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Post by belgiangulch on Jan 8, 2019 5:00:35 GMT -8
Hi all;
Just competed my 8" J tube with barrel and 3 x 4 x 4.5 tall brick bell.(5 minute riser and ceramic core) Currently my best over estimate is I have 84' of ISA. I have been burning this for 5 days now. It works better than I could have hoped for! Yesterday I checked my stack temps, they had been 130-150 F the first few days. After apx.6 hrs burn yesterday chimney temp was at almost 190 F! I'm thinking I need a taller bell ? More ISA, maybe up to the 95' that an 8" batch box can supply ? What should my optimal chimney temperature be ?
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Post by peterberg on Jan 8, 2019 12:28:16 GMT -8
Thomas, I'd say a bell system without a bypass need at least 60º C (140º F) stack temperature in 20 minutes, starting from cold. Otherwise, you are running the risk of condensation in the chimney which would stall the thing altogether. My optimized batch box / bell combination is doing just that, with 80º C (176º F) tops, starting from cold. Two fires a day means the temp would rise to 110º C (230º F) at the top of the burn and running full tilt.
So your J-tube made it up to 190º F (87.8º C) after a 6 hour burn, which I'd classify as very good. Admittendly, a J-tube is different to a batch box in that it's ideally kept at a constant burn rate. In my opinion, you would do best to leave it like this as long the stack temp isn't any higher than 140º F, starting from cold.
So it'll start whatever the circumstances without belching back lots of smoke. I'm assuming the temp is measured in the heart of the stack, not just the pipe.
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Post by belgiangulch on Jan 9, 2019 8:19:56 GMT -8
Peter; My numbers yesterday were external pipe temperatures not internal gas temps.
I Have an update this morning. Checked with the wife last night and she was willing to donate her old analog candy thermometer to my cause. I'm glad I had already ordered one, as hers tops out at 220F.
Brick temps were the same as before, rite around 51F or so. So covering the feed tube at night had little effect. I suspect that the ceramic parts going cold eliminates most draft from the feed tube. Dilled my chimney and inserted the probe. Internal pipe temp was 60F before startup. 2 minutes into getting the fire burning , pipe gas temp was over 100F at 5 minutes (dragon was roaring) pipe temp was 130F at 20 minutes it was at 175F and at 40 minutes I pulled the probe as it was just below 220F.... ! I will have to wait for my new gauge to arrive, before I can find out just how hot this baby dragon is getting. I think this spring she may have a growth spurt...
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Post by Orange on Jan 10, 2019 11:41:22 GMT -8
Peter, at which hight do you measure stack temp?
I've found that 1m chimney length can lower the temp by 10C or more.
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Post by peterberg on Jan 11, 2019 1:25:47 GMT -8
Out of practical considerations mine is at 165 cm high from the floor so it's at eye level. It doesn't matter much where it is, as long as you get an indication about how the heater is going. Those cheap thermometers aren't that accurate anyway, I used the Testo to see what happened at certain temp levels. Since then, I know when running well how it sounds, look like and what temp at the stack it is. It turned out to be quite easy to reproduce the right conditions this way.
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Post by Orange on Jan 11, 2019 5:08:29 GMT -8
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Post by peterberg on Jan 11, 2019 5:37:38 GMT -8
What I meant was: at least 60º C within 20 minutes. So not keeping close to, but above 60º C instead.
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