Isle Royale Over Firing...Install a damper?

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It's burning season here again. I started up our Isle Royale the other day for the first time this season. It started really easily by using the rear air and a fully open primary air control. I turned the rear air control off shortly after I had a fire going and turned the primary control all the way down and the fire burned great. I burned a few logs for the first fire to make sure all the recently cleaned piping was seated correctly, which it was, every seemed to be good to go. Note that we have a basement setup, interior chimney, the stove is vented horizontal and the 6" stove exhaust goes back a couple feet where it increases to the existing 8" single wall stainless pipe that tees about a foot behind the increaser. The 8" pipe then goes up at a 25 degree angle where it meets a rectangular 5.5"x7.6" flex liner, which straightens out and goes to the roof, in total about 25' of lined chimney.

After burning the first round of wood I reloaded the stove with a full load of dry maple and ash. The stove quickly got going really well. I took out my IR temperature gauge after I saw the Rutland stove thermometer getting into the 450 range (I have it set up on the top left of the top loading cover), when I noticed the temperature starting to get into the 600's in the center of the griddle. The fire was really going at this point and I had the primary and of course the rear air control all the way closed. The stove kept getting hotter and hotter to between 750-800 in the center and around 600 on the temp gauge. I could hear the stove sucking air even with everything closed up. For the record I understand these stoves cannot be completely shut down.

I was concerned, from all I've read about wood stoves this was way to hot and I didn't add anymore wood into the fire and let it calm down. I started reading on here about similar situations and I found this article.

I was really concerned that I might have a defect in my stove too. I checked the front and side of the stove for visible cracks, did not see any, I also checked the front and side seems with a candle and lighter and I couldn't find anything there. I had small fire going and I could definitely hear air getting pulled through the primary air controller and confirmed that there was a small amount of air going through there. I didn't find any leaks in the gaskets or any part of the front and sides of the stove.

I called the dealer and explained to him the situation and my concern. He was helpful but had never heard of a situation like this before. He stated the he had a similar setup with his stove (in the basement, tall chimney) and had a lot of draft too. He confirmed that I should look for leaks, which I explained to him that I did and didn't find any obvious ones. His suggestion was to put a dampener inside the 6" pipe a couple feet back from the exhaust, which he provided to me at no charge. I know it's not generally recommended to put a damper on these stoves? Is that accurate?

My question to this community is there a better way? Am I just a victim of a heavy draft or a bad sealed stove? I cannot say for sure I don't have a leak in my stove but I did not find an obvious one. I really want to protect our investment and have a safe stove that works as it is supposed too. Thanks for the responses.
 
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If you are having trouble controlling it there is no reason not to put in a damper but if you used to be able to control it and now cant something has changes and you need to figure out what that is. Have you checked all of the gaskets?
 
I have checked gaskets, anything I should specifically look for? I did the lighter test around gaskets, no obvious leaks. The stove was a never used floor model. Only used it for a couple months last season.
 
Look for any obstructions in your primary and secondary air inlets.
 
If you're loading full of dry, smaller splits, that will cause a super hot fire.
 
I have checked gaskets, anything I should specifically look for? I did the lighter test around gaskets, no obvious leaks. The stove was a never used floor model. Only used it for a couple months last season.
In that case I would put in a damper. Also do the dollar bill test on all the doors.
 
This sounds about the same as my IR. It loves to run! If it's loaded with dry wood it'll take off on ya. Perhaps your wood is properly seasoned this year and was not so good last time around? Keep in mind that griddle will run drastically hotter than the surrounding stovetop. I monitor the temps around it, not the top lid itself though.
 
The rest of the stove seems is a more reasonable temperature, 500-600. It's seeing those really high temps in center of the griddle scares me a little. Knowing that griddle temp is not unusual is comforting. The stove really runs smoothly. It just really cranks out the heat and has an appetite for dry hardwood. The wood is better seasoned this year. Also the chimney was not as clean when we installed the stove last winter.
 
It's an easy breathing stove. A strong draft can make it burn hot. I wouldn't hesitate to add the damper and burn thicker splits on a reload. Maybe burn down the coal bed a little further and not use the rear air at all on a reload.
 
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Thanks for all the good pointers. I think I will move forward with installing a damper and be more aware that the wood I am burning is a lot dryer this year. Seems to me there are a variety of things going on and I need to be aware of them. I've read it on here before, it's never just burning wood, every situation is unique.
 
Pardon the resurrection but I have a Dovre Cape Cod (Quadrafire Cape Cod) that has this same issue with a rear vent setup and 22ft of single wall straight liner up a clay lined chimney (exterior).

There is roughly a 1-1.5 run of single wall stove pipe from the back of the stove before it hits the T cleanout. Is that enough room to install a key damper or is that too close to the stove?

The other solution I was going to test was slowly adding foil tape over the OAK inlet in the rear of the stove. I can hear and see it drawing air in from there while everything is closed up.

My stove runs at 700-750 with hellish secondaries on a half or 2/3 load of mixed maple and 2 yr red oak.