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Post by canyon on Oct 25, 2009 22:56:34 GMT -8
So I'm finally building my mass bench. I bedded my flue ontop of an urbanite layer and decided to fire it up before covering it up. It pitches down hill from the rocket for twelve feet (with a 45 in there) and then doubles back through a pair of tee's (so I could have a cleanout for each run) and runs mostly up hill back to my vertical stack near the rocket. First firing had lots of condensate where I expected it at the low end but then it also started to come out of the pair of adjustable 90's where there is a low spot as well. I was surprised at the amount. All joints were well caulked with RTV (or so I thought). The second firing was a repeat although I think perhaps less condensate? My hunch is not to worry and just go ahead and bury the flue as I think the stuff has a tendency to plug up its own leaks or create a layer that lessens the condensation after a few firings. This has been my experience with vertical stacks anyway. Any thoughts?  |
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Post by Donkey on Oct 26, 2009 7:01:12 GMT -8
Probably had a lot of wet cob, bits pieces and whatnot down in there..
Seems that they do that the first firing or so. I don't think it's gonna be a problem.
Good that you fired it up before burying stuff. How'd it run?
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Post by canyon on Oct 26, 2009 8:50:23 GMT -8
It ran awesome! I'm really looking forward to packing it in and checking the midstream exhaust temp at the exit when it is fully cranking. I laid the base and set the flue three weeks ago and it is fully dry so the condensate is from combustion and perhaps a small amount from drying out the schedule 40 pipe in the first 13 feet of horizontal ( the last 11 is regular 24 guage). I'll fire it again tonight and report back. Thanks for the feedback! |
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Post by canyon on Oct 26, 2009 23:42:57 GMT -8
Still a fair amount of condensate on the third firing although some of the places it was coming out of before are now self plugged. I think I'll pull the cleanout cap tomorrow and inspect before firing(methinks there is quite the puddle in there). I'd like to mop it up and start relatively dry (minus the malted beverage in my hand of course) and see if there is any difference. |
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Post by Donkey on Oct 27, 2009 8:28:13 GMT -8
Hmm.. It's odd, if the works are completely dry, 12 feet ain't THAT long a run.. 24 feet isn't very long either.
Is this an 8 inch or a 6 inch system?
Either yer burning VERY wet wood or yer pulling the heat out of the system at a tremendous rate (or both). You might need to figure out some sort of condensate trap with a hose (or something) to take it away.
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Post by peterberg on Oct 27, 2009 14:05:11 GMT -8
Canyon, you wrote something about running downhill from the rocket for 12 feet. What is the difference in level? Running horizontally or say, 10 degrees downhill will make a huge difference in extracting heat. My guess is that the downhill duct runs quite hot compared to the uphill end. Actually, I am surprised the rocket runs well nevertheless.
My own project suffered problems lately with condensation. I was forced to tune the thing down to overcome the difficulties.
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Post by canyon on Oct 28, 2009 8:09:40 GMT -8
I am burning dry wood. The flue is not buried so it is radiating the heat instead of conducting it. I get the feeling that that happens at a much faster rate and causes the condensation. It is a six inch system. The 12 foot run drops one inch and the 12 foot return rises the same. The dropping run is much hotter but it is also the first leg with hotter gasses. I pulled the cleanout cap and sure enough there was a pool. I cleaned it out and fired the system. It ran out about a cup of condensate into my collector from the two large armloads of 2 year seasoned alder and dry spruce kindling. Just now I pulled the cleanout cap again and the system apparently got hot enough to stop running condensate and dry out the low spot. I think (hope really)I just need to bury the flue and not worry. Peterberg, could you explain about your problems with condensate and what you did to take care of it? Thanks for responding ya'll |
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Post by peterberg on Oct 28, 2009 12:02:20 GMT -8
One inch drop over a course of 144 inch? Unless I am mistaken, that equals to about 0.3 degrees. Not enough to make a significant difference in absorbing heat.
But... every high-efficiency stove produces some condensate during startup. Once the whole labyrinth in the bench warms up, the moist will evaporate again and will come out the stack as water vapor. In your case, the condensate start running and accumulates at the lowest point. That is to say, my two pennies worth.
The fact that the ducts are not covered by mass, means the soon-to-be-bench will lose too much heat in the startup phase.
In short: nothing to worry about, cover the whole thing and enjoy the warmth.
My own project: an upscaled version is ready. About 60% of the mass is refractory concrete. At first the absorbing of heat wasn't good enough, as a result I've enlarged the thing twice. But after getting rid of masses of water the second bell was way too large, resulting in such low temps the chimney couldn't cope anymore and smoke came out everywhere. Lowering the second bell and some other small tricks provided a solution. Keep an eye on rocket/bell project.
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