Fisher TECH IV Air Intake help

[Vitali78]

Hi there, I seen a post regarding this same stove on here so thought I would give it a try to see if I can also get some help. I have a Fisher TECH IV stove which actually works great but I can't figure out how to control the burn. The burn at times I think is too much and I was hoping to slow it down for overnight once it's hot. I do not see where I would be able to reduce the air intake. Is there a way to adjust the air intake? Or how would I control the burn? Thank you.

 

[coaly]

Is there a insulated chimney liner the same size as outlet all the way to the top?

Chimney height?

The intake should only be wide open when door is open. Has this always burned this hard?

You’re describing an over drafting chimney. That’s why all the chimney questions. The chimney is the engine that makes the stove go. It’s not cold enough outside yet for a strong draft, pointing to needing a flue damper to reduce excessive draft.

 

[Vitali78]

Is there a insulated chimney liner the same size as outlet all the way to the top?

Chimney height?

The intake should only be wide open when door is open. Has this always burned this hard?

You’re describing an over drafting chimney. That’s why all the chimney questions. The chimney is the engine that makes the stove go. It’s not cold enough outside yet for a strong draft, pointing to needing a flue damper to reduce excessive draft.

Hi Coaly, there is not chimney liner. Basically the fireplace has a 6" diameter hole and that is just open into my brick chimney which is about 8x17. Not sure on the chimney height though. The intake is actually interlocked with the door. So to open the door I have to slide the intake open. I dont know how it burned before. I just got this, sanded it, painted it and installed it. Ran it few times to see how it works and thought that it burns way too fast.

But as for the flue damper, I think I do have one. Inside the chimney (although rusted) there is a lever. So the actual opening to the chimney is not 8x17 from bottom to top. The opening is about 2" X 17".

 

[coaly]

You cannot install any Insert or stove using the existing chimney flue. It must have a liner the same size as stove outlet for code (US National Standard NFPA -211) and preventing creosote formation. Depending on proper clearance to chimney, an insulated liner is required. Most chimneys will not be built to code required for a stove that can produce creosote in the flue. When you change the use of the chimney from fireplace to Insert, it must be brought up to current code.

The issue with using large flues for a fireplace is the expansion of hot gases in the flue cools as it expands below the 250* condensing point. The entire flue must remain above this critical temperature all he way to the top when smoke is present to prevent creosote formation.

The chimney is the engine that makes the stove work. It needs to create the correct draft within limits of the stove design. The flue damper is a velocity control that decreases NET draft which slows rising gases, slowing incoming air. The correct chimney and correct draft should get your stove under control.

 

[coaly]

Doing a quick calculation for your chimney size, a 6 inch outlet stove is radius squared or 3x3 =9 x pi or 3.14= 28.26 square inches. When allowed to expand into an 8 inch round area of 50.24, the temperature drops almost in half as it expands. That means you have to let about twice the amount of heat up, to stay above the 250* condensing point. Smaller stoves can’t even do this. They run out of heat and can’t heat the area they’re in. Your flue is 136 square inches. Code only allows 3 times the size, which would be 84.78 but certainly not recommended.

Chimney size determines the capacity, or how many btu it can carry. Like a larger displacement engine, to get more horsepower, you need more fuel. Fuel for a chimney is heat. So you have a huge displacement engine with very little fuel to make it go.

There are two reasons the liner needs to be insulated. Open fireplaces get plenty of oxygen so burn clean and lose lots of heat up the chimney. Stoves can deprive the fire of oxygen, less heat rises and creosote forms. Clearances around chimneys for fireplaces were not made for a creosote fire, many having framing members in contact with chimney. This is why changing the use requires the chimney to be brought up to code for its new use.

 

[Vitali78]

Thank you Coaly for the reply. I did not know this about the chimney. But I also been asking people who installed their inserts without knowing any of what you mentioned above. They said they have no issues at all and they basically have a slider which they open wide to build the fire nice and hot and then close it and the fire completely dies down.

So after reading allot about this, it seems like my stove has auto air intake. This would mean that everything you mentioned above would make my stove work properly.

What I tried was this. And curious to know if this is a bad option. I can get my stove very hot and it actually heats the basement and upstairs really really good as-is right now. But of cource the wood burns super quick. 2 logs about 14" long will last less then 2 hours. What I tried is actually putting a gasket between the door in 3 out of the 4 sides. This worked absolutely perfect. The stove got to about 250 degrees on the gauge which is on the stive (don't think that's internal temp) and then I shut the door with gaskets installed and the fire completely died down. This burned for about 5 hours and the stove stayed nice and hot. It actually heated the entire house which is about 2600 sq/ft. The only issue is that wood stove seal I bought came off. It was the thin seal with self adhesive. If that would of stayed on then the stove would work perfect. The only thing is I don't know the consequences by doing this seeing as the chimney is not for this particular stove.