Fisher Grandma

[snowplow]

I just got my Grandma up and running in our new (to us) house. I haven't been in a house with a wood stove since I was a kid so I have a couple of new guy questions for you experts if you dont mind.

FYI I have the standard 7" double wall pipe. No damper. No door seals. But I did install a 3/8" thick sliding baffle that angles down slightly to the front. So I can use my poker to slide if forward which acts like opening the flue damper. I figured I could fine tune it this way. I'm burning seasoned fir.

So...

The stove guy told me if any stove has intake air adjusters to not run a flue damper. However, every one I have ever been around has had a flue damper. Anyhow, I didn't put one in and the stove didn't get near as warm as I would have expected. So I built the baffle and am trying it out as we speak and it seems to be warmer. Any thoughts on that?

Also today I noticed about 10-15 mins into starting the fire I had liquid dripping off the inside of the doors on to the front pan. Kinda seems like water, kinda seems like resin. Not sure, is this normal?

Should I seal the doors? How do you seal the big gaps on top and bottom of the double door seam? (mines a 76 with the round seal)

So all the wood stoves I have been around have always operated like this: At the end of the night, you load her full, close the damper 90 percent, and almost shut the air off and let it bake all night. Is there a better way I should do things?

Thanks for the help fellas.

 

[Fort Wisers]

You will be happy with this stove, they throw a lot of heat (assuming good burning techniques and properly seasoned wood of course).
We run dampers on all our stoves.
The fisher stoves have a "seal" inherent in the design of how the casting form of the door fits up to the opening on the stove. However the "seal" is not a typical gasket material seal as seen on many other stoves. Bob Fisher wanted a near zero maintenance stove and designed in the system of channels that should close tightly when the door hinges are in good shape and the channels are lapped well. Coaly's "Everything Fisher" section goes into some great detail on how the door system works, how to lap it and why it should not have a gasket (see his post#53 in that thread). Some people do add gaskets but technically this is not correct on a fisher stove and takes away from Mr. Fisher's original concept.

In regards to the fluid, does it have a colour or is it clear? Did you happen to put new fire brick into the stove?

In terms of how to burn, that you will learn with time, it depends on many factors such as your stove condition, chimney, wood being burned etc.
Typically we don't like to close our stoves up too tight otherwise the fire smoulders and can cause a lot of creosote buildup but we certainly don't leave it anywhere near wide open either during the normal burn cycle (except upon startup, but even then only for a short period of time). With our big grandpa we typically bring the stove to temperature with the flue damper open and air intakes either open or close to it. Then as the stove begins to heat up we start closing the damper to reduce the roar of the chimney draw and then set the door intakes to allow for a gentle, slow rolling flame on the firewood (you have to go by sound with a fisher since there's no glass). Even when we reload we typically allow the new wood to char a few minutes before starting to damp everything down. Helps with the smoke output.
Hope this all helps.

 

[coaly]

First, your stove guy should know a flue damper is for control of the chimney which in turn affects the stove. There are many factors that determine the need for a damper and its use.
Rising gasses in the chimney flue causes positive draft, or a low pressure area in connector pipe and stove. The connector pipe, elbows, screen, and flow through stove add resistance to this draft. The damper is a variable resistance added when more resistance is required. (adjustable due to temperature and atmospheric pressure changes) A large flue such as for a fireplace that the stove was designed to vent into would need to be left wide open to allow enough heat up to stay clean. Your correctly sized flue IF insulated requires the minimum amount of heat, so you can add an internal baffle (which adds resistance in the firebox) allowing the damper to be farther open.
It should never be closed 90% overnight. The damper controls velocity of rising gasses, which slows draft, decreasing incoming air. That's how the chimney affects the stove. Control the burn rate with air dampers.

In the case of a double door stove designed for fire viewing through the supplied screen, a flue damper IS required to control the fire with doors open in Fireplace Mode. Manuals for later Fireplace models require it and were supplied in kit form with the stoves. With screen in place and fire established, slowly close damper until smoke appears at top and open enough to prevent smoke roll in, yet slow all the rising heat up chimney. It is NOT considered a radiant heater in Fireplace Mode.

You'll find another use for the damper is when starting with it wide open, as it roars (the sound mentioned by Fort Wisers above) you can slowly close the damper to slow the roaring kindling from loosing all the heat up the stack. This is when you need all that heat to ignite larger pieces while starting. Closing too much will decrease oxygen coming in, so only close until the roar stops. (this is a good indication of how much to close the damper getting you close to the correct draft too) If you tend to create creosote more than a mid season cleaning, open it more.

Combustion of any fossil fuel creates a byproduct of water vapor. When the stove metal is cold, this vapor condenses on the surface and it will be wet until hot enough to evaporate. This shows how much water vapor is produced by combustion, not the water vapor expelled from unseasoned wood which add much more. This is why the chimney flue must be over 250* all the way to the top when smoke is present. Unburned smoke particles stick to the flue surface creating creosote. Over-use of a damper slows the rising gasses even more giving the smoke particles more dwell time in the chimney to stick.
The first fire of the season will be more noticeable since the fire brick absorb moisture from the atmosphere over the summer and it takes time to evaporate the extra moisture in the brick. (or new brick as mentioned above)

Your baffle plate should be lower at the back and raised at the front to make the flames change direction as they rise. (force them forward against incoming air flow forcing heat forward instead of rearward toward exhaust) Tilting it upward at front allows better evacuation of smoke when opening doors to prevent smoke roll in. This was tested by Fisher research and development for decreasing smoke in the later models.

Your stove doesn't have the door seal designed by Bob that Fort Wiser was referring to. Yours is the inventors design which was not near as good and was changed the following year. (He went on to become Frontier Stoves and continued using his own design) If you add flat gasket to the curved door seal area on the doors, it won't close as far creating a larger leak between the doors. Not much you can do about your model with a door leak. You can only run your air dampers closed more than tight fitting doors.

 

[Fort Wisers]

My mistake on the door seal, thanks for the correction @coaly

 

[snowplow]

Thanks. The fluid is clearish but not straight water. No new brick but this has sat in the barn for a year or so. Just got a few burns on it.

Can l add a damper to my new 7" double wall pipe? Or do l need to add a segment with a preinstalled one?

Would you expect this stove to burn all night with dry fir?

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[snowplow]

Sorry l replied before l saw you post coaly. So l wont worry about the liquid. I mainly just want to get a coal to be there for me in the morning. Last night l only slept 6 hours and the stove wasnt really even warm anymore. That was filled 3/4 with very dry fir medium size and the baffle in with air turned off. Maybe ill put a whole big round on tonight.

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[snowplow]

Also is it normal for there to be 2 MIP ports for a water heater on back? It also has a heat shield on back.

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[snowplow]

My grandma

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[coaly]

No, the coil and shield were added.
I assume that's a cement non-combustible floor.
Cheaper to add your own damper.

You're burning wood that us east coasters have zero experience with. That is the trees on the door and the most popular wood in the area where the stove was designed. Our area is tall oaks of many varieties that not only give you a lot of wood in each tree, but leave a good pile of coals in the morning. When we burn 24/7, the coals become so deep we need to open the air occasionally and burn them down during the day before loading in the afternoon ! Wet lots here will have long needle pine and everyone shys away from burning it. Can't give it away. Occasionally someone will pick it up for a campfire but the consensus here is not to burn it in a stove. Probably because they used to use it sticky with sap and didn't have a clue how to season it.

 

[snowplow]

Yep concrete floor. So you can drill the double wall and slip a damper in like you would with single wall?

I wasnt sure if the stainless inner would give you fits to drill or if the damper pin would be long enough.

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[snowplow]

One other question- what exactly will the baffle do? It seems to me it would do the same as a damper just non adjustable.

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[Fort Wisers]

Assuming your pipe is standard manufactured stove pipe then yes you can add a damper in.
Look for something like this (except you'll need the proper size to fit your flue (I think 8"), sorry, it's often hard searching home depot U.S. website from here in Canada):

http://www.homedepot.com/p/6-in-Cast-Iron-Damper-D6/202516615

You'll simply drill two holes on either side of the pipe. The damper has two parts to it, the cast section and the rod.
The rod is interlocked into the cast but can be removed with a push and a twist. You'll slide the cast part up the pipe to where you drilled the holes.
Then you'll fit the rod through one hole, through the cast part and then out the other hole. Get used to how the rod interlocks into the cast before you do this so you have a feel for it. We run double wall on our all stove and have had no problems adding flue dampers. When you drill it, drill a small pilot hole first, then drill it out to size with a larger bit.

I've never burned much softwood in ours so I can't comment too much on burn times with softwood. I do know with good dry "softer hardwoods" such as say poplar, if we were to throw a few larger chunks on we can still get a good 10-12 hour burn time. My brother runs a grandma at home, let me ask him if he's ever burned a softwood overnight.

The baffle helps reflect heat back into the fire and also out the front of the stove, follow what coaly mentioned about angles and you'll be surprised how well it helps.
The damper is used to control the rate of draw (IE "suction") the chimney causes, it will help with your burn times similar (but in a different manner) to your air intakes.
A baffle and flue damper have two very different purposes, the baffle opening should never be small enough to restrict draw.

 

[Fort Wisers]

Talked to my bro a bit, he says there's no issue burning large softwood chunks overnight in his grandma.
He is running a flue damper.

 

[snowplow]

Thanks guys thats real helpful. Ill get me a damper.

Any guidelines on how high above to mount it?

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[Fort Wisers]

Not sure if there's a set guideline, none that I'm aware of but that doesn't mean there isn't something.
Ours are all at roughly 12" above the stove top.
Hope the damper helps, keep us posted the result.

 

[coaly]

Height doesn't matter, it only adds resistance like a valve would in a water line. Put it where it is within easy reach.

The baffle plate is adjustable. Set it on bricks on each side and cut brick corner to lower plat to desired height. You should make a cardboard template the size of baffle to set in place and measure smoke space above baffle plate to bend in top. It should be no less than 38 1/2 square inches for your 7 inch flue. This is the most efficient plate setting, so if you need more heat due to a taller chimney, or your longer connector pipe vertical run, drop it slightly until you reach the flue gas temperature goal you need for 250* at the top.
The only way you will know the correct temp is with a probe thermometer using the double wall pipe.
An IR thermometer is the best for the top. (creosote formation tells the story but needs to be checked frequently until you know what you're creating)

 

[bholler]

I am sorry guys if he has moisture running down the inside of the doors and out that is a problem. If moisture is condensing that much in the firebox i can only imagine what the chimney looks like. It indicates to me either wet wood or way to low temps. Also a standard damper will not work with double wall without modification. There are a few options one is drill your 1/4" holes then on the side with the handle drill a hole large enough for the base of the spring to fit through. Another is trim down the spring. And the last is use a rod from an 8" damper with the 7" plate.

But honestly if you have water running out the bottom of your door you dont need to reduce the draft any.

 

[bholler]

Thanks guys thats real helpful. Ill get me a damper.

Any guidelines on how high above to mount it?

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Standard is 12 to 24 above the stove but like coaly said it really doesnt matter put it where it is conveinent to use.

 

[snowplow]

Thanks guys. I ran it last night and didnt get a bit of liquid. I must have had to just evaporate the moisture in the bricks.

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[snowplow]

so coaly are you saying the baffle should set on the factory bricks in back and get higher in front (height being determined by available area above to match outlet dia)? Does that create the 30* baffle angle?

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[Piney]

Our old grandma with an 8" flue only sees pine. With each new load we run really hot for a few minutes watching fire box and chimney temps and the result is that the frequent cleanings (safety first!) are only ever inspections as the chimney (single wall inside the room, double wall everywhere else) is always clean. It still drops to -40 here and even with 2x6 insulated construction we go through 6 cord a year. We burn for more than 7 months and non-stop for over 5 (a lot of years this over becomes 7!) We have a damper and never use it except when the front is open, the screen is on and we are using Grandma in fireplace mode. This uses lots of fuel! My daughter likes to roast hotdogs inside. So when the fuel is reduced off comes the screen and out come the roasting sticks. For regular burning the air vents do the job of controlling the fire spectacularly. We adjusted one so it can go out further so we can add a LOT of air before opening doors to load (since the baffle this has become more important to clear smoke from the firebox so it doesn't waft in to the room when doors are opened than it used to be) or if lighting from a 'not burning' situation during shoulder seasons. We have installed a baffle and believe the stove is cleaner burning with it and under some conditions burns last longer and more heat seems to be in the house. Certainly we think rolling heat forward to burn more smoke is better and changing the air flow is easier on flue collar - mind you the stove is nearly 40 years old and we have only had the baffle for a couple years and nothing is wrong with the smoke outlet.
Coaly guided us through the baffle thing. It has worked out well. (We thank you again, Coaly!)
We get 12-14 hour burns at moderate temperatures because we only need moderate to minimal heat but in the dead of winter (when we keep the house an even 70 degrees) and we tend to only go about 9 hours at night because we run a bigger and hotter fire and by 9 hours we are dropping a bit from 70 as we are using up some of the heat soaked in to structure during the day. But I detest getting up extra if I don't have to. At -40 I often only go 6-7 hours at night. During the day we tend to just add 1/2/3/4 or 5 pieces as seems appropriate from time to time (4 to 9 hours depending. I know this is useless info). It's all a function of what our solar gain situation is like, how hot the burn is going to be, how much fuel gets loaded and fuel size. I will say that neighbours with smaller epa type stoves are cold at -40 and loading wood every 2-3 hours and running wide open. We never do either of those things. The Fisher is great. Of course, burn times etc are particular to each application (stove/home/fuel).
Neighbours who exclusively burn fir love the wood and report it to be very clean and won't go back to pine. I live in a pine swamp so..........

 

[coaly]

so coaly are you saying the baffle should set on the factory bricks in back and get higher in front (height being determined by available area above to match outlet dia)? Does that create the 30* baffle angle?

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Yes. Set 2 new bricks on edge on each side. (this depends if stove has a second course of brick above the first)
Sliding the bricks forward and back to adjust plate height. (newer models have one piece angle iron brick retainers, other have brick retaining "clips" that the added brick sets between. You may have to notch a brick around retainer or clip the corner to lower plate. They cut very easily with a masonry blade in a circular saw. The opening must be no smaller than chimney flue square inch diameter. This may or may not be the same as stove outlet diameter.
Plenty of pictures in the baffle thread here;
https://www.hearth.com/talk/threads...d-fisher-more-heat-less-smoke-under-25.74710/

 

[Fort Wisers]

I am sorry guys if he has moisture running down the inside of the doors and out that is a problem. If moisture is condensing that much in the firebox i can only imagine what the chimney looks like. It indicates to me either wet wood or way to low temps. Also a standard damper will not work with double wall without modification. There are a few options one is drill your 1/4" holes then on the side with the handle drill a hole large enough for the base of the spring to fit through. Another is trim down the spring. And the last is use a rod from an 8" damper with the 7" plate.

But honestly if you have water running out the bottom of your door you dont need to reduce the draft any.

Based on our experience, I disagree that double wall black pipe (IE flue pipe) will require modification for the addition of a damper.
We have four installations all running dampers, all double wall and the installation was no different then in single wall.
We run Selkirk 2100 pipe pipe on all, perhaps a different manufacturer with different dimensions would be a different story.
I do like your idea of opening the hole through the first layer on the spring side however.

 

[coaly]

Not all damper handles are long enough to extend through outer wall on each side. That's why he recommended using a damper handle from the next larger size damper. That works very well.

 

[Fort Wisers]

Fair enough, apologies if anyone was insulted.

I agree both modifications (the larger hole through first layer to allow the spring side to sit into the inner layer, or the longer damper handle) are great ideas.

Only issue will be is if he's running 8" flue pipe; in which case, sourcing a 9" handle may prove very difficult.
So, I was just offering, that in our case, neither modification was required....that's all.
Thanks and enjoy the cooler temps!