Minimally Invasive Stove Surgery

[EJL923]

Im probably and hopefully not the only person who has been bitten by the EPA bug. EPA stoves are great. They're efficient, throw more heat, burn less wood etc... -IF- you have the correct chimney.

I havent measured my actual chimney draft, but all indications are it is too much for efficient stove operation. My chimney is 25', stainless steel liner, upper and lower block offs, straight up through an interior chimney. At times, my stove likes to burn near 700, which is with the primary air all the way down. Gaskets seem ok. I have an insert, so any type of key damper cannot be done due to access. The only thing left is to limit the amont of air entering the stove. I feel the the secondary air is the culprit. I want to add a slide over the entry for the secondary air, so i can adjust the air entering to better suit my conditions.

So the question is, has anyone done anything like this to have better control over their burns? What was the outcome? Is there another way to decrease the draft on an insert? Whatever I do, it has to be "minimally invasive" in case I ever want to sell the stove.

 

[LLigetfa]

I found that controlling zipper (doghouse) air was far more effective. I would not jury-rig a slider on the secondary air but I would look closely at the current configuration to see if it could be made a little tighter.

 

[EJL923]

LLigetfa,

Do you say that from a stove you've had in the past?

 

[Highbeam]

If your stove is capable of being fed with outside air through a single entrance to the stove I would be inclined to try and block that entrance so that both primary and secondary air are effected. This would make the stove think that it has a shorter chimney since draft across the board would be less but the proportions going to primary and secondary would remain unchanged.

I agree that the secondary air being dumped into the stove is huge and is the best thing to limit. When my stove runs up out of control it is doing it with a secondary fire and flames on the wood.

 

[SmokingAndPoking]

Primary air (airwash and coal bed) is what controls the burn rate and temperature of the unit, primarily.

 

[bluefrier]

being that every stove design is different you have to experiment to find what works. The outdoor air kit thing might not work because the secondary and tertiary air is still running unrestricted. On my stove the "zipper" or doghouse air at the coal bed level was the culprit for the short, hot burns.

 

[EJL923]

OK, i now understand the term doghouse air, perfect word for it actually.

Blue frier, Did you have to go around inner seams with furnace cement?

My primary air enters just above the front door, secondary air enters through the bottom rear.....meaning i cannot limit just one intake for the whole stove. I feel like the primary air is cooling my stove and driving the heat up my chimney.

 

[bluefrier]

no inner seams here....on the englander 13 the doghouse is just two holes in the front bottom of the stove.

 

[savageactor7]

humm...I'd try what LLigetfa did.

 

[SmokingAndPoking]

I feel like the primary air is cooling my stove and driving the heat up my chimney.

This is not true at all. Your primary air is driving the entire fire to burn hotter and faster. More primary = hotter fire.

The coad bed air (zipper, doghouse) is mostly in the stove to help create a pilot flame on a new load of wood. The airwash air lacks the velocity to create a flame on a smoldering piece of wood in the fire with the air control closed. This is the purpose the coal bed air serves.

 

[LLigetfa]

On my RSF, the primary and secondary air are controlled as one, meaning you cannot reduce one independent of the other. Primary air is from the airwash. I have a dedicated OAK and while I did install a positive shutoff on the OAK, it was not to control the fire but rather to close it off completely when the stove is not in use.

I modified the zipper air on my stoves to get better control of the fire. The zipper air draws room air through a 3/8" hole that is not connected to the OAK. In my former home I had a taller interior SS flue that created too much draft. What I did was shove a bushing with a 3/8" OD and 1/4" ID in the hole. I found that reducing the zipper air reduced runaway fires and preserved coals. That was good for overnight burns but when it got down to -40 I was getting too much coal buildup. I would remove the bushing through the day and put it back in at night.

I have the same model RSF in my current home with a chimney that is too short for adequate draft and had coaling problems so I drilled out the 3/8" hole to 1/2" which was an improvement but shortened my overnight burns. I then decided to make the zipper air adjustable and drilled it to 3/4" and installed a valve. I can now have faster burndown of coals or a slow overnight burn with coal preservation or something in between.

 

[EJL923]

Wait a minute, maybe i didn't know what the doghouse air was, but now i do. It is the jet propulsion pack which eats through the middle of the wood! That is also why my wood burns slower when i build up the ashes too thick. So if that zipper air eats through so fast, why do they put it in there with no adjustment? I guess i have to find out where that inlet is coming from. I thought I found all the air, but apparently i missed one.

 

[EJL923]

well i found it, looks like a 1/2" hole and its tucked up underneath 2 heat shields above my blowers. Not easily accessible at all.

 

[LLigetfa]

You could always put a small firebrick in front of the doghouse to simulate a full load of ashes.

 

[savageactor7]

So if that zipper air eats through so fast, why do they put it in there with no adjustment?

It's designed to help keep the stove glass clean.

 

[EJL923]

I would also like to see what can be done internally, but its always tough to stop the stove during cold weather. I may just try a firebrick or some other blockage for now. How do you theink the stove would run if that hole was always blocked?

 

[LLigetfa]

So if that zipper air eats through so fast, why do they put it in there with no adjustment?

It's designed to help keep the stove glass clean.

The zipper air has no influence over the air wash that keeps the door glass clean. THe zipper air accelerates the fire at the base and helps to burn down the coals. It's the modern equivalent of the bellows.

 

[EJL923]

Looking at the design I would agree that the zipper air has no influence on keeping the glass clean. I am guessing that the glass might stay cleaner if i can slow down the zipper air. It would require more primary air which in turn would provide more air wash.

 

[bluefrier]

You hit the nail on the head. The glass will stay cleaner without a third air source in the stove.

 

[EJL923]

Are there any instances where slowing down or completely getting rid of zipper air would be a bad thing?

 

[LLigetfa]

Are there any instances where slowing down or completely getting rid of zipper air would be a bad thing?

How much of a factor it is would depend on the individual stove so there is no pat answer. I imagine fires would take longer to get going, both new and reloads. Coal buildup would be more likely.

I experimented for a long time (15 years) with minimum and maximum zipper air before I designed my air control. I made it notched so that it cannot be turned off completely and I was careful not to open it too far and have an over-fire situation.

Some people use a magnet to partially cover the intake to test.

 

[bluefrier]

not really, I could see where the long lasting coal bed could be a problem for some people. If your stove is properly sized and your home can hold the heat for a long time then you should be able to let the stove cycle through the coal bed phase.

 

[bluefrier]

Agree with LL about the startups and reloads but you can compensate by leaving the door cracked for a minute or two. I think the stove manufacturers should make the zipper adjustable but if I should choose between zipper or no zipper guess which one?

 

[LLigetfa]

I thought of tapping the zipper air supply downstream of the main control so that the main control also regulates the zipper. I also thought of mechanically tying the zipper control to the main control in a non-linear fashion. This was mainly to make it easier for my wife to operate but she hasn't been able to master the main control either. Funny though, she seemed to catch on to the zipper control pretty quick.



I think the stove manufacturers don't want too many complex controls.