Everything Drolet Tundra - Heatmax...

[TheBigIron]

On the Tundra I wonder if you could make that large plenum opening like on the Caddy? Instead of using the 2 side by side outlets or the 2 front to rear outlets could you just utilize that whole space where the 4 outlets are on top of the Tundra and install a plenum that is big enough to cover that entire area? Then off of that plenum install ductwork to wherever you would need it. Would this make a difference in how hot the unit would get? Some thoughts for the experts.. Or would this cause bigger issues? Any input would be great.. Thanks Dave

 

[laynes69]

The door openings are the same, but the Caddy had an air jacket built around the face of the firebox, or mine does. So the entire surface is cooled. I've questioned SBI about utilizing the 4 openings and they said no, not sure why. I would have to assume between the lower density firebrick and the 2 8" openings, the Tundra runs with a hotter firebox.

 

[TheBigIron]

The door openings are the same, but the Caddy had an air jacket built around the face of the firebox, or mine does. So the entire surface is cooled. I've questioned SBI about utilizing the 4 openings and they said no, not sure why. I would have to assume between the lower density firebrick and the 2 8" openings, the Tundra runs with a hotter firebox.

laynes69,
I spoke with an SBI tech and he informed me that using the 4 outlets, there would be velocity issues.. Maybe a larger blower in the tundra??

 

[brenndatomu]

The exhaust stream exits the firebox in the back corners going into the heat exchanger tubes on each side. Those come together behind the HE cleanout door merging together to exit though the center tube. I think they prefer using the side duct connections because...
1. The exhaust will be hottest there (when I say exhaust I mean flue gasses)
2. The heat exchange will be best there because exhaust velocity is lower due to the 2 into 1 HE tube design. (longer contact time with the metal)
3. Both sides should be equal temp whereas if using the front to rear connections the temp would be hotter in the front one than the rear due to both being on the same tube. And I'm sure there are differences in airflow between using the 2 different sets of holes to, as far as how the blower cools the firebox and HE tubes.

Not sure why they are so dead set against using all 4 connections or even a plenum, other than that's the way it was designed and tested so allowing anything else introduces an unknown variable. Also, it may be a case of it's better to make a smaller airflow volume hot than to make a larger airflow volume warm. Another thing may be creosote issues if HE tubes are cooled too much (and too cool exhaust could cause draft problems for some chimneys too)

 

[DoubleB]

I spoke with an SBI tech and he informed me that using the 4 outlets, there would be velocity issues.. Maybe a larger blower in the tundra??

I asked SBI about 4 outlets about a year ago, and the tech said it could be done, but resulted in poorer air flow. It sounds counterintuitive, but there might actually be a good reason. Here's an analogy:

If you aren't getting enough heat into one room of your house, the answer isn't necessarily to give it a bigger duct/register or increase fan speed; rather it might be better to partially shut down registers in other rooms.

With the Tundra, the objective is to remove heat, but the point is the same: if it's too easy for air to blow past cool areas of the furnace, then not enough air will blow past the hot areas that most need heat removed. One solution could be to crank up the fan speed, but that doesn't always work effectively, depending upon duct systems, and even power outage. In fact, this idea is used in a lot of heat exchangers: that by adding restriction to the easy flow paths, it's actually possible to reduce total flow (and power) required to remove the same heat from the heat exchanger. For the Tundra, specifying two of the outlets might actually be better than all four (if in fact this is the principle, but I do not know this for sure.)

 

[DoubleB]

laynes69 said: ↑
I've read posts where they've burned open for hours. I never let ours burn open for more than a 1/2 hour. When it closes at that point, it cranks out the heat. Now once the coaling stage approaches, it can stay open if it wants. .
This is exactly how I run mine, never wide open damper for more than 30mn, and that is for a cold start. Reloads are usually 10-20mn depending on amount of remaining coals. I figure the furnace is most efficient up to temperature with a closed damper.

If I'm not mistaken, both of you guys have a thermostat connected? If so, any tips for how to avoid the thermostat from keeping the damper open for quite a while? Do you just set the tstat a couple degrees colder than the temp when you load the furnace, so that the damper doesn't open roughly until it's just coals?

3fordasho, you posted that you have the high temp cutout in your flue, but are temps high enough with damper closed to keep that switch open, and if not, then how long does the tstat open the damper to bump temps above the tstat?

I'm just getting confused how much your damper might or might not be open during peak heat in the cycle. Thanks for your advice.

 

[Wisneaky]

Here is an update on my Tundra with the cracks. Originally SBI said I would need to return the furnace to Menards and they would ship a replacement furnace to them or I could receive a credit. I replied to their email about how much it weighs and also asked about how the credit would work. They said I would get an instore credit for my original purchase price. I told them I would like to go the credit route until I could determine if the issue was fixed. I then received an email saying that they would contact the store and I would only need to bring in the sticker from the furnace along with my receipt and a form they emailed me. I took everything to menards today and received the credit with no issues. I'm going to wait and see if sbi comes out with that bigger tundra I've heard about. I must say SBI customer service is excellent and they are extremely good at honoring any warranty issues. I think they went above and beyond what some manufacturer's would of.

 

[David_QC]

Good to know that the service is good !

Concerning overheating issues or damper full open more than 30 minutes... would it be a good idea to add a second damper motor on top of the first one ?
Motor #1 with a short chain link to the damper... connected to a timer
Motor #2 with a longer chain link to the damper... connected to the tstat

Honeywell M847A1031 cost 80$

 

[Wisneaky]

Good to know that the service is good !

Concerning overheating issues or damper full open more than 30 minutes... would it be a good idea to add a second damper motor on top of the first one ?
Motor #1 with a short chain link to the damper... connected to a timer
Motor #2 with a longer chain link to the damper... connected to the tstat

Honeywell M847A1031 cost 80$

Do you have a barometric damper installed? Do you know what your chimney draft is?

 

[laynes69]

If the furnace is sized properly, it shouldnt have to remain open for an extended amount of time. For us, usually within 20 minutes after loading the house will hit 72 in the morning if it's dropped. If it's bitter cold and I know it's going to work harder, after let's say a half hour, I'll close the damper and the house will continue to rise. Once it hits it's setpoint, I'll up the thermostat and it will maintain that temperature. If there is a call for heat, the damper only opens a couple minutes at most and closes. If I know the furnace won't keep a set temperature (-20 degree temps) I'll settle for let's say 70 instead of 75. I will say since we've tightened up our home, the furnace works alot less. If the furnace must stay open during the first couple hours of the burn, it's the wood or its just not enough.

 

[3fordasho]

I do have a thermostat but its set point is set low and it never calls for heat. I thought it might be beneficial but with the other controls I've added it's really not necessary. Part of the problem is I'm heating way more than the tundra can handle and if I moved the set point up it would call for heat most of the heating season.

The other controls I've added:

0-60mn "hot tub" timer connected to terminals on back of tundra- used for cold starts and reloads. Typically 30mns for a cold start, 10-20mn for a reload on coals. Purpose is to get the firebox hot enough to maintain secondary action after the timer ends and allows the damper to close. I don't use the manual damper switch the factory provided.

Flue temperature monitor - a thermocouple mounted in the flue connector pipe about 12" above the rear exit-
this is my furnace and chimney protection device- the thermocouple is connected to a digital temp control with relay outputs- the temp control normally closed contact is wired in series with the factory high temp limit snap disk. Once it reaches the temp I've selected as maximum safe (currently 625F) it opens that NC contact and shuts the air damper just like tripping the factory high limit would. The temp control allows the damper to reopen once temps cool to 425f (assuming the timer is still closed) This control lets me load the furnace, set the timer and walk away worry free knowing the temp controller will keep temps in check.

Now since my thermostat never calls for heat (reason explained above) the inlet damper will not open after the initial start up or reload and thus the heat output is low for the second half of the burn and I get a build up of coals at times - for most this is where the thermostat would be beneficial. I again utilize the flue temp control (this time the low temp alarm) to open the air inlet once temps drop too low (currently set to 250F) getting more heat and burning down the coals.

If I'm not mistaken, both of you guys have a thermostat connected? If so, any tips for how to avoid the thermostat from keeping the damper open for quite a while? Do you just set the tstat a couple degrees colder than the temp when you load the furnace, so that the damper doesn't open roughly until it's just coals?

3fordasho, you posted that you have the high temp cutout in your flue, but are temps high enough with damper closed to keep that switch open, and if not, then how long does the tstat open the damper to bump temps above the tstat?

I'm just getting confused how much your damper might or might not be open during peak heat in the cycle. Thanks for your advice.

 

[DoubleB]

Laynes and 3ford, thanks for the good explanations, that clears it up for me. I like your systems too.


Wisneaky,

I must say SBI customer service is excellent and they are extremely good at honoring any warranty issues. I think they went above and beyond what some manufacturer's would of.

I'm glad it's turning out well for you, all things considered. They're handling my cracking the exact same way as yours, and I feel the same of SBI.

 

[DoubleB]

Concerning overheating issues or damper full open more than 30 minutes... would it be a good idea to add a second damper motor on top of the first one ?
Motor #1 with a short chain link to the damper... connected to a timer
Motor #2 with a longer chain link to the damper... connected to the tstat

Seems to me you could do it all with only the existing damper motor, just like 3fordasho did. The only advantage I can think that a 2nd motor might add is if you were to try to achieve a "medium" burn rate with the damper only partly open. Is that what you have in mind?

 

[David_QC]

Seems to me you could do it all with only the existing damper motor, just like 3fordasho did. The only advantage I can think that a 2nd motor might add is if you were to try to achieve a "medium" burn rate with the damper only partly open. Is that what you have in mind?

Exactly, sorry it wasn't clear what was the purpose of this...
As Laynes explain how he is running his caddy, I suppose it's my wood and next year will be better, but for now at damper full open my burn time is really bad and at full close my furnace is a creosote machine, so I have to run middle open to be happy. If I adjust the existing chain a bit longer I have to use a strap on the damper open during 30 minutes while loading and not forget it... If I use a shim under the damper to keep it middle open, it could be bad if a power loss happen. So that's why a second motor would be usefull in my case.

I think that middle open could help for overheating as well if wood is good... don't know... never run it with good wood for now :- )

 

[DoubleB]

David QC,
My wood is doing me ok, but sometimes it's a bit damp. Only had 1 year to dry most of it, but it's fairly low density. I think you and I both are going to enjoy next winter more with drier wood. There's not enough time left in this winter for me to try messing around with a 2nd motorized damper, but if you want to, we'd enjoy hearing your results. I might yet, though, add a timer and high temp cutout this spring.

 

[DoubleB]

So as the posts the last couple days have been talking about burning practices, high temps, and air distribution, I vaguely remember a long time ago hearing that a bunch of Amish families near them are running Caddies in gravity air flow only, without electricity or fans. I think that was here on hearth.com.

Does that jog anyone's memory? If so, that's curious to me because they wouldn't have as much cooling as the rest of us with electricity, nor automatic high-temp cutout, etc., yet I assume those Caddies have worked well enough? Just thought I'd bring that up if it helps provide insight for us.

 

[brenndatomu]

I vaguely remember a long time ago hearing that a bunch of Amish families near them are running Caddies in gravity air flow only, without electricity or fans. I think that was here on hearth.com.
Does that jog anyone's memory?

Yep, I think that was over on AS, in the big Tundra thread? (Edit, just looked, yep...post #140 by Fyrebug) (also, check out the first line of post # 142 and #154!)
I believe Caddys are available without a blower. So with no blower and very likely no filter of any kind, gravity flow could be pretty substantial.

After a lil prodding, SBI responded to my most recent email asking about expected lifespan of Tundra. They said with proper setup, and under normal use, they would expect 10 years.

 

[JRHAWK9]

After a lil prodding, SBI responded to my most recent email asking about expected lifespan of Tundra. They said with proper setup, and under normal use, they would expect 10 years.

My guess what pretty accurate then when I looked at them at Menards. I figured 5-10 years. Like they said 10 years is the max life one should expect out of them under perfect conditions. I'd expect closer to 5. I just don't see how they save anybody money in the long run. Save $$ now to spend more when everything is said and done.

 

[Smoke Signals]

My guess what pretty accurate then when I looked at them at Menards. I figured 5-10 years. Like they said 10 years is the max life one should expect out of them under perfect conditions. I'd expect closer to 5. I just don't see how they save anybody money in the long run. Save $$ now to spend more when everything is said and done.

Every one would like a new car (or truck) but some times it's not in the budget so you have to buy a used one or two for less money to get you by until your situation allows you to buy brand new. Yes, you may spend a little more in the long run but at least you never have to walk

 

[JRHAWK9]

One can make an argument that older/used vehicles will actually cost you LESS to own. So that's not a very good analogy

With a walk-out basement, installing my furnace was a cakewalk compared to what some of you guys had to go through installing yours. Even so, I wouldn't want to install a new one every 5-7 years, even with how easy my walk-out made it. I couldn't imagine some of you guys having to yank the old one out and put a new one in multiple times over a time period where one well built furnace would last. I guess I'm the crazy one though. Wonder how long Caddy's are designed to last?

 

[brenndatomu]

Like they said 10 years is the max life one should expect out of them under perfect conditions

Hmm, I don't remember the words "max" or "perfect" in what I posted. The way I read what they sent me was more like, If installed and run properly, we would (or you could) expect at least 10 years.

Nobody here is saying that your furnace is not awesome, or the best, whatever, no need to keep rubbing non Kuuma owners noses it. People are buying an affordable clean burn wood furnace made by a fairly reputable company that is at least located on the North American continent. Unfortunately, there have been some bumps in the road, but instead of critiquing, how about some kudos for not buying a chinese made smoke dragon from the local farm supply store?

 

[STIHLY DAN]

After a lil prodding, SBI responded to my most recent email asking about expected lifespan of Tundra. They said with proper setup, and under normal use, they would expect 10 years

This can't be true, how can you offer a lifetime firebox warranty but say the unit should last 10 years. The fire box is basically the unit. Something spells fishy. I am not a fan of units lasting 30 years, with technology as it is 10-15 years is perfect. I am sure in 15 years I won't be burning my unit because of advancements.

 

[Smoke Signals]

One can make an argument that older/used vehicles will actually cost you LESS to own. So that's not a very good analogy

Well I didn't think it was bad for short notice . But think about it this way, burning a Tundra is going to save a lot of money over burning propane so a efficient wood furnace is better than no wood furnace at all kind of like a used car beats walking. Guess walking would be cheaper than a used car but who wants to walk?

 

[BrotherBart]

This can't be true, how can you offer a lifetime firebox warranty but say the unit should last 10 years.

Limited lifetime warranties have long been legally recognized as ten years or after the unit isn't in production anymore.

 

[JRHAWK9]

This can't be true, how can you offer a lifetime firebox warranty but say the unit should last 10 years. The fire box is basically the unit. Something spells fishy. I am not a fan of units lasting 30 years, with technology as it is 10-15 years is perfect. I am sure in 15 years I won't be burning my unit because of advancements.

But if it lasts 30, you can sell it after 15 and re-coup some of the money. Can't sell one which is junk