Everything Drolet Tundra - Heatmax...

[DoubleB]

On page 21 a bunch of people were reporting the left outlet was much warmer than the right when starting a fire. Tonight is my first fire, and I noticed that my right outlet was warmer than my left. (Right side is the side with the door handle, electrical cord, damper motor, etc.)

So, sure enough I'm another datapoint for the phenomenon, although mine was backwards. Recall that my outlets are 12 inches long before dumping into a common plenum. So it looks like a circulation loop in the air jacket/outlet/plenum instead of through the filter, until the blower kicks on.

 

[brenndatomu]

Yeah, I checked it again once I got my infrared thermometer rounded up, there was ~20* difference from left to right, until the blower kicked on, then they were roughly even

 

[KARB2014]

Thanks for the mini review KARB!

Is that with the damper fully closed?

No kiddin?! Man, Ima hafta do some more checking and tweaking. How long does it take for the duct temp to get to 120 after the tstat calls for heat? And how/where are you measuring that?
Blower on speed 3 huh? Have you ever checked your SP?

Sorry everybody I don't check in here that often. Those measurements are with the damper wide open. Once it closes it will slowly work it's way down to -0.05. The lowest I have seen it drop to is -0.04 but that was on a 59 deg day with just coals in the box. As far as how long it takes to get to 120, it all depends how far I'm into the load. On a rather fresh load I would say about 5mins. On an older load 10mins. I haven't measured the SP but my duct work is so poorly design I need to have more air moving through the house. If not the thermostat seems to call for heat more often. My house was built in 1905, and is a Brick on terracotta build so only the attic is insulated. My windows are old so I plastic them in the winter but even at that it only goes so far. So when it get really cold out the thermostat calls for heat about every 90 mins and will call for about 20mins before it's satisfied.

 

[KARB2014]

Thanks for the mini review KARB!

Is that with the damper fully closed?

No kiddin?! Man, Ima hafta do some more checking and tweaking. How long does it take for the duct temp to get to 120 after the tstat calls for heat? And how/where are you measuring that?
Blower on speed 3 huh? Have you ever checked your SP?

Sorry everybody I don't check in here that often. Those measurements are with the damper wide open. Once it closes it will slowly work it's way down to -0.05. The lowest I have seen it drop to is -0.04 but that was on a 59 deg day with just coals in the box. As far as how long it takes to get to 120, it all depends how far I'm into the load. On a rather fresh load I would say about 5mins. On an older load 10mins. I haven't measured the SP but my duct work is so poorly design I need to have more air moving through the house. If not the thermostat seems to call for heat more often. My house was built in 1905, and is a Brick on terracotta build so only the attic is insulated. My windows are old so I plastic them in the winter but even at that it only goes so far. So when it get really cold out the thermostat calls for heat about every 90 mins and will call for about 20mins before it's satisfied.

Welcome to the Forum, KARB2014!

Did your unit came with an adjustable snap disc? Or did you add it? I'm serial #8xx and mine is a fixed snapdisc.

I added the snap adjustable snap disc. It doesn't fit under the cover so you have to modify it or just leave it off.

 

[KARB2014]

I really want to make the controller. I do believe it will cut down the amount of wood I use. I reason this because on the really cold nights It will call for heat for 20-30 mins(my house is an energy hog). In that time the top of the furnace gets to 185-190 never hot enough to cut out the damper(200deg snap disc). If I could get it to shut down before the thermostat is satisfied there is more than enough heat to get to the set point with out having to have the damper open that long. I can really see now why Kuuma doesn't use a thermostat Just the Hi, med, low on the furnace itself. But still 6 cords I used last year I don't think is too bad.

 

[Matt78]

I finally believe I'm getting this thing figured out. I'm getting loads to last a good 8 to 9 hours. That is on a large load. Which I think it works best with. Seems like small loads don't last very long. I'm amazed how long this things holds coals.

After about 2 1/2 weeks burning I decided to tear stove pipe apart and see what it looked like. I was happy to find it was pretty clean. So far I'm very Happy. We'll see if that remains when it gets really cold out. I did get three cords of wood in basement this past week.

 

[DoubleB]

So far I'm very Happy.

Great to hear, I think you'll be happy when it's really cold, too, even though you might need to change your burning a bit to prevent coals from building up. Not too hard.

 

[DoubleB]

It will call for heat for 20-30 mins(my house is an energy hog). In that time the top of the furnace gets to 185-190 never hot enough to cut out the damper(200deg snap disc). If I could get it to shut down before the thermostat is satisfied there is more than enough heat to get to the set point with out having to have the damper open that long.

Hate to say it but 185F air jacket temp with blower speed 3 might cause you trouble. The hottest air temp I ever measured was 140F and that was with a full load of small and dry wood with the damper open quite a while and the slowest blower speed 1. That was a test and not normal operation. And I still eventually got cracking on my furnace. You're probably right that your ductwork is too slim, and it sounds from your numbers like your blower isn't carrying the heat out of your furnace very well and could cause overheating and excessive temperatures. Especially since your tstat is wide open for 20+ minutes at a time.

What I did to try to mitigate the same problem is I replaced my 160F damper cutout snap disc with a 130F snap disc. I normally cruise around 115F with the damper closed and the slowest blower speed. If the damper opens it only takes 3-5 minutes for the air jacket to reach 130F and the damper closes again even if the tstat is calling for heat. It'll take about 15 minutes with the secondaries cruising until temp settles back down below about 122F when the damper snap disc closes and allows the damper to open again for 3-5 minutes. Although it doesn't allow me to overfire the furnace on extremely cold days, I'd rather assist with the LP furnace.

In other words, I learned that connecting and using a thermostat as SBI instructs is risky without adding more protection yourself.

 

[KARB2014]

Hate to say it but 185F air jacket temp with blower speed 3 might cause you trouble. The hottest air temp I ever measured was 140F and that was with a full load of small and dry wood with the damper open quite a while and the slowest blower speed 1. That was a test and not normal operation. And I still eventually got cracking on my furnace. You're probably right that your ductwork is too slim, and it sounds from your numbers like your blower isn't carrying the heat out of your furnace very well and could cause overheating and excessive temperatures. Especially since your tstat is wide open for 20+ minutes at a time.

What I did to try to mitigate the same problem is I replaced my 160F damper cutout snap disc with a 130F snap disc. I normally cruise around 115F with the damper closed and the slowest blower speed. If the damper opens it only takes 3-5 minutes for the air jacket to reach 130F and the damper closes again even if the tstat is calling for heat. It'll take about 15 minutes with the secondaries cruising until temp settles back down below about 122F when the damper snap disc closes and allows the damper to open again for 3-5 minutes. Although it doesn't allow me to overfire the furnace on extremely cold days, I'd rather assist with the LP furnace.

In other words, I learned that connecting and using a thermostat as SBI instructs is risky without adding more protection yourself.

Where are you measuring? Because the newer furnaces come with the shut off at 200 on top of the furnace in between the two 8"outlets. I have talked to SBI about my temps and they said if your draft is under control you should never hit the high limit. Like I said I have yet to hit it, I just think lowering it would help with wood usage. I really can't complain on wood usage 6 cords for last winter, I like to tinker with it. I take my reading on top of the front outlets block off plate. That is also where I moved the snap disc. I have recorded that the highest I have seen on the stock location in between the two outlets is 172. That was with a full box of smaller split locust. No signs of over fire or damage. My secondary tubes are still straight and come right out by hand.

 

[Builderml]

I wonder why you would be worried about hitting the high limit of 200°? Isn't that why SBI has that high limit set at 200° to keep it from being an issue. I understand you are concerned about cracking as am I but if 200° was to high wouldn't they have put in one at lets say 180°? I have left the damper open after starting a fire to see how long it takes and to see what my stack temps are before I hit the 200° and the damper closes. I would say with a full load of softwood I can hit that 200° mark in about 20 mins roughly. My stack temps are consistent at about 400-430° on the surface temperature gauge when I let it hit the high limit. The next time I let it cycle the high limit will cut in and my stack temp went down to about 350 on that same load.I can tell you nice hot air comes out the registers. I did this for two reasons as a test to see how it would perform on a really cold day and I needed to get the temp up some in the house and to see if I would hit the over fire range on my stack temp if it did stay open for some reason. No it does not hit the overfire range it stops just short and the next cycle after that the stack temp is even lower. I guess If it cracks that's an issue I will address at that time. But and a big but at that I think that with the softwood I am getting a lot of flames in the heat exchangers without having the firebox overfiring. I could be wrong but I sleep better thinking that way

 

[brenndatomu]

Well guys...I'm not impressed. Something has to change or I'm going back to using the Yook.
I'm sitting here under a blanket because the Tundra refuses to blow hot air! My daggum chinese made 1.2 CF stove in the fireplace does a better job of heating the house, using a 1/3 the wood! It will at least make it 75* in here for 3 or 4 hours! I'd hafta shovel wood into this thing like a fireman tending the firebox on a loaded steam engine headed up the mountain side to get 75* outta the Tundra!
I can get the duct air temps up to 120 after the damper is open for a while...10 to 20 minutes depending on what part of the burn cycle it is, but the temp dies off pretty quick when the damper closes and is usually in the low 90s 4 hours into a burn. By the time the air makes it to the register, and across the room to my feet, it feels like cold air.
I have had this thing running nonstop since last night and it is 70* in the house, my Yukon would have used less wood and made it 75* in the house, at the least. I mean heck, its not really that cold out (28) and our house doesn't take that much to heat, we are only "actively" heating 1200 sq ft.

I have cleaned the HEs several times without much, if any difference. I tried different fan speeds and static pressures, not much difference. My draft is running right in the required range per a calibrated Dwyer. My wood is popcorn fart dry (BIG-time secondary action) The heat is just not being "exchanged".
It is supposed to be a little warmer this week to where I can go back to using the fireplace stove to heat with, I'm gonna tear into the Tundra. I had an idea this afternoon that may pay off. I have never had the baffle out and it appears that there may be an "insulating" layer of soot all over the top of the firebox, above the baffle. I couldn't get a great look because of the hot coals in the back were threatening to melt my plastic mirror, but I looks like a good cleaning is warranted. Keep in mind this is my first season with it, but I am the second owner of this unit and it is 3 (ish) years old.
If cleaning the "primary" HE doesn't help I am gonna pull the insulation blanket out from behind the firebricks on the sides of the firebox, try to get more heat from the actual fire/coals. I think the blanket is more for reducing CTC than it is for protecting the steel of the firebox, and I have plenty of clearance so...
I'll keep y'all updated

 

[Builderml]

Well guys...I'm not impressed. Something has to change or I'm going back to using the Yook.
I'm sitting here under a blanket because the Tundra refuses to blow hot air! My daggum chinese made 1.2 CF stove in the fireplace does a better job of heating the house, using a 1/3 the wood! It will at least make it 75* in here for 3 or 4 hours! I'd hafta shovel wood into this thing like a fireman tending the firebox on a loaded steam engine headed up the mountain side to get 75* outta the Tundra!
I can get the duct air temps up to 120 after the damper is open for a while...10 to 20 minutes depending on what part of the burn cycle it is, but the temp dies off pretty quick when the damper closes and is usually in the low 90s 4 hours into a burn. By the time the air makes it to the register, and across the room to my feet, it feels like cold air.
I have had this thing running nonstop since last night and it is 70* in the house, my Yukon would have used less wood and made it 75* in the house, at the least. I mean heck, its not really that cold out (28) and our house doesn't take that much to heat, we are only "actively" heating 1200 sq ft.

I have cleaned the HEs several times without much, if any difference. I tried different fan speeds and static pressures, not much difference. My draft is running right in the required range per a calibrated Dwyer. My wood is popcorn fart dry (BIG-time secondary action) The heat is just not being "exchanged".
It is supposed to be a little warmer this week to where I can go back to using the fireplace stove to heat with, I'm gonna tear into the Tundra. I had an idea this afternoon that may pay off. I have never had the baffle out and it appears that there may be an "insulating" layer of soot all over the top of the firebox, above the baffle. I couldn't get a great look because of the hot coals in the back were threatening to melt my plastic mirror, but I looks like a good cleaning is warranted. Keep in mind this is my first season with it, but I am the second owner of this unit and it is 3 (ish) years old.
If cleaning the "primary" HE doesn't help I am gonna pull the insulation blanket out from behind the firebricks on the sides of the firebox, try to get more heat from the actual fire/coals. I think the blanket is more for reducing CTC than it is for protecting the steel of the firebox, and I have plenty of clearance so...
I'll keep y'all updated

Brenn, All i can say is wow. At 1200 sq ft you should be getting cooked out of the house. I don't have that much experience with the Tundra as i am sure you know but i can only tell you what i am able to get out of it. Like i have said in other post i have the tundra ducted into rooms that total about 2000sq.ft. but all the doors are open to those rooms so in reality i am trying to heat 2800 sqft. We did have a couple days in the 20's here already and i was able to keep the house at about 70* with just the secondary burn. I think as you look further into it you'll find something isn't right. Now at 2800 sq ft my house has 10' ceilings as the lowest and others at 12' and 14' thats alot of cubic footage i am trying to do with the Tundra. I wasn't expecting the Tundra to do as well as it has with being over its stated capacity. Also i haven't even burnt hardwood yet this is all on softwood.
I hope you get this figured out as i am sure you will.

 

[laynes69]

I don't understand if the Tundra shares the same firebox as the Caddy, why all 4 outlet's can't be utilized. If the ceiling of the firebox is built up with soot, it could affect heat output. Do you think the temp controller has anything to do with it? We have the same firebox but an open plenum and I loaded 4 or 5 splits at 7:30am and reloaded almost 10 hours later. We did have the oven going at the end, but the house was at 75 all day and increased to 76 when the oven was on. You very well could be doing the best, and if it's not keeping the heating demand then it's just not big enough. Of course every home is different. Since the cold weather hit, I broke out the thermal cam and found some bad air leaks in the basement. A can of foam later, they're fixed. I'll be watching for updates, and hoping you figure things out. I went thru the same thing and it's very frustrating. In the end I found the issue and have been happy since.

 

[brenndatomu]

Wow, sounds like your Tundra is walkin n talkin like a big dog!

I hope you get this figured out as i am sure you will.

Thanks, Ima give 'er heck trying! I like a good mechanical/electrical mystery, and I don't give up easily. I guess I am blowing off some steam because of getting meager results from what I thought was a "dialed in" installation.

I don't understand if the Tundra shares the same firebox as the Caddy, why all 4 outlet's can't be utilized.

I'm with ya, seems like the HEs are more or less the same too. I guess I can experiment with my sisters Tundra, I mounted a plenum right to the top of the furnace, only have 2 outlet holes open right now, could open all four later once a "baseline" is established.

If the ceiling of the firebox is built up with soot, it could affect heat output.

Do you think the temp controller has anything to do with it

I don't think the controller has anything to do with it, it has only been used for a few burns now, and the quick look that I got at the soot looked like it has been building for a while. It looks like a really dry fluffy type of soot from what I could see. Looks like pretty good insulation to me.

You very well could be doing the best, and if it's not keeping the heating demand then it's just not big enough.

I really feel something is not right because the same amount of wood in the Yukon would have completely different results. As I said before, this house is not that hard to heat. Back when I heated with fuel oil it only took 600-700 gallons per year depending on how cold it was, and I have added a lot of insulation and new windows since then so...

 

[Matt78]

Something must not be right. I think your on the right track. Our home is 1850 square feet.I do not have a thermostat hooked up to it. So the blower is on low most of the time. I have a run going to both ends of the house. Its been about 86 at those ends and 76 toward the middle. I have opened windows already! My duct temps have been around 98. Good luck and keep us posted.

 

[DoubleB]

I can believe it could be good insulation, and fortunately it's just a flat surface that's easily accessible to clean.

The other thing is have you made sure that your baffle is moved to the rear to make sure the hot gases exhaust at the top front and travel under that HX surface?

 

[DoubleB]

Regarding the high temp cutout; my manual and the current online manual both describe the snap disc (item 44060) as an L200 snap disc, which might seem like 200F. However, paragraph 9.3 indicates that the snap disc opens at 160F to shut the damper. I honestly do not know if it actually opens at 160F or 200F, but the text alone is more conclusive for 160F so that's what I'm going with. Since I've never hit 160F anyways it doesn't matter for my situation.

I wonder why you would be worried about hitting the high limit of 200°? Isn't that why SBI has that high limit set at 200° to keep it from being an issue. I understand you are concerned about cracking as am I but if 200° was to high wouldn't they have put in one at lets say 180°?

Well that's a very good point. I'm just going on the fact that I've never hit my overtemp cutout (that I know of) and I didn't keep the damper open too much and I still got cracking, so my point is mainly just that I'm cautious not to rely upon the stock overtemp protection.

 

[brenndatomu]

The other thing is have you made sure that your baffle is moved to the rear to make sure the hot gases exhaust at the top front and travel under that HX surface?

Yep.
I had 'er rocking and rollin this morning before we left for church and then came home to 70*...
And when I say rockin and rollin, I mean over 500* internal flue temp (per the display on the controller) and a firebox FULL of flames. It was hard to stand 2.5' away from the door with shorts on...HOT! And my duct temps just barely got to 120* (measured ~2' above the furnace via digital internal temp probe)(oh, and the fan was running the whole time) Now 120* duct temp will raise the temp of the house, slowly, but as soon as the damper door closes, then that temp drops to below 110*...and slowly drops from there. If I use the Tstat, it is just not satisfied soon enough, and I just blast a bunch of heat (and wood) up the stack, even using the temp controller. Seems the way @3fordasho is using his is working the best for me too, no tstat.
If I had a fire like that going in my Yukon it would result in 150* duct temps (and open windows on a day like today in the 30s-40s) But it is a much larger unit at 140k BTU (gross) with a very large HE.

Anyways, these two machines are very different but I think the Tundra is not running up to par...yet

 

[Builderml]

I am going to have to look at the manual again when I get home tonight. Here is how I thought the tundra worked. Please correct me if I am wrong???? You start a fire from a cold firebox lets say, now when the temp hits 160* in the air jacket the fan comes on now once the temp goes down to 120* the fan turns off, but if the temp hit 200* in the air jacket it closes the damper that is if the damper is open. Again please correct me if I am wrong. To me if your only getting 100*-120* air getting pushed out by the time the air goes thru the Ductwork it will be cold.

 

[Builderml]

Brenn, could you have your controller stack temp set to low at 500*. I think your the one that told me that the magnet type suface temp gauges read about 1/2 of what the internal temp is. With the damper open and a full firebox I have no issue hitting 400-440 surface temp. At which point if I just let it go the damper door automatic closes. With the damper closed and in cruise mode its about 150-200 surface temp. But if it is true and surface reading is half the internal temp I am running at almost twice the temps you are. Just an idea, keep us posted

 

[brenndatomu]

I am going to have to look at the manual again when I get home tonight. Here is how I thought the tundra worked. Please correct me if I am wrong???? You start a fire from a cold firebox lets say, now when the temp hits 160* in the air jacket the fan comes on now once the temp goes down to 120* the fan turns off, but if the temp hit 200* in the air jacket it closes the damper that is if the damper is open. Again please correct me if I am wrong. To me if your only getting 100*-120* air getting pushed out by the time the air goes thru the Ductwork it will be cold.

I have one of the older models that had the fan and limit switch on the back of the firebox instead of over the HEs like it is now, so my duct air temps run a little differently than on the newer ones. It also has an adjustable switch instead of the preset factory one. I have though about moving the switch up top but I know that is more of a fine tuning issue and isn't going to help me get the heat exchanged, which I feel is the real issue right now.
I did bump the controller temp up some, but that really only gets the duct temps up (somewhat) while the damper is open and doesn't make any difference once the damper is closed for a while. Like I said before, I have quit using the tstat for now because it wants the damper open too much and the wood just goes POOF! Well, I get a pile of coals that don't seem to heat the house, which I understand if it is really cold out, but if this thing can't heat the place under warmish conditions then I gotta think there is an issue somewhere here. Don't get me wrong, this thing is makin heat, I'm just heating the chimney instead of the house.

I won't be tearing into it tonight as it is still pretty cool here today and the lil stove upstairs would have a hard time keeping up tonight, that and the Tundra is still hot from this mornings load. It did OK today but I loaded 'er up pretty good with wood this morning too...a good bit more than what would have been required by my Yukon at these temps.
Oh, and you are correct, ducts temps much under 100* feel pretty cool, at least from across the room...

 

[JRHAWK9]

FWIW, my plenum temps on my Kuuma are usually 100-110 according to my HVAC thermometers I have stuck in the ductwork. I have my low limit set to turn on at 115° and it shuts off I believe at 95°. The blower will run the whole time and then cycle towards the end of the burn.

 

[laynes69]

I think the 2 outlet restriction doesn't help. We have a total of 9 takeoffs (4-8" and 5-6"). If we had the 2 outlets, we would be in the same boat. Still though, 1200 square feet isn't much for a epa firebox that size. Our duct temps are usually 90-110 depending on the fire, sometimes higher.

 

[brenndatomu]

1200 square feet isn't much for a epa firebox that size

Thank you! Like I said, my little 1.2 CF stove does it, just has short burn times (4-6 hrs) And BTW, it doesn't take much wood to fill up 1.2 CF box lemme tell ya, kinda like playing Jenga, or whatever that game is, trying to get it all to fit
If I can get the duct temps up higher (than current temps) when the damper is open, get the tstat satisfied, and then get the temps up a few degrees from where they are running now once the damper is closed for a while...I think we'll have something

Just to clarify, we are "actively " heating 1200 sq ft, 90% of the duct work goes to this area. There is also the 1200 ft of the basement, but, there is only two small ducts to that area, mostly radiant heat keeps the basement warm enough. There is also 600 ft more upstairs (cape cod style) but the ducts are normally turned off unless we have overnight guests or some other special goings on

 

[maple1]

brenn - a couple of your latest posts are sounding like some of those from our Nfld. friend of last year who also couldn't seem to get any heat. (Name escapes me right now). And nobody could understand why.

Hmmm...