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Old 05-25-2019, 04:28 PM   #1
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Default Making an Onan Quiet Generator Quieter!

Making an Onan Quiet Generator Quieter - Mike Mas



Hello - I thought I would share one of my recent projects - For the most part the “Q” Onan generators which stands for “Quiet” have very respectable noise levels today, since unlike earlier generators which had thin steel cases with no insulation, modern generators use composite cases and some insulation.

Onan generator noise levels can be easily reduced further if Onan would add a throttle/ load speed control, so instead of running near wide open all the time, they could just idle when not under heavy loads somewhat like a Honda generator. Instead Onan runs their engine almost at full rpm even with no loads at all, which wastes fuel and adds extra noise.

For the most part - I find both my Onan 3600 LP generator on my Leisure and my Onan 2500 LP on my Sprinter very quiet. Even though the noise levels are respectable, I figured if I can spend a few hours and make it quieter, it would be an improvement.

Fortunately, I ended up with half a box of Road Kill from my last project, so I decided to use it on my genny to reduce its noise level further. If you’re not up to speed on Road Kill;

https://stingerelectronics.com/catal...ping-roadkill/

It's an amazing product which I use on aircraft, cars, trucks motorcycles, etc. which consists of a layer of thick composite type rubber which is foil backed on one side and sticky on the other, so you can apply it to almost anything and its heat resistant as well. For vans with generators side mounted or under belly, you can add this to the generator box or even the undersides of the floor to help deaden noise, let me tell you, this stuff works!



On my Leisure Wonder the generator is very quiet already thanks to the fact its mounted behind a thick fiberglass door and the exhaust exits on rear drivers side, but since the generator is on the "Patio" side, I wanted it as quiet as possible.

Before I began the project, I first wanted to record the sound level on my iPhone DB meter. As I opened the app, I registered 56 DB in general noise with everything shut down. Next, I started the generator and stood back 6 feet and registered around 79-80 DB, which is very quiet for a generator when considering a vans diesel engine registers about the same noise level.





To begin the project on my coach - I decided to first cover my Leisure’s generator door with Road kill since some noise was passing through the door itself. On this coach the door is fiberglass which deadens the noise somewhat, however many coaches use a thin aluminum door which will actually amplify noise from the generator, this is where you'll see an amazing difference.







Next, I removed the generators inspections panel and and added some Roadkill to the areas the that were not covered from the factory to kill so noise.



To keep the noise from spreading to the right and left of the generator, I added a few pieces to the right and left side panels of the generator housing box to deaden some of the noise.



After I completed all my stick-on RoadKill applications, I noticed there was a void on top of the generator between the coaches floor, so I cut some non-sticky double sided foil backed insulation material we had in the shop from a roll, then slide it on top of the generator and held it in place with some foil tape. This will help deaden noise from reaching the floor of the coach.







After I wrapped the job up, I moved the coach back outside and started the generator again. With a full load, I noted a major difference of 5 DB less noise for a reading of only 75 db, which is now no louder than a Powerstroke or Sprinter diesel engine running at 1500 rpm, therefore making the project well worth the time that it required.

Regards - Mike



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Old 05-25-2019, 09:12 PM   #2
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Onan's can't use a throttle for speed control as they are fixed rpm AC generators and would lose 60 hz power. They would have to totally redesign to be an inverter generator to be able to run rpm control instead of governor/load control at fixed speed.
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Old 05-26-2019, 12:34 PM   #3
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Thanks for the reply Booster - Onan needs to advance their systems, piratically every generator available today had a throttle / load feature, it would reduce both the units noise level and fuel usage.

Thanks!
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Old 05-26-2019, 01:00 PM   #4
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Thanks for the reply Booster - Onan needs to advance their systems, piratically every generator available today had a throttle / load feature, it would reduce both the units noise level and fuel usage.
Why should they? "I thought I would share one of my recent projects - For the most part the “Q” Onan generators which stands for “Quiet” have very respectable noise levels today"

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Old 05-26-2019, 02:01 PM   #5
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Thanks for the reply Booster - Onan needs to advance their systems, piratically every generator available today had a throttle / load feature, it would reduce both the units noise level and fuel usage.

Thanks!

I think you will find that statement only to be true for smaller portable units where the inverters are more practical. The last time I looked the bigger units are still fixed speed design, just like the Onans are. I don't ever recall seeing an mounted RV generator that was inverter style. If you know of some let us know.
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Old 05-26-2019, 05:20 PM   #6
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Thanks for the replys - More than likely some of you guys would not remember just how noisy generators actually were back in the late 70's when I started RV'ing in my 1978 26' Winnebago Brave. When you started the generator, everyone knew it was up and running. All the noise from the rattle of the engine and exhaust was amplified by the thin sheet metal shrouding.

Onan Q generators are fairly quiet, especially when you get in the 6-8-10Kw diesel range which were really loud. Most new QD generators are mounted in the nose between the frame rails and you can barely hear then in the coach or even on the patio side.

I spoke to one of the top guys at Cummins years ago, asking why they didn't lower the speed according to load like other generators and was told they wanted the engine to stay "Ahead" of the load for the heavy amperage to start a AC compressor. Even if they reduced the RPM 50% during compressor cycles it would be a major improvement. My Kawasaki generator drops down to idle when needed and it's now well over a decade old. I used it for pull behind AC units and it never choked when starting the AC unit.

As I mentioned, my Newmar New Aire was equipped with the Xantrex 3000 inverter and during compressor starts the inverter drops in the line with up to 5000+ watts to help the grid power start the compressors. In fact, in my garage the amperage is so low it never would start a AC unit on my older coaches, but the Newmar 15Kbtu AC started fine.

If you're going to run an AC unit the best choice is the EU3000 (20 amps) which is quiet @ 55 DB. It has its own electric start system, which can run overnight on its 3.5 gal tank. The only problem its heavy if you're not going to hitch mount it, its 130 lbs requires a few guys to get in the back of a truck or in an RV.

Regards - Mike
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Old 05-26-2019, 05:36 PM   #7
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Thanks for the replys - More than likely some of you guys would not remember just how noisy generators actually were back in the late 70's when I started RV'ing in my 1978 26' Winnebago Brave. When you started the generator, everyone knew it was up and running. All the noise from the rattle of the engine and exhaust was amplified by the thin sheet metal shrouding.

Onan Q generators are fairly quiet, especially when you get in the 6-8-10Kw diesel range which were really loud. Most new QD generators are mounted in the nose between the frame rails and you can barely hear then in the coach or even on the patio side.

I spoke to one of the top guys at Cummins years ago, asking why they didn't lower the speed according to load like other generators and was told they wanted the engine to stay "Ahead" of the load for the heavy amperage to start a AC compressor. Even if they reduced the RPM 50% during compressor cycles it would be a major improvement. My Kawasaki generator drops down to idle when needed and it's now well over a decade old. I used it for pull behind AC units and it never choked when starting the AC unit.

As I mentioned, my Newmar New Aire was equipped with the Xantrex 3000 inverter and during compressor starts the inverter drops in the line with up to 5000+ watts to help the grid power start the compressors. In fact, in my garage the amperage is so low it never would start a AC unit on my older coaches, but the Newmar 15Kbtu AC started fine.

If you're going to run an AC unit the best choice is the EU3000 (20 amps) which is quiet @ 55 DB. It has its own electric start system, which can run overnight on its 3.5 gal tank. The only problem its heavy if you're not going to hitch mount it, its 130 lbs requires a few guys to get in the back of a truck or in an RV.

Regards - Mike

How do you lower the speed on an AC generator that requires 3600 or 1800 rpm (depending on winding style) to generate 60 hz power? It just plain can't be done that I know of. You can't run a 60 cycle AC air conditioner on 30 cycles as even if it would start it would quickly fail. If they switch to a DC generator and you had to add your own inverter it would work, by why would they do that when everyone wants AC power anyway?



I have heard that same statement from Cummins, but what they told me they were talking about when I asked a development engineer about it (he showed up to buy a saw I was selling on Craigslist) he said they are talking about he questions they get about why the units are running at slightly above 60hz, like 62hz or so. This is to allow for the rpm sag in the engine when a big load is added to keep the frequency from dropping to low and causing a death spiral of power.


We need to see how this could be done without a full redesign to inverter technology, so please fill us in on how they would do that.
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Old 05-26-2019, 06:26 PM   #8
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How do you lower the speed on an AC generator that requires 3600 or 1800 rpm (depending on winding style) to generate 60 hz power? It just plain can't be done that I know of. You can't run a 60 cycle AC air conditioner on 30 cycles as even if it would start it would quickly fail. If they switch to a DC generator and you had to add your own inverter it would work, by why would they do that when everyone wants AC power anyway?

.
It's simple you just run the output of the generator into an inverter!

In most cases the generator puts out multiphase AC current from an alternator which is converted to DC. This DC current is feed to the generators inverter which converts it back to 120 volts AC @ 60 cycles regardless of generators speed. The inverters microprocessor maintains a solid set voltage at 60 cycles and controls the generators throttle to maintain the constant amperage needed for the load.

Regards- Mike
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Old 05-26-2019, 07:22 PM   #9
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It's simple you just run the output of the generator into an inverter!

In most cases the generator puts out multiphase AC current from an alternator which is converted to DC. This DC current is feed to the generators inverter which converts it back to 120 volts AC @ 60 cycles regardless of generators speed. The inverters microprocessor maintains a solid set voltage at 60 cycles and controls the generators throttle to maintain the constant amperage needed for the load.

Regards- Mike
I'm running a 2800 watt(3100 surge) Champion inverter genny. It has a switch for eco or full speed, eco being the setting for variable speed. My 10k BTU room type A/C on the R/T starts just fine on the eco setting, though I can hear the genny doing all it can to bump up the speed. It comes up fairly quickly. If nothing else major is drawing current the bump up in speed is minor. Kick in the toaster oven and that genny is singing like an Onan, though still quite a bit quieter.
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Old 05-26-2019, 08:18 PM   #10
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I'm running a 2800 watt(3100 surge) Champion inverter genny. It has a switch for eco or full speed, eco being the setting for variable speed. My 10k BTU room type A/C on the R/T starts just fine on the eco setting, though I can hear the genny doing all it can to bump up the speed. It comes up fairly quickly. If nothing else major is drawing current the bump up in speed is minor. Kick in the toaster oven and that genny is singing like an Onan, though still quite a bit quieter.

Steve thanks for the reply - hey what would be nice is if the gen companies would give us a "variable" user throttle setting, so if we're using high load devices, we could turn up the high-idle a bit so the engine can stay on top of the loads.

Mike
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