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Author Topic: small air cooled gen sets, I know they are noisy, but how noisy?  (Read 2405 times)
zubzub
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« on: November 15, 2007, 08:20:39 AM »

I noticed a kohler maybe 5kw gen set for sale.  I need to get some extra power for my drive home, looked around at the 3.5 kw gen sets, that's all I want, but this one is older and cheaper and more powerful.  My question basically is how noisy is a kohler?  Seems this one came out of a motor home, so it can't be that bad, I'm also looking at a slightly used 3kw porter cable, which will do the trick (power my tools, charge the batteries until I can fix the charging sysytem etc..)It is almost new,looks cheap but what do i know from generators.  I presume the liquid cooled gen sets are the quietes longest lasting ones, but I really just need reasonable back up power.  The kohler also has the advantage of electric start.  I have read here to buy onan or kohler, but I have also read that the onan air cooled is noisy, is the kohler just as bad?  Bit a a ramble, trying to get my stuff together for road trip next week, Patrick.
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« Reply #1 on: November 15, 2007, 08:44:49 AM »

I have had a couple of Onan 4kw's that I did not think were that noisy.  This is not expressed with any scientific data, but the 3.5 Generac I once had seemed worse.  I found that routing the exhaust somewhere, like with an appropriate hose, really helped too.
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« Reply #2 on: November 15, 2007, 09:07:13 AM »

I had an Onan 2.5kw from my 73 winnie.  Exhaust was quiet with the rv muffler, but the mechanical noise was significant.  I also had for my home a Campbel Housfeld 4kw unit that could be heard from 3 counties away.  Stay away from Briggs and Strattons for noise!  The same probably goes for Techumseh's as well.  I ended up with an old Kohler 4cylinder 7.5kw that may have been a marine application - mine is gold in color, but I have seen the same one painted white for marine applications.  Mine does have a water cooled exhaust manifold.  This thing runs so smooth!  Mechanical noise is negligible, easily boxed and currently has 2 small auto mufflers.  I paid 450.00 for it on Craigslist.

Glenn
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« Reply #3 on: November 15, 2007, 09:17:08 AM »

Me too,

My old 6.5 Onan was not bad and it wasn't in a box and the muffler was not very large.  You need 5.5 to comfortably run one ac unit.  I think that 5.5 would give you a min of flexability.

mtc,

John
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« Reply #4 on: November 15, 2007, 09:24:44 AM »

3K @ 120v = 25 amps. Plenty to start and run 1 AC.
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« Reply #5 on: November 15, 2007, 09:29:40 AM »

While the Diesels are much quieter then they used to be, a 3600rpm unit will be noisy-with as stated alot of mechanical noise.  If you could go with water cooled, that would be substantially quieter.  In my opinion, a 3600rpm water cooled Diesel will last long enough where you don't need the size and bulk of a 1800rpm unit.  Along with building a suitably quiet enclosure, a 3600rpm would be sufficient for 10,000 hrs of use.  Considering that my big 10kw Powertech has only about 700 hrs on it (like 28,000 miles on a car) and the fact that you can get over 20,000 hrs out of the Kubota engine, the 3,600rpm is looking better all the time (less money and weight).  Good Luck, TomC

PS-Redbus- 3k is NOT enough to start an A/C.  Typically you should have twice the capacity on the generator to start the A/C from the surge that is necessary to kick start the compressor-it is enough to run it though-but starting it can be a problem.  The suggested 5.5, even a 4.0 can start and run one full size A/C.  Good Luck, TomC
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« Reply #6 on: November 15, 2007, 09:39:02 AM »

If A 13,500 AC pulls more than 25 amps to start it has problems. I used a 2000 Honda for 2 years before I got my new genny, it would start 1 AC o-k but nothing else.
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makemineatwostroke
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« Reply #7 on: November 15, 2007, 10:21:45 AM »

Tom C if thats true why do they install the 2800w onan in some of the motorhomes with 1 AC and microwave
« Last Edit: November 15, 2007, 12:29:05 PM by makemineatwostroke » Logged
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« Reply #8 on: November 15, 2007, 01:08:20 PM »

What I have discovered is just because it is installed in some El Cheapo sticks and staples, doesn't mean it will work in every circumstance.  And many times those smaller gens are only powering a 11,000 or even smaller A/C.  When you're that close to capacity, anything varying, like being high altitude, on a over 100 degree weather day, dry humidity, air cleaner a bit dirty, etc., and you'll have a generator that will be running slow (and creating lots of electrical heat in the appliances), might not even start the A/C in hot weather, and at altitude, stall when it kicks on.  On my over the road truck, I had a 6.5 Onan 2 cylinder 1800rpm commercial gen.  I was up at 9000ft elevation in Colorado, and the gen had a really hard time running the A/C in my sleeper.  I had to goof with the carb settings, it stalled a couple of times, and even went into a knocking seizure. The normal rule of thumb is to have triple the generating amps for the running amps of the A/C.  So if you have a 15 amp running A/C, you should have a 45 amp generator-which works out to be 5400 watts.  You can run a smaller gen, but in my opinion, and this after running smaller gens, it is not worth the headache.   Good Luck, TomC
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« Reply #9 on: November 15, 2007, 01:23:09 PM »

One thing you should do before buying is to test the gen set.  If not possible, then essentially you may be taking a risk purchasing something that may or may not work for you.  Everything is kinda relative--if the APU does what you want it to do, good, if not, well, heck.  One takes a chance.

You would think that a certain sized gen set would start at least one A/C.  Well, maybe it will, maybe it won't.  Too many variables like condition, age, temperature, altitude, (how high are you?) both with the APU and what you want to run.  Crazy combinations of situations occur.  Are we still having fun?

The amount of noise the thing is going to produce is also very relative.  I for one am very middle age (do I mean OLD?) and am quite deaf in my left ear.  Long ago and far away.  What for me is quiet is for others quite intolerable.  I can't hear high pitched noise at all, but can still hear low sounds.  Good luck.  Smiley Smiley Smiley
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makemineatwostroke
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« Reply #10 on: November 15, 2007, 01:27:03 PM »

Tom C I live it AZ and have a 13,500 Carrier and a 2800 onan on our S&S that we use for short trips like to Vegas and other places and have never had a problem with 120 degree heat and for high elevation it has setting on the carb that i have never used yet
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« Reply #11 on: November 15, 2007, 05:15:28 PM »

Tom,

I read all the warnings about 3600 rpm generators but bought a Honda EV6000 which is gas powered, water cooled and 3600 rpm. It is quiet and smooth, if I extended the exhaust pipe a bit I probably couldn't hear it. The best part is it costs half what a diesel WC does and I will never live long enough to wear it out in my bus. I figured that if Honda can makesmooth running 6000 rpm cycle engines that 3600 would be no problem for them. Besides, how can you beat Honda quality?

My old gas Onan air cooled 1800 rpm gen was a very noisy, shaking monster that weighed double what the Honda does. It shook the whole bus even though it was on 3" rubber cushions.
« Last Edit: November 16, 2007, 07:14:41 PM by gus » Logged

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« Reply #12 on: November 15, 2007, 05:25:35 PM »

We had a 2.8 Onan installed in our last fifth wheel.  It was noisy but not near as noisy as the contractor's Kubota unit that the previous owner put in our bus.  FWIW, the 2.8 started our 13,500 roof air just fine.  Except for when we really needed it on Boca Beach about a day south of Mazatlan.  Down there the compressor would kick in and the little Onan would die on the spot.

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« Reply #13 on: November 15, 2007, 07:43:35 PM »

I have a 3500 Coleman with a B&S I believe. I had both ends rebuilt. I don't think it's that noisy for a neighbor hater. Inside it's not bad at all and that's what really counts. I hate it and can't wait to replace it but for now I'll live with it.
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« Reply #14 on: November 15, 2007, 10:21:39 PM »

I think Honda anything is great (hate to say it since I prefer American made-course alot of Honda stuff is made here in the USA now).  Honda takes their 6000 water cooled and mounts it in a sound proof box for the studios.  The guys with the dressing room trailers mount the gen on an extended hitch in the front of the trailer.  When it is running, you can't hear it until you're right on top of it, and then it just sounds like a room air conditioner running-truly amazing. 
Panda generators makes 3600rpm water cooled Diesels for both boats and RV's that also are about as quiet as an air conditioner.  Proof positive that a quiet 3600rpm gen can be made.  When I do my next conversion, I'll probably use a Panda (even though they are expensive)  Good Luck, TomC
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« Reply #15 on: November 16, 2007, 05:39:11 AM »

If A 13,500 AC pulls more than 25 amps to start it has problems. I used a 2000 Honda for 2 years before I got my new genny, it would start 1 AC o-k but nothing else.

Hi Red,

It is not uncommon for a RV A/C to pull 3 times it's normal running amps during start up.
The normal would be 13/14 running amps, so that would be over 40 amps at start but briefly..
At worse, over a long period of time you could damage either the A/C or the genset if the gen is only rated at 3000w.
Good Luck
Nick-
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« Reply #16 on: November 16, 2007, 07:46:40 AM »

I have a pd4903 with 2 13,000 a.c. I use two honda 3000su hooked together to run every thing on bus. I just speent a week in Terlingua tx,in the desert, no hook up and had no problems. These gen sets are very quiet. Several of the 5000 or so campers at the chili cookoff came by and admired the set up. Combined, they put out 5500 watts. run 14 hrs on 2.5 gal fuel. Nearly pure sine wave for you computer guys. Honda now sells a 6000 watt su .Were not available when I bought mine. If you go this way, E-mail me. I can save you some problems. I am a Kubota dealer, but I bought honda!
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