My HR1 is at 0.75 and my HR5 is 5.9 which should make my HR2 2.03,HR3 3.32, HR4 should be 4.61. On HR 4, I'm currently pulling 580 degrees on the door.
slow process
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Earlier I was thinking and remembered that before I sealed off the gap where my 3" exhaust goes into 8x12 clay lined chimney that it's only about 4" to 5" away from backside of clay liner and why the heck I didn't cut that shorter the other night before I sealed it off is a question I may never be able to answer. For some reason I was thinking about turbochargers and it turned into a thought I had about air movement and a surging draft fan. Is it possible the draft fan moves such a large quantity of air that when it comes out of exhaust it goes the 4 or 5 inch gap hits the liner and creates enough restriction that it actually heats the exhaust at stove outlet to high or makes a backpressure to high that it slows draft fan down to compensate than speeds it back up to get it going again and so on and on and on and on or does this go back to the C6 and C7 settings? Any ideas? Thanks
While it would cause a backpressure issue, I wouldn't think it would be so great as to cause that serious of an issue. I would probably go ahead and pull that back out of the chimney and shorten it up and if you have room to do it, put a 90 on it to turn it up. The problem I found with tall chimneys on a pellet burner is the exhaust cools so much by the time it gets to the outlet that the air column slows down reducing the strength of the draft, causing you to have to increase the fan run time to maintain the draft. Going from a pipe with an area of roughly 7.1 sqin(3" round) to a pipe with an area of 96 sqin(clay liner) will also act as a reverse venturi, slowing the air flow further. While I understand where your thought about turbocharger dynamics is coming from, you're thinking the wrong direction. Look into pulse wave tuning in exhaust systems and apply that to your chimney system. It'll all come into perfect focus when you look at it that way. It may even be beneficial for you to go to a 4" double wall pipe into the chimney or lengthen the section of 3" pipe further up into your clay liner to keep the gasses warmer, longer. That's why my chimney works so well with very little draft fan. My chimney is only a total of 8' of travel and it's all double wall insulated. There's a very small temperature drop between the furnace outlet and the chimney outlet and it never changes volume so the pulses and columns of air maintain a fairly consistent velocity. Yours changes direction 4 times, runs 30', and changes volume quite considerably at the chimney. All that together will cause a slowing in the air column causing you to lose velocity, causing you to have to run the draft fan harder to maintain the draft.
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I've done some researching on pulse wave tuning it makes sense. I'm thinking I can cut the piece in 3" pipe in chimney a little shorter and add a 90 to get turned upwards thus going in right direction and hopefully improving draft as it would be heading straight up from a curved pipe rather than hitting a wall 5 inches away scattering around than deciding if it's going up or where it's going. I think I should be able to add a run of 3" or possibly 4" double wall/insulated pipe inside chimney on top the 90 to gain that straight up draft position. As for the down draft of cold air in chimney creating a wall when hot gases hit it I'm not sure what I'll do there but it makes since that it would slow the natural draft due to hot coming out of area 13 times smaller than the heavy cold air filled area it's going into. At the bottom of my chimney there's a clean out door that I could crack open a little to help the warmer (than outside) basement air create a draft up and maybe help keep exhaust warmer as it travels upward? This may be the dumbest idea ever in the history of mankind but what about going off the effect of the exhaust pipe shape on something like a 250R and putting something on top of clay lined chimney outside closing it off a little to get outlet down to about 6 or 8sqin to help keep hotter exhaust in chimney longer creating a positive pressure improving updraft rather than negative pressure of the current 96sqin opening letting the cold air come down? Any thoughts? Thanks
I don't think it's dumb at all. You're creating a venturi at the end which would increase the amount of vacuum through and behind the venturi area. I think that would be a cheap and easy way to get some more velocity through the clay lining without running a 30' section of pipe through the chimney. Not sure I'd open the basement door to the chimney other than for testing purposes though. That could create more issues than it solves.
After further review opening the door on bottom doesn't sound so good in case the pressure of heavier colder air outweighed the exhaust from stove and than possibly lead to a smoke filled basement but maybe just one time for testing purposes. I'd run a 30' pipe only if were a must but I keep thinking how years ago chimneys had no liners other than clay or mortar and they did just fine minus the occasional failure for whatever reasons. I'll do the 90 on 3" pipe in chimney and try a piece of sheet metal with a 4x4 square cut out to give it 16sqin on top of chimney to create the venturi and can make the hole bigger if needed. I did notice on the C6 and C7 settings that if a ran the C6 down lower (I had it on 80 last night and C7 still on 500) that the draft fan even though it still surged the surges were spaced further apart than when I ran it up to say 150 where surges were much closer but never a steady flow. For C7 it didn't seem to make that big of difference but it's only on HR3 at the current time with thermostat at 68deg and great advice from a previous post to only do adjustment there in increments of 10 (I went to many at first and 20 minutes later fire was out). Thanks
The reasoning behind the bigger flues back in the day was due to log wood. A tremendous amount of heat comes off of and is lost from log burning. Plus the fire is significantly bigger on a log fire as compared to a pellet fire. Most log burning appliances use a 6" or 8" flue pipe off the burner compared to the 3" that our appliances use. A log fire can maintain heat in a space that large without trouble, while our furnaces are designed to have lower operating temps and maintain heat in a 3" or 4" flue. Keep me updated on how your venturi idea works out. I'm interested in the results.
Yesterday evening I was running out of time faster than daylight so rather than cutting a piece of sheet metal with a 4"x4" hole in it for top of chimney I grabbed a some bricks(6 of them) with three 1"-1 1/4" diameter holes each brick and laid them two high crossways on top of chimney creating that venturi effect. The door temps didn't climb as I hoped but after an hour I didn't think that was very much time for any changes to take great effect and I also had side cover off(below control panel) to plumb in extra return air duct so it was pulling in colder basement air. This morning it was 67deg in house but I realized I'd forgotten to install the side cover last night (got busy on a different project) so it ran all night pulling in cooler basement air for room fans. I had HR1 at 1.5lbs/hr and HR5 at 5lbs/hr C6 at 100 and C7 still at 500. I was impressed that it kept house to 67deg with side cover off pulling in cooler air and running HR3 considering it got down to mid 20's overnight. Unless I can get an update on temps this afternoon from wife it'll be later today that I'll check things over and see if the addition of bricks on top of chimney was a good move or back to drawing board. Thanks
Interesting. My door temps dropped a little last night also, but I was able to maintain 560-580 on HR4 and 121 on the bonnet. Could you feel the hot air being sucked up out of the chimney when you were up there? Did it feel like it had any effect on velocity after you put the bricks on? Maybe you need to open your bottom slide air door a little further to allow some more air to come through.
I could certainly feel the hot air coming out of chimney and about 20 minutes after I put the bricks on even with a very light wind it appeared the smoke was shooting up higher than it ever did so I guess that's a win for the venturi effect
When I get home later Ill check things over and go from there. I have slide on bottom currently at 1 1/2 inches out.Well, the venturi sounds like it's helping to pull the hot gasses out and away then, so that's good. I'd say with your fan parameter set as high as it will go, you're either not getting enough air through the slide door or too much air now. At least you're getting closer and it's keeping some heat in the house even with the door oversight and yes it got chilly last night. We have some snow coming our way tonight and 50s again by the weekend. Lol, welcome to Indiana.
Got to love Indiana weather it's the only place I've lived where you can experience all four seasons in one day so the saying is If you don't like the weather at current time just wait 15 minutes. LOL
Yesterday I got the under control panel cold air intake hooked up and WOW That's possibly the first and foremost thing to do when hooking one of these units up. The airflow gain is like comparing the exhaust of a fart to the exhaust of a F-16 at max thrust, maybe not that dramatic but you get the idea. I currently have HR1 @ 1.5lbs/hr and HR5 at 5lbs/hr. After hooking the extra return air the door temps went up to about 300deg while on HR1 and about 350ish on HR3 and the bonnet was warmer. Flame quality needs help so I adjusted C6 to 50 and C7 to 220 which did improve flame and now draft fan comes on for about 1 second off for about 3-4 seconds than back on and so on so forth. It's keeping house at 68deg so I'm impressed but next on the list is OAK than probably more adjustments. Do you think I could get my cold air for OAK from chimney that's about 6 inches away from stack that's exhaust from pellets without pulling that smoke back down? I could even do some sorta elbow if needed. Of the two chimney's the one has never been used so it's still good and clean. Thanks. Here are some photos of cold air intake under control panel.Attachments
And I have slide door(dampener) at 1 1/2 inches out. I messed around with different openings and at current time the 1 1/2 inches out seemed to give it better flames than any other attempts. We're gaining on it
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