Deciding on a new Furnace

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.

brenndatomu

Minister of Fire
Aug 21, 2013
7,223
NE Ohio
I assume you burned all the 6 inch pieces as well?
Yup, just threw em in on top.
No more 26-30 inch deep 7cuft fireboxes. I wonder why that is?
The bigger the firebox the harder it is to make it burn clean...although the newer downdraft gasifiers (boilers) can make it work...
 
Last edited:
  • Like
Reactions: Highbeam

laynes69

Minister of Fire
Oct 2, 2006
2,669
Ashland OH
I'm on my third woodfurnace. The ol' hotblast 1500 would burn at least 10 to 12+ cord a winter. Stuff it with 6+ cuft of locust rounds and you'd be lucky to sleep through the night (maybe 6 to 7 hours). If you slept in over the weekend, you would have a cold house. They would consume wood at a high rate, or if you tried to slow it down remove 5 gallon of creosote a month from the chimney. We buttoned up the home a bit and upgraded to an old school Caddy which cut our wood in half. Now with the new furnace, it will be better. I would NEVER go back to an old school furnace!
 

sloeffle

Minister of Fire
Mar 1, 2012
986
Central Ohio
I’m hoping for a cold winter. I’m really jealous of the guys who get to start burning in September and burn through April or may. Trying to keep the house warm at -10 sounds like a lot of fun, to someone who never gets to do it.
I only burn from Dec - March, and by March I'm done with feeding the wood furnce. I have a 10 year old closed loop geo system, in March I'm very happy to turn it back on for another 8 months. :)
 
  • Like
Reactions: Ncguy427

woodey

Feeling the Heat
Feb 8, 2018
325
ST. Lawrence Valley N.Y.
Trying to keep the house warm at -10 sounds like a lot of fun
If you are looking for fun and are willing to move to the foothills of the Adirondacks here in Northern N.Y. for the months of January and February I would be happy to switch houses with you for those months!>>
 

trx250r87

Burning Hunk
Nov 30, 2012
211
NE Wisconsin
Hello all,

I’ve been running an old 1970s Virginian model 103 wood stove for the last few years and I’m going to buy a furnace this weekend. My house is fairly large, 3000sqft 2 story plus a 1100sqft finished basement. Closed floor plan, average insulation. The stove struggles. The stove is in the basement, and the furnace will take its place. Located in central NC, so our winters are pretty mild.

I have 2 very reasonably priced options. A 1557 hot blast, or a old simple huntsman; I’d guess 1970s or very early 80s. Out or only those two options, which would you choose? Neither has to last forever, I’d say 3 years. Down the road id like to upgrade to a Kuuma 100, or possibly an OWB. But I can’t afford that now.

I’ve read about some of the complaints with the hot blast. I can replace blowers and wiring etc. Assuming the firebox isn’t cracked, it should be good to go right?

Firebox for the huntsman is around 5cuft. And the hot blast appears to be close to 7. My current stove is 2.9.

I appreciate any suggestions on which to go with.
I have personally owned the following wood furnaces:
Daka 621
Vogelzang Norseman 1500
Drolet Tundra
Drolet Heat Commander

If the Hotblast is anything like the Vogelzang, which they see like the same stove to me, then you are wasting your time! I only had the Vogelzang less than one season, what a piece of crap!

Eric
 

Ncguy427

Member
Oct 23, 2021
40
Greensboro, Nc
If you are looking for fun and are willing to move to the foothills of the Adirondacks here in Northern N.Y. for the months of January and February I would be happy to switch houses with you for those months!>>
I actually grew up in NY. Born and raised outside Albany (Clifton park), then went to cortland for college. Cortland is a cold place. We had a camp up in Watertown for a while when I was young, on the thousand islands. So I definitely know the cold… moved down here to Nc in 2012 and never left. i love it down here, but there’s definitely some things I miss about the north. One is snowmobiling and snow in general. . I also miss the mild summers up in north. 75-80 degree days. Here in the south it’s above 80 minimum from late April through sept or even October. With 90+ June-august. The temp isn’t even the worst part, the crazy high humidity is…
 

Ncguy427

Member
Oct 23, 2021
40
Greensboro, Nc
I only burn from Dec - March, and by March I'm done with feeding the wood furnce. I have a 10 year old closed loop geo system, in March I'm very happy to turn it back on for another 8 months. :)
Ya I’m the opposite. I’m so excited when it’s finally cold enough to light up the stove and I’m never sick of it once spring comes. Probably because our burning season is fairly short. And I’m always sad when it’s too warm in the spring And I always keep it going a little longer than I should in the spring. if I burned from sept to may I might be sick of it at the end, but idk. When it’s not cold enough to burn, I’m still living the woods life of cutting skidding splitting and milling. I’m really not a fan of the summer heat either. I especially like being out in the woods cutting when it’s cold. think I might like living in a climate where it’s always cold enough to burn,
 

woodey

Feeling the Heat
Feb 8, 2018
325
ST. Lawrence Valley N.Y.
The first winter I used this furnace was one of the few times I put in a full load (IIRC 5-6 twenty inch splits and 2 sixteen inch splits on top). The temps were mild, night time lows 30 the next day 40. By turning off the computer the next day( at the coaling stage) i went 24 hrs before reloading. I burn mostly maple, beech and ash. If I had the wood mentioned in your post I could have squeezed out a few more hours. Check out some of my other posts and you can see what I'm heating.
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,223
NE Ohio
I load once a day in milder weather...but that is a partial load too, which basically means a new fire everyday...when it gets a bit colder I go to 2 smaller loads, which I can squeak out a "hot coals" relight usually...when "real winter" hits I do 2 medium loads per day and get plenty of coals for easy reloads...only during the coldest weather have I ever gotten close to a full load, which at that point I either turn the computer up to medium and load 3 times per day...or load twice and do close to full loads...but keep in mind that the VF is probably just a touch on the big side for our house and heat load...I've never had to run it on high.
@JRHAWK9 is the king of full loads...and did a full firebox of Locust one time when leaving for the weekend...something like 20 hours until the VF's blower shut off IIRC...
 
  • Like
Reactions: Ncguy427

Ncguy427

Member
Oct 23, 2021
40
Greensboro, Nc
The first winter I used this furnace was one of the few times I put in a full load (IIRC 5-6 twenty inch splits and 2 sixteen inch splits on top). The temps were mild, night time lows 30 the next day 40. By turning off the computer the next day( at the coaling stage) i went 24 hrs before reloading. I burn mostly maple, beech and ash. If I had the wood mentioned in your post I could have squeezed out a few more hours. Check out some of my other posts and you can see what I'm heating.
Damn, that’s a long time! I burn quite a bit of maple and ash as well. I have so many dead ash trees on my property. Just took one down yesterday. It’s a shame what happened with the beetle. Anyways, I seem to get about 25% longer burn time with oak or hickory Over ash and the kind of maple I have here.

Can you elaborate more on turning the computer off? Can you manually set the air when it’s off? And I assume the blower turns on and off based off the thermostat in the house, separate from the computer?
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,223
NE Ohio
Can you manually set the air when it’s off? And I assume the blower turns on and off based off the thermostat in the house, separate from the computer?
No...its preset, "pilot air"...and you have to give the wood enough burn time to be down to coals before shutting the computer off so you don't make creosote.
The blower generally runs the whole time there is a fire...the t-stat just kicks the blower from low to high...I don't even use it...no need really. Once you learn the machine and what it takes to heat your house you just load the furnace with about the right amount of wood and set the computer to the approximate burn rate and done. Mine is on low 99% of the time.
 

JRHAWK9

Minister of Fire
Jan 8, 2014
1,869
Wisconsin Dells, WI
Burn times, IMO, are kinda subjective. Lots of variables and there is no real solid definition of when one defines the end of the "burn".

Starting a fire in a cold firebox vs reloading on coals will also affect the "burn time". The furnace will be more efficient when you start stacking loads and reloading on coals. The burn time will also differ when using wood volume as a gauge of quantity, as, obviously, soft woods have less BTU's vs hardwoods when comparing volumes. Using weight is much better, as all species have ~ the same BTU's to give per POUND. Having said that, I believe, on low, you can safely assume ~4-5 lbs/hour when on low and still have coals to load on.

@JRHAWK9 is the king of full loads...and did a full firebox of Locust one time when leaving for the weekend...something like 20 hours until the VF's blower shut off IIRC...

I loaded 99.4 lbs of BL and had 21.5 hours of blower runtime :)
 
Last edited:
  • Like
Reactions: sloeffle

brenndatomu

Minister of Fire
Aug 21, 2013
7,223
NE Ohio
4-5 lbs/hour when on low and still have coals to load on.
Yeah somewhere I ran across a quote from Daryl a while back that said design was 4-5 lbs/hr on low, 5-7 med, and 7-9 lbs/hr on high...(IIRC)
 

JRHAWK9

Minister of Fire
Jan 8, 2014
1,869
Wisconsin Dells, WI
Here's last night's 32lb load for instance.

Red is flue temp, blue is supply temp. I do have a variable speed blower system which constantly adjusts blower speed based on supply temp to keep the supply temp as high as possible all the time. It also allows me to slow my blower down to keep supply temps high. This may work for some and not for others....all depends on your home. IMO, there is not one "setup" which works optimally for every house. It took me 4 years or so of trial and error to come up with a blower setup which optimizes heat output for my house. The original blower setup was just too much for our house. It was passing too much air through the air jacket. I needed to drastically slow down the air. It seems I am in the extreme minority when it comes to having to do this though.

I started a fire in a cold firebox (flue and supply temps were both ~64°) at 11:45pm. Loaded 32lbs (which turned out to be too much, as it didn't get as cold as I thought outside and the house got up to 74° last night). Blower kicked on at 12:06am and ran constantly till 7:50am. The computer was doing the pilot - '1' thing till about 12:40am, then it went on pilot and stayed till about 1:20am where it went back to the pilot - "1" thing till about 2:10am. It then stayed on '1' till 3:10am where it went to '2'. Stayed on '2' till about 3:45am where it went to '3' (coaling stage) at about 3:45am. This will make MUCH more sense to you once you get yours and see first hand what the computer does to keep the fire burning optimally.

When the blower shuts off, I will have minimal coals left. I can do a matchless re-light easy enough though if I have to. If the outside temps/inside temps are such that to warrant a re-load, with only 32lbs initially loaded, I could have probably done a re-load soon after the computer went to the coaling stage and loaded on a nice bed of hot coals after raking them forward. Once temps start getting colder, I will start re-loading on a nice bed of coals. This is what I typically do once winter sets in.

Supply (blue) and flue (red) temps:
1635691155466.png



Just supply temp:
1635691271466.png
 
Last edited:

Ncguy427

Member
Oct 23, 2021
40
Greensboro, Nc
Interesting. I’ve been reading some of your and others past post about the furnace and computer trying to get a handle on things. The graphs are pretty cool.,

I have a few other questions. What size supply duct did you guys run from the Kumma to your plenum of your central furnace? Or warm air trunk line. I pretty much have room to do whatever. I was thinking of starting with 1 12 inch round duct, and possibly a 6 inch as well. And see if those together move enough air to heat the house. If not, I have room to tie in atleast another 12 inch or 2 more 8 inch.

2nd question is regarding the stack. My current setup is a 8 inch terracotta thimble that my stove pipe goes into. The terracotta thimble is about 18 inches long and dumps into my chimney. I will have to plug this up as it’s only 30 inches tall. The Kuuma needs to go up about 6ft and then it can go into the chimney. I don’t really want to do another terracotta thimble at 72 inches, if I don’t have to. Instead I would do one of these steel zero clearance or minimal clearance thimbles as I can most likely do the work myself. What do y’all suggest?
 

Ncguy427

Member
Oct 23, 2021
40
Greensboro, Nc
My Kumma has arrived. Didn’t take long at all, it was delivered to the shipping terminal where I picked it up just over 3 weeks after I ordered. Dang is that thing heavy as hell though, it was interesting getting it off the trailer without forks. It’s sitting outside tarped until Sunday when my friend can come with his forks and bring it up to the basement door. I think I’ve found a company who will come install a new thimble, close up the old one and probably add a clean out on the backside of the chimney. Although I hope I dont have to clean it out much anymore, once a year when I have a pro come and sweep and inspect would be ideal. Im tired of doing it every few weeks with my current 50 year old stove.

Going to install some zones and put in a new duct or two for a dumping zone in the garage, so when the house is up to the temp, it’ll close off those ducts and open up 1-2 big ducts that will go to the garage and dump the heat there. My wife’s keen on a heated garage.
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,223
NE Ohio
I think I’ve found a company who will come install a new thimble, close up the old one and probably add a clean out on the backside of the chimney. Although I hope I dont have to clean it out much anymore, once a year when I have a pro come and sweep and inspect would be ideal. Im tired of doing it every few weeks with my current 50 year old stove.
What do you have for a chimney flue? Clay liner? What size inside? Height?
 

woodey

Feeling the Heat
Feb 8, 2018
325
ST. Lawrence Valley N.Y.
You don’t have to worry about having to clean out your chimney every few weeks like you do now. This is my chimney this morning (with fire)in a 11x7 clay liner. I am on year 6 with the Kuuma and have yet needed to brush the chimney but I still check it weekly. The hornet on my wrist didn’t get me!

371208D1-1CAA-4484-BF81-FECF4E8E3A8C.jpeg
 

Ncguy427

Member
Oct 23, 2021
40
Greensboro, Nc
Congrats on the new furnace! What are your plans for making up the air that you dump into the garage? Without some type of return air you will be putting a positive pressure on the garage and negative pressure on the house.
I was thinking about that last night. Do you think I need an outside return to pull new air in to the house? If not, I was thinking about running a duct from all my current returns to the new furnace. If I do need to pull air from outside to replace what’s dumped out, I can do that.
 

Ncguy427

Member
Oct 23, 2021
40
Greensboro, Nc
What do you have for a chimney flue? Clay liner? What size inside? Height?
Ya a clay liner, inside size is 8x12 I want to say. Or maybe it’s 8x12 overall and 7x11 inside. It’s tall, 3 stories and ends up above the highest peak, so it’s roughy 30-35ft tall. Dale was saying I’ll probably have a bit too much draft and need to set my barometric damper accordingly. But too much draft is better than not enough right?
 

Ncguy427

Member
Oct 23, 2021
40
Greensboro, Nc
You don’t have to worry about having to clean out your chimney every few weeks like you do now. This is my chimney this morning (with fire)in a 11x7 clay liner. I am on year 6 with the Kuuma and have yet needed to brush the chimney but I still check it weekly. The hornet on my wrist didn’t get me!

View attachment 285862
That’s awesome. I will not miss sweeping at all lol.

How much radiant heat do you guys get from the Kumma? My stove room is in a spare bedroom in the basement. With my current setup, it’s totally unusable during the winter because the room gets so hot.
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,223
NE Ohio
But too much draft is better than not enough right?
Yeah it is.
The only issue you might run into is great draft while a new load is coming up to temp (higher flue temps) and then when the furnace starts to run on pilot air more (lower flue temps) the draft just collapses because that huge clay flue is a heat sink...just have to try it and see...some people get away with running an oversized clay chimney, some don't.