Everything Drolet Tundra - Heatmax...

[brenndatomu]

Without any mods installed, out of the box setup, does the distribution blower stay on without the thermostat calling for heat.

Yes, it runs strictly based on firebox (actually, plenum) temps.

Also looking for a video on how the Caddy operates.

They operate the same. They are very much the same unit, just the changes (that we discussed here recently, somewhere) made to drive the price down some....Chevy vs Cadillac kind of thing...

 

[Boilers]

hows everyones furnace keeping up in these cold midwest temps? Its been getting down into the low single digits here in Indiana and my furnace is losing ground on overnight burns. went to bed at 65 last night and woke up to 60 this morning. I'm not sure what else I can do at this point...other than the "through wall" installation I talked about before. I called Drolet and said they do not recommend the through wall installation. They said it hasnt been tested, and therefore they cannot "okay" it, however they said its ultimately my decision. In my opinion, the manual does not explicitly say that you cant do it and I can still abide by all the rules laid out in the manual about installation. Therefore, I cannot see a problem. Im going to set this on the back burner... but if I cant make this thing run better by spring. Its going through the wall! (or maybe the wall will move )

 

[brenndatomu]

hows everyones furnace keeping up in these cold midwest temps?

https://www.hearth.com/talk/threads/uh-oh-whats-this.172989/page-5#post-2331965

I called Drolet and said they do not recommend the through wall installation. They said it hasnt been tested, and therefore they cannot "okay" it,

Hmm...that sounds familiar...

 

[Boilers]

https://www.hearth.com/talk/threads/uh-oh-whats-this.172989/page-5#post-2331965

Hmm...that sounds familiar...

yeah you were right. He did say I could do it if I wanted, but that it could put the furnace at risk by not allowing it to breathe, and also my home/family at risk of house fire. I promptly responded that the only thing touching the furnace would be at most 1/8" sheet metal surround. and the rooms on either side of the furnace would be completely open, and also that I dont see how its a fire risk if I abide by all combustible clearances in the manual. Thats when he mentioned that since it wasnt tested, he couldnt "okay" it and that my insurance may have an issue as well. I just dont see how this would induce any more risk than what I have currently. Insurance is commonly "okay" with this type of setup on an insert. This furnace doesnt even get hot other than the front.

Dont go sending me links about your Kuuma stove! We cant all change stoves every other year and spend twice as much as the Tundra!

 

[JRHAWK9]

hows everyones furnace keeping up in these cold midwest temps?

Start at post 116 and read down:
https://www.hearth.com/talk/threads/uh-oh-whats-this.172989/page-5#post-2330679

Dont go sending me links about your Kuuma stove! We cant all change stoves every other year and spend twice as much as the Tundra!

oops, just saw this and also saw bren posted the same thread, but different post. Good thing we have Kuuma furnaces and not stoves then, eh?

https://www.kumastoves.com/

 

[brenndatomu]

spend twice as much as the Tundra!

Me either...that's why I bought used

To be fair, I still have affectionate feelings toward the (modded) Tundra...although it probably does not feel the same for me, since it sits freezing away in my garage right now...

 

[Wood1Dennis]

Question regarding the operation of the Tundra II.
.....
Trying to get a better understanding of how this furnace functions. I know the thermostat controls the primary air by opening/closing a flap. Just wondering how many people actually use the thermostat to control the heat.

Can’t locate any videos of this unit on YouTube.

Also looking for a video on how the Caddy operates.

I use the thermostat on my Caddy. On my Caddy the stat open and closes the primary air damper / flap. I only made one minor modification to it, I added an adjustment so that I can control how far it is opened when the stat calls for heat. I posted in this thread #2103. In my opinion that is a really good addition to furnace. When it closes, the furnace still gets enough primary air to keep it burning cleanly, and not smoldering, but closing the damper slows it down to help control the temp in the house. Secondaries are wide open, not regulated.My Caddy was new in early 2016, they have made updates since then so I am not sure how the newest ones compare.

With some ash in the box I can easily hold good hot coals and get a matchless relight in 11 or 12 hours.

 

[brenndatomu]

I posted in this thread #2103.

https://www.hearth.com/talk/threads/everything-drolet-tundra-heatmax.140788/page-85#post-2138788

 

[JRHAWK9]

I was thinking about those furnaces which use a call for heat to open the primary air and then close once the house makes temp. I would think it would be of high importance to properly size the furnace to the heat demand of the house? I would be very nervous if the house is constantly calling for heat which is keeping the primary air hanging open. I'd think this could lead to overfiring the furnace in short order. Take for instance if you are being subjected to some crazy azz below normal cold temps and the house temp you have the thermostat set to can't be obtained; leading to the primary damper being held open throughout a burn cycle. What would you guys do then? I'd assume there would have to be some monitoring going on at some point to keep the furnace from going nuclear?

 

[trx250r87]

I'm pretty sure the high temp limit should trip and shut the damper.

Eric

 

[brenndatomu]

I was thinking about those furnaces which use a call for heat to open the primary air and then close once the house makes temp. I would think it would be of high importance to properly size the furnace to the heat demand of the house? I would be very nervous if the house is constantly calling for heat which is keeping the primary air hanging open. I'd think this could lead to overfiring the furnace in short order. Take for instance if you are being subjected to some crazy azz below normal cold temps and the house temp you have the thermostat set to can't be obtained; leading to the primary damper being held open throughout a burn cycle. What would you guys do then? I'd assume there would have to be some monitoring going on at some point to keep the furnace from going nuclear?

Thats exactly the reason for the temp controller mod...which to be fair, they do have a factory switch to override the "call for heat" if the furnace gets too hot...but at least on the T1, it was pretty stinkin hot at that point...one reason SBI updated the switch location from rear, to top after they started having crack issues. Even if it doesn't overheat the furnace, its an inefficient way to run...

 

[JRHAWK9]

I'm pretty sure the high temp limit should trip and shut the damper.

Eric

Isn't this limit measuring plenum temps though? Depending on your install, plenum temps may not be a good indication of actual firebox temps, as plenum temps seem to differ quite a bit from install to install.

Thats exactly the reason for the temp controller mod...which to be fair, they do have a factory switch to override the "call for heat" if the furnace gets too hot...but at least on the T1, it was pretty stinkin hot at that point...one reason SBI updated the switch location from rear, to top after they started having crack issues. Even if it doesn't overheat the furnace, its an inefficient way to run...

yeah, I can definitely see the advantage of the temp controller. I'm thinking more along the lines of controlling them while stock. So, the limit switch is just measuring air jacket/plenum temps then? Interesting.

It -is- an inefficient way to run, I was just curious how one goes about keeping them from over-heating.

 

[brenndatomu]

The original T1 had a snap switch mounted so it read the temp of the back of the firebox...but that had such a delayed response time that they moved it to above the center heat exchanger tube...that was better...but I like having the TC of the temp controller right inside the stove pipe 1-2' away...

 

[laynes69]

The open and close damper works well in subzero weather. You just use common sense, if your house won't hit 73 with a hot fire, you don't set it to 75 and go to bed. By the time I close down our furnace, it will climb when I go to bed. If I set the thermostat at 72, I will wake to 70-71 in the house in the morning. Our furnace isn't modified (yet), just the temp settings and it works just fine. My previous furnace would eat almost twice the amount of wood with a 2 to 3 hour less burn in this weather. In mild weather, the open close damper will keep the house at a set temperature for hours.

 

[laynes69]

It -is- an inefficient way to run, I was just curious how one goes about keeping them from over-heating.

I've fallen asleep with our damper set at 80 in subzero weather and I've fallen asleep with the loading door ajar all night, without any damage. I know this because I've had the air jacket off the firebox. Hell, there wasn't even any signs of burnt paint anywhere on the furnace. I set our plenum limit at around 175 degrees. It produces a damn hot furnace and closes the damper until the plenum drops to 140 then opens back up. While the Tundra's were cracking, the Caddy line has a full air jacket surrounding the entire firebox, including front to keep them cool. I'll tell you from first hand experience, they will crank heat and take a beating.

 

[3fordasho]

Question regarding the operation of the Tundra II.

Without any mods installed, out of the box setup, does the distribution blower stay on without the thermostat calling for heat.

Trying to get a better understanding of how this furnace functions. I know the thermostat controls the primary air by opening/closing a flap. Just wondering how many people actually use the thermostat to control the heat.

Can’t locate any videos of this unit on YouTube.

Also looking for a video on how the Caddy operates.

Distribution blower completely independent from the thermostat. I've had a thermostat connected but never turned it to the "heat" position.
I just disconnected it a couple weeks ago so I could use the extra wiring to connect my new wifi thermostat and hook up the 2nd stage for the propane FA furnace. (propane seldom runs but is a backup when I am away and the wifi thermostat has some nice remote access, logging and alarm features that are neat).

To me a thermostat calling for heat on a Tundra (II) or caddy just put it in inefficient wood hog mode

 

[Highbeam]

I'm pretty sure the high temp limit should trip and shut the damper.

Eric

Also known as "bouncing off the rev limiter"!

Why can't you just set these furnaces for "medium" output? I guess I really like a thermostatic stove that you can choose a desired output and the burn rate is automatically controlled to deliver that output safely, constantly, and without fiddling with the intake settings.

That's a kuuma isn't it?

 

[JRHAWK9]

Also known as "bouncing off the rev limiter"!

Why can't you just set these furnaces for "medium" output? I guess I really like a thermostatic stove that you can choose a desired output and the burn rate is automatically controlled to deliver that output safely, constantly, and without fiddling with the intake settings.

That's a kuuma isn't it?

yes, it is.
This is why the amount of wood you load is imperative. You load too much wood on a warmer day and set the computer to low. The furnace doesn't give two $hits if your house is currently sitting at 85°; it's going to burn whatever's in the firebox cleanly and optimally at the heat output you have the computer set to.

 

[laynes69]

To me a thermostat calling for heat on a Tundra (II) or caddy just put it in inefficient wood hog mode

Not necessarily. I've had the damper remain open for hours and still got 8 hours between loads with the heating demand kept. I could disable the damper and get a much longer burn time, however it wouldn't heat the house. That's where the unit should be sized correctly. If the call for heat requires the damper to remain open for the majority of the burn, then the furnace is too small. Our old furnace would burn 6 cuft of wood or more in 6 hours....that's a wood hog!

 

[JRHAWK9]

<edit>sorry, I just realized I posted this in the Tundra thread. I wasn't paying attention to what thread I was in and was just going with the flow of the conversation. I am the master of pulling threads off topic. </edit>

Just to give those not up on how the Kuuma operates.

On Sunday, for the heck of it, I put the Kuuma on max burn after loading a smallish 38lb load. It brought our pig of a house up to 76° in double digit below zero outside temps. During the process I was watching the firebox temps (by way of a MyPin) and damper automatically do their thing. Obviously, when trying to maintain internal firebox temps which are that high the damper will open and close repeatedly during the burn process. The firebox temp setpoint for max burn is around the 1,385° area. The damper will close when the internal firebox at the tc location reaches this temperature. The tc is located in the collar between the firebox and the heat exchanger, which is where/near where most of the secondary combustion takes place. When temps reach that 1,385° setpoint, the damper closes, firebox temps will continue to rise for a bit (1,450° or so) and then they will gradually start to come back down. When they drop a couple degrees under that 1,385° threshold the damper will open back up to '1' (the smallest open position) until they once again reach 1,385°. Rinse and repeat. It does this for the whole burn cycle, until at some point the temperature fails to reach 1,385° and the damper then remains open at '1'. Does this same thing for stages '2' and '3', at temps I did not take note of. I was getting pretty much consistent max plenum temps (within a degree or two) throughout the burn into when the damper opens to '3'.

Burning like this will consume wood at a rate of about 8lbs/hr. So a full firebox of oak in ~8-9 hours with lots of coals left yet.

 

[DoubleB]

I put the Kuuma on max burn

Burning like this will consume wood at a rate of about 8lbs/hr.

Isn't 8 lbs about 56,000 Btu/hr total heat produced, or maybe 40-45,000 BTU into the ductwork? Isn't Kuuma max burn rated for three times more than that? Just curious where the numbers are disappearing, unless maybe the Kuuma rating is at peak burn.

 

[brenndatomu]

Isn't 8 lbs about 56,000 Btu/hr total heat produced, or maybe 40-45,000 BTU into the ductwork? Isn't Kuuma max burn rated for three times more than that? Just curious where the numbers are disappearing, unless maybe the Kuuma rating is at peak burn.

Cut from the Kuuma site...
"In mild weather you use a low setting for 15-25,000 BTU’s/hr., in moderate weather a medium setting for 25-45,000 BTU’s/hr., and in cold weather a high setting for 45-60,000 BTU’s / hr."

 

[Teglovinvtec]

Seems to be better after cleaning it I had 110 on duct work temp and 226 on stack temp but it’s goin off a inferred what’s your temps like this thing was rippin when I measured

 

[JRHAWK9]

Isn't 8 lbs about 56,000 Btu/hr total heat produced, or maybe 40-45,000 BTU into the ductwork? Isn't Kuuma max burn rated for three times more than that? .

No, if it was rated for that much output it would be two times that of what the Max Caddy is rated at! It would also be consuming A LOT more wood at a -much- faster rate that what it does. I'm not sure there's even a wood furnace currently on the market which is rated for 150KBTU/hr. I'm talking realistic output, not marketing jargon. 150KBTU/hr is boiler output, those are not burning 24/7.

 

[Wood1Dennis]

I was thinking about those furnaces which use a call for heat to open the primary air and then close once the house makes temp. I would think it would be of high importance to properly size the furnace to the heat demand of the house? I would be very nervous if the house is constantly calling for heat which is keeping the primary air hanging open. I'd think this could lead to overfiring the furnace in short order. Take for instance if you are being subjected to some crazy azz below normal cold temps and the house temp you have the thermostat set to can't be obtained; leading to the primary damper being held open throughout a burn cycle. What would you guys do then? I'd assume there would have to be some monitoring going on at some point to keep the furnace from going nuclear?

JR, this is pretty much exactly why I added the adjustment for my primary air. When it get really cold, and the firebox is loaded full, I adjust the primary air damper way down so it is really open just a slit. That way even when if the stat calls for heat all day it will not over-fire. It works great! In other cases, maybe shoulder season when I only have a small load because I don't need as much heat, I set the damper to a more open position and let her go. Its my simple control system, simple but it works.