Everything Drolet Tundra - Heatmax...

[sloeffle]

Instead of running the fan like a variable speed motor, could you run it through some controller that changed to speed 1, 2, 3, or 4 based on temp? Would it be better to get that temp signal from the flu or the plenum. Any pro, cons, or thoughts on this?

I have run my Caddy similar to this way for the past couple years. The Caddy has a two speed fan limit switch and I would run it on low speed during the coaling stage. Fan speed 2 was my "normal" setting and fan speed 1 was my "low" setting. The fan speed controller is much better in my opinion because it is all automatic. My low speed fan was tied into a switch and sometimes I would forget to turn it on or I didn't want it run all night etc.

The only pro that I could think of is that you are using the low speed factory setting and not monkeying with the motor voltage. Earlier in the thread there was some talk that the speed controller could possibly lesson the life of the blower motor.

 

[brenndatomu]

Earlier in the thread there was some talk that the speed controller could possibly lesson the life of the blower motor.

True. There is still this possiblity on the long term, but for me the motor runs so cool that i don't believe it is going to affect things much if at all...just my personal opinion.
I believe their concern with slowing the motor down is overheating...but these motors in this application run in a cool environment naturally anyways, and as the speed drops, the load does too...that is not always the case in other applications...lower speed, but same load...bad combo.

 

[JRHAWK9]

FYI, it requires about 4700 Btu/hr every hour of the entire day to evaporate 14 gal. I'm sure you know that's a significant portion of the heat your Kuuma makes, especially this time of year which isn't the dead of winter yet.

(But maybe that's ok, since you have 10 yrs of firewood drying).

I would be concerned pumping 14 gallons a day into my old house that's for sure, it would be collecting as frost on windows, inside walls, all kinds of places you don't want it especially when outside temps warm up and it all melts. Hope your vapor barriers are in good shape. ( I suspect if they were, you would not need 14 gallons a day).

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.

I just wanted to give props where props were due. You guys were 100% right (and I should have known better....lol)

I saw some icicles hanging outside on the eaves and my GF also saw a couple drops of water coming from the peak. This was when outside temps were at or around zero and RH was 35% in the house (which is more than it should have been at those outside temps). I immediately stopped all humidification.

As soon as I stopped, the house temp creeped up and since then it's been easier to heat. Temps are again below zero and we have about 20% RH, which is on the low side for the outside temps, but o well.

All this, along with the frost building up on the inside walls and other various cold areas/spots has led me to get a energy audit done.

 

[TDD11]

Yesterday morning it was around 5°F outside and when I got out of bed it was 64°F in the house. 7 small/medium splits of ash, and it brought the house up to 71°F in a matter of 3 hours. This is without the variable speed blower mod. I was thrilled with that. I don't usually stuff that much firewood in it.

Of course the house temps drop off a bit around 5 hours on a load - but I'm hoping the variable speed blower will help reduce that drop.

Brenn, can you link me to the power supply you used for your blower speed mod?

 

[brenndatomu]

7 small/medium splits of ash, and it brought the house up to 71°F in a matter of 3 hours.

Geez, I'd pee myself if I could raise my house temp 7 degrees in one load...especially at 5F outside!

Brenn, can you link me to the power supply you used for your blower speed mod?

I just used one I had layin around here...about any 24 VAC transformer would do...but here is a link for one...there is tons of different ones out there that would work though...(broken link removed to https://www.ebay.com/itm/FUNCTIONAL-DEVICES-INC-RIB-TR20VA001-Class-2-Transformer-24VAC-20-VA-1-PH/331325779347?epid=671727141&hash=item4d248e2d93:g:c7UAAOSwO9JaB~MA)

 

[TDD11]

Geez, I'd pee myself if I could raise my house temp 7 degrees in one load...especially at 5F outside!

I just used one I had layin around here...about any 24 VAC transformer would do...but here is a link for one...there is tons of different ones out there that would work though...(broken link removed to https://www.ebay.com/itm/FUNCTIONAL-DEVICES-INC-RIB-TR20VA001-Class-2-Transformer-24VAC-20-VA-1-PH/331325779347?epid=671727141&hash=item4d248e2d93:g:c7UAAOSwO9JaB~MA)

Like I said, I don't usually pack it that full and I don't recall it ever being that effective before. Just imagine if I had fresh cleaned HX tubes - It's been about 2 weeks since i have cleaned those. It is a small house - 1700 total square feet. No ductwork to the 2nd floor besides an open staircase..

Thanks for the link, everything I kept finding was $25, although I guess I had searched for

 

[Craig9702]

When i bought my tundra 2 years ago I hooked it up, and when I got it running i barely felt anything blowing out of the vents.....just no air volume.....so if I remember correctly I changed the fan speed from its factor 2 setting to 3......it helped but with what the temps have been here in northern wisconsin I'm really considering moving it to the highest setting.....im just wondering if it is gonna help or hurt me.......i load it up with nice dry red oak 1/4 and 1/2 splits.......

 

[KC Matt]

I have run my Caddy similar to this way for the past couple years. The Caddy has a two speed fan limit switch and I would run it on low speed during the coaling stage. Fan speed 2 was my "normal" setting and fan speed 1 was my "low" setting. The fan speed controller is much better in my opinion because it is all automatic. My low speed fan was tied into a switch and sometimes I would forget to turn it on or I didn't want it run all night etc.

The only pro that I could think of is that you are using the low speed factory setting and not monkeying with the motor voltage. Earlier in the thread there was some talk that the speed controller could possibly lesson the life of the blower motor.

That's how mine runs: I use speeds 1 and 3 and there is probably very little to gain by switching between all 4 speeds. At full load and with the stove screaming, it outputs 100*F at 6" above the furnace and when it's down to coals it's in speed 1.

It's been unusually cold here and my Tundra is just not cutting the mustard. Last night was -11 with wind chills in the -30 area and after feeding the furnace all it would eat of Hedge/Oak mix of 2+ year old wood that's been stored under cover, it was 59 in the house this morning. I gave up and turned on the gas; it took over 2 hours to get back to 70 in the house. After it warmed back up, I fired up the Tundra and it did fine keeping temp during the day with help from an insert in the basement, but I'm going back to gas for the week. I have a job and can't sit here and babysit this thing.

I should have bought the bigger furnace. Or the real deal, the Kuuma. As it is, I'm looking at updating the insert to keep the house warm, which is another $2k by the time it's installed. I wish I could use an OWB.

 

[brenndatomu]

I hooked it up, and when I got it running i barely felt anything blowing out of the vents.....just no air volume.....

There is a balance between getting volume, and letting the air pass over the furnace slow enough to actually pick up some heat (temp rise) think about the hot potato...it won't burn you if you don't hold on to it for long...same with the air, if it goes by too quickly there is not much heat transfer.
I'd say experiment with it and see what works for you...

 

[KC Matt]

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

The tundra is nearly useless as shipped IMO. It really doesn't work without the damper controller and the factory on/off switch is a joke. Mine would have supply temps anywhere between 140 and 165 before the fan kicked on, and by that time the load was half burned. Of course with these things, adding wood during the cycle results in excessive coaling which is a huge problem when it's really cold. You need to let it burn out but during the last few hours where it's just coals, the temp in the house is dropping. When the coals are reduced to a level where you can load it, the house is getting cold and the next load of fuel will barely raise the temp before it's back to coals. And that's with a slew of controllers and dozens of hours tweaking them.

It's important to size the Tundra to a suitable heat load. My house is a touch more than the Tundra can supply in the coldest days.

 

[brenndatomu]

It's been unusually cold here and my Tundra is just not cutting the mustard. Last night was -11 with wind chills in the -30 area and after feeding the furnace all it would eat of Hedge/Oak mix of 2+ year old wood that's been stored under cover, it was 65 in the house this morning. I gave up and turned on the gas

I don't think its reasonable to expect the same wood furnace to heat the house when its 30 or 40* out, and then at -10*/-30 wind chill too...its just the nature of the beast, wood heat is a cyclical type of heat and just not good at running outside of a certain range based on firebox size (mainly)...even the Kuuma has its limits...there was one for sale here last winter by a guy who just bought it and it didn't even come close to heating his house...and it wasn't this cold then either.
I think the best setup is to set the gas furnace Tstat to ...68* for example, then the Tundra can take the majority of the heat load, let the gas furnace take the balance if Tundra runs low before it can be stoked back up...there's probably very little gas actually used in a years time doing it this way. Gotta remember, this is really extreme weather, I don't think most people would be happy (over the long term) buying a wood heater big enough for "worst case scenario" unless it was their only heat, and no other option.
Or you can do like I do, fire up a second stove (sounds like you did)...I haven't used any oil in years this way. The lil stove in the LR fireplace hasn't been cold in a week...the furnace takes most of the load, then the stove fills in the cracks so to speak. It does take some dedication to keep 2 fireboxes going...they hardly ever seem to need fed at the same time...it can be a lot to figure out a good schedule and not get the house too hot or too cold...sometimes its tempting to want to just flip the oil Tstat on...I would sometimes but with the way I'm setup right now it would take some work to run oil...plus I'm not sure the oil heat exchanger isn't cracked or something...was getting a wiff of smell once in a while...so not gonna run it until I know what's up for sure...

 

[brenndatomu]

The tundra is nearly useless as shipped IMO. It really doesn't work without the damper controller and the factory on/off switch is a joke. Mine would have supply temps anywhere between 140 and 165 before the fan kicked on, and by that time the load was half burned.

Agreed! For most people they are not plug and play...at least the T1...dunno if T2 is any better or not...

 

[KC Matt]

I don't think its reasonable to expect the same wood furnace to heat the house when its 30 or 40* out, and then at -10*/-30 wind chill too...its just the nature of the beast, wood heat is a cyclical type of heat and just not good at running outside of a certain range based on firebox size (mainly)...even the Kuuma has its limits...there was one for sale here last winter by a guy who just bought it and it didn't even come close to heating his house...and it wasn't this cold then either.

That's true. I'm frustrated because I spent $3,000 and many hours on this installation and here I am burning gas. Then again today's high was 3 and last night was -11 it's -3 now and the demands on heat are outrageous. In perspective, thousands of people have lost power and hundreds more lost water because even utilities don't work. So yeah it's probably not the end of the world for the house to be 59*. Tell that to the better half.

During normal conditions this furnace, after extensive and expensive modifications, can keep a normal house at a reasonable and survivable temperature. Notice I didn't say comfortable. Right now I'm outside the bell curve.

 

[sloeffle]

It's been unusually cold here and my Tundra is just not cutting the mustard. Last night was -11 with wind chills in the -30 area and after feeding the furnace all it would eat of Hedge/Oak mix of 2+ year old wood that's been stored under cover, it was 59 in the house this morning. I gave up and turned on the gas; it took over 2 hours to get back to 70 in the house. After it warmed back up, I fired up the Tundra and it did fine keeping temp during the day with help from an insert in the basement, but I'm going back to gas for the week. I have a job and can't sit here and babysit this thing.

These really cold temps definitely make keeping the house warm a PITA. I have been babysitting my Caddy for the past couple weeks too. I can't wait until it warms up and I can run the geo. Speaking of the house being cold. Woke up at 530 and the house was 66. Turned the wood furnace thermostat on to 65 so I could burn some coals down. Wife woke me back up at 7 and I fell back asleep and finally woke back up at 745 and the house was 62. Ran both furnaces and had it up to 70 in a couple hours.

I should have bought the bigger furnace. Or the real deal, the Kuuma. As it is, I'm looking at updating the insert to keep the house warm, which is another $2k by the time it's installed. I wish I could use an OWB.

Funny you say that, I was looking at Portage and Main OWB's yesterday on the internet. I am a little jealous that you don't have to handle a piece of wood three times to get it into the stove. A bunch of my buddies have them and they really like them except the amount of wood they use. I'd rather burn two cords a year in my furnace instead of ten in an OWB. They all have pre-EPA models though. Plus the wife would kill me if I told her we spent 30k on a geo system and OWB. If money wasn't an object I'd have a Froling with 2k gallon of storage in a building next to house.

 

[laynes69]

The worst it's been has been 68 after 8 or 9 hours, didn't want to get up. Within 10-15 minutes with the gas furnace, it climbs to 72. I don't mind running the furnace if that's all it takes. Since we've tightened the home, the LP doesn't work hard at all. This weather I wished we had a larger firebox, but then we would be oversized much of the time. Once the sun comes out, we warm up to 74 or so in this cold. I have a couple friends with OWB's and right now they are burning a cord a week in this weather, but their houses lack both insulation and airsealing.

 

[maple1]

A cord a week?!

 

[laynes69]

A cord a week?!

Yep! The one home used almost 60 truckloads one year, and the other at least 40 and a couple of tanks of LP. Unfortunately, the one just spent 40k on a roof and windows, and that should've gone to insulation and airsealing. We by far do not have a small home, yet we burn nothing compared to them.

 

[TDD11]

Let me bounce a thought off of you guys. I would have an HVAC contractor come out to get their thoughts, but I figure they are probably pretty busy right now. I tried to google this but did not have many results that matched what I had in mind.

I either need a separate supply system for the wood furnace, or a damper system. Currently, I use a sheet of drywall in my propane furnace in place of the filter, to block air from the Tundra from backflowing through the propane furnace. This is only moderately effective, and also prevents my propane furnace from running in the event that the house gets cold - think "emergency /don't make it home as expected" type scenarios.

I have been mulling over some options and ideas. What are your guys' thoughts on having a separate trunk ducts in my basement for my propane furnace and Tundra? My house is small, with a small footprint of 570 sq ft per floor. That's why I think this might be viable. There are only 2 branches off of my supply trunk, and both are short runs of 6" round duct. I actually wonder if that is creating too much backpressure and not allowing the system to flow efficient and effectively - not to mention when both furnaces try to run at the same time.

I considered having an HVAC company install backflow dampers on both furnaces - but I believe they would need to be automated, and open during a power outage to let the Tundra heat flow. Having backflow dampers would eliminate any backflow concerns. But my concern is when both are running - like when the house is cold. Turn on the propane while I'm building a fire, trying to warm the house quickly. The blowers from both furnaces run and create a high static pressure.

Since I only have a short trunk duct, and 2 branches (at the moment anyways) and such a small footprint, I don't think a 2nd duct system would cost that much. Plus, I would never have to worry about backflow through either furnace. And both furnaces could run simultaneously without creating high static pressures and putting excessive load on the blowers. The biggest drawbacks would be a second trunk duct in the basement making the small basement room feel even smaller - and having to install 2 more registers blowing into the ground floor living room.

I do not have cold air return ducts in the house - the layout of the house wouldn't make adding them easy, and with the small footprint, I don't think it's necessary anyways. Instead, there are 2 vents through the ground floor into the basement - and I may add a 3rd in the kitchen - venting to the basement laundry/bathroom. Also, the door to my basement has louvers to allow my basement stairs to be a cold air return.

 

[JRHAWK9]

The three past nights here have gotten down to -12°, -15°, and -12° with highs during the day of under 5° and dropping to -5° to -8° already by 7pm. House was 68° in the morning all three mornings with a LP furnace run time of under 30 minutes for all three mornings -combined-. So the LP ran an average of under 10 minutes each morning. I was able to warm the house back up to 74° with the wood furnace (aided by solar gain) during the day while I was home by doing smaller partial loads, loading 4 times a day instead of 3 (like I do when not home during day) and pretty much running the pants off of it. I was burning as much wood as it would let me! LOL Considering the heat load of our place (~70K-80K BTU's/hr at those nighttime temps keeping house at 70°), I was happy. Not so happy with the 13-16% RH the house is now sitting at seeing I about faced on the humidity thing after getting it to rain inside the house!

 

[sloeffle]

I considered having an HVAC company install backflow dampers on both furnaces - but I believe they would need to be automated, and open during a power outage to let the Tundra heat flow. Having backflow dampers would eliminate any backflow concerns. But my concern is when both are running - like when the house is cold. Turn on the propane while I'm building a fire, trying to warm the house quickly. The blowers from both furnaces run and create a high static pressure.

I installed a 24V power damper in the plenum of my geo furnace. That closes when my wood furnace turns on. I also have a 24V power damper on the pipe going from the wood furnace into the geo furnace plenum. The closes when the geo turns on.

When I want to run both furnaces I just unplug the power dampers. If I was smart I would just install a little switch on the power dampers. The only thing that sucks about that setup is that I cannot run both furnaces unless I manually have to intervene. I also have to take the back off the wood furnace off because there isn't enough return air for both furnaces. Ninety-percent of the time it isn't a big deal. I can generally keep the house between 66 and 72 ( too hot IMHO ) with the wood furnace alone.

I am not an HVAC person but I don't see a problem with your setup. I would double check your building codes too. Are you just pulling return air from the basement for your wood furnace ?

 

[JRHAWK9]

Let me bounce a thought off of you guys. I would have an HVAC contractor come out to get their thoughts, but I figure they are probably pretty busy right now. I tried to google this but did not have many results that matched what I had in mind.

I either need a separate supply system for the wood furnace, or a damper system. Currently, I use a sheet of drywall in my propane furnace in place of the filter, to block air from the Tundra from backflowing through the propane furnace. This is only moderately effective, and also prevents my propane furnace from running in the event that the house gets cold - think "emergency /don't make it home as expected" type scenarios.

I have been mulling over some options and ideas. What are your guys' thoughts on having a separate trunk ducts in my basement for my propane furnace and Tundra? My house is small, with a small footprint of 570 sq ft per floor. That's why I think this might be viable. There are only 2 branches off of my supply trunk, and both are short runs of 6" round duct. I actually wonder if that is creating too much backpressure and not allowing the system to flow efficient and effectively - not to mention when both furnaces try to run at the same time.

I considered having an HVAC company install backflow dampers on both furnaces - but I believe they would need to be automated, and open during a power outage to let the Tundra heat flow. Having backflow dampers would eliminate any backflow concerns. But my concern is when both are running - like when the house is cold. Turn on the propane while I'm building a fire, trying to warm the house quickly. The blowers from both furnaces run and create a high static pressure.

Since I only have a short trunk duct, and 2 branches (at the moment anyways) and such a small footprint, I don't think a 2nd duct system would cost that much. Plus, I would never have to worry about backflow through either furnace. And both furnaces could run simultaneously without creating high static pressures and putting excessive load on the blowers. The biggest drawbacks would be a second trunk duct in the basement making the small basement room feel even smaller - and having to install 2 more registers blowing into the ground floor living room.

I do not have cold air return ducts in the house - the layout of the house wouldn't make adding them easy, and with the small footprint, I don't think it's necessary anyways. Instead, there are 2 vents through the ground floor into the basement - and I may add a 3rd in the kitchen - venting to the basement laundry/bathroom. Also, the door to my basement has louvers to allow my basement stairs to be a cold air return.

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The setup I have will probably work with what you want to do. I don't have my return air of the wood furnace connected to the main cold air of the house either. I use an open staircase for that.

I have a powered close/spring open damper in the supply duct connecting the wood furnace to the main supply duct. It's wired by way of a relay to only CLOSE when the LP blower is the only blower running. It remains open the rest of the time. I then have a gravity damper in the plenum of the LP furnace. I power it close because I need it to be open in case of a power failure.

My setup allows BOTH blowers to seamlessly "dance" with each other without flipping a single switch or manually doing anything. My SP in my supply duct is 0.4" when both my LP blower (using low speed tap) and wood blower (using low speed tap) are running at the same time.

I'm using the 120V EAC and HUM circuits on my LP furnace, a normally set snap switch, a "overtemp" snap switch, pressure head controller, spring open/power closed damper, gravity damper, 120V minute timer and 4 relays to accomplish everything I want to.

If you want more info, PM me.

 

[DoubleB]

Instead, there are 2 vents through the ground floor into the basement - and I may add a 3rd in the kitchen - venting to the basement laundry/bathroom. Also, the door to my basement has louvers to allow my basement stairs to be a cold air return.

Can you convert those 2-3 vents into supplies that come from the Tundra? Use the basement door/stairs as the cold air return for both furnaces? For my house I have three 6x12 floor vents dedicated to the Tundra, and as it turns out I only need two of them and still get plenty of airflow with less than 0.2"H20 static pressure.

Maybe that's not the exact solution but I'm happy with my separate ductwork for my Tundra, it's quite simple.

 

[brenndatomu]

I ran separate duct (and new/seperate vents too) for my sisters Tundra...works pretty well.

 

[TDD11]

Thanks everyone.. so I'm not crazy! I've been thinking that besides the visual perspective, separate supply systems made more sense.

 

[TDD11]

I installed a 24V power damper in the plenum of my geo furnace. That closes when my wood furnace turns on. I also have a 24V power damper on the pipe going from the wood furnace into the geo furnace plenum. The closes when the geo turns on.

When I want to run both furnaces I just unplug the power dampers. If I was smart I would just install a little switch on the power dampers. The only thing that sucks about that setup is that I cannot run both furnaces unless I manually have to intervene. I also have to take the back off the wood furnace off because there isn't enough return air for both furnaces. Ninety-percent of the time it isn't a big deal. I can generally keep the house between 66 and 72 ( too hot IMHO ) with the wood furnace alone.

I am not an HVAC person but I don't see a problem with your setup. I would double check your building codes too. Are you just pulling return air from the basement for your wood furnace ?

I thought about something like that but I really want to not have to have any manual work in order for the propane furnace to run. It's more of a backup thing, in case the house was left unattended for some sort of emergency, it would maintain maybe 50°F.

You are correct, I'm just pulling air from the basement floor for the wood furnace.

Can you convert those 2-3 vents into supplies that come from the Tundra? Use the basement door/stairs as the cold air return for both furnaces? For my house I have three 6x12 floor vents dedicated to the Tundra, and as it turns out I only need two of them and still get plenty of airflow with less than 0.2"H20 static pressure.

Maybe that's not the exact solution but I'm happy with my separate ductwork for my Tundra, it's quite simple.

I could do that, but I would have to run the ducts perpendicular to the floor joists under them and besides the trunk duct, I hoped to avoid that.