Over fire control

[Doddington]

Hello,
I have a wood stove in my new to me house that seems to over fire very easily even with the wood stove air damper completely shut. It is a Century Heating FW3000 wood stove with approximately 26’ of double wall flue. I am wondering if I should look at adding a flue butterfly damper to assist when over firing due to too much updraft.

Also what is the best way to reduce heat during an over fire situation? I have successfully gotten the wood stove temp back to normal operating temperatures with opening my exterior door in the room as well as the wood stove door but as of recently had a situation where that was not effective. Thanks for any advice.

 

[Northern NH Mike]

Be sure your thermometer is relatively accurate. A probe thermometer in the flue pipe is helpful in running a stove well and an handheld IR thermometer helps to know how the stove is performing. I installed a key damper in the flue pipe for that extra control Where is the air intake on that model? I purchased an end cap for my VC Encore non-cat to plug up the rear bottom air intake in case of run away. Have rarely used it in the past few years as I learned to run it even in its finicky ways. Hope that helps a bit.

 

[30WCF]

One or two key dampers is often recommended.
Opening the stove door can help let a lot of air move through the system and cool down.
Possibly covering the intake. I have a jar lid that snaps perfectly into the 3.5” opening for the OAK.

 

[Doddington]

One or two key dampers is often recommended.
Opening the stove door can help let a lot of air move through the system and cool down.
Possibly covering the intake. I have a jar lid that snaps perfectly into the 3.5” opening for the OAK.

I have read there is pluses and minuses about key dampers? Seems it can create more creosote in some situations? If I add one i would just keep it wide open unless I was having issues with too much back draft driving the fire beyond normal temps.

 

[Doddington]

One or two key dampers is often recommended.
Opening the stove door can help let a lot of air move through the system and cool down.
Possibly covering the intake. I have a jar lid that snaps perfectly into the 3.5” opening for the OAK.

Also what is OAK? I keep seeing this acronym used across this website but have yet to learn what it stands for.

 

[weee123]

Also what is OAK? I keep seeing this acronym used across this website but have yet to learn what it stands for.

Outside air kit

 

[Wildflush]

With a 26’ chimney and strong draft a key damper makes sense installing about 18” above your strove collar. If you need it it’s there as an emergency brake so to say. It can help reduce draft so you don’t burn through wood also.

Many key dampers today are not as restrictive as the ones of years ago. Even when closed they let air by it. The one from Excel has cutouts in it.

Overfire open widow near stove or in your case the door. Open door of stove slowly letting cold air in. It will drop flue temps. Stay with the stove.

 

[30WCF]

Also what is OAK? I keep seeing this acronym used across this website but have yet to learn what it stands for.

As Weee123 said, it’s an outside air kit. I suppose I’m referencing the air intake incorrectly by calling it an OAK, if you don’t have the kit installed to bring in fresh air from outside.
Lots of people don’t use it. I don’t have the kit, but I refer to the hook up location as an OAK at times. If you do have the kit, a small key or iris damper can be added to slow down the air intake.

 

[30WCF]

I leave my damper wide open. I think I have adjusted it twice in a year when things were hotter than I needed for the weather we had and I loaded it too hot.

 

[Todd]

How are you running your stove? What kind and sized splits are you burning? Maybe you’re not turning the air down soon enough. Sometimes the wood can all off gas at once if not turned down at the right time. A flue thermometer is a great tool to fine tune your burn.

 

[Eman85]

Not familiar with your stove but I saw it's EPA rated so I'd say it's supposed to be pretty air tite. Before I put akey damper in I'd make sure the stove is functioning correctly. I'd do the dollar bill test on all gasketed openings and see how it seals. You should see a big difference in the flames when moving the air control, if not it's sucking air somewhere.

 

[Doddington]

How are you running your stove? What kind and sized splits are you burning? Maybe you’re not turning the air down soon enough. Sometimes the wood can all off gas at once if not turned down at the right time. A flue thermometer is a great tool to fine tune your burn.

They are bucked at 12” and roughly 6” wide split wood. I have had this fireplace take off into over fire a couple times in the 2 years I’ve operated it so I tend to monitor and reduce the air regularly to have it slowly get to temp vs quickly. I have a stove top thermometer as my flue is double walled so I use that to gauge my temps.

 

[Doddington]

Not familiar with your stove but I saw it's EPA rated so I'd say it's supposed to be pretty air tite. Before I put akey damper in I'd make sure the stove is functioning correctly. I'd do the dollar bill test on all gasketed openings and see how it seals. You should see a big difference in the flames when moving the air control, if not it's sucking air somewhere.

I’m not very familiar with wood stove specs but this is the model I have. https://www.century-heating.com/file/45632A_22-02-2013.pdf

Ya I’ll try doing that again. I replaced both the door and glass gaskets last year as I was suspected that was causing the over fire so easily. We did have fairly strong winds last night so wondering if that didn’t create a larger updraft than usual as otherwise it’s been quite responsive to the air damper moving.

 

[begreen]

Draft varies with outdoor temp and wind. The greater the difference between outdoor and indoor temps, the stronger the draft.

It sounds like a single key damper will be good. The Century is an easy breathing stove so a single key damper won't negatively affect operation. In mild weather just leave it open. On cold and/or windy days, you may want to close it once the fire is burning strongly. Even in closed position it should still pass about 25% of the flue gases.

 

[30WCF]

Let’s see your stove top thermometer. It’s easy to over fire a single wall pipe thermometer on a stove top. The scale is different for the two types of thermometers. Can you retell us exactly what it is or post a pic of it?

 

[Doddington]

Let’s see your stove top thermometer. It’s easy to over fire a single wall pipe thermometer on a stove top. The scale is different for the two types of thermometers. Can you retell us exactly what it is or post a pic of it?

This is the one I currently have. After doing some research today I learned the manufacturer of my dual wall flue does allow a flue thermometer so I’m wondering about installing one if it’s a better metric to go by vs stove temp.

 

[30WCF]

Ok. Thats a stove top thermometer. Sometimes when people talk about over firing the stove, but are using a flue thermometer for stove top temp (SST). The flue thermometer is labeled as “over fire” at a much lower temperature. So you have the correct one.
If I was going to spend $30, I would buy an IR to verify the accuracy of your STT thermometer. It should outlast your magnetic thermometer, and be more reliable. You can also instantly scan the stove and find the hottest spot to measure.
I have this one and it does well. It goes over 1000*. Make sure you get one that reads atleast 900 or so. Lots of them max out at +/-500* which doesn’t really help when it’s hot.

https://www.lowes.com/pd/Kobalt-10-1-Digital-Non-Contact-Laser-Infrared-Thermometer/5012911909

Double wall pipe really needs a probe drilled into it to get a good read on flue temps. I’d go digital.

 

[Caw]

Ok. Thats a stove top thermometer. Sometimes when people talk about over firing the stove, but are using a flue thermometer for stove top temp (SST). The flue thermometer is labeled as “over fire” at a much lower temperature. So you have the correct one.
If I was going to spend $30, I would buy an IR to verify the accuracy of your STT thermometer. It should outlast your magnetic thermometer, and be more reliable. You can also instantly scan the stove and find the hottest spot to measure.
I have this one and it does well. It goes over 1000*. Make sure you get one that reads atleast 900 or so. Lots of them max out at +/-500* which doesn’t really help when it’s hot.

https://www.lowes.com/pd/Kobalt-10-1-Digital-Non-Contact-Laser-Infrared-Thermometer/5012911909

Double wall pipe really needs a probe drilled into it to get a good read on flue temps. I’d go digital.

View attachment 322277

858 seems fairly hot for STT, no?

My stove likes to cruise at 700 +/- 50 at the hot spot. I don't like it to get past 775 if I can avoid it. SBI considers 840 an over fire for my model.

 

[begreen]

While not essential, I agree to get one that reads higher. Normally readings will be under 700º but the greater range allows measurements when unusual things are happening, like a glowing flue collar or liner.

 

[30WCF]

858 seems fairly hot for STT, no?

My stove likes to cruise at 700 +/- 50 at the hot spot. I don't like it to get past 775 if I can avoid it. SBI considers 840 an over fire for my model.

It’s on the hot end for me for sure. If you can get anything out of VC for an Aspen C3 other than if it glows it’s too hot, let me see it in writing.
It doesn’t take much to get this little gem up to 750-800 STT for a few minutes at peak, but then it drops 100 or so pretty fast and settles in for a few hours.
This particular day it was 858 on the hottest spot. 800 on the rest of the front 1/4 of the top. The Auber was about 630. I don’t always read the STT, but it’s not uncommon to see mid to upper 600s in the flue, about 24” above the stove. I did turn the damper down that day since I saw 858.
700-750 STT is very normal.

 

[30WCF]

While not essential, I agree to get one that reads higher. Normally readings will be under 700º but the greater range allows measurements when unusual things are happening, like a glowing flue collar or liner.

Right.
I’d surpass the target range by atleast a couple hundred to monitor the anomalies. I’d your IR stops at 600, you don’t know what happened after the 600 mark.

 

[weee123]

I try to keep my STT below 650 if I can help it as anything above that gets a little too warm for my house, but I have had it go up to 700 on me before. On my auber my flue temps are usually around 520-560 with the flue damper open. Surface temp of the pipe is around 320 give or take a few degrees.

Once I start closing the damper to get the draft in spec the auber temp drops a quite a bit but surface temp stays the same.

If my stove ran up to over 800 that would mean I’ve lost all control of the stove.
My osburn 1600 had a leaky glass gasket and once that hit 600-650 it would run away to 800 and that was never fun. That smaller stove when functioning properly needed to be run around 700 to properly heat the house. The Englander can do it at a lower temp.

 

[Caw]

700-750 STT is very normal.

That smaller stove when functioning properly needed to be run around 700 to properly heat the house.

Yeah my stove is a 2019 Osburn 1600i and as we've been discussing it likes to live around 700 +/- 50. I'm very comfortable with that. I have a strong draft, it burns clean, and heats the house well. Can set it and forget it for 6-8 hours.

Every so often it'll kiss 775-800 on a stuffed full reload which gets my attention but then it'll come back down to normal range after 5-10 minutes of air shutdown and high blower. I've only gone past 800 a few times accidentally when I've forgotten about it.

 

[30WCF]

This morning I hit 775 with a few splits of Bradford Pear.

 

[30WCF]

Ended up at 826 STT