Outdoor Wood Furnace Info
Outdoor Furnaces - Manufacturers WITH EPA-Certified Models => Central Boiler => Topic started by: smithbr on January 02, 2018, 07:21:27 AM
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Hi Gang
Attached is a chart of my furnace's performance for the last 24 hours. Things to note:
- House has forced air HX for upstairs, basement is radiant floor loop heated, DHW has a sidearm heater and the electric is shut off to it when the OWF is running. Upstairs setpoints are 18C during the day, 16 at night; floor loop is 18 C constant.
- We fed the furnace once last night, at 6 PM, and won't need to feed it again until late afternoon.
- Outdoor temperature hit -24 C last night.
- when you see close cycles, like those between midnight and 3 AM, my basement floor loop is running.
- the long quiet cooldown before and after that is typical when the house is not calling for heat.
- the steeper cooldown after 7AM indicates the forced air system is doing the morning warmup.
I believe my furnace reaction chamber TC is misplaced; if it was really running that cool, I'd expect to be clogged with creosote, but it's doing quite well unless I load with lousy wood. I have a replacement, but can I just push the existing one further in?
Thanks
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This is mine I'm busy now but will reply later but it runs every hour very consistent we are at 0-4f degrees at night up to 15f at daytime.
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This is a live shot at 10 am 1-2-18
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Thanks, 5050. I'm seeing a few things there:
- your high temperature "stage 3" burns are much more frequent and consistent
- your cycling is much more regular (You only have one load, is that correct? I'm quite sure I can identify my floor and forced air cycles, and sometimes I can spot the thermal load for DHW when we use a lot).
- you are doing pulses a lot less frequently; we're doing them every 12 minutes, for 52 seconds. First winter I had a few FO instances trying to run with longer gaps between pulses, but now I suspect that was due to other 'newbie' factors. What are your settings for pulse timeout and length?
- your temperature is much higher; we reached those numbers when first installed (but I didn't have data logging then). Is it possible for that thermocouple to move? Or maybe I hit it? Can it read a lower number in the same circumstances, over time (maybe encrusted with crap)? I've never heard of a degradation mechanism for a TC that led to that effect.
Thanks!
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What I'm thinking is, I'm doing a lot of stage 1 and stage 2 burning, not really hitting that intense stage 3 very often. That's probably why I seem to be cleaning out more often than some have to. Is that reasonable?
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Read my post on charcoal ,my boiler in 4th season n all of sudden lots of charcoal not hitting temps! What's happens the hole below the charge tube burns wider n wider over time n then to much coals drop down then the 3 rd stage doesn't kick in things just compound after that? Look at what I welded as a grate to stop this from happening, you can replace it at $160 I think but I don't like to give in,so far working great!!
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Here is another live shot
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Okay, 5050, a little more info please.
What's the scale of the thing - do the left and right 'ears' rest on the side shelf? Does this rig fit front to back right above the tube? So it holds big chunks up, sure, but anything 3" or less can drop down in all 4 corners, no? Or maybe I'm misunderstanding where this goes in your furnace. Any chance you could take a picture of it in place?
This is only our second year on this unit, so I'm a little doubtful the firebrick has eroded that far, unless my wife has been chipping away at it when she takes her turn cleaning and feeding every day.
Thanks
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Our local hardware store has a fireplace grate that might work (I'm not a welder). I'll have to measure it up. Might have to adjust it with a hacksaw.
http://www.homehardware.ca/products/300/55152671.jpg
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Really I modified it a little from pic it goes under charge tube all I did was trim n bend side ears to fit under tube as not to lift it n some clearance from tube. There are many things can cause bad temps I had a wire all of a sudden off of a solenoids or that elbow half clogged,pm with your phone number I you want n I will call u. The grate has been in over a week n not one bad burn and nothing but a pint of ash in reaction chamber.also with theses outside temps I've been throwing a little bit of wood in the door!
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Ahhh. below the charge tube. Makes more sense now. also a lot smaller than I was thinking. Ok.
I might PM you in a day or so, I've got to look it over first. Tomorrow is only 14 F for the daytime high, but it's the best it'll be for the next week so I'll be doing my cleanout. I'll look it over then.
I'll also take a closer look at the air path from the air box to the charge tube, as I still get the odd piece of charcoal spit back into the airbox. Been through the manual, and they suggest 15 seconds and gentle action on the bypass is all that's needed, but we're already doing all that.
Thanks a lot for the replies.
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The piece is only made out of 5/16 stainless total of 8" long n about 4" wide
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Thanks!
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Took a good look at the top of our reaction chamber firebrick, along the edge of that channel. Not much wear and tear, look pretty square-edged still to me. I'll think about how I might make it harder for chunks to fall through, but I don't think this is having a major impact. When we clean next, I'll take a better look at the air path to the sidewalls, as it looks like I've got a lot more creosote on one side than the other, which wouldn't be normal.
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The dealer told me the gap in the firebrick under charge tube is like a 1" mine was at least 1.5,the grate is still working perfectly only a pint n half maybe in reaction chamber even in this very cold run this week with lots of wood going in it.
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smithbr i have a length of rebar that I poke the firebox airchannel holes open with if necessary a couple of times a week. Pay special attention to the lower holes so any creosote in channels can run back into firebox. I've found that 1-4 inches of coals covering the air charge tube in firebox gets me the highest burn temps. When cleaning reaction chamber I always give the thermocouple a tug to make sure it is fully extended into chamber. Clean rear exchanger tubes as necessary. Primary elbow can be cleaned twice a season or so by some, but I only need to do at the end of the season. I've also raised the primary solenoid so cover gap is an extra 1/4" higher than owners manual specs. Puts more air in firebox and helps push down into reaction chamber better.
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Thanks, Boilerman. We keep those tube openings clean. Haven't checked the elbow since startup this fall, so I'll look at that. Haven't messed with the thermocouple, didn't realize it was prone to moving, so I'll do that next cleanup.
Good idea on the solenoid, but I'll do that as a controlled experiment, when I can change only that and see if there's an effect over the next 48 hours running.
Cleaned it today, and a bit more charcoal in the reaction chamber than usual, but as I said earlier, the edges of the firebrick below the charge tube look very good, so I don't think they've degraded much; I was thinking that if they had, I'd just turn them around to put a 'virgin' edge back into service, see if it makes a difference, but I don't believe there's enough difference to warrant it.
We'll see. I'm still getting the occasional Stage 3 burn, but also some Stage 2, and lots of demand cycles never get out of Stage 1; yet they complete within 15-20 minutes (175 ->190, with 3-5 degrees overshoot). So I don't think things are running poorly. My wood is certainly not what I'd like to be burning, so that may be a factor as well. Just wish I'd had the wifi remote last year, so I could do some longer term comparisons.
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How green is your wood? Those reaction temps seem pretty low. Is the stove gasifying well? Any blue smoke visible from the chimney once its up and running? With good seasoned hardwoods I see 1000-1200 degree burns with my Edge.
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Hi Pointblank
Stage 1 <550; Stage 2 550->750; Stage 3 >750. We occasionally see temperature peaks between 800 and 850, no higher. The higher the demand, the better the burn, because it runs for longer before hitting the high cutoff.
That being said, I have a real suspicion we're running higher than that TC is measuring, because we're not going creosote-solid. We're generating more creosote than last year, by a long shot. My wood is cut 4 years, left in block until last spring, split, and stacked in an open shed. So six months of open air circulation. The 4 years in block didn't do much drying, mostly grew fungus. Last year's wood had shed dried for three years, so it was almost too dried.
I know, this year's is horrid wood by any reasonable standard, but it's what I've got right now. Next year's wood will be similar, but mixed 50-50 with two-year-dried poplar, so things should improve. Then I'll hit the thee year wood cut last year in the year after that.