Am I OVER-FIRING my JOTUL F-500

[Sootfoot]

I've asked this question before. But I haven't received an creditable answer based on location of temperature. Forgive me if I'm being difficult....


Right now, as we speak , I have a bunch of small American elm 2-3" logs shoved onto a HOT bed of hard maple coals. My stove is so packed, I probably couldn't fit a toothpick in it. Trying to heat my 1100sqft bungalow from the basement with Strickly firewood.

-My stove top temps right now read 700-850F ** on the oval cook plate**

-My right back corner of the stove reads 350F.

-My air control is fully closed, and damper on stove pipe is also fully closed.

-I Might add, dual burners are running at what appears to be 100%, and firewood is ignited with many lazy flames.

-I have a medium sized fan placed behind my jotul, constantly blowing air on stove top/ stove pipe trying to extract as much heat as possible to reduce heat loss up the chimney.

My understanding is the proper place to determine stove temp is back right corner. Also I understand that the oval plate is not an accurate reading spot because it's directly above dual combustion tubes that shoot 1000F + flames making that obviously the hottest part on the stove. The hottest I've never seen that oval plate is 950F. I try to keep it under 850F. Let me know what you guys think.

 

[St. Coemgen]

damper on stove pipe is also fully closed.

Wait a minute.... Do you mean you closed the damper on the exhaust pipe/chimney? If so, my first thought would be what a great way to potentially build up carbon monoxide in the stove room....

Open the damper on the exhaust pipe. You should only fully close the stove exhaust pipe damper when the stove is off and not being used. When in use open the damper and allow the gas from the burning fire to exhaust to the outside. Do not try to "trap" every bit of heat into the stove by suffocating the fire or preventing it to exhaust the combustion gases.

Also, suggest reading the Jotul F500 manual which says:

Wood consumption

Jøtul F500 has a nominal heat output of 8,5 kW. Use of wood, with nominal heat emission: Approx. 2,7 kg/h. Another important factor for proper fuel consumption is that the logs are the correct size. The size of the logs should be:

Kindling:
Length: 30 - 55cm
Diameter: 2 - 5 cm
Amount per fire: 8 -10 pieces

Firewood (split logs):
Recomended length: 35 cm
Diameter: Approx. 8 - 13 cm
Intervals for adding wood: Approximately every 80 minutes
Size of the fire: 3,5 kg
Amount per load: 2 - 3 pieces

Nominal heat emission is achieved when the airvent is open
approximately 50%.​

So I would say you are giving too little air, and overloading with wood as per manufacturers specs.

 

[Nick Mystic]

That is an awfully large difference between your temperature readings on the right rear corner and top center. That leads me to think that the wood burning n the stove hasn't been burning too long yet. The corners take longer to heat up than the top center. So, as far as temperature is concerned you'll have to wait until the stove temperature stabilizes to see how hot the corner reading will reach. However, over firing is not only judged by stove temperature. And this leads me to the main concern with your burning scenario. In my opinion it is often risky to pack a stove with small pieces of wood like you described. With that much surface area the fire can easily take off and become an inferno, which is extremely difficult to bring back under control in my experience. It sounds like you have a stove pipe damper, so perhaps one can stop such an over fire by closing it down as you described doing. I hope your stove doesn't take off on you. Good luck.

 

[revdocjim]

I'm also very curious about your description, "damper on stove pipe is also fully closed"... If it were fully closed that would mean no smoke or gases can go up the chimney and you would no longer be alive. It must be some sort of design that doesn't allow you to "fully" close it, but I'm not familiar with such a design. The air control is different because there is a secondary air control that is not adjustable and always provides some air for the fire.

Secondly, I concur with Nick. You'll get longer burning, more consistent heat with larger pieces of firewood and reduce the chance of over-firing.

As for your question of whether you actually are over-firing, I apologize because I don't have specific info about the relative temps for different locations on the stove top.

 

[Sootfoot]

I'm also very curious about your description, "damper on stove pipe is also fully closed"... If it were fully closed that would mean no smoke or gases can go up the chimney and you would no longer be alive. It must be some sort of design that doesn't allow you to "fully" close it, but I'm not familiar with such a design. The air control is different because there is a secondary air control that is not adjustable and always provides some air for the fire.

Secondly, I concur with Nick. You'll get longer burning, more consistent heat with larger pieces of firewood and reduce the chance of over-firing.

As for your question of whether you actually are over-firing, I apologize because I don't have specific info about the relative temps for different locations on the stove top.

My stove pipe damper can be fully closed and still let airflow by. It might choke off 75% or less, but will not completely extinguish chimney draft. I rarely close it completely, I only closed it to prevent stove temps from increasing. With a HOT stove like this, and a hot chimney, I have good draft for being in a basement. I highly doubt this would ever create a backdraft, sucking carbon monoxide into the living space. I also have a leaky house, which im trying to tighten up.

I normally don't burn small pieces, I do have large chunks of maple I use I get 7-8 hour burns. I'm just trying to understand with the temps described, if I'm actually doing harm to the stove

 

[Firewood Daddy]

Why are using a key damper with the Oslo? This stove should be fully controllable with the front air control lever. If the temperature runs away I would look at door seals. Let the stove go out and try the dollar bill test.

 

[semipro]

Wait a minute.... Do you mean you closed the damper on the exhaust pipe/chimney? If so, my first thought would be what a great way to potentially build up carbon monoxide in the stove room....

How so? A properly operating flue creates a draft that pulls air through the stove. Wood stoves are typically somewhat leaky and meant to operate under a vacuum only.
Most flue dampers only partially restrict flow.

If the OP has an OAK they can obstruct it to see what difference that makes. The air control lever only limits the air coming in through the doghouse. It does not limit what enters via the secondary burn tubes.

Based on my understanding of the OP's description, I don't believe your stove is overheating.

 

[Sootfoot]

Why are using a key damper with the Oslo? This stove should be fully controllable with the front air control lever. If the temperature runs away I would look at door seals. Let the stove go out and try the dollar bill test.

I did try that with a small piece of newspaper. If my temps are 750F with the air control wide, and I turn it right down, dual combusters run full blast and temps increase. I use damper to try to reduce temps further

 

[semipro]

Why are using a key damper with the Oslo? This stove should be fully controllable with the front air control lever

Not true. the Oslo can overfire if the draft is too strong. The air control lever does not restrict all airflow into the stove, only what comes in through the doghouse.

 

[Sootfoot]

Another member once posted, he could careless what the stove top ( oval plate ) temp is. He said his manual says to read temps in back right corner. That's what he does.

Now that can be dangerous because in this situation, I would be like " oh my stove is only 350F" when my oval plate is really 850F, probably getting to the point of glowing red and potentially warping. I think a user should keep an eye on both.

Now that the stove has settled down, I have an oval plate temp of 500F, and my back right corner is around 250F.

 

[Wood Duck]

Not true. the Oslo can overfire if the draft is too strong. The air control lever does not restrict all airflow into the stove, only what comes in through the doghouse.

Is this accurate? I have a Lopi stove so it might be designed differently, but with my stove the primary air control does not impact the air flow through the doghouse, nor the secondary air flow. Of course you wouldn't want to restrict secondary air flow in a hot stove because you can't restrict the release of gas from the wood, and you need the secondary air to burn those gases.

 

[St. Coemgen]

I normally don't burn small pieces, I do have large chunks of maple I use I get 7-8 hour burns

Some stove are designed and built for very long burns, and others are not.

This type of stove was not really designed for 7-8 hour burns. Read the specs from the manufacturer I provided above. Clearly says you need to load approximately every 80 minutes.

If you want long burns, you may need to buy a different stove. For example, the JOTUL 118 CB can sustain long burns (I once had a slightly earlier model and it was a very nice stove).

I'm just trying to understand with the temps described, if I'm actually doing harm to the stove

It goes beyond the wood load specs in the manual. So, yes, you might be shortening the working life of the stove by overloading the stove like that or end up risking your own life: i.e. risk overheating the stove if given too much air with a lot of wood, or by cutting off airflow you may risk CO buildup on a smoldering fire (buy a CO alarm for your home, just to be safe).

Also, regarding heating:

Square feet of your house is really only part of the issue, but what is most important is cubic feet to heat (after all, you may have a tiny number of sq ft, but cathedral ceilings and all that air space needs to be heated).

A 8,5 kW stove, like the Jøtul F500, will heat about 9000 cubic feet of air for a well insulated house and only about 5000 cubic feet of air for a poorly insulated house. So figure out your cubic feet (your basement where the stove is and all your living space) and the insulation quality of your home, and then calculate if this stove can even heat your entire living space. If it can, then the issue may simply be in moving that warm air around the house (i.e. getting the warm air around the stove in the basement into the rest of the living space).

 

[St. Coemgen]

How so? A properly operating flue creates a draft that pulls air through the stove. Wood stoves are typically somewhat leaky and meant to operate under a vacuum only.
Most flue dampers only partially restrict flow.

If the OP has an OAK they can obstruct it to see what difference that makes. The air control lever only limits the air coming in through the doghouse. It does not limit what enters via the secondary burn tubes.

Based on my understanding of the OP's description, I don't believe your stove is overheating.

The stove is maybe overheating, but the real issue is the OP overloaded it with wood beyond manufactures design use specs (which I posted) and is possibly suffocating the fire in an attempt to compensate. You should not overload and long burn all stoves. Reducing all air sources will not change drifting from the designed use and expecting different results.

I did not say to not use a damper, I said one should not fully close a damper during normal operations. Reducing flow to the chimney using a damper because the draft is too strong should be an occasional issue only (such as during high winds). If you have to use a damper all the time, or fully close it, then your chimney and stove are then most likely not correctly matched and that should be properly corrected.

 

[semipro]

Is this accurate? I have a Lopi stove so it might be designed differently, but with my stove the primary air control does not impact the air flow through the doghouse, nor the secondary air flow. Of course you wouldn't want to restrict secondary air flow in a hot stove because you can't restrict the release of gas from the wood, and you need the secondary air to burn those gases.

Its correct for the Oslo. I disassembled my stove when I bought it to determine this. I don't know about the Lopi.

 

[claydogg84]

Another member once posted, he could careless what the stove top ( oval plate ) temp is. He said his manual says to read temps in back right corner. That's what he does.

Now that can be dangerous because in this situation, I would be like " oh my stove is only 350F" when my oval plate is really 850F, probably getting to the point of glowing red and potentially warping. I think a user should keep an eye on both.

Now that the stove has settled down, I have an oval plate temp of 500F, and my back right corner is around 250F.

So you're not here for advice, you're here telling us how we should be running our Oslo? This is like the 3rd thread you've created in which you've been told the exact same information. If you want to run your stove by the oval plate, go ahead. Me? I'm going to run it as per the manufacturers directions.

 

[claydogg84]

Some stove are designed and built for very long burns, and others are not.

This type of stove was not really designed for 7-8 hour burns. Read the specs from the manufacturer I provided above. Clearly says you need to load approximately every 80 minutes.

If you want long burns, you may need to buy a different stove. For example, the JOTUL 118 CB can sustain long burns (I once had a slightly earlier model and it was a very nice stove).

This is terrible misinformation.

 

[Sootfoot]

So you're not here for advice, you're here telling us how we should be running our Oslo? This is like the 3rd thread you've created in which you've been told the exact same information. If you want to run your stove by the oval plate, go ahead. Me? I'm going to run it as per the manufacturers directions.

k a


Ok yes and no. I've been told similar information but at the same time I've not been given a clear answer . If my oval plate is 850F & my right corner is 350F 2 hours into a burn, what am I doing wrong and is this dangerous in terms of stove longevity

 

[claydogg84]

k a


Ok yes and no. I've been told similar information but at the same time I've not been given a clear answer . If my oval plate is 850F & my right corner is 350F 2 hours into a burn, what am I doing wrong and is this dangerous in terms of stove longevity

You have been given clear answer, you're just choosing to ignore it.

 

[begreen]

Wait a minute.... Do you mean you closed the damper on the exhaust pipe/chimney? If so, my first thought would be what a great way to potentially build up carbon monoxide in the stove room....

How so? A properly operating flue creates a draft that pulls air through the stove. Wood stoves are typically somewhat leaky and meant to operate under a vacuum only.
Most flue dampers only partially restrict flow.

If the OP has an OAK they can obstruct it to see what difference that makes. The air control lever only limits the air coming in through the doghouse. It does not limit what enters via the secondary burn tubes.

Based on my understanding of the OP's description, I don't believe your stove is overheating.

You are right SemiPro. This is an incorrect statement. Key dampers are slotted so that they can not block off all the flue gases. They are commonly used to reduce strong draft. In our old setup with the F602 the key damper was always closed fully once the stove got going. Ran the stove for 10 yrs that way and never had the CO detector make a peep.

 

[begreen]

Some stove are designed and built for very long burns, and others are not.

This is terrible misinformation.
View attachment 174464

Agreed. This is incorrect and not helping anyone. There are thousands of Oslos delivering nice overnight burns of 8+hrs. The F500 can easily match the F118 for burn time.

 

[semipro]

I did not say to not use a damper, I said one should not fully close a damper during normal operations. Reducing flow to the chimney using a damper because the draft is too strong should be an occasional issue only (such as during high winds). If you have to use a damper all the time, or fully close it, then your chimney and stove are then most likely not correctly matched and that should be properly corrected.

Why a damper during high winds?
A flue damper is great way to address over drafting. How else would one address the issue? In many cases high drafts are caused by tall chimneys. Are you suggesting that there's a better way to address that then with a damper?

 

[St. Coemgen]

This is terrible misinformation.
View attachment 174464

Sorry, I do not see where is the misinformation? What in the image counters what the official Jotul manual for the 500 states, or Jotul's own description of the 118 model having a "maximum burn time"? For example, rated BTU has nothing to do with amount of allowed load or load times.

Edit (yes leaving the above for a reason): Sorry, I see now the "burn time" line in that image. This conflicts with the manual. I would still trust the manual over an image because the manual will be what will be considered for warranty.

 

[St. Coemgen]

dampers... are commonly used to reduce strong draft.

Which is what I said. But strong drafts should not be constant. Else it is a more fundamental chimney problem.

In our old setup with the F602 the key damper was always closed fully once the stove got going.

Modern stoves, with modern chimneys that match the stoves specs do not need much damping. I built two new chimneys, have not had to do any damping when running my stoves to spec.

 

[begreen]

I've asked this question before. But I haven't received an creditable answer based on location of temperature. Forgive me if I'm being difficult....


Right now, as we speak , I have a bunch of small American elm 2-3" logs shoved onto a HOT bed of hard maple coals. My stove is so packed, I probably couldn't fit a toothpick in it. Trying to heat my 1100sqft bungalow from the basement with Strickly firewood.
.

As previously noted, the thermometer should be located in the corners. The cook plate is designed to get hotter. That's why it's a cook plate.


The other issue could be the way the stove is loaded and the timing of reloads. Small 2-3" wood should be used for starting the stove, but it will burn too quickly and hot for a sustained fire. Burn larger splits that are 5-6" and that will provide a slower burn. Another thing to try is letting the coals burn down more before reloading. To do this open the air up and put one or two of those small splits on top. Let them burn down for ~30 minutes and then reload with large splits. Also, try turning down the air as soon as possible, as long as this does not snuff out the fire. Try for lazy flames.

 

[St. Coemgen]

Why a damper during high winds?
A flue damper is great way to address over drafting. How else would one address the issue? In many cases high drafts are caused by tall chimneys. Are you suggesting that there's a better way to address that then with a damper?

I am saying that each stove comes with specs on the draft for the chimney that should be used with that stove. Testing your current chimney draft and buying the stove that matches it is the best option.

Just sticking a stove to an existing chimney may not be a good match. If you need to consult with a chimney contractor who can help adjust your chimney draft to better match your stove.

Also, if you need to reduce the draft to prevent over firing, also check the manual of your stove, you may be adding too much wood. Sorry this comes as a "shock" to some, but yes, as I said above, not all stoves can be stuffed with wood to fire them under the manufactures design. Failure to read and follow the manual that comes with your stove and saying I am "wrong" will not change that.