Grandma Fisher with new baffle has cold pipe

[Smokey Baggs]

Wow, this forum is amazing. Having had several periods of wood heating in my younger years I thought I knew how to set up my new (old) Grandma but boy do I learn a lot on here.

I have a 50 year old house with masonry chimney with 3 flues. Fireplace second floor, fireplace in finished basement, and extra flue in basement originally for oil furnace. I removed the oil furnace and connected Grandma Fisher. The stove is about 6 feet from the chimney and has 8" pipe leaving the stove back by elbow then running about 6 feet to the chimney at about 45 deg angle and enters the masonry inlet about 6 feet from the floor, then upward about 25 feet out the top. I have damper in the first section after the elbow leaving the stove that usually is closed to 80-90% during operation.

I had the steel baffle plate made per forum recommendations and propped it upright on firebricks sitting vertically on top of the lower course and got the 2 inch gap right at the rise. The stove burns long and hot and nearly smokeless, temps on stove top usually 400 - 600,

Because of a slight downdraft in the other chimney I was initially getting smoke smell in house. It is a heat pump with too much return but too much to fix now so I extended the masonry chimney with stovepipe up about five more feet and solved that, maybe helping the chimney draw too?

My concern is the cool pipe. At the last section where it enters the chimney it is often cool enough to lay hand on it. Temp below the damper is typically below 150 and above almost unmeasurable. After a few weeks burning I can hear and feel creosote? build up crunching around the damper when turned and I am becoming concerned.

Any advice appreciated.

Smokey

 

[TheRambler]

What kind of pipe is this? Single or double wall?

 

[Smokey Baggs]

What kind of pipe is this? Single or double wall?

It's a single wall

 

[TheRambler]

That is way too cool to run single wall pipe, and would explain the creosote build up. What do the temps run at with the pipe damper open fully? What is the reason for this damper to begin with, too strong of a draft?

 

[TheRambler]

That low of a temp is dangerously low. I would cease burning and do a clean out and then begin troubleshooting the problem. Last thing you want is to get it burning hot and light off a chimney fire due to the heavy creosote buildup.

 

[Smokey Baggs]

That low of a temp is dangerously low. I would cease burning and do a clean out and then begin troubleshooting the problem. Last thing you want is to get it burning hot and light off a chimney fire due to the heavy creosote buildup.

Thanks for the warning. It's been warm here and I have let the stove die so now is a good time to fix it. I have read elsewhere on the forum that I could be better off reducing to a 6" pipe. Any thoughts appreciated.

I added a couple pics for clarification of my descriptions.

Thanks again

 

[Smokey Baggs]

Also I have been wondering if I have set the baffle plate at the right position. I could easily raise the front higher and still block the exhaust vent but allow more heat into the upper level. I don't see how lowering it would help anything. I have never operated the stove without the baffle as I installed it right after purchase. I assume it would raise the pipe temp if I removed it but would I lose the good performance I am now getting? Thanks

 

[Smokey Baggs]

That is way too cool to run single wall pipe, and would explain the creosote build up. What do the temps run at with the pipe damper open fully? What is the reason for this damper to begin with, too strong of a draft?

If damper is left open the stove top temps can go to 900deg and above with door vents screwed only a 1/2 to 1 turn open.

 

[coaly]

Because of a slight downdraft in the other chimney I was initially getting smoke smell in house. It is a heat pump with too much return but too much to fix now so I extended the masonry chimney with stovepipe up about five more feet and solved that, maybe helping the chimney draw too?

Not sure I understand that;
Do you mean you have 5 feet single wall pipe at the top of chimney extending it higher?

Agreed, check the flue for creosote accumulation !

Stove top temps are about right, but the pipe should be about half the stove top temp where it goes into chimney. Is the flue 7 X 7 all the way up?

Lowering the baffle front increases the smoke space (area smoke travels through) allowing more heat out. Yours should not be a problem, lets get the chimney correct first.

The heat pump return can be a real issue if the stove is going with air handler running.
Depressurizing the area the stove is in is the same as closing the damper even more. Back to basics; the atmospheric air pressure pushing into stove inlets rushes through air inlets and is slowed slightly by baffle opening, and slowed more with damper. Lowering the air pressure mechanically slows the flow like closing the damper more since there is less differential air pressure between inside flue and inside building pressure. The stove may need an outside air (pressure) source with the air handler running.

Now you see why lowering front of baffle plate increases the air pressure by enlarging the square inch area into flue.

 

[Smokey Baggs]

Hi Paul, Thank you for your response. I have learned much from reading your contributions on the forum and I thank you for that, too. A lot of the difficulty in pinpointing the problems is because we are also doing much remodeling including finishing the basement. There have been no mods to the hvac system in our work, however, it is a 2007 retrofit heat pump/ac duct system into a 1963 house with oil/hot water. What I have read on the internet suggests that we have "too much return" relative to vents but frankly we can't afford a hvac service at this time. The issue was that upstairs smoky cold air would stream from the upstairs fireplace, even with damper and glass doors closed. All three flues had caps that adjoined and the stove smoke would just drift under the caps a couple feet and get sucked down the fireplace chimney. So I removed the cap over the stove flue and added 4 feet of 8" pipe with a cap on top. The chimney flue is 6 x 10 so i used a galvanized 6 x 10 to 8" round register boot. That basically solved the smoke odor problem and I read that it may help the chimney draw. Sun's not up yet but I'll add a pic in a little while. Thanks for listening and for any advice. Mark

 

[Smokey Baggs]

Not sure I understand that;
Do you mean you have 5 feet single wall pipe at the top of chimney extending it higher?

Agreed, check the flue for creosote accumulation !

Stove top temps are about right, but the pipe should be about half the stove top temp where it goes into chimney. Is the flue 7 X 7 all the way up?

Lowering the baffle front increases the smoke space (area smoke travels through) allowing more heat out. Yours should not be a problem, lets get the chimney correct first.

The heat pump return can be a real issue if the stove is going with air handler running.
Depressurizing the area the stove is in is the same as closing the damper even more. Back to basics; the atmospheric air pressure pushing into stove inlets rushes through air inlets and is slowed slightly by baffle opening, and slowed more with damper. Lowering the air pressure mechanically slows the flow like closing the damper more since there is less differential air pressure between inside flue and inside building pressure. The stove may need an outside air (pressure) source with the air handler running.

Now you see why lowering front of baffle plate increases the air pressure by enlarging the square inch area into flue.

The masonry chimney flue is 6" x 10". I just pulled off the pipe and ya'll are right; it is caked with creosote after only a couple weeks burning.

 

[coaly]

Extending the flue would increase the draft if the flue was insulated from the cold outdoor air. You can't have any single wall pipe outside. That defeats the purpose of the chimney to create the low pressure in the stove allowing atmospheric pressure to enter the stove. You have a condenser at the end of your chimney where the inner temp is already the coolest. As the outside temp chills the pipe, the hot lighter exhaust that is rising cools becoming heavy in the pipe slowing the rising gasses, or reducing draft. When the rising gasses stall, the stove can start back puffing which is the gasses rising off the stove, stalling and dropping back into the stove. Eventually this can bring oxygen back down with it and the stove chuffs like a steam engine as the draft alternates up and down....... You absolutely have to keep it hot and above 250* all the way out.
I'd remove that extension and cure the air handler causing the reduced pressure inside. For whatever reason, the return air from that living level is using the chimney for it's air source and the handler should only be exhausting and returning the same air from inside the house. Must be making a lower pressure area on that living level. The return air should be balanced in effect pushing the same amount into each heated room as it returns. Air entering is "make up air" needed for combustion of appliances and making up the air that's removed with bath, kitchen, or other mechanical fans venting to the outside. The air handler shouldn't do that. Can you slow the fan or open doors to other levels to balance the air pressure?

In remodeling it would be good to get the stove closer to chimney if at all possible. You have a little larger chimney than necessary with 10 square inches of area to heat every foot of height to the top. So you need more heat in that chimney than a 8 inch or 50 sq inch all the way up. Cooling the flue gasses with the single wall first is robbing more heat that the chimney needs. Double wall pipe downstairs will raise the temp entering chimney. Try for 350 to 400 mid burn at chimney base. The object is to keep inner flue temperature above 250* all the way to the top to stay above the condensing point of any moisture in the flue allowing smoke particles to stick. I'd experiment with air handler off during stove operation until you get it figured out.

 

[Smokey Baggs]

Thanks, That all makes sense. I do need to solve the problem without spending much. I can easily remove the extension up top and put the original cap on. The room in which the stove sits is not being finished and I can easily shove it closer to the flue. The air handler does not run much when the stove is hot and I can definitely cut it off a while. So at this point two thoughts occur to me. One is the idea of reducing to 6" to keep exhaust gases hotter as I read elsewhere on the forum. The other thought is removing the new baffle to send more heat up the pipe. What do you think?

 

[Smokey Baggs]

Thanks, That all makes sense. I do need to solve the problem without spending much. I can easily remove the extension up top and put the original cap on. The room in which the stove sits is not being finished and I can easily shove it closer to the flue. The air handler does not run much when the stove is hot and I can definitely cut it off a while. So at this point two thoughts occur to me. One is the idea of reducing to 6" to keep exhaust gases hotter as I read elsewhere on the forum. The other thought is removing the new baffle to send more heat up the pipe. What do you think?

Also, do I need a cap on top of the chimney or can it just stay open? Maybe that would help release the smoke from being trapped under the 3 contiguous caps and help dissipate it rather than going down the other chimney

 

[coaly]

I'd keep it covered, but maybe a piece of flashing or sheet metal stood vertical between the two as a partition? I assume it's only when the air handler is running? Do any doors slam shut when the fan is turned on? It should not pressurize some parts of the house and depressurize others. Sounds like you are depressurizing the area with the fireplace causing atmospheric pressure to push air down the chimney to balance the air pressure inside and out of the building. Make sure each room or area it heats (or cools) has return from the same area. You don't want it pulling outside air in during cooling in the summer or heating in winter.

I don't think it's a stove issue, the baffle is the least of your worries. Move the stove closer to create a steeper angle upward, get rid of the caboose chimney, and try with the damper about 1/4 to half closed. I'd check with thermometer on stove top and pipe just below chimney.

Your fuel hasn't been mentioned, and I say this because 1 1/2 turns open should not burn that hot (900* stove top). Unless you have overly dry wood that gassifies easily and is burning like crazy. Then you would need to turn the air down or damper it off. There's a lot of variables when it comes to wood.
When you have an established fire, you should be able to close air intake draft caps and have it all but go out. It should glow with very little to no flame when you open the door for a quick peek. If it continues to flame and burn well closed, check door seal channel iron to make sure both doors and sealing channel iron are clean. No door gasket material was used, and gasketing the stove normally isn't necessary.

 

[Smokey Baggs]

I'd keep it covered, but maybe a piece of flashing or sheet metal stood vertical between the two as a partition? I assume it's only when the air handler is running? Do any doors slam shut when the fan is turned on? It should not pressurize some parts of the house and depressurize others. Sounds like you are depressurizing the area with the fireplace causing atmospheric pressure to push air down the chimney to balance the air pressure inside and out of the building. Make sure each room or area it heats (or cools) has return from the same area. You don't want it pulling outside air in during cooling in the summer or heating in winter.

I don't think it's a stove issue, the baffle is the least of your worries. Move the stove closer to create a steeper angle upward, get rid of the caboose chimney, and try with the damper about 1/4 to half closed. I'd check with thermometer on stove top and pipe just below chimney.

Your fuel hasn't been mentioned, and I say this because 1 1/2 turns open should not burn that hot (900* stove top). Unless you have overly dry wood that gassifies easily and is burning like crazy. Then you would need to turn the air down or damper it off. There's a lot of variables when it comes to wood.
When you have an established fire, you should be able to close air intake draft caps and have it all but go out. It should glow with very little to no flame when you open the door for a quick peek. If it continues to flame and burn well closed, check door seal channel iron to make sure both doors and sealing channel iron are clean. No door gasket material was used, and gasketing the stove normally isn't necessary.

Thanks Coaly, Following your advice will be easy to perform and that's great news for me. I think you are on the money with the pressure diagnosis and I am going to try venting the upstairs to downstairs to help balance it.

I did modify the baffle today by raising the back end to on top of a brick and propping up the sides a bit. I have attached a pic and would much appreciate your opinion of whether this is an improvement over the original set up or not.

Earlier today I moved the stove much closer to the flue. I have both a complete 6" and 8" pipe set up and would like very much to hear your opinion on which would be best.

I am burning 2-3 year old, very dry, locust and oak. The temp has gotten away from me a couple times when I left the damper left full open by oversight after opening it to load logs. I have checked the door and it seals tightly.

Thanks again for all your help.

 

[coaly]

Much better pipe connection.

Your studded wall will require heat shield if within 36 inches of stove.
I think there is a 2 inch clearance for combustible framing, floor and sheathing to masonry chimney ?? That's not my expertise.

I try to mix that kind of over dry wood with 1 year stuff. It creates too much flammable gas too fast.

The 6 inch connector pipe would only be used with a 6 inch liner. It will physically work, but not legal to reduce the flue size, as you've probably read. The same size firebox stoves with single doors use 6 inch outlet and yours is 8 due to the option of open door burning in Fireplace Mode. If insurance and codes are not an issue, an insulated 6 inch chimney if far better than a masonry 8 or larger. Some members here have reduced to 6" insulated flue along with the added baffle with no smoke roll in problems. It's one of those laws that says no reduction in size from flue collar so people can't choke a stove down since most require the flue size they are built with.

I prefer the angled baffle only because Fisher designed them that way on a few stoves that had them. It was proven to reduce smoke as tested, and I don't know what the results were with other designs. A few have added them in the flat horizontal fashion on Inserts since the firebox isn't as high with the raised rear section. They seem to have good results as well. I put a flat one in a Papa Bear (6 inch) connected to a 8 inch masonry chimney that works well too. The technical term would be more flame impingement which is more for heat conducting in the plate for boiler purposes. In this case, the baffle keeps th eparticles in the stove longer and makes a longer path out. It also rolls the smoke down into the fire and is hotter where it slips over the baffle edge and can ignite with enough oxygen. That's another reason I'm against gasketing doors. Any leakage around the door can be beneficial to getting oxygen above the fire allowing more smoke particles to burn in the stove. It's not like a secondary burn, but the baffle edge is the hottest part and that is where it is most likely to reduce particulate if oxygen is present. It certainly isn't going to have any excess if the doors seal tightly and all the oxygen is used that comes through reduced air intakes. You would have to try in both positions and report back. It probably isn't measurable without a IR thermometer and opacity or particle measuring. You should see a huge improvement with what you have done chimney and connection wise already.

The flat plate gives you more of a reverse burn, meaning the fire must consume the fuel towards the incoming air. This is more beneficial in a deep narrow stove and gives a different type of burn with longer duration. That is more the shape of an Insert or single door stove.

 

[Smokey Baggs]

Wow, thanks Coaly, truly amazing amount of invaluable info. I'm going to get it all set up today for the cold spell arriving tomorrow. I am going to try the flat baffle set up and will post anything interesting. Thanks again and Happy New Year to everyone! Mark

 

[Smokey Baggs]

Update:

I removed the chimney extension on the roof and replaced the original cap.

I changed the newest flat baffle plate position to a compromise position with the previous angled one by resting the rear edge of the baffle on two chunks of brick on top of the rear course, raising the baffle rear edge by about 1.25", and consequently narrowing the air/exhaust gap from about 2" down to about 1.5". I left the 6" connecting stove pipe to the masonry chimney and the stove positioned in the corner exactly as shown in the photo. This makes a baffle opening about 33 sq in (22" x 1.5") and the area of the 6" pipe is about 28 sq in. There is no damper in the pipe.

I am not able to make any changes in my firewood at present so am continuing with very dry oak and locust..

So, I lit the stove and it has now been burning for about 5 hours. I first shut down the heat pump to eliminate any interference with the neg room pressure. I was immediately disappointed that the air draft was so weak. Even after 15 minutes and while it was burning along pretty good the smoke still rolled out with both doors open and even a little with just one door open. So I opened the caps all the way and waited a while thinking maybe after the pipe and chimney heated it would pull better.

An hour later stove top was at 800* and pipe is around 300* and I was happy to finally get the pipe temp up. Still had some smoke roll out even with slow door opening. So I added wood and closed the caps down about halfway. A check a little while later showed decent burning, very little flame, top temp now down to 500*. But now pipe was down to 150*. I checked it at several positions above and below the top elbow with little difference. Vent caps were set about 1.5 turns open.

Another hour later the stove was running pretty good at about 550* on top but pipe temp still around 150*.

Now after 5 hours it seems to burn and draw fine, though still some smoke still escapes when open, especially with both doors. The top temp is around 475* but the pipe temp remains low now around 125*

Any thoughts would be appreciated.

 

[Smokey Baggs]

Now 8 hours after lighting stove is burning well, stove top is at 550*. Opened both doors to make adjustments - no smoke came out. Draft seems adequate and everything seems great...except.....pipe temp just below top elbow is still below 150*

Okay, 9 hours now, stove burning great 475*, no smoke, good air control, but pipe temp is still only at 120* above the top elbow.

What's left to change but the baffle?

 

[Smokey Baggs]

Now next day the pipe temp is up to 235*. Everything is working well, generally decent draft but clearly less than with the 8" pipe. I wonder if I could raise pipe temp if I go back to the original baffle position with rear edge resting directly on the brick top, resulting in greater baffle plate angle and approx. 3/4" wider air gap to top and exhaust outlet, a 40-50% increase (1.5" - 2.25").

Thanks again for all the help

 

[Piney]

So... Whatever happened here? Every time I reread this I just want to yell 'get the masonry chimney cleaned or switch entirely to manufactured chimney'.

 

[coaly]

I don't know, but I believe he took my advice from post #17 to go back to the original angled baffle plate (and set the smoke space opening above it to 60 square inches to match the chimney), and use 8 inch connector pipe in the vertical configuration. That would give the proper connection providing the proper amount of heat into the chimney.
With the reduced flow of the 6 inch and flat baffle slowing velocity it would take quite a while to heat that masonry chimney and was the reason for smoke roll in until it heated the entire flue. (by the next day) When set up correctly he should see about 300* pipe surface temp with 600* stove top temp. It would be good to get an update.

 

[Piney]

Yes. And this isn't the only thread where an OP returning to provide an update would be both interesting AND illuminating. Even if it only confirms conventional wisdom!