The Do's, Dont's and Why's of Wood Stove Temps

  • 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.
Status
Not open for further replies.

soupy1957

Minister of Fire
Hearth Supporter
Jan 8, 2010
1,365
Connecticut
www.youtube.com
Someone will undoubtedly say........there's already a thread about this, and I'm sure they'd probably be right. But I'll risk that, in order to take a fresh look at the subject of operating temperatures in wood stoves used for heating.
I'm a 52 year old grampa who spent many years in the woods, lighting campfires. In my backyard, on a river waterway, at campgrounds.......I consider myself to be a master at starting and maintaining OUTDOOR fires.
Over the years I've known many folks who had wood stoves in their homes, but didn't really get into any discussions about temperature unless someone was saying it was too hot, or were complaining about cold spots around the house.
This week, as a prelude to a major re-construction of our home, there will be the installation of an Avalon Rainier 90 in our living room, so I've been reading up, and watching lots of YouTube videos on the subject.
One thing I'm going to implement in particular, is the use of a magnetic temperature gauge, (which I presume gets mounted on the flue, at about eye level), because I happened to stumble on a video that mentioned the use of one, but didn't go into too much detail.
Before talking about the how and why of temperature monitoring, perhaps a bit about our intended use of the wood stove is in order, as that might have an affect on the responses I receive.
We had bought a new oil-burning, forced hot air furnace to replace our old one, about two years ago. It has been our only source of heat up til now. It works great and we keep it maintained.
Our desire for a wood stove was more about the snap, crackle, pop of the wood; the smell of the wood burning; the visually hypnotic effect. It was not our intention to turn the furnace off and make the wood stove the sole source of heat for our 1200 sq. ft. home.
That being said, the wood stove is being installed in our living room, on the main floor. It will no doubt feed the living room (kicking off the furnace thermostat which is located in there), the kitchen, the bedrooms and bathroom upstairs. We don't expect it to heat the family room nor the laundry room which are both located on a lower level, so we thought we might supplement the heat down there with space heaters.
I don't see us trying to maintain a fire in the wood stove "constantly," but we are not adverse to doing that, either. I think we have a "wait and see" attitude about it for now.
Considering our "part time" usage of a wood stove as described, does that have an affect on what temps we try to achieve in our burning times? What is the best range to operate a wood stove at, and why? How do you regulate the temperature? Are there time limits on how long you should or should not allow certain temperatures to be sustained?
We will be using only properly seasoned and dry hardwoods for our burns. Newspaper and Fatwood and smaller wood pieces are our kindling of choice for cranking up the fire.
Any specific advice is welcome ..........
Regards,
-Soupy1957
 
I'm no expert, but...

- Most stoves have thermostatically controlled air intakes that will automatically damper down if the fire gets too hot. Even on my 1982 stove, I have an adjustable intake that I can open, close or set somewhere in the middle at most burn temps. (But so far this year with green wood, I'm mostly running wide open.)

- Sounds great that you have forced air... good to move that heat around the house. I've got a ceiling fan on low in the stove room, and rely on heat rising in my 3 floor house. Seems to be saving me a lot of oil I think the stove is handling at least half our heating load. It would be much more even with a forced air variable speed blower. (I'm shopping AC with a geothermal heat pump which would be separate from our oil fired radiators.)

- The stove temp and fire temp are obviously going to be different. It seems most folks want their stoves between 400 and 600 degrees most of the time. The flue temp could be anything it seems. You want to keep the fires hot for efficient burns and minimal creosote (to avoid chimney fires). Dry wood is obviously going to help that. If you get too hot, damper down the air. Pretty simple. I'm pretty happy if I can get running at 600 degrees... heck even 500 with this wood.

BTW: I've been complaining about the rutland magnetic thermometer I bought at Home Depot. Mine won't tell actual temperature, but maybe give me a number to multiply to guess the actual temperature. It seems that an IR is ideal for accurate measure. The ATD-701 is apparently on $40 and measures over 1000 defrees F. The ATD-702 goes up to 1800 but is twice the price.
 
Based on my reading here and my own personal experience, you'll find that different types of stoves run at different temps. For example, some soap stone stoves manufacturers tell you not to over a surface temp of 600F or 650F. My plate steel Lopi Endeavor says 800F is considered to be "overfiring" the stove. Cast iron might run hotter than some soap stone stoves, but a little cooler than plate steel.

Other things that will affect your "cruising temp" (as I like to call it) include: size of the load; orientation of the splits (north/south vs. east/west); draft; length of flue/chimney system; dryness of your wood; species of wood, etc.

My Lopi Endeavor will run just shy of 675F on a fresh load with fully active secondary combustion for about 30 minutes. It will then settle into the 650-600F range for an hour or so, then it will drop to 500F, then to 400F for several hours. Eight hours after a full load of oak, it will read about 275-300F and maintain a 2" or 3" coal bed when they are raked out even.

How much heat you want will also dictate how hard you run the stove. In weather like we're having now (20s for highs, single digits for lows), I run it up to 650F every time I reload. In milder weather, I might only load 4 splits of soft wood and run it around 500F and then let it die.

Whatever stove you chose, you will find it's normal operating range in time.
 
There is only one or maybe two models of stove available that have thermostatic air control and they are not particularly common stoves either so I expect that you will be manually setting your air control. The huge majority of stoves sold are non catalytic which means that you are unable to turn the air down too low so the "low burn temp" will be determined by the fuel load and will usually run no lower than 400. The high burn temp is the temp that you have to intentionally run to and the max limit depends on material. Most rooms aren't too comfortable for too long with a stove over about 500 in them. Running your stove intermittently you will want to be sure that you get it goon-n-hot occaionally to burn out the gunk. You'll know if you aren't burning hot enough by the color of the inside of the stove and by the cleanliness of the stove glass.

I suspect that you will enjoy burning so much that you will burn most of the time. We love it, pyros at heart, and burn as often as we need to for heat without using any kind of furnace.

So what stove are you getting? We'll need pictures.
 
Inferno: What kind of stove? I had stated that in my post: "This week, as a prelude to a major re-construction of our home, there will be the installation of an Avalon Rainier 90 in our living room........" (I'll post pictures after the install, when it's burning).

Pyro Extraordinaire: you talked about soapstone stoves........my wife liked the looks of those. The retention of heat in the soapstone was an interesting selling point, but I wanted a more traditional basic stove (costing less, too).

Fire Honor Society: You said "Most stoves have thermostatically controlled air intakes." Mine doesn't. the air controls are manual. In fact, I didn't see a single unit in the showroom that had anything automated about them, except for the ones with blowers on them, (which I didn't want).
speaking about the forced hot air furnace, I find it an interesting idea to encorporate that into the heat coming from the wood stove. If I could find a way to turn the fan on....................wait a minute..........there IS a "fan" control I think on the wall-mounted thermostat in the living room........lemme go check this out............this could be the key!!! (excitedly runs upstairs to investigate)

-Soupy1957
 
Soupy, I too tried the fan on the cold air return to move heat. Unfortunately for me, it was a dismal failure and didn't move any heat by the time the air traveled through the cold duct work. You may have more success with your home's layout, though. I wish you success. I'm considering adding a blower to our Endeavor to improve it's natural convection properties, but for now I'm using a ceiling fan on reverse with some success. I'm too tight to part with the $250 they want for a glorified fan.
 
"I" as well, hope that my success with using the "fan only" setting on my thermostat, yields better results than you had. I'm only heating 1200 sq. ft. (split level) and the wood stove we chose is plenty large enough for that size dwelling.
Because we are on the precipice of a major renovation here, we are replacing the existing kitchen ceiling fan, and adding another ceiling fan in the new dining area. Thus.........we're exploring the movement of air outside the ductwork as well.
Obviously you, (and probably many others) have considered the use of the "fan only" setting on the thermostat, to move the heat around. It may very well be that when all is said and done, not much gets transferred, because it cools too quickly.
We have a very "tight" house and even if I DIDN'T use space heaters in the lower family room and laundry room, I'm willing to bet that without furnace heat, the temps in those two rooms (which are below grade, by the way), would not drop below freezing. So any added heat from running "fan only" would just be a plus.
I'll try the "fan only" and see what it does for me.........anyone else have any experience trying out the furnace fan (obviously related to forced-hot air systems only......not base board heat) as a heat exchanger for the wood stove? I'd be interested in hearing how it worked out for YOU?

-Soupy1957
 
Yup. There are two issues with central system blowers on 'fan-only':

(1) if they run full speed and full time, they use more elec than you really want for the benefit. This is not an issues if your system is set up to run the fan at reduced speed, or on a 30% on/off cycle on 'fan only'.
(2) The temp lost in the ductwork depends on whether your ductwork is within the insulated envelope of your house or not, its degree of insulation if it isn't, and how much CFM its pushing.

If your ducts are inside, and the fan is one that doesn't pull too much juice, you are in business. Otherwise, you are unlikely to be satisfied.

The fan on my HP install can run full time at 30% CFM, or 30% cycle at 30% CFM, so I'm good on (1), but my ducts are in the attic (and very well insulated). If I break out the IR thermo, I can see that on 'fan only' the duct outlets run about 3°F below the return inlet temps, steady state. Thus, if the rooms' temp diff were a lot higher than this without the fan, it might be useful; in practice natural circulation (and ceiling fan circ inside the envelope) do a lot more for me.
 
Don't know what my "CFM" is, but I DO know that my ductwork is all insulated and within the envelope of my home. Nothing is external except the final couple of feet of the chimney. That's going to work in my favor, no doubt.

I also stumbled on an "Eco Fan" video (those fans that sit on top of the wood stove, that run from the heat radiance). Ordered one within minutes of seeing the video. Cool idea!! I'll point it toward the upstairs (probably won't need it since the furnace fan should do well IMHO).

With regard to the "Eco Fan," ..........I saw a number of videos on it, but here's the one that sold me:

http://www.youtube.com/watch?v=ksOZhxeCAvU

One additional thought: I have "Central Air" on my house. When I tell the thermostat to use "Fan Only" .......is it going to use the FURNACE fan, or the CENTRAL AIR FAN, by default?


-Soupy1957
 
Soupy, CFM is Cubic Feet per Minute. A measure of the volume of air moved in a minute by a given device.
 
Yea, I know what it means............I just don't know my CFM.
-Soupy1957
 
Sounds like you should try the 'fan only' setting as see if it works for you. FYI, a lot of folks around here find the enofans amusing, but not really effective at moving heat.

As for the CFM--when your on fan only does the air flow seem similar to when the furnace is running, similar noise (if you can isolate it from the burner noise)? If so, then you might want to watch your electric bills, your electric meter, or look up the manual for your air handler unit on the net. If it seems noticeably slower/quieter, you are probably aok.
 
I'm so new at this wood burning stove stuff, that I haven't even fired up the new wood stove yet. Installation is Monday. I'll find out by Monday/Tuesday if the fan sounds different. My electric bill will end up being higher this year anyway, since my wife wanted a Central Air unit put in, which was done last month. I'm assuming that the draw by THAT bugger, will be more than the 3 window A/C units, combined, that we USED to use. Anyway, I'll be paying more for electricity. (Since it's all about "being green," I wonder if I should consider not using electricity..........hmmmmmmm? Maybe I should become "Amish?" Naw..........too old for that........lol)

-Soupy1957
 
Status
Not open for further replies.