Wood furnace chimney draft ???

[andym]

I'm in the process (final testing phase really) of installing a Heatmax2 wood furnace. I installed a new 6" double wall insulated chimney. The only option was to run it out the basement wall and up the side of the house. I have 22 ft of pipe above the tee. There is a 2 ft piece going through the wall (pitched nearly 1 inch). Connecting to stove (see pic) I've got 2 45° elbows with a barometric damper in between. Below the damper I used a short piece of stovepipe with a drawband to make final connection.
Got some cold weather (48 F) so I lit a fire to test my set up. I measured flue temp with a magnet gauge as well as my inkbird temp controller (Celsius only). With the first small load it struggled to reach .07 on the Dwyer25. Peak flue temp was around 360F (internal). After the coals burned down some I tossed in 6 smaller splits (14-20% MC) They took off beautifully. Flue temp reached 460F so I closed the draft. Immediately the flue temp plumetted to around 230F. Draft was measuring .02-.03. Secondaries disappeared and even back puffed a few times. Is that normal? Opening a window didnt seem to help. I opened the draft again and it took off. With a smaller load it never did really burn with the draft closed. Even with a nail holding it slightly open I would only reach 240F. Do I need bigger loads to see more pleasing results?

After the second load burned down to coals with occasional flames (draft closed) it was registering .03 draft. Cracking the door open it jumped to .04. Opening the door increased draft to .05 yet a lot of smoke still escaped. Why is there smoke coming out the door?

Sorry for the long post! It seems to me like I don't have enough draft. The BD was covered with tin foil during most of this time. There are some stovepipe connections that could be leaking a bit.

Please give me your advice!

 

[brenndatomu]

Draft was measuring .02-.03. Secondaries disappeared and even back puffed a few times. Is that normal?

Not normal.
Seems like you have the bases all covered...but I wonder about your wood...and it could be you just need to go through a few cycles of open/closed damper before secondary burn is stable...especially with a new furnace, sometimes it takes a few fires before the firebrick dry out well.
How did you test the wood MC? In the middle of a fresh split face?
Where are you taking the draft measurement, and where exactly are you getting the internal temp measurement?
How far is the TC tip inserted into the pipe...that can make a big difference too.
With 22' of new class A chimney I would expect better draft than that...does it meet the 10-2-3 rule?

Chimney "2-3-10" Rule

The chimney 2-3-10 rule states that a chimney must extend 3 feet from where it penetrated the roof and be at least 2 feet higher than anythi...

pignottipropertyinspections.blogspot.com

 

[salecker]

Yes how is the chimany configured outside?
Is it high enough to get a draft going or is the roof line interfering with the draft.

 

[Gearhead660]

Dumb question, but gotta ask. Is there a cap on the bottom of the T outside?

 

[andym]

Dumb question, but gotta ask. Is there a cap on the bottom of the T outside?

Yes. Only dumb questions are the ones that are not asked.

 

[andym]

Not normal.
Seems like you have the bases all covered...but I wonder about your wood...and it could be you just need to go through a few cycles of open/closed damper before secondary burn is stable...especially with a new furnace, sometimes it takes a few fires before the firebrick dry out well.
How did you test the wood MC? In the middle of a fresh split face?
Where are you taking the draft measurement, and where exactly are you getting the internal temp measurement?
How far is the TC tip inserted into the pipe...that can make a big difference too.
With 22' of new class A chimney I would expect better draft than that...does it meet the 10-2-3 rule?

Chimney "2-3-10" Rule

The chimney 2-3-10 rule states that a chimney must extend 3 feet from where it penetrated the roof and be at least 2 feet higher than anythi...

pignottipropertyinspections.blogspot.com

Tested the wood on a fresh split at 66°. The first load I did not test and they did sizzle a little. The second load was better.

I may have just closed the draft too quick. The fire seemed to be roaring tho. The secondary burn tubes were starting to glow red. My old EPA stove never did that.

I'm taking draft measurement just above the 1st 45° elbow and about 8 inches below the BD.

Internal temp is in the same location, but different positon on the pipe. The sensor I'm using came with a threaded collar/sleeve that gives about 1/2 inch of penetration.

I'll try to post a pic of the chimney tommorrow. It just misses the overhang on the 2nd floor, and extends approx 50" above the roof edge. With a 4/12 pitch roof that means I'm about 10" instead of 24". Should I add another foot or two? The reason I didn't go higher is because if I do I won't be able to see down it without removing some pipe.

 

[andym]

This evening I did another test run. I put high temp silicone on a couple stovepipe connections that needed it. 51° outside. Manometer showed zero draft when it lit the fire. No smoke spillage at all. Draft climbed predictably with flue temp. I did not test MC but there was almost no visible bubbles on the end grain as the logs began to burn. Half full of mostly red elm. I left the draft open until around 450 internal. Draft .08. In just a couple minutes the flames disappeared completely. Draft dropped of course but never below .04. Opened the draft and it took off again. Repeated the process again with same results. Set the timer for about 15 minutes and put the children to bed. Returned to the basement soon after the timer ended. Things were really cookin! External temp showed almost 400. Draft at .10. Internal temp was dropping already but still showed over 460F. Plenum temp was 159 with the fan on speed ?4?. After this the secondaries kept burning. Right now the external temp is 150F, internal is 91C (200F). Draft has been steady at .04 to .05. We are about 1.5 hrs into the burn. Logs are starting to fall apart, secondaries still burning. (I've had a piece of #12 copper wire keeping the draft door cracked open.) The fan has begun cycling off then on.

I am much happier tonight. I am beginning to suspect my internal temp readings. I'm certain that the second load would do even better.
Please read my previous post as well and give me your thoughts.

 

[brenndatomu]

The sensor I'm using came with a threaded collar/sleeve that gives about 1/2 inch of penetration.

That's not much penetration
I think you will find if you check it with a 3-4" TC, the center of the pipe is a good bit hotter.

Draft climbed predictably with flue temp. I did not test MC but there was almost no visible bubbles on the end grain as the logs began to burn. Half full of mostly red elm. I left the draft open until around 450 internal. Draft .08. In just a couple minutes the flames disappeared completely. Draft dropped of course but never below .04. Opened the draft and it took off again. Repeated the process again with same results. Set the timer for about 15 minutes and put the children to bed. Returned to the basement soon after the timer ended. Things were really cookin! External temp showed almost 400. Draft at .10. Internal temp was dropping already but still showed over 460F. Plenum temp was 159 with the fan on speed ?4?. After this the secondaries kept burning. Right now the external temp is 150F, internal is 91C (200F). Draft has been steady at .04 to .05. We are about 1.5 hrs into the burn. Logs are starting to fall apart, secondaries still burning. (I've had a piece of #12 copper wire keeping the draft door cracked open.) The fan has begun cycling off then on.

You need 3 things...a bath fan timer, a temp controller, and a blower motor speed controller...you would be thrilled to death with how things operate with those items installed (you may have already mentioned getting them?)
You set the fan timer, that opens the damper until the temp controller senses your preset temp, damper closes until the preset low temp is met, then, IF there is still time on the fan timer (or a tstat calling for heat) the temp controller will allow the damper to reopen...rinse repeat until time runs out or tstat is satisfied...by then secondary combustion will be sustained if you have dry wood. And just FYI, I wouldnt bother hooking up a tstat...the fan timer is all you need, tstat will just waste wood and pizz you off...you'll end up unhooking it anyways, most people do!
The blower speed controller will keep the blower from cycling on/off like that...and in effect ends up putting more heat to the house, less up the stack...and its a quite noticeable difference too!

 

[andym]

That's not much penetration
I think you will find if you check it with a 3-4" TC, the center of the pipe is a good bit hotter.

You need 3 things...a bath fan timer, a temp controller, and a blower motor speed controller...you would be thrilled to death with how things operate with those items installed (you may have already mentioned getting them?)
You set the fan timer, that opens the damper until the temp controller senses your preset temp, damper closes until the preset low temp is met, then, IF there is still time on the fan timer (or a tstat calling for heat) the temp controller will allow the damper to reopen...rinse repeat until time runs out or tstat is satisfied...by then secondary combustion will be sustained if you have dry wood. And just FYI, I wouldnt bother hooking up a tstat...the fan timer is all you need, tstat will just waste wood and pizz you off...you'll end up unhooking it anyways, most people do!
The blower speed controller will keep the blower from cycling on/off like that...and in effect ends up putting more heat to the house, less up the stack...and its a quite noticeable difference too!

I'll see what I can come up with on the thermocouple.
I've got the temp controller but it's currently only hooked up to read the temp. Im going to exchange it for one that displays Fahrenheit.
I have the bath timer connected, but haven't used it much because I've basically been watching it during the initial burn.

I also purchased a speed controller, but am not sure I really need it. The Heatmax2 operates the fan much differently than the older models. I might start a separate thread on that later.

I appreciate all the info you have posted in the past on these mods. I'll do some posts later on detailing how they apply to the Heatmax2. I won't get it dialed in until the fall heating season, but I'm glad for this spell of cold weather to do some test runs.

 

[brenndatomu]

The Heatmax2 operates the fan much differently than the older models.

Not really...the only difference is that is CAN bump the speed up if it gets hot enough...but from what I hear about them, they very rarely ever adjust...still cycle on/off all the time, same as with the T1's...and that drove me crazy! Fortunately I bugged enough people about it that somebody finally came up with a suggestion for a way of doing variable speed that was pretty easy/affordable...and it works great! Thanks to @STIHLY DAN for the idea!

 

[andym]

I am very frustrated this morning again. I left the furnace last night (11pm) with a fairly large pile of charred logs/coals 2 hrs into the burn. I would have said the amount of flames and secondaries were weak, but steady. Draft was wiggling between .03 to .04. This morning at 7 the blower was still coming on occasionally. There was still a half gallon of coals, plenty to get the next load started. However under the stove connector there was a small puddle of creosote (1/2 tablespoon). I threw in 4 pcs of red elm (20 lbs?) Took off quick with no sizzling. This time I ignored the internal temp, watching only the external reading and draft reading. Allowed it to reach 280F external before closing draft door. Same results as always, less than one minute and no secondaries almost no visible flames, yet the draft measured .06 steady. Gave it another 10 min open draft, closed it again. This time the flames continued, but very weak. Temp gradually tapered until I noticed creosote starting to drip from stovepipe! HELP! This wood is not that wet. It burns great in my other EPA stove. Is an exterior chimney that bad? The manual should not allow it if it is. What am I doing wrong? I know this is a smaller load, but the manual says to match the load to your heating need. Should I have to leave the draft open for 3/4 of the burn? If I did it would get way to hot. It just acts like the fire is not getting the air it needs. Whenever the damper door is shut the temps start going down. How big of load should it need to see strong continuous secondaries like the manual says? HELP!

 

[andym]

Is it possible that my blower fan is removing too much heat? Supply pressure downstream of the plenum barely registers on the manometer. Closing some registers increased it to .01. Any thoughts?
I did not use the 6" round pipes. I made the plunum simply dump into an 8x22 duct that tees into the existing ductwork. That gives me 176sq inches. Installation manual recommends 170 min. Return is 10x20.

 

[superex87]

It sounds like you have a drafting problem. What kind of class a chimney is being used? Is the chimney pipe insulated? If your getting condensing in the chimney then the chimney is giving up too much heat outside or your flu temps leaving the furnace are too low. I believe you want to maintain around 400F. The reason your fire dies when you close the damper is lack of draft. Are your draft readings positive or negative? The draft should be sucking the smoke up i.e. you should be seeing negative numbers unless this has a inducer motor on it.

 

[brenndatomu]

Is it possible that my blower fan is removing too much heat?

Put the speed controller on...the blower would have likely ran all night. Do it.

 

[Gearhead660]

I am very frustrated this morning again. I left the furnace last night (11pm) with a fairly large pile of charred logs/coals 2 hrs into the burn. I would have said the amount of flames and secondaries were weak, but steady. Draft was wiggling between .03 to .04. This morning at 7 the blower was still coming on occasionally. There was still a half gallon of coals, plenty to get the next load started. However under the stove connector there was a small puddle of creosote (1/2 tablespoon). I threw in 4 pcs of red elm (20 lbs?) Took off quick with no sizzling. This time I ignored the internal temp, watching only the external reading and draft reading. Allowed it to reach 280F external before closing draft door. Same results as always, less than one minute and no secondaries almost no visible flames, yet the draft measured .06 steady. Gave it another 10 min open draft, closed it again. This time the flames continued, but very weak. Temp gradually tapered until I noticed creosote starting to drip from stovepipe! HELP! This wood is not that wet. It burns great in my other EPA stove. Is an exterior chimney that bad? The manual should not allow it if it is. What am I doing wrong? I know this is a smaller load, but the manual says to match the load to your heating need. Should I have to leave the draft open for 3/4 of the burn? If I did it would get way to hot. It just acts like the fire is not getting the air it needs. Whenever the damper door is shut the temps start going down. How big of load should it need to see strong continuous secondaries like the manual says? HELP!

Couple questions. How air tight is your house? Possibly not allowing draft? Try cracking a window. Sorry if I missed where you are checking temp, what are you referring to with internal and external temps?

 

[brenndatomu]

I am very frustrated this morning again. I left the furnace last night (11pm) with a fairly large pile of charred logs/coals 2 hrs into the burn. I would have said the amount of flames and secondaries were weak, but steady. Draft was wiggling between .03 to .04. This morning at 7 the blower was still coming on occasionally. There was still a half gallon of coals, plenty to get the next load started. However under the stove connector there was a small puddle of creosote (1/2 tablespoon). I threw in 4 pcs of red elm (20 lbs?) Took off quick with no sizzling. This time I ignored the internal temp, watching only the external reading and draft reading. Allowed it to reach 280F external before closing draft door. Same results as always, less than one minute and no secondaries almost no visible flames, yet the draft measured .06 steady. Gave it another 10 min open draft, closed it again. This time the flames continued, but very weak. Temp gradually tapered until I noticed creosote starting to drip from stovepipe! HELP! This wood is not that wet. It burns great in my other EPA stove. Is an exterior chimney that bad? The manual should not allow it if it is. What am I doing wrong? I know this is a smaller load, but the manual says to match the load to your heating need. Should I have to leave the draft open for 3/4 of the burn? If I did it would get way to hot. It just acts like the fire is not getting the air it needs. Whenever the damper door is shut the temps start going down. How big of load should it need to see strong continuous secondaries like the manual says? HELP!

Don't get too hung up on how long the secondary flame lasts...even with a full load of really dry stuff you'll only get 2-3 hours at most of steady secondary flame.
This time of the year is a really bad time to get first impressions of a new wood burner...sounds like your setup is just fine and will perform well when real winter comes back...in the fall and spring (shoulder season) the outdoor temp is fluctuating wildly, along with barometric pressure, and the wind can be erratic too...terrible conditions to maintain any kind of steady draft. Add on top of that you are doing small loads to try and not overheat the house...insult to injury...easier to burn some fossil fuel in this weather...but I get it, new furnace and all.
The best way to get a decent burn in this weather is to burn low BTU wood (light stuff) so that you can load more of it in the firebox...I have 20#'s of poplar burning right now...would have easily been double that weight if it was Ash or Oak...looked like a lot, but really light.
If you don't have any light stuff, the next best thing is to use small stuff...or re-split what you have to smaller pieces...then stack it in the firebox in a way that makes it "tall"...it will burn better that way...Iike to stack it in kind of a log cabin style pile...if your wood is too long to get any of it sideways, then you can do a skewed log cabin style pile...everything goes in at an angle...2 pieces on the bottom layer angled right, two pieces on the next layer angled left, so on and so forth.
Don't worry about the creosote puddle...just clean it up and know that this will very likely be a distant memory when winter comes back later this year...basically, I don't think you have any actual issues...just the warm weather blues...hopefully you have a fossil fuel furnace that you can use until it gets cold again.

 

[brenndatomu]

I'll see what I can come up with on the thermocouple.

This is like what I used on my T1...not this exact one, but very similar...worked good.
Only rated to 750* F, but I had the controller programmed to never let it get that hot so...
(broken link removed to https://www.ebay.com/itm/3m-0-400-Stainless-Steel-Probe-K-type-Sensors-High-Temperature-Thermocouple-TOP/333240441967?_trkparms=ispr%3D1&hash=item4d96ad9c6f:g:5nMAAOSwIbFdC1ZS&enc=AQAEAAACcIQvEcHUrT7nmUC3yY5qbPyaBN1nJEDYW8MyypsJPgXKjzb4uel3XQiGEzY4CITgmr126F0zY42l9BvVtFfuJc444XQe4oNyxH2U2j33AMc%2Flj5CQdobhOfjBqlsw5%2B3gtmqpNbiN2iT0ywVI3KJgxYofBqBjN7DtHi3fftTn8U0p8%2FyiMHc2%2FM6bC54LSMap6SzaVcz%2FPxw9TESL9x1zR%2BVqOZccOOtSvp42EyeatWMm3LYA%2Fbd6uGzmfyj8dm%2FoyThWfkm2LNmm0MMjAyZ1uXjHoLynf2E7vLI7DVU6Krpq8mwHQm0%2FpONED0zdNSoK1Rms8YiBnejM1Prw1HZbqketmCMdlI0cpu6HVM14IZdgRie7XhuEIkXZkR%2FsuWgff3rnJUjkhZ1kExjVHz%2B2bP43n8kYzSiRTRb4%2B5Mg6irl194rGjQhuvuARlViGKy%2Fz4pRmCBQeR9y0Rolx%2FKkYcX7olHCZaaYCZnk24LLY60QLS77c2kTbwL4ti9AcU4Zd9GU8%2F83xTNZyYfwv3%2F%2BcLv6CAbaNxzjfcK53XTaY6moEudYg617temhykrVk5y0ldfDhymUUSLecDPnV4Jll8lWN1hTYn1Mlzxta2WvSua%2Bacn2h2uBCrelb5reM9NDrpkjLdx0JKh13Q7yL1zLrCZ55a0sRMyi%2BZQM7%2F%2BH1PpNdRQConkHi2vJ1HbowuSwHxEd0k%2FohInzkF6diLj2Uz%2FXpp8a%2Fe18TbVWbiDBCWHPe0%2Fxb0MuaIit2VuI80qgzxJy17Dw1pBBMJxzWkeTmbKQUXsichaLTf1TpB8jVeMxBIMPKYcbxRrQvGGOgbAtA%3D%3D&checksum=333240441967bc0ca17b06fe499d844cd9d2689fe729)

 

[Highbeam]

If any of your wood emits any bubbles, hisses, or dribbles of water then your fuel is too wet. An epa stove doesn’t have a huge heat exchanger and blower stealing so much heat from the exhaustlike your furnace so the stove can squeak by more easily on wet wood.

I do not trust your flue temp probe. It is reading too low. When your surface temperature is 400 your probe should be reading around 800, or double.

If you had a thermostat and it was asking for heat the draft would be open constantly until/unless you ran out of wood or you hit the safety overtemp switch. This furnace is made to run. You’re shutting the draft very early on wet wood so it’s not getting warmed up. Flue condensation is likely.

 

[brenndatomu]

Don't get too hung up on how long the secondary flame lasts...even with a full load of really dry stuff you'll only get 2-3 hours at most of steady secondary flame.
This time of the year is a really bad time to get first impressions of a new wood burner...sounds like your setup is just fine and will perform well when real winter comes back...in the fall and spring (shoulder season) the outdoor temp is fluctuating wildly, along with barometric pressure, and the wind can be erratic too...terrible conditions to maintain any kind of steady draft. Add on top of that you are doing small loads to try and not overheat the house...insult to injury...easier to burn some fossil fuel in this weather...but I get it, new furnace and all.
The best way to get a decent burn in this weather is to burn low BTU wood (light stuff) so that you can load more of it in the firebox...I have 20#'s of poplar burning right now...would have easily been double that weight if it was Ash or Oak...looked like a lot, but really light.
If you don't have any light stuff, the next best thing is to use small stuff...or re-split what you have to smaller pieces...then stack it in the firebox in a way that makes it "tall"...it will burn better that way...Iike to stack it in kind of a log cabin style pile...if your wood is too long to get any of it sideways, then you can do a skewed log cabin style pile...everything goes in at an angle...2 pieces on the bottom layer angled right, two pieces on the next layer angled left, so on and so forth.
Don't worry about the creosote puddle...just clean it up and know that this will very likely be a distant memory when winter comes back later this year...basically, I don't think you have any actual issues...just the warm weather blues...hopefully you have a fossil fuel furnace that you can use until it gets cold again.

I guess I didn't fully explain why you want to stack log cabin style...basically you just want the wood stacked as tall as possible...getting some wood burning right up close to the baffle/tubes will help keep the secondary burn going once you close the damper...after the firebox is up to temp of course.
Log cabin style just gets the pile as tall as possible without having to load "too much" wood...might need to half your splits from their current size though...small splits burn faster/hotter...better for small loads

 

[salecker]

Tested the wood on a fresh split at 66°. The first load I did not test and they did sizzle a little. The second load was better.

Your wood sounds like it is way to wet to be using.And the cresote puddle reinforces that fact.

 

[andym]

Thanks everyone for your input so far. Maybe I was expecting too much for the conditions brenndatomu mentioned earlier. All the talk in the other thread about temp controllers made me picture a wild beast that must be reined in to avoid a meltdown i guess! I think you have probably hit the nail on the head as they say.
I will get a new thermocouple as suggested. The temp controller I purchased ONLY displays celcius for reasons I cannot fathom. I'm going to exchange it for another model that does both.
I think I will like the furnace if I can get thing ironed out come fall. Delivered heat efficiency is great. Now my basement may be too cool.
Here's a pic of the chimney:

 

[Highbeam]

Couple things about your chimney. Looks pretty unsupported. There is a spec for how often it needs support and especially on top it can't stick up above the last support more than 5' without another support.

The 10/2/3 rule means you need the top of chimney to be 2 feet above anything within 10 feet of the top of the chimney and at least 3 feet above the roof. You look fine from here on the 3 foot part but a 4:12 roof needs 5'4" above the roofline to be compliant unless the peak of the roof is within the 10 feet. I don't think that the stack looks too short overall.

That cap! That style of cap looks very difficult to keep clear. Hopefully it's not that one with the little louvers sliced into it. Chimney caps often have these silly screens or other filters in an effort to keep birds out but the filter can clog easily which will kill your draft.

 

[andym]

That cap! That style of cap looks very difficult to keep clear. Hopefully it's not that one with the little louvers sliced into it.

There are no louvers. I don't know how to describe it but it's the style that Menards carries now. I used it for 6 years at our old house. I want to add a wall band on the lower portion for sure. I may add a 2 ft piece before winter.
At some point I may insulate and box in the lower half.

 

[brenndatomu]

I think I will like the furnace if I can get thing ironed out come fall. Delivered heat efficiency is great. Now my basement may be too cool.

Yeah, I think you will like it a lot once real winter comes back, and you get ahead enough on your wood supply to ensure dry wood...try to build up to 3 years ahead (probably 12-15 cords of wood) pretty much anything you cut in Ohio will be dry after being CSS (cut, split, stacked) for 3 years...especially if the top is covered, leaving the sides open for airflow.
Once you are burning full time your basement will stay warm...not hot, but not cold either...some think these units throw too much heat to the basement and have changed the door glass to a reflective type so to limit heat "wasted" to the basement.
And just go ahead and do the mods I mentioned earlier...you will thank me later...seriously...it makes these machines almost as easy to run as the Kuuma's...not kidding.

 

[hedge wood]

I would second getting a head on your wood. It's a lot less chimney maintenance if you have dry wood. I hope the access to the screw cap on the bottom of the T is good it seems that's were the build up on that type of system is. I would add a few more wall hangers also. I think unless there are a lot of trees we can't see in the picture blocking the wind the height should work.