DoubleB
Minister of Fire
If I remember how to use my psychrometric chart, indoor air at 68F and 40% humidity will condense to water within the parts of your walls that are 43F or cooler. Not saying you shouldn't humidify, but just for reference.
Everything Drolet Tundra - Heatmax...
- Thread starter brenndatomu
- Start date
-
Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.
We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.
We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
If I remember how to use my psychrometric chart, indoor air at 68F and 40% humidity will condense to water within the parts of your walls that are 43F or cooler. Not saying you shouldn't humidify, but just for reference.
JRHAWK9
Minister of Fire
So, what you're trying to tell me is I should have drains put at the bottoms of my walls?
Man, are you a Mechanical Engineer? You are bringing back some memories of Thermodynamics classes I took back in college in which I remember NOTHING of.
DoubleB
Minister of Fire
So, what you're trying to tell me is I should have drains put at the bottoms of my walls?
Well, you might get lucky if your house is so drafty that the air escapes to the outside faster than it can cool down to 43F!
Actually, yes I am a mechanical engineer.
Thermo was one of my faves, although I haven't used it in ages.
JRHAWK9
Minister of Fire
Well, you might get lucky if your house is so drafty that the air escapes to the outside faster than it can cool down to 43F!
Actually, yes I am a mechanical engineer.
Maybe I should let up a bit on the amount of water and see how things are at 30% RH. It's just so comfortable in here when there's normal humidity. Makes it feel warmer compared to the same temp at lower humidity.
I have a BS in Civil Engineering and also took Thermo. I actually enjoyed it too and did rather well in that class but I just don't remember much of it, unfortunately. Where did you go to school? I went to UW-Milwaukee. Graduated in Dec of '97.
DoubleB
Minister of Fire
New guy here so I'd like to say hello and thank you for this forum. First off let me start by telling you all that I bought my Tundra in June of 2015 so this is my 3rd season of running it and I have been thoroughly disappointed in the unit. I have grown up with y family burning wood but never really did it myself until now. My unit is serial number 1525, I don't know if that's good or bad but I contacted SBI for any update kits so I don't know if or what I will get.
I have my unit set up going into my heat ducts that my propane furnace uses, I have spring dampers on my 8" ducts coming off the wood furnace and I am having a anti backdraft damper installed this week in my propane furnace. I have my tundra hook up to a thermostat next to the propane one and I am happy with the damper door closes on the tundra. I have a 7" clay chimney good draft of -.06 to -.04 when my bd is set up but my flue temps via a laser temp gun measure 120-150, I've had 185 once. I closed completely closed the bd and my draft is off the charts. I have temps of between 70-90 degrees coming out of the 8" ducts that I have set up using the left and right outlets. My blower is set on 3, I've tried every setting and it doesn't seem to make any difference. I get very little secondary burn and I am using 1 1/2 - 2 year seasoned oak, ash and a very small amount of various soft woods. My static pressure in the heat outlet tubes are .15-.2 so I know that needs to be bumped up some. I am also adding a cold air make up from outside to see if that helps at all.
I have a 2000 sq ft house and I leave my basement door open and also cut a hole in a cold air return duct from up stairs to help pull more air down stairs. I was really happy when I read up and purchased this furnace because of the features but it has done nothing but let me down. It maintains heat the house rather than heat it. I figure if I don't get it figured out this year I may move on to something else.
I have my unit set up going into my heat ducts that my propane furnace uses, I have spring dampers on my 8" ducts coming off the wood furnace and I am having a anti backdraft damper installed this week in my propane furnace. I have my tundra hook up to a thermostat next to the propane one and I am happy with the damper door closes on the tundra. I have a 7" clay chimney good draft of -.06 to -.04 when my bd is set up but my flue temps via a laser temp gun measure 120-150, I've had 185 once. I closed completely closed the bd and my draft is off the charts. I have temps of between 70-90 degrees coming out of the 8" ducts that I have set up using the left and right outlets. My blower is set on 3, I've tried every setting and it doesn't seem to make any difference. I get very little secondary burn and I am using 1 1/2 - 2 year seasoned oak, ash and a very small amount of various soft woods. My static pressure in the heat outlet tubes are .15-.2 so I know that needs to be bumped up some. I am also adding a cold air make up from outside to see if that helps at all.
I have a 2000 sq ft house and I leave my basement door open and also cut a hole in a cold air return duct from up stairs to help pull more air down stairs. I was really happy when I read up and purchased this furnace because of the features but it has done nothing but let me down. It maintains heat the house rather than heat it. I figure if I don't get it figured out this year I may move on to something else.
Last edited:
Howdy SMW!
That pipe temp is external so that is probably about right, 150-175* is where mine runs, sometimes up to 200...which equates to about double that on the internal temp.
1.5 -2 year Oak probably won't burn real well...about the slowest drying wood there is. 3 yrs CSS works a lot better. I'd run the blower on speed 1 to try and get some temp rise through the furnace.
Until you can sustain long term secondary burn you will not get a ton of heat off 'er...they love their wood dry dry dry!
Throw a couple ECO bricks on top of your usual load, see what that does. Some kiln dried lumber scraps in place of the ECO bricks can work too...
3fordasho
Minister of Fire
Ditto to what Brenndatomu said. You are in Wisconsin correct? Gotta have a Menards near by, pick up a couple packs of these:
https://www.menards.com/main/heatin...49-c-6855.htm?tid=-4035453073623230604&ipos=5
and see how it performs on a load of 6 - 10 of these blocks. I mix in a few on those especially cold nights, I've yet to try a full load of the bricks but will try it at some point. All these EPA burners need consistently dry wood. 20% moisture content OK, 15% even better.
Your comment about very little secondary burn screams wet wood issue #1, maybe draft issue #2.
FWIW I'm heating 3400 sq ft in MN with a Tundra, and yes it can be tough or near impossible to raise temps more than a degree or two if I let things drop off too much. In those cases I run the propane for 5 minutes and let the Tundra maintain over the next 8 hrs.
I will definitely try those bricks. I have been measuring my wood and I want to say that it’s at 11% ish but I will check again when I get home. What draft issue are you thinking because my chimney draft is good according to my meter. I will slow the fan down also, I haven’t burned in it for 2 days so it’s a good time to work on the thing.
11%?! Where do you live? 11% is all but impossible unless kiln dried or you live in the desert.
How do you test? It needs to be on a room temp split, that has been re-split, and tested with pins parallel with the grain, in the middle of the split.
3fordasho
Minister of Fire
Be sure to check the moisture content on a freshly split face, and a better measurement will be had with the piece warmed up to room temp.
We'll suspend draft talk until after we hear the results from the ECO brick test, very possibly not a draft issue but I brought it up because secondary burn action is also dependent on adequate draft. I've noticed secondary burn on my set up is harder to maintain as outside temps rise above 30F even with no BD (that tend to leak a bit even when closed), all double wall connector pipe to 18' of 6" class A insulated chimney pipe.
DoubleB
Minister of Fire
Welcome @smw !
I agree with @brenndatomu and @3fordasho , wet wood sounds like your culprit, even though at first it might tell you it's dry. You could also try throwing some dimensional lumber (but not treated) to see if you can get good secondary action and good heat. If you do, then your cordwood is wet.
Also, have you cleaned out your HX tubes, and made sure the connector pipe between your furnace and baro damper is cleaned? When I first started I had some wet wood and got a lot of buildup on the ID of the single-wall connector pipe, which meant that even when the draft at my baro was -0.05", it was much lower (0.03 ish) at the furnace so I couldn't get good secondary burn. If this is occurring, you might not even get good secondary burn with dry wood during your upcoming tests.
I agree with @brenndatomu and @3fordasho , wet wood sounds like your culprit, even though at first it might tell you it's dry. You could also try throwing some dimensional lumber (but not treated) to see if you can get good secondary action and good heat. If you do, then your cordwood is wet.
Also, have you cleaned out your HX tubes, and made sure the connector pipe between your furnace and baro damper is cleaned? When I first started I had some wet wood and got a lot of buildup on the ID of the single-wall connector pipe, which meant that even when the draft at my baro was -0.05", it was much lower (0.03 ish) at the furnace so I couldn't get good secondary burn. If this is occurring, you might not even get good secondary burn with dry wood during your upcoming tests.
I’ve been measuring without respiltting, I just resplit a piece and it’s 19%. The piece was in my basement so it’s about 60 degrees. I want to thank you guys for the replies and help. I won’t be having a fire again until Friday so that’s when I will try those bricks
Lets see what your guys thoughts are. If my flue temps are below 200° than my blower is running on/off and I'm really not heating the house, maybe barely sustaining temperature depending on the outside temperature. I intend to - but have not yet - installed my variable speed fan controller. I just cleaned my HX tubes.
I have my blower wired on the #2 setting. I guess I need to measure my plenum temps and see what you guys think, maybe I should drop it down to the #1 setting and see how it performs.
I also only have 1-2 year old CSS ash, but it was not always covered from precipitation. And it was stacked under pine trees so it didn't get much sun. All of the wood I have been processing lately, now gets stacked in a new location in the middle of the yard with plenty of direct sunlight & wind, but I won't get into burning any of it until next winter at the earliest.
EDIT: I thought you were saying internal flue temps of 200. I still wonder if #1 speed is worth a try.
DoubleB
Minister of Fire
That's what I get too.
The first 2-3 hours of the burn, plenum temps 130-140+F, blower always on will increase my house temp.
After that, secondary burn dies out, mostly coals, 100-120F, blower on less than half time, that's ~1/4 as much heat. Doesn't increase house temp but will maintain house temps 3-8 hours depending upon outdoor temp and wind.
What I have been doing the last 2 seasons with my Tundra is getting the house to 68 with my propane and then maintaining the heat with the Tundra. I'm goin to make a fire tomorrow and try those wood bricks and see what I get, I'm weird about having a fire going when nobody is home. I also cleaned out my heat exchangers and the pipe going to the chimney, I clean my heat exchangers every other week because its easy lol.
That's why the temp controller works so well, you can wire the blower to a higher speed to take advantage of the higher temps early on in the burn, but then it still will slow down and run non stop (until the VERY end) at a lower speed, stripping heat from the flue gasses instead cycling on/off/on/off, and "waiting" on the snap switch to turn the blower back on wasting heat up the flue in the meantime...you get a lot more blower run time with a speed controller...and more heat to the house.
But if you have wet wood and are not getting sustained secondary burn, then that needs to be dealt with first.
3fordasho
Minister of Fire
how often are you starting a fire in a cold furnace? (no coals) Every day? I put a match to mine about a month ago and have not needed another.
Full load at 5:30 am, go to work, 3/4 load at 4pm and another full load at 10pm. Rinse and repeat every day. That cold start load never has as good of secondary burn as a reload on a bed of hot coals.
During the weekdays I rake the coals in the moring and go to work. After work I light a new fire if there aren’t any hot coals left, weekends I rake the coals in the moring and throw wood on the hot coals. I burn my wood furnace on the weekends and about 3-4 days on the week days. I’m nervous about a fire going when we aren’t home which is goofy I know.
Matt78
Burning Hunk
Is the kuuma vapor fire as good as described? Maybe not the right place to ask this question, I guess just wanting your opinions.
3fordasho
Minister of Fire
And in the interest of full disclosure if you've read this entire thread you'll find that many of use have added a temperature control that monitors flue temps and opens/closes the air inlet to both keep the burn hot enough to maintain adequate flue temps and also prevent an overfire situation in case the thermostat calls for heat for too long or someone inadvertently leaves the air inlet switch in the open position. Then there is the timer mod for cold starts and reloads, and the variable speed blower motor control... probably more to come. Yes the furnace is not ideal as factory supplied....
3fordasho
Minister of Fire
Have not heard of any disappointed owners. It comes with a variable air inlet control based on furnace output that some of us Tundra owners sort of try to emulate.
Last edited:
Matt78
Burning Hunk
I'm gonna upgrade one of these years. I'll put the tundra out in the shop. Which I believe the tundra will do a good job of heating. With all the radiant heat it puts out the glass. I like the tundra don't get me wrong. it's so easy to run with the temp control, but it sure can be a fussy little botch!!
I have seen on this forum where you guys have added controllers for the fan and damper, I have to look thru the posts again to find exactly what controllers were used and how they are wired in, I told SBI that I shouldn’t have to do all that but if it makes these Tundras work better and you guys seem to be a lot happier after it’s done then I guess I’m on board doing it
JRHAWK9
Minister of Fire
It's not just the Tundra's which work better with a variable speed blower controller, pretty much ALL solid fuel burning furnaces can benefit from one. Your fossil fuel furnace's blower is setup with a certain heat rise, meaning the delta between return air and supply air. The larger this heat rise the more efficient the heat transfer will be, as long as it stays within the specs found on the data tag. When your fossil fuel furnace runs, it's pretty much putting out the same BTU's over the timeframe it's running. So one blower speed works fine for that. Our wood burning furnaces don't, they ramp up and down over the course of a burn cycle. So at the very beginning (cold light) and end of the burn cycle you will have a very small heat rise with a static rpm blower and it will be cycling off/on with very inconsistent and dropping supply temps. Adding a variable speed controller will increase this heat rise by varying blower speed based on heat output and will keep the blower running MUCH longer at the end of the burn with consistent supply temps. This will increase delivered efficiency towards the end of the burn cycle.
I added one to my Kuuma last winter and it DID make a difference, especially at the end of the burn cycle.
Similar threads
