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Old 10-25-2007, 11:58 AM   #1
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Why are Honda Generators quiet?

Hi guys,

Question: Why are the Honda generators so much quieter than the contractor types? Is it simply the mufflers? Could you not put a good muffler on a Coleman and have quiet power at 1/3 the price?

Or is there more to it? Vibration, etc.?

As well, I know this question has been beaten on here before, but is 2000 watts enough? I was talking to my dad about it; his buddy powers his a/c with an EU2000i Honda. Says it does just fine. Well, do the math and the a/c pulls 11.4 amps which at 120v gives you 1368 watts. That's about 68% capacity on the 2000 watt generator, so why not? I thought I'd read on here not to do that, that you'd burn up the a/c. I never questioned it until I talked to Dad. Dad say "Why? you've got more than enough power." You can't run the microwave and the a/c at the same time, but you can run the TV and the a/c. So why do you need more than the 2000? Or is it just that you're running at too high a percentage of the capacity of the generator?

Thanks,
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Old 10-25-2007, 12:08 PM   #2
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Hi Jim -- We'll need a more expert statement from an RV tech. Yes, I've also heard that the steady draw is lower like you mention. It's always said that the compressor draws around 22 amps at startup. It strains if not provided that amount of current and that leads to the damage. Of course the compressor comes on frequently in response to demand from the thermostat.
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Old 10-25-2007, 12:19 PM   #3
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Part of it is the muffler and there is a whole science dedicated to canceling sound as it passes thru a muffler. Witness some cars which you can hardly hear running even though the engine is producing the same exhaust noise as it exits the engine cylinders. Put a performance exhaust on it and it almost always increases sound.

Nonethe less, a good portion of the reduced sound can be attributed to the case around the whole generator. When I studied acoustics in college, the professor had a demonstration where he had an electric ringing bell. He would turn the bell on....loud loud.... then he would put a coffee can over it....quiet! Thus, noise contained.
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Old 10-25-2007, 01:35 PM   #4
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Why are Honda Generators so quiet

Here goes:
The contractor generator that you can hear three houses away are built using old technology, that is they are a two pole generator and as such must turn 3600 Revolutions Per Minute (RPMS) inorder to put out 60 cycle Alternating Current (AC) electricity. (Speed is Constant, 3600 rpms)

The Honda is an "inverter" type generator. This is how they work.
There is a permanet magnet alernator on the end of the motor crankshaft. It puts out an infinately variable frequency AC. It is also a multiple phase device. Probably 6 phase or more.
Each phase is rectified and filtered (converted to Direct Current [DC]) and applied to a DC BUSS. I have no idea what the buss voltage is. On a Variable Frequency Drive (VFD) it is as low as 400 volts.
This other end of the BUSS is connected to the inverter input terminals. The inverter takes the DC voltage/current and ELECTRONICALLY creates the 60 cycle AC (Pure Sine Wave I understand).
This is why three things are possible:
1. With the interconnect cable you are able to hook up two 2KW Honda Generators and have a 4KW power source.
2. The Kawasaki Inverter with the battery start actually uses power from the battery to "boost" power output above the rating to start larger electric motors when needed.
3. The generator is so quied because the muffler and the engine is designed to be quiet and the engine speed is no longer tied to the output frequency of the generator.
Speed is not Constant.
At low power requirements the generator is very quiet and the gasoline engine is running very slow. When the power requirements go up so does the RPM of the gasoline engine.
Hope this helps.
Hope I haven't put anyone too sleep.
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Old 10-25-2007, 01:40 PM   #5
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generator ratings & A/C

I saw somewhere (I couldn't find it again, duh!) when researching generator ratings the Yamaha 2400 w. gen/inv would be ok for an A/C, but I don't think it said what size. My gut reaction is it would be ok for a 10 k BTU, but not 13.5 k BTU. When I see 2400 w at 120 v., I get 20 amps for surge. Since I don't have the trailer yet, I can't look on the plate to see the surge amps. Seems to me when you're 10% below the rating (based on Canoe's 22 amp figure), you cause slow, but sure, damage to the A/C and/or generator.

Also the Yamaha info online seemed to say the 2400 w. was really a 2000 w with 2400 surge capacity. If that's true, why not buy a 2000 w Honda (46.3 lbs. vs. Yamaha at 70 lbs)? Honda was about $40 cheaper too. The 1000 w. sound ratings were about 10 db less for the Yamaha which, I think, means half the noise for a Yamaha.

Seems like a 2000 w will run just about anything except A/C. A 3000 w will do that too, but is 100+ lbs. (and cost something like 50% more) and something between might do A/C but isn't made unless the Yamaha 2400 can.

The more I learn, the less I know.

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Old 10-25-2007, 01:48 PM   #6
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I was at a major golf tournament a couple of weeks ago and there were 3 Honda 3000's running. I could not believe how quiet they were. From about 10 feet away you could hardly hear them. Amazing!
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Old 10-25-2007, 01:57 PM   #7
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Quote:
Originally Posted by CanoeStream
Hi Jim -- We'll need a more expert statement from an RV tech. Yes, I've also heard that the steady draw is lower like you mention. It's always said that the compressor draws around 22 amps at startup. It strains if not provided that amount of current and that leads to the damage. Of course the compressor comes on frequently in response to demand from the thermostat.
Your home ac unit is marked with Start Up Amps, Run Amps, and Locked Rotor Amps I think if you look up the specifications for the RV the draw should be listed. The Lock Rotor Amps are when the compressor is locked up; you do not want to go there. Generators like to be loaded so running at 60 or 80 percent of capacity should be no problem.

The EU2000I is listed as: Specifications - Honda EU2000i Generator and Honda EU1000i Generator
120V
2000W max. (16.7A)
1600W rated (13.3A


Max at 16.7A seems a little low for a 22 or 20 amp start load. Something has to give more than likely the AC.
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Old 10-25-2007, 02:43 PM   #8
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Jim,
Ah, ran through this when deciding on my generator. The long and the short of it is a Honda 2000 MIGHT work. For a 31' Airstream I think it's pretty marginal. As others have stated it's not running the AC that's the problem but STARTING the AC. The startup current is much higher than after it's running. How much startup current for your AC; that's the big unknown. Besides the actual BTU of the AC (which isn't always easy to determine) it depends a lot on the motor start capacitor. Some ACs have what's called and "easy start" kit installed which is as I understand it not much more than an oversized capacitor. Other things to take into consideration are:

How old the unit is (capacitors dry out and lose effectiveness with age and an older compressor may just take more amps to turn over).

What's the outside temperature? This can be a biggy. The current draw goes up as the temperature rises and who needs an AC when it's cold

How long (and what gage) is the power cord plugged into the generator. That can suck an amazing amount of power if you're not careful.

What altitude will you want to run at? Generally speaking the power of the gasoline motor on the generator decreases with an increase in altitude. This will most likely derate the watts the generator is capable of producing.

What else to you expect to be running? If your fridge is like mine (a dumb Dometic 3-way) it automatically switches to A/C power whenever its available (no user input required or possible). It's also quite likely the inverter will be pulling juice to recharge the trailer battery.

All in all what it keeps coming down to is a Honda 2000 might, might not work for you. There's plenty of examples of people using them and working out great but that's generally in trailers 24' and under. There's also examples of people that tried it and it didn't work. Then what?? Sell the Honda and buy a bigger one or buy an addtional eu2000 and the parallel kit?

If you want to be sure that it will work I'd be looking at something bigger. People keep thinking you have to make the jump from 2000 up to 3000 watts. Not true. I bought a Yamaha ef2800i which I'm very happy with. It wieghs in at just under 70 pounds and while not as quite as the Honda 2000 it's by no means objectionably loud. For one thing it's usually loafing along at idle. It lacks the shrouding of the Honda eu2000 or the Yamaha ef2400 but that makes it easier to access. I have the parts to convert to propane but haven't done it yet. Not having to deal with removing and cutting the shrouds was a plus for me. I also figure a "dog house" could be fashioned fairly easily that would cut the sound dramatically and double as a storage container; another project I haven't done yet

Consider this when sizing a generator. What other uses do you have for the unit? I for one wanted back-up power for the house. As luck would have it ours arrived last winter a couple of days before a major windstorm that knocked out power for a week. The 2800 was able to run two household refigerators and the fan for the gas furnace plus lights, etc. If we wanted the microwave we had to unplug the fridge but for whole house use the 2800 is about as small as I'd want to go.

Someone else already touched on the 3600rpm constant speed thing of the "contractor" cheapo generators. Note that units like the Honda EU series and the Yamaha EF series that use an inverter have a "smart throttle" or "economy mode" where they match engine speed to load. What this means is that a Honda 3000 running a half capacity (i.e. 1500 watts) is going to be quiter by quite a bit than the eu2000 running almost flat out. It's also going to have a much longer run time since it has a larger gas tank. Think about how often you want to shut everything off. Refuel and restart the generator and then go back and turn everything back on. This can get old in a hurry!

The other big factor with the invertor type generator is that they produce "clean" power. That is to say there aren't a lot of spikes and voltage sag which you will get with the contractor type units. This is an absolute MUST if you want to run something like a computer. Say you don't have a computer? Mmmm, thing about what is operated by a computer now days. Most certainly any microwave is computer controlled. Most of the new inverters for recharging your batteries have computer chips in them. In short just about everything except a light bulb or a power tool is going to be sensitive to "noisey" power. Audible noise aside I wouldn't even consider anything that didn't use an inverter.

A final consideration is fuel source. It's not for certain that you will see a power drop if you switch to propane but it's highly likely. So, bottom line is you might get by just fine with the eu2000 but if you go that route have a backup plan if it fails.

-Bernie
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Old 10-25-2007, 07:08 PM   #9
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Guys,

Thank you for the replies. I see the difference now. The inverter type is definitely the way to go.

I've been reading a bunch on this today. I kind of like the looks of the Yamaha 3000 with the boost feature for startup. Does the 3000 Honda have that?

I'd like to cover the roof with solar panels too, but that's another topic

Thanks,
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Old 10-25-2007, 07:58 PM   #10
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The Yamaha 2400 puts out 2400 and surges higher. It works fine running on LP and powering my 13,500btu air conditioner.
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Old 10-25-2007, 09:47 PM   #11
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Wow!

I'm impressed with this thread and how much you guys know about inverter generator technology!!!!

I won't add to any of the good info here, but let me say that when I spoke to Yamaha about their claim that the EF2400iS will properly power a 13,500 BTU air conditioner, I was told that they actually used one for the test and it powered up with no damaging amp draw and ran perfectly for the 2 days that the test was conducted.

I have a friend that uses an EF2400iS with an LP conversion to run his A/C when boondocking and couldn't be more satisfied.

Note to Bernie: Just go into the back of the outer fridge compartment and pull the 120VAC plug from it's socket when you want the gen to run the A/C only. Your refer will then convert to LP and stay that way until you plug it back in. It does not need 120VAC to operate....just 12VDC for control voltage and LP . Unfortunately, it's a Dometic thing and the priority is to run on 120VAC if it is present. If you pull the plug.....IT AIN'T PRESENT!!!!
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Old 10-29-2007, 11:37 PM   #12
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Wow. You are all amazing...I've learned more about the "whats-and- why-fors" on generators on this thread than I've been able to piece together elsewhere. Thanks!

And thanks, Lew for that tip about disconnecting the 120VAC if you want the frig to run on LP even if you're "plugged in" or using a generator...so I read that and then I go out to the Bambi and look at the back of the frig...I am not certain which plug is the 120VAC plug. Hmmm. Any hints? This would be a handy trick to know.

Then I review the controls above the frig door inside (2006 19' Bambi SE): "off" vs "on" (button pushed in = frig on; button out = frig off...and "auto" vs "gas" (button pushed in, it's in "auto" mode which switches it back and forth between gas and 120 depending on 120v availability; button out = you're runnning on gas only). This accomplishes the same thing, yes?

Thanks for the great tips and information everyone...

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Old 10-29-2007, 11:50 PM   #13
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yep the 'gas' button keeps the fridge on gas, even when 'lectric is available.

the '120' plug is a generic 3 prong plug stuck into a normal looking 3 hole, electrical outlet...

there is ONLY one of these in the fridge compartment generally.

cheers
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Old 10-30-2007, 12:54 AM   #14
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yep the 'gas' button keeps the fridge on gas, even when 'lectric is available.

the '120' plug is a generic 3 prong plug stuck into a normal looking 3 hole, electrical outlet...

there is ONLY one of these in the fridge compartment generally.

cheers
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Thanks (once again) 2air'...I'll take another look and see if I can find a regular plug...it sounds pretty obvious... Maybe it's that "If it had been a snake..." thing.

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