Help with old wood stove installation

[Tigerpaw53]

I purchased a Atlanta Homesteader Model 2410GU wood burning stove. I have a large fireplace that is in good condition but due to the size it uses lots and lots of wood for the heat I get. Can I vent the stove into the fireplace on an emergency basis (1-2 days) without running a pipe up the entire chimney?

 

[jatoxico]

You can't really expect people here to endorse an install that you yourself realize is unsafe no matter how short the time period. Why not look around for a newer used stove and install it correctly. You'd be much warmer, happier and have peace of mind.

 

[coaly]

What is the size of the flue all the way up? The inside area of your flue determines a yes or no. If you have an 8 X 8 flue liner (tile) in the chimney it's no different than a 6 inch stove connected to an 8 inch masonry chimney. Most fireplaces have larger flues that can become the problem.
This was the common way of installing stoves when the "air tight" was first invented for many years. A block-off plate was put across the opening, and a 6 inch hole was cut for the pipe to go through, and elbow upwards a length or so. The problem is the larger area of the flue allows exhaust gasses containing smoke to expand in the larger area cooling the flue to the point of condensation and creosote. You can't have any indoor air leakage into the flue to cool it farther. Sealing the pipe at the bottom of flue is essential. As long as you understand that, and watch it closely, especially for a short time duration you should be fine. Notice the Fisher and many replicas later had a step top to allow the door to be much lower than the outlet. Since weak draft was common due to most of them being installed in older fireplaces, this prevents smoke from coming in when opening doors.

Inserts that hit the market in 1979 were designed to sit in the fireplace and vent up the existing flue as well. They had to be burned hard to keep clean, and removed when cleaning flue since everything drops behind the unit. Liners and insulated liners prevent the need for allowing so much heat up and eliminate removing the Insert constantly. This is no longer considered a "good" installation, but some exist.

 

[Tigerpaw53]

Thanks coaly. I believe I understand now the issue with the gasses cooling. If this is done for 2 days only could I have a significant build-up of creosote. This is all new to me.

 

[jatoxico]

Coaly is giving good, detailed advice and certainly has been around the block especially with older stoves. I took the short cut but my point is the addition of a block off plate (which is up to code in my neck of the woods at least) creates a solid mechanical connection to the existing flue and is far different than what it sounded like you intended to do (simply stuff a section of pipe up the flue). Such an install is at least semi-permanent and would take some time to do properly so hardly something I would want to do unless I intended to keep it that way. Even if done well it is not really the best way to do it in the long run since as Coaly pointed out, it is prone to creosote build up and you have to remove everything to clean it. Best thing is full liner.

The issue with an improper install is not only how much creosote could form in a day or two but the increased potential for flue gasses to enter the living space.

 

[coaly]

It would take longer than that , but can build up rapidly IF moisture content in wood is high, and you constantly burn low trying to save wood. This unit having a thermostat will allow the flue temps to be higher when calling for heat. The basics are keeping the flue temperature ABOVE 250* all the way to the top. This is the condensation point of any moisture going up the flue that condensates on flue walls allowing smoke particles to stick. This is more critical when first loading since temps are down and the fresh fuel load is not burning hot enough to burn smoke off. Mid burn should allow enough up the stack, again depending on flue size (square area you're trying to keep above 250*). In the coal stage, there is little to no moisture and smoke, so a cooler flue is not a problem. Once you understand these basics, YOU can make a poor installation safer. YOU can also make a safe installation unsafe with poor burning practice as well.
It doesn't seem like much of a difference going from a 6 inch round pipe to an 8, but when you use the formula pi X radius square to figure square inch area of flue, you find it almost doubles in square area. So a 8 X 10 flue being 80 square inches compared to the 6 inch round outlet or 28.26 square inches requires MANY times the amount of heat to be left up trying to keep three times that square area hot. Measuring the existing flue is critical so you know approximately how much needs to be left up. Now you see the need for a liner the same size of the stove outlet so the square inch area of flue you're heating remains low, and the insulation around liner keeps it hot inside.
Another benefit is not heating the mass of the chimney. Open burning in the fireplace relied on the mass helping to radiate inside the building. This mass also radiates UPWARD allowing a greater loss, and as the fire dies, inside warmth then is absorbed by the masonry mass and allowed to rise up out the roof as well. Once you know what your loss is all the way up in a liner or flue the correct size, a thermometer on the pipe where it dumps into chimney flue is a good gauge of the exhaust temperature to run. As an example 350 may cool to 250 in an insulated liner at the top, compared to needing 600* exhausted into a much larger flue that you may have now. An inside chimney vs. exterior, outdoor temps, and wind are all factors that change inside flue temp and creosote build up. Now you see how an 8 X 8 indoor chimney is radically different than a 8 X 10 outdoor chimney. You're not in an area that's going to chill it down in -0* f. temps either.
This is not only a safety reason, the rising exhaust also creates the low pressure area in the flue, pipe, and stove which allows higher barometric pressure to push INTO the stove intake to make it burn. So the less "vacuum" in the stove created by cooler chimney, the slower the burn and less heat output from the stove. The chimney is the engine that runs the stove. A larger flue doesn't mean you have a larger engine. It means it's capable of running a larger stove. So the flue size and height is much more critical than the stove.
So if you're serious about heating with wood or coal, get a liner.

 

[Tigerpaw53]

So are you saying there is no way to put a wood stove in for two day use and still keep the wood burning fireplace? The gasses you mention entering the living space, are you implying they will come back down the chimney or leak from the unit before going up?

 

[coaly]

The connector pipe leading from stove to chimney flue has to be connected to the flue so there is NO indoor air leakage into the flue. In other words, the draw of the flue has to pull ALL it's air through the stove. (you don't want indoor heated air going up the chimney anyway) Any leakage of indoor air up the flue dilutes the exhaust gasses bringing the temperature down. Reducing draft, allows exhaust into building.
This was originally done with a steel plate across the fireplace opening, the 6 inch hole allowing the pipe to go up the flue. You can also make a block off plate under the flue opening with the correct size hole to put pipe up.

 

[jatoxico]

So are you saying there is no way to put a wood stove in for two day use and still keep the wood burning fireplace? The gasses you mention entering the living space, are you implying they will come back down the chimney or leak from the unit before going up?

I did not mean to assume anything so if I'm off base I apologize but it sounded like you wanted to install the unit temporarily. I took that to mean you intended to do what others have done, that is take a short piece of pipe and put it up into the clay liner. This type of install is called a slammer here. If you were to do that there is not mechanical, sealed attachment to the clay liner. That being the case gasses can come into the room by getting past the pipe. This can happen if the wind blows forcing air down the chimney or late in the burn cycle as the flue cools and draft slows.

Remember we don't even know how well your set up even drafts, it could be prone to down drafting. So for the record w/o a sealed attachment to the clay liner you could have an issue.

 

[coaly]

It's safe to say w/o a sealed attachment to the clay liner you WILL have an issue.

 

[Tigerpaw53]

Thanks guys, you have been very helpful. I came here knowing nothing and now understand more of what I must do. To answer jatoxico, I was thinking of doing exactly what you call a slammer but thought first I had better check with those that know. To a novice like me it seems the wood stove is the same as a fire and therefore the chimney would draw the exhaust the same. The fireplace is not air tight so I thought the same would work for the stove. Again thanks for your knowledge, it was very helpful!