Chimney liner

ThermalJake

1928 house built with a Thermal Steam System, currently Megasteam 513 in service. The flue from the boiler in the basement merges with the flue from the wood-fired fireplace in the bedroom (formerly the livingroom.)

Last year, when i cleaned out the flue, there were small chunks of terra-cotta liner in the bottom. Also, the top of the outside had a few cracks and no cap, so the rain sometimes leaks into the basement. So i wanted to get the chimney serviced and called two local guys to come check it out. Both said they would call me before coming, and neither did. They walked around with my wife, provided estimates to repoint and cop the top and insert a liner into the flue. I call ed them both back to get more details, like... "once you place a liner inside the flue for the boiler, what happens to the fireplace?" and "once you place the liner, is the new liner only able to be cleaned form the top? I dont have a 40 foot laddar." Etc. Neither seemed interested in discussion, or giving me any feedback so i let them fade into memory.

So I am thinking about what to do for the upcoming year, and i guess this is a better time of year than November to think about it. Heh.

Anyway, what do you guys think? How does one fix the liner inside of a merged chimney? I cant figure it out. Perhaps the only solution is to run a triple wall next to the exiting chimney? I think the liner problems, along with the extra draw from the fireplace is throwing off my draght measurement anyway.

(I am also looking for help with my water quality; pH, sediment, skimming and cleaning... but i'll post that on another thread.)

Thanks in advance.

Jake

Jamie Hall

Sorry to be a pessimist, but... merged chimneys were, at one time, very common. Unfortunately. They are a very poor idea. They really weren't all that bad when all the things connected were either fireplaces or wood stoves. Granted, if you burned green or soft wood and didn't clean you chimney you go spectacular chimney fires from time to time, and sometimes they burned the house down, but...

Building codes state that anything burning solid fuel -- such as a wood stove or a fireplace -- cannot share a flue with anything burning gas or liquid fuel -- such as oil or LP or natural gas.

You can still have multiple gas or oil appliances in a single flue -- though the design isn't completely straightforward.

But not combined.

So... you need that triple wall.

ThermalJake

Thank you, Jaime. Several owners (and decades) ago, someone put a propane log setup in the hearth. I guess I could always do that again.

I don't really use the wood because its a fireplace and after you go to bed, and the fire goes out, it just sucks all the heat out the chimney! Plus, it is a two family, with the thermostat in my unit, so if I use the fireplace, the tenants get cold. Ha.

Anyway, even if I switch back to the propane fireplace (or just don't use it at all) that would be okay.

But there seems to be no way to repair the existing liner without either isolating the half of the flue or running the triple wall. Anyone else?

Any advice about the lackadaisical chimney guys?

Jamie Hall

Repairing a tile liner is pretty much a lost cause, although there is a way to insert a metal liner and fill the gap between the new liner (necessarily smaller than the old flue!) with insulating more or less cementitious infill. Problem is, of course, that if one has multiple connections all but one of them will be blocked. Which is, on the whole, probably a good thing.

EBEBRATT-Ed

They can put a baloon in the chimney and pour concrete around it to line the chimney. After it sets the baloon comes out

Jamie Hall

EBEBRATT-Ed said:

They can put a baloon in the chimney and pour concrete around it to line the chimney. After it sets the baloon comes out

Did that with one of the chimneys in Cedric's home. Worked like a charm -- and strengthens the chimney and makes it much easier to sweep all at the same time.

EBEBRATT-Ed

@Jamie Hall
Are those poured liners expensive?

Jamie Hall

Honestly, @EBEBRATT-Ed , I don't recall -- it was about 20 years ago. On the other hand, it can't have been really expensive -- the budget around here is pretty cramped. Very low five figures, at the most, and it's a 40 foot chimney.

Bob Harper

Both flues must be lined. The liners must be separated by a nominal 4" wythe of solid masonry units or the equivalent. Since you don't have a wythe the only legal solution is to do a cast in place liner. This is where you inflate rubber bladders the various diameters needed and space them at least 4" apart. The good news is the low viscosity slurry will find and fill most voids, fissures, cracks and boo-boos so the whole chimney gets structurally strengthened. Guardian has been tested by the ICC-ES and found suitable for structural repair unlike some systems so check with those in your area. The biggest problem will be getting a large enough round liner for the fireplace with 1" of liner mix around it minimum and still meet the code for sizing. Fireplaces are sized as a ratio to the net free opening of the firebox- 10:1 for rectilinear flues up to a 2:1 aspect/ ration or 12:1 for round flues. Yes, it is expensive but so is tearing down a chimney and rebuilding it.

ethicalpaul

> I don't really use the wood because its a fireplace and after you go to bed, and the fire goes out, it just sucks all the heat out the chimney!

They do that even before the fire goes out. Fireplaces are the worst.

Jamie Hall

ethicalpaul said:

> I don't really use the wood because its a fireplace and after you go to bed, and the fire goes out, it just sucks all the heat out the chimney!

They do that even before the fire goes out. Fireplaces are the worst.

As a general rule, very true. In particular cases, not so much -- but generally speaking yes. Cedric's home does have one fireplace which burns cord wood (4 foot lengths) but is only a foot and a half deep (it does have a generous hearth). It does heat the room it's in (15 by 25) with no problem at all. One of the other ones has tempered glass doors which can be closed on an active fire, with a damper to control draught. It heats its room well, too.

But as a general rule, fireplaces are nice to look at, and psychologically warming, but... lack something in efficiency!

Bob Harper

A typical 36" fireplace without glass doors sucks 400-600 CFM up the stack when burning. Glass doors reduce that to about 75-150 CFM. These were measurements by Canadian Mortgage Home Corp.
Best fireplaces run around 15% efficient. Most in the negative. Even if you drop a liner for the heater but its exposed to the fireplace flue its got that one cold side and not contained. Still wrong. Consider sidewall power venting if you cannot fix the chimney or go electric.

ChrisJ

Bob Harper said:

A typical 36" fireplace without glass doors sucks 400-600 CFM up the stack when burning. Glass doors reduce that to about 75-150 CFM. These were measurements by Canadian Mortgage Home Corp.
Best fireplaces run around 15% efficient. Most in the negative. Even if you drop a liner for the heater but its exposed to the fireplace flue its got that one cold side and not contained. Still wrong. Consider sidewall power venting if you cannot fix the chimney or go electric.

I've always heard this and have never understood it.
If typical fireplaces run in the negative how did they to heat houses with them?

ethicalpaul

https://www.curbed.com/2017/11/30/16716472/old-house-fireplace-coal-stove-history-heating

I don't think they could actually heat a house with them. Certainly not to comfortable levels. They could heat rooms with radiant heat, but each of those rooms had cold air being drawn into it the whole time.

STEVEusaPA

I think they heat by close proximity radiation. Same as if you sat at a campfire with a cool breeze at your back.
If they're putting out more heat than is being pulled into the room, it gets a little warmer.

ChrisJ

STEVEusaPA said:

I think they heat by close proximity radiation. Same as if you sat at a campfire with a cool breeze at your back.
If they're putting out more heat than is being pulled into the room, it gets a little warmer.

And if they put out more heat than is being pulled in, their efficiency cannot possibly be negative, or even zero.

JUGHNE

The negative numbers might come from some cooked up numbers for SEER or some such.
If you sit in front of any non doored fireplace smoking a cig, the smoke would go towards the fire and continue after the fire burned out.
The old design of "wing" style of overstuffed chairs were to shield you from the draft coming over your shoulders as you toasted your feet in front of the fireplace.
But they over all were usually considered a heat loser.

Especially if the mass of the fireplace and chimney is on an outside wall as it often is.
Worse than a bricked up window when you consider the chimney effect of air flow up the flue. Any metal dampers I have seen are far from air tight.

ratio

I feel sorry for all those people living centuries ago, they never knew their fireplaces were actually making them colder.

ethicalpaul

They weren't dumb. I'm sure they knew that the fireplace had cooling effects on other parts of the room or the house.

Doors I have seen on fireplaces have warnings not to close them while it's lit, right?

JUGHNE

There were some improvements over early years for fireplaces.
Simply shape of the fire box not being too deep and with an angle on the back to reflect the radiant heat out.

The real impressive one, I only read about, was called "The Russian Fireplace" IIRC.
It was built in the center of the house of massive masonry construction. Multiple pass fire box, Burn maybe once a day.
The bricks and chimney acted as a radiator for at least 2 floors.
Probably had cooktop built into it also.

Bob Harper

Have you stepped out of the shadows into the sunlight on a cold day? Your front gets instantly warmed by radiant heat while your backside is cooled by convection. Same with fireplaces. The urban legend is the wingback chair was invented to protect the face from cold drafts while sitting in front of the fire. Count Rumford's design was to constrict the throat to reduce the massive exhaust of room air and the cold air being sucked in to replace it. The Franklin stove was a great innovation but not widely adopted.
Masonry heaters are wonderful. From Russian ovens built with tons of bricks to kits of soapstone (my favorite), ceramics or other materials with a high specific heat centrally located are great heaters. You burn a hot fire x 1 hr. early morning then again at dusk. The cat typically lays on it as it radiates warmth without burning kids. You can go to an annual workshop in NC to learn how to build them with the Masonry Heater Assn.
Build one with a bake oven and you have survival heat and cooking with solid fuel. Side benefit is the smoke Gestapo in Calif. won't see your smoke because you're burning before they get to work or after. Never mind these things burn very cleanly and reduce our reliance on oil.
If you're into a fireplace that projects heat, check out the Ahren-Fire refractory fireplace system. We use it to repair fireplaces with wood forms under the firebox or hearth extension but they do crank out a lot more heat than a traditional fireplace. You can also have a skilled fireplace mason construct a PriorFire designed by Chris Prior up in Mosherville, NY. He runs M.I.T.- the Mosherville Institute of Technology. (he hosts an annual workshop at his house every July. He spent a month at Warnock Hersey test labs on his back watching smoke patterns up various fireplace shapes and measuring felt heat.
Go to mha-net.com to learn more. Look in the archives for Prof. Rosen's Fluid Dynamic Studies in 1928 on fireplace shapes proving laminar and turbulent flows with Reynolds numbers measured. Cool stuff. You can also read The Collected Works of Count Rumford on fireplaces and radiant heat. Enjoy!

ChrisJ

Bob Harper said:

Have you stepped out of the shadows into the sunlight on a cold day? Your front gets instantly warmed by radiant heat while your backside is cooled by convection. Same with fireplaces. The urban legend is the wingback chair was invented to protect the face from cold drafts while sitting in front of the fire. Count Rumford's design was to constrict the throat to reduce the massive exhaust of room air and the cold air being sucked in to replace it. The Franklin stove was a great innovation but not widely adopted.
Masonry heaters are wonderful. From Russian ovens built with tons of bricks to kits of soapstone (my favorite), ceramics or other materials with a high specific heat centrally located are great heaters. You burn a hot fire x 1 hr. early morning then again at dusk. The cat typically lays on it as it radiates warmth without burning kids. You can go to an annual workshop in NC to learn how to build them with the Masonry Heater Assn.
Build one with a bake oven and you have survival heat and cooking with solid fuel. Side benefit is the smoke Gestapo in Calif. won't see your smoke because you're burning before they get to work or after. Never mind these things burn very cleanly and reduce our reliance on oil.
If you're into a fireplace that projects heat, check out the Ahren-Fire refractory fireplace system. We use it to repair fireplaces with wood forms under the firebox or hearth extension but they do crank out a lot more heat than a traditional fireplace. You can also have a skilled fireplace mason construct a PriorFire designed by Chris Prior up in Mosherville, NY. He runs M.I.T.- the Mosherville Institute of Technology. (he hosts an annual workshop at his house every July. He spent a month at Warnock Hersey test labs on his back watching smoke patterns up various fireplace shapes and measuring felt heat.
Go to mha-net.com to learn more. Look in the archives for Prof. Rosen's Fluid Dynamic Studies in 1928 on fireplace shapes proving laminar and turbulent flows with Reynolds numbers measured. Cool stuff. You can also read The Collected Works of Count Rumford on fireplaces and radiant heat. Enjoy!

If it's heating anything via radiant it's efficiency cannot be negative. IR radiation is still energy output.

JUGHNE

I believe the overall efficiency could be negative.
Off cycle air infiltration with warm room air going up the flue.

I can feel good in my sun room with the heated floor and have the windows open....my modcon efficiency could really drop.

The fireplace efficiency would probably stay positive if you kept it burning 24/7.......not a fun job but it was done years ago.

Bob Harper

Overall efficiency. At those rates of excess air lost up the stack balanced against the little bit of radiant heat is an overall losing equation. The best advanced combustion woodstoves achieve combustion efficiencies in the high 60% range but even that's not through the whole burn cycle. Don't forget you're causing massive infiltration of cold outdoor air by this exhaust.

ChrisJ

> @Bob Harper said:
> Overall efficiency. At those rates of excess air lost up the stack balanced against the little bit of radiant heat is an overall losing equation. The best advanced combustion woodstoves achieve combustion efficiencies in the high 60% range but even that's not through the whole burn cycle. Don't forget you're causing massive infiltration of cold outdoor air by this exhaust.

So why were fireplaces used for heat for centuries? Seems like a whole lot of work to make the house colder.

Did they also keep a fire going all summer long to cool the house off?


For wood stoves I've heard of outdoor air for combustion. What about gasification stoves are they only 60?

MikeL_2

Long ago, I worked with a mason who provided direct combustion air for fireplaces via floor grates in the hearth on either or both sides of the fire box, or on either side of the hearth - sometimes in the floor and sometimes in the wall. It was my first lesson in combustion air, although I didn't know it at the time.......

JUGHNE

ChrisJ, there was a This Old House series done in the hot south.
It was a 3+ story mansion with the typical large open staircases.
Chain hung at the top was a huge gas powered "chandelier" looking fixture. It was about 5-6 gas jets that when fired produced a draft thru the house.....think whole house fan effect.
IIRC they might have fired it up just for demo purposes.

So yes, building a fire and causing air infiltration would cool your house.

And if they cooked over the fireplace hearth, yes, you kept the fire going most of the day in the summer.

Bob Harper

Why burn a campfire when most of the heat is lost? Because you do enjoy the little bit of radiant heat it gives off. If you give that infrared energy a target to absorb some of that energy, such as walls, floors and ceilings, it can release a little of that energy over time. So, while the air temp. in the room may drop, you can still enjoy the benefits of the radiant heat being released over time. Also, the walls do block cold drafts to some extent.
Cooking fires were moved to separate structures whenever possible not only because of this constant air flow but so that not if but when the chimney ignited, you didn't burn the whole house down. The chimneys could be constructed free floating from the building such that it could be pushed over into the yard in the event of fire. Early building codes required sufficient setbacks to make room for pulling the chimney down. Owners were required to provide two fire buckets and a pike pole to pull the chimney down.

ChrisJ

> @Bob Harper said:
> Why burn a campfire when most of the heat is lost? Because you do enjoy the little bit of radiant heat it gives off. If you give that infrared energy a target to absorb some of that energy, such as walls, floors and ceilings, it can release a little of that energy over time. So, while the air temp. in the room may drop, you can still enjoy the benefits of the radiant heat being released over time. Also, the walls do block cold drafts to some extent.
> Cooking fires were moved to separate structures whenever possible not only because of this constant air flow but so that not if but when the chimney ignited, you didn't burn the whole house down. The chimneys could be constructed free floating from the building such that it could be pushed over into the yard in the event of fire. Early building codes required sufficient setbacks to make room for pulling the chimney down. Owners were required to provide two fire buckets and a pike pole to pull the chimney down.

Personally I don't like fire places and have never wanted one.

I grew up around wood stoves.

I just don't buy the negative efficiency. It doesn't make sense.