Overdraft?

[Northern NH Mike]

I spent a few hours last night searching the forum and reading posts regarding fast burns, overdrafts and flue dampers and I think I have an overdraft. Would appreciate any input from the veterans.

The stove is a brand new VC Encore NC professionally installed. The stack a straight vertical shot of single wall to the ceiling (5ft), double walled through an attic crawlspace (4ft) and metal (ss?) chimney that I estimate is about 10 feet. I am burning a mix of hardwoods, some of which is kiln dried.

Last night I started the fire, got a good bed of coals and added 5 splits of mixed sizes (a few 6inch+), tight pack so that the top of the pack was just below the damper. Charred the wood, closed the damper, air regulator open full, Everburn roared and no smoke from the chimney. Began turning the air down but stovetop thermometer quickly hit 750 and slowly leveled off about 625 after air turned off. There was still some active flaming with air all off. The splits disintegrated into large coals in about 2 hours with air 100% off, stove ended up at 300 after 5 hours. With the exception of the 750 degree reading, this has been the routine for the past two months.

The air temp outside when I started was about 42 degrees, five hours later a front had moved through and we were at 51 degrees, so it was quite mild for northern NH November standards.

This morning I have checked the door, griddle and ash pan seals with the dollar bill test and believe they are tight. Stove pipe connections appear tight (ie no corrugation showing).

Based on the observations and previous forum discussions I'm thinking overdraft (jet engine) due to the stack run. I have a 6 dollar cast iron flue damper sitting on the table. Is it worth taking the pipe apart and installing or should I look at anything else?

As always, my appreciation for the collective wisdom and archive of information to refer.

 

[begreen]

19 ft of flue seems just about right. I'm surprised that it would overdraft. The kiln dried wood has me a little more suspicious. Have you tried burning with no kiln dried wood?

Before adding the damper, clean the stove out well and inspect for any cracks or leaks with a very bright light. This would be a good time to examine the refractory too just to be sure there are no factory defects.

 

[Northern NH Mike]

"The kiln dried wood has me a little more suspicious. Have you tried burning with no kiln dried wood?"

I have tried burning just the naturally dried wood, but not as a fully packed stove and it has also burned quickly. I will give a full load a try to see if there is a difference.
I'll also inspect for cracks to see if there is air infiltration elsewhere.

 

[Northern NH Mike]

Inspection for cracks found nothing obvious and the refractory appears intact. The flaps for the air flow regulation above the doors are operating and closing all the way down. I discovered that there is no regulation of the primary air entering into the refractory shoe from underneath the stove so even with the air turned down 100% the jets of air entering through the shoe are unregulated. I'm wondering if the small fan on the doorway floor 20 feet away blowing cold air toward the stove could impact the air entering the stove bottom to a significant point to throw the burn rate off?

 

[Todd]

I would give yourself a little more time since it's a brand new stove. Fool around with different sized splits and loading techniques.

 

[begreen]

i wouldn't think that the fan blowing toward the stove would influence its burning. It sounds like the stove is in good order. Burning large chunks of seasoned wood is what 'd probably try next. If that doesn't work, it's not going to hurt to try the damper, seeing as you already have it on hand.

 

[Eddie24361]

Are you sure your stove-top thermometer is correct?

 

[Northern NH Mike]

I think I will experiment a bit more with combinations of kiln and naturally dried loads. I'm thinking that the all kiln dried may be the cause of the raging temp. The fan will be a nonissue in a week as the blower unit will be installed. In regards to the thermometer I believe it to be of reasonable accuracy although I have an IR on order and could easily set a second magnetic on top today to see how consistent they are.

I appreciate the feedback and troubleshooting ideas. The forum archives are a wealth of knowledge that I'm glad are available. Happy burning.

 

[LLigetfa]

I discovered that there is no regulation of the primary air entering into the refractory shoe from underneath the stove so even with the air turned down 100% the jets of air entering through the shoe are unregulated.

The RSF Onyx I had in my former home had a runaway problem because the primary air is unregulated and I had very good draft. I modified it by reducing the air flow. In my current home I have the same model stove and the opposite problem so I modified it for more air flow.

 

[Backwoods Savage]

Mike, until you get it figured out, I'd also recommend not feeding that thing a full load. You shouldn't need a full load now anyway.

 

[Diabel]

I had something similar situation last week, however my stove read nice 600* while the pipe thermometer peaked at 700* which is around 1400* internal (no good for the pipe :bug: ).

I also thought about the flue damper...it never hurts to have that extra control...

 

[Northern NH Mike]

So I ended up installing the damper yesterday. It was a pain in the neck to get the damper in place. It was worse getting the pipe back up. We'll see how it works out.

Much thanks foe the input and experiences.

 

[tradergordo]

I discovered that there is no regulation of the primary air entering into the refractory shoe from underneath the stove so even with the air turned down 100% the jets of air entering through the shoe are unregulated.

That is NOT the primary air, that is the secondary air. And you are right, there is no secondary air control.
To me, it doesn't sound like your stove is overfiring. If there are no glowing red stove parts, it probably isn't overfiring. Don't use kiln dried wood.

If you really do think your stove is overfiring, see my comments and links here:
https://www.hearth.com/talk/threads/29401/

 

[trailblaze]

hah, this is just like my post...

seems over drafting effects others too!

not much we can do about it so i understand... unless a stove pipe control is installed

 

[tradergordo]

hah, this is just like my post...

seems over drafting effects others too!

not much we can do about it so i understand... unless a stove pipe control is installed

When you say "not much we can do about it" it gives a vibe like "oh well, just gonna let it overfire". This is the kind of attitude that will get you killed. There are things you can do about it, and if you let your stove glow red, the best case is that you destroy the stove, worst case I'll leave to your imagination. The solutions are described here:
http://www.gulland.ca/florida_bungalow_syndrome.htm

 

[Northern NH Mike]

That is NOT the primary air, that is the secondary air. And you are right, there is no secondary air control.
To me, it doesn't sound like your stove is overfiring. If there are no glowing red stove parts, it probably isn't overfiring. Don't use kiln dried wood.

If you really do think your stove is overfiring, see my comments and links here:
https://www.hearth.com/talk/threads/29401/

Tradergordo

Thanks for the link to the 11/25 discussion. In hindsight, my situation was not as extreme as the overfires described. When I read the bungalow article a while back I decided to troubleshoot my situation in the order listed in the article (with the exception of getting up on the roof with the restrictor plate). In the end, some adjustments to the mix of wood load and flue damper installation seemed to work very well this past weekend when temps were very low and stove was cooking. Temps hovered between 450 and 625 all weekend and I felt I had a better understanding of the stove. Over the holiday I will be talking with my father about building a secondary (thanks for the clarification) air control mechanism in his shop.