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Author Topic: Generator Insulation  (Read 3927 times)
DavidInWilmNC
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« on: January 09, 2007, 06:45:24 AM »

I've got the generator installed in the driver's side front bay finally.  I still need to add an air inlet for cooling and an enclosure of some sort to partition it off from the rest of the bay.  I know most use that egg-crate type of acoustic insulation, but I'm not sure where to find it.  I've also considered the type used on the engine box of my I/O boat.  It's a fairly thick, very high density black foam that's held up for years (it's a '74 boat).  I imagine the egg-crate type might be a bit more effective since it doesn't have a flat surface like the foam in my boat.  So, where's the best (quickest and cheapest) place to get heat resistant acoustic foam insulation?  Thanks for any input.

David
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DrivingMissLazy
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« Reply #1 on: January 09, 2007, 07:20:46 AM »

David, the correct term for the foam you are looking for is "convoluted" foam. I used to have it made for me in 4 by 8 ft sheets of different densities, depending on the actual use and frequencies I was trying to suppress. Sometimes used 4 inch thick and sometimes 2 inch thick. Each would yield two sheets of foam. Unfortunately, I do not remember the name of the company in California that made it for me, but maybe a search for convoluted foam would yield some information. The density of the foam as well as the thickness is information that needs to be considered.
Richard
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« Reply #2 on: January 09, 2007, 08:16:42 AM »

My 94 Eagle has the convoluted foam. It is very brittle...every time I open the compartment door, It flakes off. I don't know if this is normal or not. May be because of the temperature inside the box. I used the insulation board used by hvac installers on another genset project, it works great I also used the aluminum tape used by hvac installers to seal all cracks as well. Just my 2 cents!!! Grin
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TomC
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« Reply #3 on: January 09, 2007, 08:45:06 AM »

Highly recommend using leaded foam.  Foam on either side of a lead sheet.  That really quiets things down.  My generator (10kw Powertech) is mounted next to the drivers seat like a front engine and is accessed from inside.  You can barely here the engine noise of the gen.  The vibration that resonates through the bus is what is noisy.  Luckily, you can barely here it from the rear bedroom.  The leaded foam with foil works very well.  Available in 1" single and 2" double lead sheet.  I got mine at Camping World, although you could most likely get it else where for cheaper.  Good Luck, TomC
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DavidInWilmNC
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« Reply #4 on: January 09, 2007, 10:52:45 AM »

Thanks for the ideas and suggestions.  So far, after about 45 minutes on Google, I've not found anything really satisfactory.  Most of the acoustic foam I'm finding is geared towards musicians.  I'm sure that would work, but I'd rather have something a bit more fireproof.  Camping World doesn't show any on their website, but may stock it in the stores.  The insulated HVAC board used to quieten compressors and blowers is an idea, though I doubt it would be as quiet as some of the thicker foam.  Anyway, the search continues!

David
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DrivingMissLazy
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« Reply #5 on: January 09, 2007, 11:10:57 AM »

Click here:

www.soundown.com/AI.htm

Richard
« Last Edit: January 09, 2007, 12:00:56 PM by DrivingMissLazy » Logged

Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming:  WOO HOO, what a ride
Chris 85 RTS
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« Reply #6 on: January 09, 2007, 11:55:36 AM »

I used the sounddown product linked above.  But I'd hardly call it cheap, but it is effective. 
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« Reply #7 on: January 09, 2007, 12:22:23 PM »

Egg Crate Foam

Comes in 2x4 sheets

McMaster Carr 

I used it in mine for a temp sound proofing. So far two years later and still in great shape and quiets well!

Ace
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Ace Rossi
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DavidInWilmNC
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« Reply #8 on: January 09, 2007, 01:49:46 PM »

Thanks, Ace.  That's more like what I'm looking for.  The generator is an older Onan gasoline model that's fairly quiet anyway.  It'll be mounted in the first bay behind the driver and a sofa will be above it in the bus.  I think between that egg carton foam, insulation (thermal type), carpet, and the sofa, it should be relatively quiet.  How thick is the foam you used?

David
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sivrtnge2
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« Reply #9 on: January 09, 2007, 02:03:06 PM »

You would be suprised how quiet the genset is inside a box made from aluminum sided insulation. I think the sheets are 1/2" thick. If you double the insulation, it will give you a 1" barrier that is easy to work with. once you have the box the way you want it, you can spray glue over the box and cover it with an upholsery to make it look like a million dollar coach. Grin
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DrivingMissLazy
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« Reply #10 on: January 09, 2007, 02:26:30 PM »

Do you have any experience or guidance on building a low noise enclosure? If not, Dick Wright at Wrico would be a good contact I believe.
In general you need to make sure the sound makes two 90 degree bends before it exits the enclosure and be sure to make the sound path is large enough to not restrict the required air flow.
Richard
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Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming:  WOO HOO, what a ride
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« Reply #11 on: January 09, 2007, 02:35:00 PM »

David I think it was something like 2 inches from top of peak to bottom of flat!

It works ok for a temp quieter as we used it but my plans are to re-do it in a box. I just took the bay that the gen is in and did the walls and sides. I didn't do the ceiling of the bay  which is where I get most of my noise upstairs which by the way is very little as it is!

It's pretty loud when I open the bay door but as soon as I close it, it's really quiet with the exception of the exhaust which comes out the side underneath.

Ace
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Ace Rossi
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JackConrad
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« Reply #12 on: January 09, 2007, 03:27:26 PM »

    Here is "our way". We lined the former AC condenser compartment with 1/2" high density foam, a layer of 1/2" plywood, and then a layer of noise reduction "egg crate foam". We also ran our exhaust to near the back of the bus and remoted our radiator to the spare tire compartment with an electric fan. So now the noises of the radiator fan, generator, amnd exhaust are in separate areas. Depending on where you are standing outside the bus, you hear different noises, but not all at the same time.
    I was told the "egg crate" foam absorbs more sound because the convolutions creat a greater surface are than a flat surface.  Jack
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DrivingMissLazy
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« Reply #13 on: January 09, 2007, 04:18:59 PM »

A lot depends on the frequency of the noise also. My experience is that the convoluted material is best for the higher frequencies and the lead covered foam is better for the low frequencies. There are companies with special equipment to measure the noise, and recommend the best materials for reducing it the most. This was especially helpful when building gensets for the movie industry. .
Richard
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Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming:  WOO HOO, what a ride
Kristinsgrandpa
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« Reply #14 on: January 09, 2007, 06:04:39 PM »

This might help also.

http://www.soundproofing.org/infopages/generator.htm

Ed
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Kristinsgrandpa
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« Reply #15 on: January 09, 2007, 06:06:59 PM »

Oh, and here is another one.

http://www.defender.com/product.jsp?path=-1|311|302333&id=95982

Ed.
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ArtGill
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« Reply #16 on: January 09, 2007, 06:22:23 PM »

David,

Visit some boat yards and you can get good advice from putting generators under the decks of boats.  You might get lucky and get some material.

Art
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Art & Cheryll Gill
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Tom Y
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« Reply #17 on: January 09, 2007, 07:20:20 PM »

Sivrtnge2,  What type of material are you talking about?  The foil faced foam insulation? When you open the doors is it noticable, the noise?  Thanks Tom Y
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Tom Yaegle
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« Reply #18 on: January 09, 2007, 07:33:33 PM »

Google E.H.P., they have a lot of good stuff and advertise in Bus Conversions.

I'm on my second gen using their stuff.
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JackConrad
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« Reply #19 on: January 10, 2007, 05:11:06 AM »


 Here is "our way". We lined the former AC condenser compartment with 1/2" high density foam, a layer of 1/2" plywood, a 2nd layer of 1/2" high density foam and then a layer of noise reduction "egg crate foam". We also ran our exhaust to near the back of the bus and remoted our radiator to the spare tire compartment with an electric fan. So now the noises of the radiator fan, generator, and exhaust are in separate areas. Depending on where you are standing outside the bus, you hear different noises, but not all at the same time.
 I was told the "egg crate" foam absorbs more sound because the convolutions creat a greater surface are than a flat surface. Jack
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« Reply #20 on: January 10, 2007, 11:08:46 AM »

DML hit on the target - The perfect type of "insulation" to use is dependent on the frequency you target for attenuation. There is more than one frequency band in a genset due to the size and type of mill, intake and exhaust design/needs, head type and operating RPM, and the drive used - HTH
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sivrtnge2
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« Reply #21 on: January 10, 2007, 03:35:51 PM »

Hey Tom,
Sorry it took so long to respond. The foam insulation can be bought at any Lowes or Home Depot store. It come in 4 x 8 sheets and is covered on both sides by what looks to be aluminum foil. I used this and just doubled it for thickness. I also used the aluminum tape to join my corners and seal all cracks. Once it is together, it is full of strength. As for as looks are concerned, you can spray the insulation with an industrial strength spray adhesive then cover it with automotive carpet, or upholstery material. It is a very quiet cost efficient way. I did not cover my box because it is enclosed in another compartment.
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NJT5047
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« Reply #22 on: January 10, 2007, 07:18:33 PM »

Hey David,
Someone may have already offered this bit, but unless you set the generator on some sort of sound isolator, no matter how much insulation you use around the unit, it'll still resonate. 
Another thing is that your gasoline generator will have much higher operating temps when compared to a diesel.   Be sure and use something that is not flammable.   May want to consider monitoring the genset compartment for heat.  Jack Conrad has temp sensor in his genset compartment....I believe? 
Be good to keep up with the compartment temps.    Also may wish to treat it like a boat...with positve blower ventilation.   A boat bilge blower would be cheap and clear any fumes before lighting up the genset.   
BTW, I lined my condensor compartment with  1" steampipe insulation made by Rubbetex (Sp?). Came from Grainger...will not burn...melts, but I fire tested the stuff with a torch.  Comes in 60" wide roll.   Made a huge difference. 
Best, JR   
« Last Edit: January 10, 2007, 07:20:17 PM by NJT5047 » Logged

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« Reply #23 on: January 10, 2007, 08:50:48 PM »

Ahoy, BusConverters,

Genset noise // sound //  “noisemaker” (per Fast Fred)

This works great on my -01 Eagle genset.  The genset is on airbags within the box, and the enclosure box is done as follows:

Outer layer is ½” Russian birch plywood.  Then, two layers of 30# roofing felt.  Then, one layer of roofers 2 #/ sqft lead.  Then two more layers of 30# roofers felt.  The inside is one more layer of ½” Russian birch plywood.  There are inlet and outlet air labyrinths lined with fiberglass and expansion metal.  The hot portals use silicon rubber sheet gaskets around the pipes.  These items are very ordinary, and low cost. 

Three mufflers --  two each of Kragen’s cheapest 1 ½” in/out plus a glasspack return.  Pipe is out of the roof.  One thing as yet unanswered.  Will the mufflers soot-up and clog due to low temps?  Not so far in ~~200hrs.  If so, they are cheap, and fairly easy to change.

I had planned to put some more sound insulation inside the box, but it is already so quiet that if anyone else in the local is running their genset, I have to place a hand on my bus to know that mine is still running.

It really is not “silent” inside.  Vibration plus some sound, and I’m a “little” deaf. 

Others may think that it is terribly  loud, but I know that is far more quiet than my neighbors. 

Enjoy /s/ Bob
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« Reply #24 on: January 11, 2007, 06:21:00 AM »

Jack Conrad has temp sensor in his genset compartment....I believe? 
Be good to keep up with the compartment temps.    Also may wish to treat it like a boat...with positve blower ventilation.   A boat bilge blower would be cheap and clear any fumes before lighting up the genset.


Yes, I have the RV Safety Sytems Alarm on our bus. One of the temperature sensors is installed in the generator compartment a couple inches below the compartment ceiling directly above the engine. The air intake is passive and enters the compartment near the floor at the generator head end of the compartment. The air exhaust is active using 3  (230 CFM each) 4" bilge blowers installed in the floor of the compartment.  4" aluminum flex duct was installed on the blowers and ran up the compartment wall to near the ceiling to remove the air from the top of the compartment (hot air rises).  The radiator is remoted to the spare tire compartment and the muffler is outside of the generator compartment. The only openings in the compartment are the grilled air intake which has several bbaffles and the 3 bilge blowers.  By monitoring air temperatures inside the the compartment and the outside air temperature, we have found that the compartment stays about 5-10 degrees hotter than the outside air temperature.  Jack
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« Reply #25 on: January 12, 2007, 05:49:28 PM »

at this years Annapolis Sailboat show there was a vendor that had some foam insulation.........thier demonstration was a generator enclose with a speaker inside  cranking out generator noise..........it was very loud open...louder than any rv generator I have heard without enclosure......and just a hum closed.

stuff was not especially expensive came in 4x8 sheets, sself adheasive, water and oil proof as well as fire retardant.

would be my choice........when in doubt look to the yachting industry.......it's older than the rv or conversion industry and    items are made for much more severe service.

by the way....they had 7-8kw generators the size of a 30 inch TV......less radiator of course.....seawater cooled.

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« Reply #26 on: January 12, 2007, 07:01:12 PM »

Doug,

Great information.  Do you have a name for the vendor?

TomNPat
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« Reply #27 on: January 13, 2007, 02:39:31 AM »

I got a sample ...let me see if I can dig it up this weekend
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