Generator Exhaust Stack, will this work??

[JackConrad]

Jack, do you think it will get  hot enough to ruin a paint job on the pipe?
     My stack was made and used witth our old Onan gasoline generator. The pipe did discolor slightly in the area where the 2' piece of metal exhaust pipe ended. The temperature in this area would show about 100-110 degrees. I have not checked the temps with the diesel generator.

except I used 3" thin-wall fiberglass tubing
       Where do you get 3" fiberglass pipe? 
                                                                   Jack

[scanzel]

PVC piping has a maximum temp rating of 140 degrees before it becomes soft and starts to break down. Use CPVC piping instead schedule 40,80 or 120 it has a maximum temp rating of 200 degrees before softening and melt down. Go to www.harvel.com and you can read up on pvc/cpvc piping. I had a high efficiency boiler in my house and it used schedule 40 for the intake air and the exhaust air, probably not as hot as a diesel generator but in the winter the cpvc exhaust side would only get warm even after running for awhile. Do not use this piping as an exhaust pipe, use it as the venturi pipe around the exhaust pipe it will withstand a higher temp.

[Beatenbo]

Thanks for the info. I never got in a situation like that. Usually in a truck stop or some place like when gen running. Makes sense . Put on take off as needed. Wasn't trying to be tacky. I really don't think engine stacks up the back are attractive. Guess that's why over a 100 ice cream flavors. Thanks and have a good day.

[RTS/Daytona]

2" x 3" Alum Gutter Downspout works great for me - bright white / thin / lite weight

[KC Eagle]

I just finished building one based on the Gen-Turi design, except I used 3" thin-wall fiberglass tubing.  It's stronger and lighter than the PV stuff, not subject to the heat, and takes a paint job well.

Here's a llink to the Gen-Turi:

http://www.magnacoach.com/genturi.html

tg

tg

Can you clue me in on the thin wall fiberglass pipe? I've never seen it, where is it available? If it's cost effective, I'd think it's a better solution than 3" PVC which will be bulky & heavy.

KC Eagle

[Christyhicks]

So, I took this all one step farther. . we, let me clarify, I made Larry take it one step further, ha ha  . I had him run our generator exhaust up through the INSIDE of our bus.

Our ultimate goal is to have a bus that is peaceful and comfortable, not just for us, but also for our neighbors.  The pipe runs up and through the roof, and we made a sleeve out of double wall type B flue pipe.  This gives us an air gap around the exhaust pipe, and since the flue pipe sleeve extends down into the generator compartment, it can actually draw air up through the sleeve, exhausting up above the roof.  Larry built a "cap" that has an airgap allowing the air to travel out of the sleeve, but atually covers the outlet.  It turns at the top, sort of like a truck exhaust, so that it doesn't rain down into it. 

I will incorporate the exhaust stack into the cabinetry, further quietening it, but I agree whole heartedly with the fact that getting that exhaust up, overhead, not only makes it quieter but also allows the air currents to waft those stinky  diesel fumes away.  Larry was thrilled with me, as you can imagine, but he really rose to the challenge and built a great setup. What a guy!   Christy Hicks

[gus]

I would forget the PVC and wrap the extension with a good insulation of some sort.

I'm going to use the wet-blanket stuff from EHP on my new Honda EV6010 muffler, exhaust and extension. No body will ever get burned if that stuff is on the pipe. They also have a tube type that just slips over the pipe but I've never used it.

I used it on my current Onan and it cut down the heat more than 50% plus helped reduce the noise.

[JimC]

I agree with using the aluminum rain gutter, its large enough so the heated exhaust pulls fresh air along with it as it goes up the pipe keeping it cool (warm to the touch), light enough to mount with one small angle clip after setting it on the generator pipe, will not burn or melt, and its strong enough to hold up to reasonably heavy winds.

Two sections fit together in seconds, the entire mounting of mine takes less that 2-3 minutes, half of wich is getting it out of the bay.

Jim Callaghan 4106
Wisconsin

[akbusguy2000]

KC Eagle:  I live in Alaska where they use quite a lot of fiberglass piping of all sorts for sewer lines in permafrost zones, as well as in the oilfield.   I found a supplier here in Anchorage that had a few scraps lying around, which they gave me.  I had to buy a two-piece threaded joint, since I wanted to make up two pieces about 5 ft each.  I'm afraid if one had to buy this stuff it would not be very cheap - the joint was over $50.00 alone.

Pros:  the stuff is great to work with and the joints cemented on with Fliberglass resin, which I had lying around the garage anyway.  Its light weight, very strong, and took a paint job well.

Cons:  Only one.  The thin walls give it a peculiar accoustic effect - it seems to resonate like a straight pipe and that makes it a littlel louder than a heavier one would be.  I'm going to experiment with a wrap of some kind to see if it will help.

By the way, I did some trial and error testing when building the setup to see how long the steel exhaust pipe should extend into the venturi pipe.  I found that there is a sweet spot with the metal pipe to terminate precisely at the same point the venturi begins.  The further it extends into the venturi the louder it gets.  To make sure it's working as it should you can release a small wad of tissue paper at the bottom of the venturi and see how quickly it spits out the top.

ymmv


tt   

[H3Jim]

Christyhicks - can you send a picture of how you sealed the top? Did you use a flange at the top, and if so, how did you make it?

Thanks

Jim

[kyle4501]

Yeah Christy, we need pictures!!! 

[Christyhicks]

I'll try to get some closeup pictures for you guys, no later than this weekend.  It's pretty cool if I do say so myself, but then, I always said that Larry was the most talented guy I know!     Christy

[belfert]

My friends and I got some 4" diameter double wall fiberglass pipe free at a Flying J truck stop last year.  I think it wasn't long enough to be of any use to them.

Anyhow, I have an older Onan 7.5KW diesel generator, and 95% of the noise comes from the generator itself, not the exhaust.  We put a really expensive muffler on the exhaust and couldn't tell the difference in noise with the muffler on or off.

The generator is so loud that I really want to get one of the Powertech quiet ones if I ever come across some extra cash.

Brian Elfert