Flue pipe Damper

[Michael Cardillo]

hello all,

The draft of my stove pipe allows my Madison to keep rising in temps and the flame to stay very large in the stove, even with the air lever pulled completely out. Today the stove top remained at 625 for 1 solid hr.

I want to put a flue pipe damper in and would like to know how high above the stove top it should be installed in the pipe.

Please let me know.

Thanks,
Mike
NJ

 

[DougA]

I just bought a damper and will be installing it today about 12" above the stove. The exact distance shouldn't matter since it restricts the air flow but does not stop it. I have too much draft, especially on windy days and have run much, much higher than 625.

BTW, 625 is not all that hot. I used to run my old VC Resolute at 600+ on a regular basis when it was super cold outside. Try using larger splits and that usually lowers the temps a bit and gives you longer burns.

 

[spirilis]

The Madison manual recommends not going above 600F so 600+ is technically considered overfire. It probably won't actually hurt though.
(350F = low fire, 450F = medium fire, 550F = high fire)

Flue damper can be as little as 4 inches above the flue collar. Just needs to be able to swivel freely inside the pipe with no screws or pipe joints obstructing it.

Fwiw I have mine crusing at 640F right now, had a biobrick on top of the fuel mass... I turned the blower on high and made sure that air control is ALL the way out
Realistically though, I fully expect the stove is going to hit the 600-650F range a lot this winter because I have really dry wood (including some kiln dry stuff like biobricks) and know those burn hot. Experience so far has shown that the stove will calm down with the AC-14 on high and air control pulled out tight. You can also try partially blocking the OAK hole in the back to see if that'll kick it down a notch (there will be some unburned smoke out the flue for a little while with that but no creosote since it's too hot to condense).

edit: 10 minutes later, seeing 460F stovetop temps instead. Kicked the AC-14 down to low and there's a nice cloud of bluish-orange flame in the upper firebox.

 

[Michael Cardillo]

Nice. Thanks.

I installed the flue damper and only used it last night when we went to sleep. I allowed two big oak splits that are probably at 35% moister in the box to catch, then I dampened about 80% of the flue damper down and pulled the air control completely out. The stove burned from 11:30pm until 5:30am this morning.

Can anyone tell me if it is dangerous to stack the stove above the midway point of box? I'm looking for a longer burn time. Say 10pm to 6pm and still have embers to restart the stove in the morning.

 

[spirilis]

Were there still secondary combustion flames rolling with that setup? What was the stovetop temp before you went to bed?

There probably isn't any problem filling the stove over half but keep in mind the splits up top will burn faster (and hotter) due to their proximity to the secondary combustion zone (and insulated baffle). Bigger splits up top would probably work best for long burn times. Be careful not to bump the baffle.

 

[DBoon]

I have a small stove (~1.6 cubic foot firebox). I stuff it full on cold days using four square splits and a bunch of small pieces to fill the gaps and get the flames going early. I watch the stove closely when I do this and shut the primary air down early to avoid thermal runaway, and I use the blower to manage the heat rise as well. Still, I can get to 650 degrees F even with all of this, and I won't do this just before going to bed unless I want to keep the blower on high all night (I don't). Usually, the stovetop temps will peak for about 1 hour, then it runs out of gas.

Larger splits do help slow the burn down by spreading the intensity over a longer period of time.

 

[brenndatomu]

I allowed two big oak splits that are probably at 35% moister in the box to catch, then I dampened about 80% of the flue damper down and pulled the air control completely out

Sounds like a recipe for creosote...large splits/rounds are great for overnight but only if dry, and it takes forever to get the bigguns dry
I would bet that you lost secondary combustion shortly after going to bed...

 

[spirilis]

I am starting to consider adding a pipe damper myself... hit 750F on a reload tonight some time after AAS switched (the damper wasn't out completely, just out then pushed in maybe 1mm) but it was just engulfed in flame and bright coals up near the baffles. This was a very tall load with a few biobricks here and there, otherwise mostly chunks of poplar cutoffs. Pulling the air all the way and turning blower on High eventually pulled it down into the mid-600's but damn.

 

[Nick Mystic]

I question the notion of installing a stove pipe damper on a modern EPA stove unless there is an unusual situation such as an extremely tall flue that simply produces too much draft regardless of correct operation of the primary air control. A great deal of experimentation goes into the design of these stoves and they are built to burn properly without an additional damper in the flue under normal operating conditions. Before I installed a damper I would make an effort to really learn how to operate my stove with the existing controls and with various size loads of wood. In my experience a properly working stove can be kept from over firing by loading tight with large splits and regulating the primary air with close attention to keep things from getting out of control. A new set of problems can occur while using a damper if it is being substituted for a proper burning technique.

 

[spirilis]

Yeah my choice of fuel was probably suspect here. Loose cutoffs seem to take off once it hits critical even though they look all packed together in the stove. Just in denial about breaking out the splits... maybe it's getting to be that time.

 

[mrpee]

Back in the old days you got just the damper, now it comes in its own piece of pipe that goes on stove flue coller . I put one on the Hearthstone Hraritage when I installed it. I did it so I could slow a over fire down , but I am closing it about 1/4 and I think it slows the gasses and secondary burn is better . If someone knows more about this chime in.