it. You do get about 20% less power out of the same engine if it runs on nat gas versus gasoline. That should equate to some difference in noise, but doubt it's significant.
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I have one of those old engines on my 1950's reel lawnmower. I couldn't find the proper muffler so I screwed in a stainless gas appliance flex hose and ran it around to a larger generic replacement muffler. The exhaust note is low pitched like a car and barely audible above the mechanical noise.
jsw
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Reel good solution.
Christopher A. Young Learn more about Jesus www.lds.org .
I have one of those old engines on my 1950's reel lawnmower. I couldn't find the proper muffler so I screwed in a stainless gas appliance flex hose and ran it around to a larger generic replacement muffler. The exhaust note is low pitched like a car and barely audible above the mechanical noise.
jsw
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I made a free-standing external generator muffler from a 2" to 1-1/4" reducer, a short 1-1/4" nipple and a 2' length of fiberglass pipe insulation that hose-clamps to the nipple. It mounts on 3/8-16 threaded rod via a pipe hanger clamp.
Making it separate avoids any wear or damage from the vibration of the engine. It's very effective at quieting the exhaust putt-putt but does nothing for the loud mechanical noise which I think radiates from the cooling fins. Maybe a bead of silicone caulk down the corners will help?
The sound of an unloaded Honda EU2000 hardly changes if I cup my hand over the exhaust. I checked because I'm trying to quiet my Coleman genny to approximate it with a box made from fireproof acoustic ceiling tile, open on the back side. So far it's promising but not perfect.
jsw
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I wouldn't expect the same engine to have any significant difference in noise based on what fuel you put in it. You do get about 20% less power out of the same engine if it runs on nat gas versus gasoline. That should equate to some difference in noise, but doubt it's significant.

Not sure how much of the noise comes from where. I've have seen some Honda portable generators though that were very quiet compared to low end Chinese ones.

This was discussed here a couple months ago. Someone posted the requirements for indoor generators for their location, ie fireproofing, venting, detection, etc and it was so tough that for all practical purposes you could forget about it for a typical residential application. Don't know what other locations codes are, but I'd suspect it isn't going to be easy. But before going down the in-house road, I would check the local codes.

A neighbor here had a $7K Generac that was about 5 years old. It ran for 4 hours during the hurricane in August, then quit. Company that installed it told him it was shot and not worth fixing.
If I were looking for emergency power, I'd go with one of the portable units. There are some that are available that run on nat gas. Or there are kits available to make most of them into either permanent nat gas or even tri-fuel units that can use gasoline, nat gas, or propane. One of those together with an inlet and lockout breaker arrangement from Interlockit is what I would use. You can have the inlet installed outside, nat gas line available and just move the generator there when needed. And if that generator fails, you can buy a whole new one for a fraction of the price of the standby units. The generator is also available for other use if needed. I could put the above together for $1000
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Air cooled versus liquid cooled has naught to do with what kind of fuel it takes.
Christopher A. Young Learn more about Jesus www.lds.org .

I wouldn't expect the same engine to have any significant difference in noise based on what fuel you put in it. You do get about 20% less power out of the same engine if it runs on nat gas versus gasoline. That should equate to some difference in noise, but doubt it's significant.
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#2 Heat has a lower Cetane rating, and lacks many additives, such as the ones that lubed the injection pump.
I know the newer auto/truck pumps must cope, since the low sulphur is no help. Not sure about gensets.
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& no one will talk to a host that's close........[v].(301) 56-LINUX
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typed in rec.crafts.metalworking the following:

    Goes for other stuff too. Lady friend wants a treadle sewing machine. (It does one stitch, and it goes no faster than she can handle.) We found a beaut in thrift shop, but it turned out to be a decorative reproduction. It might have been fixable, but we're on a short budget this month.     But the folks running the store, they knew of one, at a different store "ask there - tell them Jim sent ya."     OTOH, the other store, isn't there, but the one we did drop in on, had some really neat stuff. I went back for some Christmas Shopping.

    I'll keep that in mind.
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pyotr
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snipped-for-privacy@mindspring.com says...

Hey, Pyotr, just a heads up but keep watching <http://www.proxibid.com/asp/AuctionsByCompany.asp?ahidS49 . We've got a 1920s vintage Singer treadle machine that we'll be auctioning at some point.
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typed in rec.crafts.metalworking the following:

    I'm doomed B-)
tschus pyotr
Girlfriends, they start making you do weird thing. Wear Clean Clothes. Take baths regular like. Take out the garbage when it isn't even spring yet!
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pyotr
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Existential Angst wrote:

Keeping the unit inside is a good idea. Until you need it. At that point, roll it outside. Don't forget the thing was DESIGNED to work in inclement weather.
The only thing a quiet model provides is the ability to better hear your neighbors' generators.
Extending the tailpipe increases the back-pressure on the motor. If the extension is long enough (and I have no idea how long "long enough" is), the motor won't run.
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<G> There's a reason there are "tuned" exhausts, and large diameter pipes.
<G>
LLoyd
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> fired this volley in

BTW... I wasn't being snide of facetious. How do you think large auto repair facilities get exhaust fumes away from cars in service or being tested?
They do it with LONG exhaust hoses designed to purpose.
The length isn't very important if it's: 1) large enough, or 2) tuned to the rpm at which the engine is running.
I know this might not make sense unless you understand the geometry, but running an exhaust pipe out to open air IS running it into a long exhaust pipe. The particular "pipe" happens to be very, very large in diameter, but also very, very long. And it doesn't cause the engine to stop.
LLoyd
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> fired this volley in

OR facetious
<G>
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"Lloyd E. Sponenburgh" <lloydspinsidemindspring.com> wrote in message

And a suction fan. :)
--
EA


>
> LLoyd
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On 12/20/2011 12:39 PM, Existential Angst wrote:

A very LARGE fan. I've worked in many shops that have these.
--
Steve Barker
remove the "not" from my address to email
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