Ha! I had the same thought. Ah, lemme think here... @bedrock1 I think it was, no?
Haven't seen 'im in a while, hope he comes around to post an update
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Everything Drolet Tundra - Heatmax...
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Haven't seen 'im in a while, hope he comes around to post an update
maple1
Minister of Fire
Ya, might be good to hear from him again. Sounds like he had the same vintage furnace with the control thingie in the same place - think he had a bunch of back & forth with Drolet about getting a new one & mounting it in a revised location. Not sure he got it working good though, don't think we heard any kind of good or bad final word. Sure sounds like same story though.
DoubleB
Minister of Fire
That's the correct idea, although those numbers are different than my Tundra. My manual says the blower turns on above 140F and turns off below 120F, although over many tests it seems my blower snap disc is 100/120F instead. I might just be imagining but I thought there was discussion here where SBI changed the blower snap disc to 100/120, and it might also have had to do with where the snap disc was located (as Brenn said there have been a couple locations for them).
And then lastly I think the overtemp cutout to shut the damper is 160F instead of 200F but either one wouldn't surprise me. Again, both kinds might have been issued in the past for the known different mounting locations.
Clear as mud?!?!
Well, my mirror almost spontaneously combusted but I got a bit better look at the top of the firebox. I slide the baffle forward and used my mirror and a light to get a look at the back of the firebox (above the baffle) where the HE tubes attach, it isn't terrible, but from what I could see from my quick look there is enough crud to warrant a good cleaning, it's gotta help anyways
I think you need to slow down your air via the fan or best by larger and/or more ducts. I do not believe that you should be able to feel the outlet of your ducts more than 2 ft away. A soft 120*/110* heat should heat your place fine as long as there are enough outlets providing it. At 0* I feel no moving air in the house but 115* outlet temps will keep it 70* inside. Good luck.
P.S is your ductwork insulated?
P.S is your ductwork insulated?
Fan is on low. Large ducts restricted to give .2 static pressure per the manual. Some insulated, some no. The ones that aren't are in heated space
Well this morning i wanted to get exact numbers of what the temps are when i hit the high limit. After loading the firebox 3/4 full and about10-15 mintues later the damper closed on its own. I took the surface temp reading on top just forward and to the right of the gray box. Can you see the little red dot? The temp reading was about 210*-215*, So i guess its safe to say that the high limit is in fact 200* on my unit.
![[Hearth.com] Everything Drolet Tundra - Heatmax...](https://www.hearth.com/talk/data/attachments/167/167816-b67290e77da39554829f368f40b5cd0b.jpg?hash=cCIW59_Xz9 "[Hearth.com] Everything Drolet Tundra - Heatmax...")
Brenn, just so i understand your Tundra is hooked up to existing duct work from your primary heat source? If so i think this may be part of the issue. I know its allowed in the US to hook up into existing duct work.Not in Canada. Here are my thoughts on tying into existing duct work. #1 the static pressures for residential duct work is normally about .1 . While you may have the static pressure at .2 closer to the furnace once its hits the branches and other duct work the airflow dies right down. Allowing the air to cool way down not giving you much if any heat in the areas you want them. For example myself and Matt did duct work just for the Tundra and are very please and i am getting nice warm air in my longest run but keep in mind all my duct work is designed at .2 allowing the air to really move fast not allowing it much of a chance to cool down in the ducts. The duct work i have is non-insulated in a not heated basement too, I could see the Tundra not being able to do the job if dumped into to much duct work, Just another thought and i may be off base with my theory.`
Some may have success tying into existing duct work if small enough while others with larger duct work my not be satisfied,
Brenn, just so i understand your Tundra is hooked up to existing duct work from your primary heat source? If so i think this may be part of the issue. I know its allowed in the US to hook up into existing duct work.Not in Canada. Here are my thoughts on tying into existing duct work. #1 the static pressures for residential duct work is normally about .1 . While you may have the static pressure at .2 closer to the furnace once its hits the branches and other duct work the airflow dies right down. Allowing the air to cool way down not giving you much if any heat in the areas you want them. For example myself and Matt did duct work just for the Tundra and are very please and i am getting nice warm air in my longest run but keep in mind all my duct work is designed at .2 allowing the air to really move fast not allowing it much of a chance to cool down in the ducts. The duct work i have is non-insulated in a not heated basement too, I could see the Tundra not being able to do the job if dumped into to much duct work, Just another thought and i may be off base with my theory.`
Some may have success tying into existing duct work if small enough while others with larger duct work my not be satisfied,
Thanks for doing that builder! I'll hafta check mine at that exact spot, but I was shooting temps at different places last night and I was getting numbers WAY lower than that. I assume your blower was running by this point.
Yes, Tundra is tied into existing ductwork, I hear what you are saying but my issue is there is not much heat to begin with, like I said before, the highest duct temp that I have seen (and this is at the furnace) is 120 with the blower running and the damper door open, and roaring fire is HOT!
I see now....I thought you meant you had 120° at the registers. That's sounds awfully low. Do you have the damper to close completely, or does it remain open a little?
I do have a shim in to keep it cracked just a bit.
Just to keep everybody on the same page, I am measuring flue temps internally with a TC and getting the readout from my temp controller, the duct temp is internal via a digital probe in the duct about 2' above the furnace. Other temps are from a infrared thermometer...which works pretty good on the flat black surfaces of the furnace
If I were getting 120* at the register...I'd be thrilled. Even 110-120 at the furnace works, its just that temp is frequently elusive and 90-100 at the furnace is more common, which doesn't work real well. Don't get me wrong, we are not freezing to death here, but my gut tells me this thing is capable of much more than I'm getting. Comparing mine with @Builderml results, sounds like we are comparing a Prius and a F250 powerstroke
I fired the stove this AM so I can tear into 'er tonight
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JRHAWK9
Minister of Fire
I know I don't have a Tundra, but the 100°-110° temps I see are also about 2' above the furnace in the plenum taken using an HVAC thermometer. This is with the blower on low. My blower turns off when the HVAC thermometer in the plenum reads 95°, which is what the snap disc is set to do (on at 115° and off at 95°). When I have the furnace set on high and have it really humming along in the middle of a burn I can see plenum temps 110°-112° with the blower on high. With the furnace set on low and fan on low I see very consistent 100° plenum temps. The cold air intake temps are always pretty much the same as the room temp on the main level. This tells me I have good internal circulation with using an open staircase for the cold air return.
Heck, I also have another HVAC thermometer placed about 8' down stream of the wood furnace in the main trunk line of the supply duct and even when my LP furnace runs I believe I see main line duct temps around 120°. It happens to be placed around 8' downstream of the LP furnace as well. I don't expect my wood furnace duct temps to be remotely equal to the temps I see when the LP furnace is running.
The constant 100° plenum temps with the wood furnace set on low is enough to keep this poorly insulated house warm. In these 20° nights and 35° days I can't keep a constant fire going all day as it will get too warm in the house. I've only been putting in 35lbs at night and then 35lbs in the morning and then just re-light a fire the following night again. It seems to keep the house 72°-74°. This is a little over half of the wood I would typically use a day when it's cold out and burning all day. On real cold nights last year the house would drop down cooler than I would prefer in the mornings at the end of a burn cycle. This house seems to lose A LOT of heat once the temps drop below 10° or so. It's not a very tightly built or well insulated, we averaged 1,300 gallons of LP a year from 2005-2008 (highest was 1,550 gallons), with a 92% efficient furnace in a ~1,100SF log cabin style house (lots of volume though). It's built on a 32'x42' rectangular footprint. Back when heating with LP we did not heat the basement and therefore the basement was always right around 55°. Now with burning wood, the radiant heat from the Kuuma alone is enough to keep the basement about the same temp as the rest of the house.
I think the main difference of plenum temps are the result of different duct sizes and pressures, like Stihly alluded to. Although if you really are going through that much wood, the BTU's have to be going somewhere!
I guess the whole point of this babbling post was to point out I have similar plenum temps as you and heating a house which has a higher heat load (going off of past fuel usage) without the issues you are having.
Heck, I also have another HVAC thermometer placed about 8' down stream of the wood furnace in the main trunk line of the supply duct and even when my LP furnace runs I believe I see main line duct temps around 120°. It happens to be placed around 8' downstream of the LP furnace as well. I don't expect my wood furnace duct temps to be remotely equal to the temps I see when the LP furnace is running.
The constant 100° plenum temps with the wood furnace set on low is enough to keep this poorly insulated house warm. In these 20° nights and 35° days I can't keep a constant fire going all day as it will get too warm in the house. I've only been putting in 35lbs at night and then 35lbs in the morning and then just re-light a fire the following night again. It seems to keep the house 72°-74°. This is a little over half of the wood I would typically use a day when it's cold out and burning all day. On real cold nights last year the house would drop down cooler than I would prefer in the mornings at the end of a burn cycle. This house seems to lose A LOT of heat once the temps drop below 10° or so. It's not a very tightly built or well insulated, we averaged 1,300 gallons of LP a year from 2005-2008 (highest was 1,550 gallons), with a 92% efficient furnace in a ~1,100SF log cabin style house (lots of volume though). It's built on a 32'x42' rectangular footprint. Back when heating with LP we did not heat the basement and therefore the basement was always right around 55°. Now with burning wood, the radiant heat from the Kuuma alone is enough to keep the basement about the same temp as the rest of the house.
I think the main difference of plenum temps are the result of different duct sizes and pressures, like Stihly alluded to. Although if you really are going through that much wood, the BTU's have to be going somewhere!
I guess the whole point of this babbling post was to point out I have similar plenum temps as you and heating a house which has a higher heat load (going off of past fuel usage) without the issues you are having.
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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.
So your flue temp is perfect, maybe a bit low even. So you are not losing heat up the chimney. Low temps in ductwork so no heat getting in the air. Your unit is so hot its tough to stand 2 1/2 ft away. So It sounds like your not exchanging with the air and are mostly radiant heating the basement. 1) The air may be moving to fast across the exchanger to pick up the heat. ( reasonable scenario if you feel the air blowing on you from a few ft away.) Try opening all dampers and see what happens. 2) Air moving across the HE may not be going over the whole thing, Turbulence in air flow? think fast moving water in a river, pools of water just swirling around. ( form and direction of ductwork connections at furnace) 3) your idea of severe insulating factor of some sort at/in HE. ( tear whole thing apart clean and inspect)
Anyways, these two machines are very different but I think the Tundra is not running up to par...yet
That's my thought on it also. I don't have to have a raging fire to have a good heat output. Actually, I've had some lazier fires with minimal secondaries, and the heat output was excellent. No doubt, air could be bypassing the exchanger, or there's too much pressure in the furnace.
Brenn, I have a couple more temp readings for you, I took the readings in the same spot as I did for the high limit in the earlier post with the picture. At that spot my temp reading are as follows
Fan comes on at 130-135, fan shuts off at 110-115. Can never have enough info when trying to find a problem. Good luck
Fan comes on at 130-135, fan shuts off at 110-115. Can never have enough info when trying to find a problem. Good luck
JRHAWK9
Minister of Fire
This morning seeing the Kuuma was at the end of it's burn cycle with the blower not running I decided to run our LP furnace for the heck of it in order to monitor the duct temperature. Sampled in the main line trunk ~8' away from the source. The house was 73°-74° at the time and the basement room where the furnaces are was 76°. Outside temp was mid 20's overnight.
Anyway, the temp jumped up to 110° rather quickly, and then gradually got up to and settled in at 118° where it stayed for a good 5-10 minutes. I ran it a total of 20 minutes. Never reached 120°.
It's intriguing my LP furnace duct temps are similar to and even lower than what some of you guys are seeing for wood furnace duct temps at or near the source. I have always read not to expect the same vent temp out of a wood furnace as compared to a LP/oil/NG furnace because fossil fuel furnaces cycle while wood furnaces provide constant heat throughout the burn cycle.
What am I not seeing here? lol Why are his ducts temps similar to mine but yet not enough to keep his house warm when his house has less of a heat requirement.
Anyway, the temp jumped up to 110° rather quickly, and then gradually got up to and settled in at 118° where it stayed for a good 5-10 minutes. I ran it a total of 20 minutes. Never reached 120°.
It's intriguing my LP furnace duct temps are similar to and even lower than what some of you guys are seeing for wood furnace duct temps at or near the source. I have always read not to expect the same vent temp out of a wood furnace as compared to a LP/oil/NG furnace because fossil fuel furnaces cycle while wood furnaces provide constant heat throughout the burn cycle.
What am I not seeing here? lol Why are his ducts temps similar to mine but yet not enough to keep his house warm when his house has less of a heat requirement.
Haven't contributed much, just read everything so far so I thought I would give a rundown of my install. House is 1917 bungalow, 1800 sq ft, minimal insulation. Chimney is 26 ft external with 6" insulated liner, barometric damper at -0.5 in of wc. I finally got the furnace fired up this week. One 8" duct run is about 15 feet with 2 registers then another 15 feet of 6" with two more registers (4x10s). Other run is 25 feet of 8" with two registers, then 10 feet of 6" with three registers. One register on each run goes to the second floor. Static pressure is reading 0.25 on short run and 0.3 on longer run. Coldest it has been is 24, with the days getting to mid 30's. I set the propane furnace to 65 then try to keep it and heat pump from running with the tundra. The wood I'm using right now is over 2 yr old cherry and some unknown lighter wood both reading around 13%. So on a typical day I wake up at 5 to a 65 degree house. I'll burn wood wide open for about an hour to get up to 68, top off the load and let char 20 minutes, shut the damper (thermostat controlled) and leave for work. Home at 4:30 to a 65 degree house but enough coals to relight with. Burn hard another hour to get warmed back up, reload at 9-9:30, wait 20 minutes for wood to char then off to bed. I'm not disappointed, but not totally happy either. If I am home I can keep the heat pump and propane from running and I'm sure what I am doing will help utility bills a good bit. I'm afraid the unit is a bit undersized for what I need. Years ago my dad insulated the floor between the basement and first floor and I am in the process of moving that insulation to the attic. It's hard to really insulate this old bungalow due to inaccessible areas above upstairs bedrooms. I really don't see this furnace hanging in there when in gets below 10 degrees like the last two winters, but I think it will be ok down into the teens. Last year at -12 degrees my 120,000 btu propane ran 50-55 minutes per hour to give you an idea of my heat load. Other observations.....if I shut the damper too early I can get some clear liquid that smells strong out the back of the furnace at the stove pipe connecter. Break in fires I didn't get any smoke, but smell has lingered and is gradually decreasing. Blower is on high. Gives me correct static pressure and seems to deliver the most heat to the house but is pretty noisy. I feel I did everything according to the manual except my duct runs may be too long. Was hoping for some better burn times, but that's getting a little better as I learn how to deal with the furnace on a daily basis. Any insight or comments will be welcome.
DoubleB
Minister of Fire
Nate,
Thanks for the write-up. Good datapoints.
Agreed that based upon 50-55 minutes per hr of 120,000 Btu LP furnace, sounds like your Tundra isn't going to cut it alone on those coldest days. But it'll still get rid of most of your LP bill.
One thought--you report that you burn with the damper wide open for an hour on a new load to get the house up to temp. Although SBI doesn't prohibit it, I'd avoid doing that myself since I'm leary of my cracking.
Also, with the damper open you burn the wood twice as quickly but only get a fraction more heat output. You'll be more efficient with the damper closed, and I prefer that even if it takes a bit longer to increase the house from 65 to 68.
Just some thoughts. Glad it's working well enough at least out of the gates.
Thanks for the write-up. Good datapoints.
Agreed that based upon 50-55 minutes per hr of 120,000 Btu LP furnace, sounds like your Tundra isn't going to cut it alone on those coldest days. But it'll still get rid of most of your LP bill.
One thought--you report that you burn with the damper wide open for an hour on a new load to get the house up to temp. Although SBI doesn't prohibit it, I'd avoid doing that myself since I'm leary of my cracking.
Also, with the damper open you burn the wood twice as quickly but only get a fraction more heat output. You'll be more efficient with the damper closed, and I prefer that even if it takes a bit longer to increase the house from 65 to 68.
Just some thoughts. Glad it's working well enough at least out of the gates.
Thanks for the temp stats guys. Hey @Builderml, would you mind getting me a pic of what it looks like on your unit where the blower attaches to the furnace. Just pull the filter and show me that area, if ya don't mind, thanks!
An update on the case of the "missing heat heater"
I'm away for the holiday and I forgot my camera, so y'all gonna hafta wait for the pics. But I tore the Tundra apart last night to clean the firebox above the baffle and super clean the HEs. Good news was that the secondary air tubes came right out. I had read where some said that the tubes warp after a while and are very difficult to get out. Baffle came right out and looked to be in relatively good shape. There definitely was some light colored (white) fluffy soot build up in the front part of the upper firebox. It was more creosote lookin at the back of the firebox and going into the HEs. Things cleaned up pretty well in there. What I found interesting was that the top of the firebox is double walled. They have a thin piece of sheet metal plug welded to the actual top of the firebox. The light colored soot was where the double wall is, with some darker spots where the welds are, probably due to the heat transfer to the main body being cooled by the blower. The darker stuff was in the back where it goes to single wall.
I cleaned the HEs again, I found that the 4x6 rectangular wire brush that I have for cleaning the HEs on my Yukon actually worked pretty well getting into the side HEs of the Tundra, even the center one. I thought they were pretty clean until I shined the light in there and could see ridges where some of the buildup came off. It looks like maybe there was a thin layer of creosote once upon a time that got baked on and was REALLY hard to get off, lots of scraping with various tool and brushes. Kinda like when the dental hygentist scrapes plaque off your teeth.
I ran out of time to get it all, but 95% of it is gone. If Santa brings me a Soot Eater for Christmas I will try to get the rest off with that. The tricky thing is, without very close inspection, you would have never been able to tell that the HEs weren't clean, like down to bare metal, it was black and smooth.
My theory was that I wasn't getting any heating from the top of the firebox (like you do from a stove) but after finding the double wall firebox top, it is apparent to me that they are not that concerned with getting heat from the firebox and are relying mostly on the HEs to do the heavy lifting. I fired back up last night but was running out of time to play with things so I don't know if I made any real progress or not. My initial impression was that it didn't make a big difference.
Because I'm not getting duct temps as high as yours. The temps I stated were 2' above the furnace, I haven't checked duct temps further down the line, or at the registers, I probably should though. I only get temps above 100* while the damper is open, or maybe for a while after the damper closes during the intense part of the secondary burn. Once that is over we are definitely under 100* duct temps right above the furnace. Like I said before, If I had 110-120* duct temps (consistently) I would have no problem heating the place with that, but 90s, even 80s (remember, I have the old style fan switch in the back) during the end of the burn cycle are barely cuttin it, and the weather is pretty mild, so I don't have a lot of faith that this is gonna work out when the temps drop. I guess I need to move the fan switch, see if that makes any real difference, one thing at a time though.
My 2 cents, lower your blower speed 1 or 2 speeds, your static pressures are higher than they need to be.
An update on the case of the "missing heat heater"
I'm away for the holiday and I forgot my camera, so y'all gonna hafta wait for the pics. But I tore the Tundra apart last night to clean the firebox above the baffle and super clean the HEs. Good news was that the secondary air tubes came right out. I had read where some said that the tubes warp after a while and are very difficult to get out. Baffle came right out and looked to be in relatively good shape. There definitely was some light colored (white) fluffy soot build up in the front part of the upper firebox. It was more creosote lookin at the back of the firebox and going into the HEs. Things cleaned up pretty well in there. What I found interesting was that the top of the firebox is double walled. They have a thin piece of sheet metal plug welded to the actual top of the firebox. The light colored soot was where the double wall is, with some darker spots where the welds are, probably due to the heat transfer to the main body being cooled by the blower. The darker stuff was in the back where it goes to single wall.
I cleaned the HEs again, I found that the 4x6 rectangular wire brush that I have for cleaning the HEs on my Yukon actually worked pretty well getting into the side HEs of the Tundra, even the center one. I thought they were pretty clean until I shined the light in there and could see ridges where some of the buildup came off. It looks like maybe there was a thin layer of creosote once upon a time that got baked on and was REALLY hard to get off, lots of scraping with various tool and brushes. Kinda like when the dental hygentist scrapes plaque off your teeth.
I ran out of time to get it all, but 95% of it is gone. If Santa brings me a Soot Eater for Christmas I will try to get the rest off with that. The tricky thing is, without very close inspection, you would have never been able to tell that the HEs weren't clean, like down to bare metal, it was black and smooth.My theory was that I wasn't getting any heating from the top of the firebox (like you do from a stove) but after finding the double wall firebox top, it is apparent to me that they are not that concerned with getting heat from the firebox and are relying mostly on the HEs to do the heavy lifting. I fired back up last night but was running out of time to play with things so I don't know if I made any real progress or not. My initial impression was that it didn't make a big difference.
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DoubleB
Minister of Fire
Thanks for the detailed report. Hopefully you underestimated the insulation of what you removed, but the double wall ceiling does sound like reduced heat transfer no matter what. I don't remember mine having a double wall when I cleaned it in the spring, but I often don't observe everything.
Just a really long shot here, but maybe you could take off the front/rear covers and inspect inside the air jacket. Who knows how well the previous owner used a filter, or what else could be in there, and wouldn't it just be something if there is junk on the outside of the HE tubes and firebox. I know I'm stretching it, but it's an easy check.
Just a really long shot here, but maybe you could take off the front/rear covers and inspect inside the air jacket. Who knows how well the previous owner used a filter, or what else could be in there, and wouldn't it just be something if there is junk on the outside of the HE tubes and firebox. I know I'm stretching it, but it's an easy check.
Thinkin about it, even if it turns out to be clean, I'd just like to know how it is made and put together, exactly.
I wouldn't have noticed it either if not for giving things a VERY thorough inspection, that and the one back corner was slightly warped and hanging down just a bit. I started pokin around more after I seen that. They have things tucked in pretty good, you never notice unless maybe you were looking at a brand new one. I got some good pics so I can point it out to y'all
DoubleB
Minister of Fire
Me too. I can't wait for the pictures. It's always great when someone else is willing to do the work. Thanks!
I plan on giving the Tundra the first chimney cleaning tomorrow(Friday) to see how dirty she got over the time it has been used. I'll try to get you those pictures of the blower attachment area, won't be that easy to do. I have a 12" return duct tied into the side of the plenum giving me no access points.I sealed everything up so i wouldn't be sucking in basement air. Once i pull the filter out all i have is a 1" slot. I was thinking of drilling an inspection hole in the return plenum so i could see in there and check the filter without taking it out. Maybe cover the hole with plexi glass. I'll see what i can do.
Enjoy your Turkey everyone!!
