| Author | Message | ||
| Jim Stewart (H3jim)
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Gary, I saw in an earlier post that you run your generator exhaust up through your living area and out through the bus roof. I am wanting to do the same thing in mine, and I have several questions on how you did it and how it works. How did you join the 3" pipe to the roof so it is mechanically secure and weather tight? How did you fasten the 1 1/2" exhaust pipe to stay somewhat centered in the 3" pipe? Did you use double wall 3" pipe? How hot does the 3" pipe get inside the coach? what size generator do you have? It seems like this is a great way to go, but over the last several years, I have also seen criticism of this concept. Thanks for your response. Jim ps, I live in Lakeside and would like to see your coach sometime if convenient for you. | ||
| Luis (Sundancer)
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Would it be possible to do the same for the 6V92 exhaust? (Almost) anything is possible, but is it practical? | ||
| Gary Stadler (Boogiethecat)
Rating: N/A |
Hi Jim, (1) I welded it right to the roof, which is steel in my case. A flange and silicone would have worked had it not been weldable- (2) On the top I actually made an aluminum flange with my lathe that had holes in it and fit both the inside and outside pipe. It could have easily been done with three 1/4" screws with nuts welded to the outer tubing, which is what I did for the bottom (3) simple 1-1/2" EMT conduit for the inner and 3" EMT for the outer (4) The 3" pipe get hot enough that it's hot, but you can hold your hand on it as long as you want...although just barely. I've never measured it but it's not dangerous, that's for sure (5)7kw genset runs 2 A/c's... I tested it for an hour at full load on a hot day( a bunch of heater elements as load) to make sure it was ok There are a bunch of photos here, and in the batch are a few of the pipes although not completely documented as I was doc'ing the genset install overall more than the exhaust stuff http://www.heartmagic.com/zzOnanDays/ (6) Love to have a visit from you... call me 858 four 1 4 five 1 hundred Luis, I'm sure it would be doable with an engine exhaust. You'd have to give the inner tube at least an inch for air convection to keep the outer tube safe, so the outer tube might get kinda big in diameter.... Some systems use fiberglass or other insulation with a thin metal skin...if you do that, you need to specifically obtain high temperature insulation as normal household stuff has organic binders in it that will smoke forever and make a giant mess. Otherwise, ceramic cloth blanket insulation would also be a good choice- you can get it from McMaster-Carr, covering the pipe a few inches thick and skinning it with thin sheetmetal would probably work very well. The four things you want to consider are, (1) safety of kids and other humans who may touch it (2) general fire hazard from something too hot (3) having it heat your cabin space on an otherwise hot day (4) possible engine noise in the cabin if you have anyone occupying it while underway | ||
| Randy Davidson Rating: N/A |
Jim, I ran my Onan CMQD 12kw and Aqua-Hot diesel exhaust out the roof of my H3-40 as well. I had both exhausts come to a central point between the two bays, expanded them to standard exhaust 2" pipe turned them straight up to go through the floor. I used 5" double-wall stove pipe to enclose the two 2" exhaust pipes between the floor and the roof. Since the 2" pipes touched the 5" walls on the way up I felt there was too much heat radiating from the second wall. So, I surrounded the 5" pipe with a 7" heat duct (like for homes) with holes drilled 1" from the floor and 1" from the interior ceiling. I will expect interior convection to bring cool air from the floor, rise, and exit near the ceiling. Either my exhaust fan will suck the excess heat away or the roof airs will cool the air again. I capped the whole thing outside on the roof with a 5" exhaust cap (hard to describe). It has a flap inside and a screen on the outside to keep rain splatter and bugs out respectively. I've run this a bit and am confident there is zero heat on the outer pipe and essentially no convection heat detectible. I suspect the 'over kill' will pay off once I enclose all this pipe in a cabinet with wood all around. I plan to have a small vent in the toe kick and a small vent at the roof line for circulation. Should work great! But, I have to build the cabinets yet for the real test. Oh, here's the second class part. I used aluminum tape to seal the 5" pipe at the floor and the ceiling to ensure no gases from the bay or the outside could enter the bus. I wish I had done this more professionally but didn't have the tools or ideas on how to do it. After reading Gary's I think a simple flange with some sealant would have worked better. But, nobody should ever see this anyway. That's my rationalization. Randy | ||
| Nick Morris (Nick3751)
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I'm considering the same thing only using a 4" pvc as an outer and it doubling as my vent for my waste tank. I'm planning on sealing the bottom off where the exhaust comes in and stableizing it with metal braces inside the pipe. Also to cool it off some and reduce noise I'm going to have the exhaust under the bus go through a few turns, I've got about 12 ft to go from the genny to vent anyhow a I figured that would be a good use of the space. I'm hoping for pretty cool egt when it makes the turn verticle so I don't think the pvc will be any trouble. | ||
| Gary Stadler (Boogiethecat)
Rating: N/A |
I don't think I'd do that with PVC... it's other name is "thermoplastic" and it will turn to the consistancy of american cheese slices when it gets as hot as it probably will. A good part of why the "tube within a tube" thing works is that you allow free air convection between the tubes... if you use your sewer system for the outer tube there will be no airflow from bottom to top and the outer PVC will get a LOT hotter than you'll likely find acceptable. ~WITH~ fully free convection, my outer tube gets almost uncomfortable to touch over its whole length, and that's a good 12 feet from the gene's exhaust port. A few feet of tubing under the bus won't dissipate enough energy to get the EGT down enough. If you have any inkling to do a test, simply try it with the tubes hooked up outside of your bus, and at least you'll be able to see it work or not work before all the construction goes into installing it. You might be real glad you tested it first... Don't forget to fully load your genset, the EGT goes waaaay up... As an alternative, maybe think about using 4" metal EMT conduit for your outer jacket instead of PVC. That stuff is cheap, galvanized and won't mind poop vapors at all... and it won't have a tendency to melt or otherwise be a fire hazard... ..then a last concern is "what if"... ...what if your genset backfires during a start or stop and sends a nice burst of flame up the exhaust pipe, and you have a nice combustible mixture of methane and air in your poop tank/vent system. The two exiting at effectively the same place in time and space might just cause a real stinky situation...pun intended...I'd hate to be the one having to explain why my black tank just exploded... My advice would be to separate the two and do it a little more "right" than a lot more "trick". Safety first.... | ||
| Jim Stewart (H3jim)
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Gary, Thanks, I left you a message tonight. Randy, How did you seal the top to make it weather tight? The exhaust cap, where did you get it, what does it look like? Does it stick up above the coach roof very far? Thanks | ||
| Phil Dumpster2 Rating: N/A |
Black tank exploding? Oh S#!t ... | ||
| Gary Stadler (Boogiethecat)
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Didn't happen by "explosion" but since this thread is apparently heading in a slightly different direction, and I'm an avid Burning Man + Busnut, I couldn't help but share this with you...  http://www.burningman.com/blackrockcity_yearround/tales/davedarling.html | ||
| Nick Morris (Nick3751)
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I forgot to mention the ceramic insulation I'm planning on. As for the exploding tank last time I brought this up someone pretty well decided that it would be a one in a million shot to get the mix right for it to go boom. | ||
| Jim Stewart (H3jim)
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Gary, thats a pretty funny story, hard to top that one. Great to see your bus, your place and all your creative projects. | ||
| Marc Bourget Rating: N/A |
Rule of Thumb" measurement guideline. If you can touch something and maintain contact (barely) it's usually not more than 150 deg. F. Dave Galey in the "Bus Converter's Bible mentions use of the concrete vent pipe. PVC melt temp is above 350 deg F. (but I wouldn't use it CPVC pipe has much better Temp tolerance but I wouldn't use it for this purpose, either |