wood furnace/not enough heat

[samhell]

I am looking for any input concerning my 8yo Newmac oil wood comb furnace. When I use the oil, (which is rare) it heats the house fine. When I heat with wood, it struggles to get the house much over 60 if it is 20 or below outside.
It is a big rambling farmhouse(3500sqft) with r38 wall insulation and mostly newer insulated windows.
The fires that I burn are cranking hot hardwood fires. So hot that you cant get your face too close to the fire box.
That hot fire does not translate into a warm house. I also go through 10 full cords per year (oct to april)
I am pretty good with maintenance, dismantling and cleaning the angled steel chimney (6') that goes to the house chimney 2 to 3 times per year. I also scrape the soot that accumulates around the plenum, and change the air filters yearly. Any suggestions to improve this situation would be appreciated.

 

[NE WOOD BURNER]

try lower speed on fan and have it come on earlier and run longer.

 

[Fred61]

Are you burning on the coal grates or have you installed a floor for wood burning? My wife had one of these in her house years ago and it was very difficult to control. It would burn up a whole firebox of wood in two hours and deliver all the heat all at once and them go cold. The only way to be comfortable was rto add two sticks at a time and add again after they burned.

 

[Mark Ellsworth]

I have the Cl86/96 and have the same issue. The problem with this furnace is it will not heat the plenum unless the fire box is full. I used to fill mine at 12 in the night and 3 to 4 am the oil would cut in. I spent a week fooling with it last year and found that the heat was not rising and going out each side of the heat exchanger and out the chimney. This was not caused by excessive draft as I adjusted the flapper on the chimney and it was not the issue. I kept checking all parts with the temp gun and with a half full firebox the plenum was at only 72 degrees. Finally I made two plates for each side of the furnace two inches wide and 10 inches high with a piece of flat bar that fits in the track on each side of the stove. This blocks part of the area around the heat exchanger forcing the heat to rise before it goes out the chimney. Wow what a difference I could close down the draft and the furnace would run for hours and hours.

 

[Gasifier]

Where is the intake air coming from for the furnace?

 

[Mark Ellsworth]

Where is the intake air coming from for the furnace?

Intake for the plenum comes from cold air intakes on the first floor and second floor of my house. As for combustion air it is supplied from the frontside of the furnace. Before I made the addition I had to keep the draft a little more than halfway open above the door to get enough heat to heat the plenum. Now I can turn it way down almost closed and get constant heat and double the burn Tim of before.

 

[Gasifier]

I'm wondering why it heats the house fine with oil, but not with wood. What is different? How long do you season your wood? A fire can be too hot to get near with the face and still not be as hot as that oil burner is throwing out. Is everything else the same as far as dispersing the heat from oil? Is the same plenum and fan used by both oil and wood? Same cold air intact, etc.?

 

[Mark Ellsworth]

The plenum is the same for both as well as cold air. The oil pot is in the back of the furnace and the oil burns and is forced upwards by the blower heating the plenum the heat then has to work its way to the front towards the firebox and then out around the heat exchanger and then towards the back of the furnace. The wood will heat fine as long as the firebox is full. The firebox is very deep and once the fire burns down the fire flows towards the outside of the heat exchanger and out the chimney not giving it enough time to rise and heat the plenum. By adding the two pieces of plate the exhaust gases from the fire no matter how small or large the fire must rise to heat the plenum before exiting.

 

[STIHLY DAN]

Time to get a furnace designed for burning wood only and well.

 

[Mark Ellsworth]

I agree this hybrid is not efficient in my opinion. I wish there had been more choices where I live when I built the house. I was not sure what to get at the time and the oil seemed ok at the time and was cheap. In the last few years with the oil prices I have been burning wood and I was amazed at how bad this furnace was. I put my beer fridge in the garage and if I was having a few I would grab a beer and throw in an arm load of wood the same time lol. It was that bad before I installed the plates I would go to my woodshed with my truck put a full tier of birch across the tailgate level with the top of the box and burn all of it in a 24 hr period plus oil at 4 am. I am thinking of putting something else in the house for heat but I am not quite sure what to put in.

 

[STIHLY DAN]

IMO there is only 2 choices. PSG caddy (Canadian large mfg) or KUUMA American small mfg. Save 1/2 the wood, and be comfortable.

 

[Mark Ellsworth]

Thanks so much I will check it out.

 

[Gasifier]

Ja. The Kuuma looks like a nice unit. Does anyone know anyone that has been running one for many years? How long have they been building them? I am curious about reliability. They sound nice, but I have no experience with them and know no one who has one. Are there any Kuuma owners on Hearth?

 

[hobbyheater]

(broken link removed)

Installed this furnace for Granny last spring but it is not gasaifiction like the Kuuma. Compared to her old wood,coal,and oil combination furnace it burns a lot less wood and is thermostat controllable . Although not well know back east it has been made in western Canada for 30 years with a good reputation . Out here it was know as RSF. but has recently been sold to eastern interests so hence its new name .

https://www.hearth.com/talk/threads/grannys-new-wood-furnace.108241/#post-1419909
The installation

 

[brenndatomu]

Ja. The Kuuma looks like a nice unit. Does anyone know anyone that has been running one for many years? How long have they been building them? I am curious about reliability. They sound nice, but I have no experience with them and know no one who has one. Are there any Kuuma owners on Hearth?

Stihly Dan has one himself https://www.hearth.com/talk/threads/kuuma-vapor-fire-100-wood-furnace-results.112796/ If you go on Kuumas site, (broken link removed) it may take a bit of digging, but I seem to remember them saying they have been around since early 80s or late 70s? It sticks in my memory that the old man has a Vaporfire in his house, has never had to clean the chimney in 27 years or something like that.
There was also a post by a guy that goes by Iowa over on Arboristsite recently, he has pics of doing the annual cleaning on his Vaporfire, nothing but a bit of white powder! Thread called "Kuuma Vaporfire clean out", last post by lampmfg on 10/11/13. I'll post a link to the thread, but if this is not cool with the powers that be, feel free to delete it (broken link removed)

 

[STIHLY DAN]

Yup, I have one. Gasifier, if you have any questions feel free to ask. I will tell you all you need to know and more.

 

[hobbyheater]

Yup, I have one. Gasifier, if you have any questions feel free to ask. I will tell you all you need to know and more.

Do a thread as I /we always love to hear of the success of a product new to us !!

 

[STIHLY DAN]

I did. Its under Kumma vaporfire 100 results. Check it out.

 

[hobbyheater]

I did. Its under Kumma vaporfire 100 results. Check it out.

Thank you I will have a look!

 

[Gasifier]

Yup, I have one. Gasifier, if you have any questions feel free to ask. I will tell you all you need to know and more.

Oh I just wonder how they are for reliability and the like. I certainly do not need to spend more money! I have a Wood Gassification boiler for my home and a new Wood Pellet stove for the camp. Zoikes!. Like, going to have to skip a few pizzas and burgers to pay for those scoob.

 

[STIHLY DAN]

Oh I just wonder how they are for reliability and the like. I certainly do not need to spend more money! I have a Wood Gassification boiler for my home and a new Wood Pellet stove for the camp. Zoikes!. Like, going to have to skip a few pizzas and burgers to pay for those scoob.

25 yr warranty, works great with power or no power.

 

[lampmfg]

Oh I just wonder how they are for reliability and the like. I certainly do not need to spend more money! I have a Wood Gassification boiler for my home and a new Wood Pellet stove for the camp. Zoikes!. Like, going to have to skip a few pizzas and burgers to pay for those scoob.

Give my dad a call at the shop (800-258-2049) if your ever interested in learning about wood burning with the Kuuma Vapor-Fire. He has spent his entire life creating the perfect wood burning furnace. It' near impossible to burn wood any cleaner!!

 

[heaterman]

If you have a stack thermometer, watch it to see what your flue temp is with wood vs oil. Sounds like most of the heat is going up the chimney when you burn wood. Not so much with oil.

 

[Frozen Canuck]

Odd as likely the most reported issue with wood furnaces is that they run too hot & short cycle. Agree with heaterman that there is a reason that you are dumping most of the heat when using wood, more research needed as to why. Has this been an issue since the install date?

 

[Mark Ellsworth]

Yes it has been an issue with my furnace since install. The issue is it is a combo not an add on. All of the add on units in our area are excellent and all of them have a plate over the firebox forcing the heat to rise before it moves to the back of the furnace warming the plenum. The cl86 does not and I believe it is the biggest design flaw in the unit. The heat goes right out the chimney that is the reason I laid the plates in to make the heat rise before going out the chimney. My grandfather had one in his house several years back and had to remove it as it would not heat his house with wood. He then installed an add on unit in the exact same place and it works fine. I spoke with a guy who used to install them a few years back and he said many people had to take them out. My uncle has one and burned almost a full tractor trailer full of seasoned birch last year. As I mentioned before once the firebox burns halfway down it will not heat the plenum unless the homemade plates laid in the firebox. I used these last season with great results but before that it was amazing how much wood it would consume with very little heat. Oil heat was fine but expensive thus the reason I bought a wood furnace. I am looking at changing it out in the near future.