My Stainless Steel Liner is a Heat Exchanger-Gets a lot of heat out of an insert instead of going up

[jimtmcdaniels]

Why doesn't anyone mention that the stainless steel liners are the perfect heat exchanger???

I wish someone had told me this before. I can't believe the difference in the heat it gives.

I found a great installation arrangement:

I had first installed my Morso fireplace insert (it was the best fit for my small fireplace dimentions) and found that when I followed the manufacturer's instructions which state to stuff the areas around the stove (sides, back, top) with fiberglass insulation, the chimney mass was hot but the room was cold and the insert would overfire when really loaded.

I tried several arrangements to increase the heat output, like taking out the insulation. I just couldn't get the room to really heat nicely. I even tried temporarilly installing the outlet for the vacuum to the bottom inlet of the insert's heat exchanger, just where many insert manufacturers install an optional fan, but that'd didn't make a real difference either.
The thermostat on the wall in the other room woudn't even rise, but instead fall with the furnace heat off.

It then hit me that I had to get the heat out of the chimney and that the stainless steel liner was much the same material and design as my natural gas furnace is made of.
I cut a square hole in the interior chimney wall high but not at the top of the ceiling, using a circular saw with a fiber mason cutting disc and chisel and hammer in the second floor above the insert which is on the first floor. I stuffed fiberglass insulation above the cut and then installed a vent grill in the hole.

I need the heat to go to the first floor where the larger rooms are, but before I got to the next step of installing a fan to draw the heated air down and out the chimney above the insert, the heated air would naturally rise out into the bedroom from the vent I had installed.
The bedroom was 90 degrees one nite in the middle of a cold night!

I then installed a sheet metal block off plate over the insert in the fireplace and installed a stove approved fan with an automatic on temp 100 degree and above sensor to a round hole I cut in the sheet metal block off plate. I caulked with fireplace silica.

Even though this insert manufacturer doesn't offer a fan, their aluminum surround already had a factory hole on the side for a switch where I installed the on/off/auto switch for the fan.

My old ornate wood mantel top is close to the insert so I installed an upper heat shield over the insert to the bottom of the surround to reduce the heat and any flames that may come out while loading the stove, my old mantal is subjected to.
(I made it from a 1/8 " thick x 6" flat aluminum I bought on E-bay and spray painted with stove paint after I cut it with a jig saw to a nice shape to match the mantel) I also installed a heat shield to the underside of the mantel from left over cutting of the lower heat shield.

To allow heat to come out the chimney just above the insert, I used extra long bolts and two nuts each for the attachment of the upper heat shield to the surround (I had to drill holes in the surround for the bolts) so that the surround would sit about an inch over the insert instead of on it leaving a gap for the blower to force out chimney air.

I installed an outlet in the fireplace for the fan. I wrapped the fan cord wiring with strips of fiberglass insulation and then electric tape and then with aluminum tape (from auto zone heat rated to 300 degrees).

The fan now draws air from the bedroom down the chimney and out just over the insert at up to 220 degrees.
Then that air mixes with the super heated air coming out of the insert's top heat exchanger and really kicks it out some hot air.
It seems the insert now generates as much as 3 times the heat compared to without the hole in the chimey arrangement and the thermostat on the wall in the other room proves it, it goes up.

The gap between the insert top and the bottom of the surround is really not noticable, looks perfessional, not odd at all.
I have several CO sensors in both floors of the house and they never have gone off. This installation is more like a stove now where many times the vent pipe travels across an open ceiling on it's way to the exterior of the house, allowing the vent pipe to exchange heat with the room.

It's been two months now and I feel this is a very safe installation. It seems the insert manufacturers aren't thinking out of the box "fireplace" box in the installation design.

I've attached photos.

 

[Hogwildz]

Hope you never have a chimney fire in excess of 2100 degrees for very long, and the liner doesn't let loose. Or that bedroom will be the first place to burn.

 

[moondoggy]

that just cant be safe. work yes. safe no.
sure its a great heat exchanger, but there is a reason its in the chimney.... away from you.

my car exhaust pipe is a great heat exchanger, but you dont see manufacturers cutting vents in the floor boards with controls.


that is a beautiful stove by the way.

 

[granpajohn]

my car exhaust pipe is a great heat exchanger, but you dont see manufacturers cutting vents in the floor boards with controls.

Guess you've never worked on an air-cooled VW. That's almost exactly how they're heated. And, I think others will also recall, that the heater boxes were rather expensive items to replace.

Seriously though....I only see one primary danger spot. JimT has insulated and protected the wiring to the fan, but is the fan itself rated to the sort of heat it will see on top? It is stove approved, but I've noticed that most of the installed blowers I see are protected from the heat. And as noted, if a fire gets into that chase it can spread rapidly. In theory there is no fire load to feed it, however, and the sealed block off plate should keep fire out. But there must be a small hole for the fan intake.

Assuming the FP was used for wood burning in the past, I would have expected a sooty smell to be blowing through the room everytime you run the fan. How did you get around that?

BTW, this is a good explaination of why inserts need blower fans.

 

[EddyKilowatt]

Did not fully understand your installation, but nice job on recovering heat from the flue. I have an in-fireplace installation myself, and I know I spend some time pondering how much heat is going straight up the flue rather than into my room.

Caution points would be make sure you leave enough heat in the flue to keep the top exhaust end of the pipe well above 212F at all times, to prevent condensation... and to install a heavy self-closing fireproof door or damper on that upper air inlet (which will become an outlet in event of chimney fire), held open with something that's easily melted or burned.

Eddy

 

[moondoggy]

just because they did something 20yrs ago doesnt mean its ok and safe today. seat belts were an option then too. i like to think we know better now to some extent.
i understand what he's trying to accomplish, just having the hole in the chimney, that blower rigged just looks wrong, unsafe and scares the crud out of a newbie burner like me...... doenst it get crazy hot above that stove?

the unit is, i assume, to old to have come with a blower?

 

[swestall]

Looks very nice, but, I think you just violated fire code. It would be good for you to know if you did, don't you think? And, no amount of heat is worth having your entire family pass on from a problem that occurs when you least expect it.
I am not trying to be a doubting Thomas here....just telling you what I would tell my brother....

 

[Jags]

If Elk would have read that, his head would explode.

At a very minimum, please consider a fireproof, self closing door for the vent in the bedroom (as stated above). It could save your butt if you made a mistake somewhere. Without it, you have basically created a direct path to your bedroom for smoke and fire. Keep in mind, you have a metal box with 1000+ degree internal temp located just below that hole. Safety first, my friend.

 

[backpack09]

I would also add that you are adding extra cooling to a flew pipe/liner. I would imagine that this will increase your creosote build up. Please have a professional look at that...

 

[rg500930]

yes i wouldnt put the blower above the insert.that motor must get really hot.i would have the blower outside with something like that tin exhaust hose they use on dryers connected to it.is that the liner in the wall going throught your bedroom?isnt that suppose to be a double wall chimney?

 

[granpajohn]

The bedroom was 90 degrees one nite in the middle of a cold night!

I then installed a sheet metal block off plate over the insert in the fireplace...

Another thing; it would be nice to know how much heat would've come through that vent after the addition of the block off plate. This would tell if you're recovering most heat from the pipe or from the stove itself. And; like the blower, this may illustrate the importance of installing a block off plate.

I mention this because it is probably a design that doesn't meet NFPA, (as has been well pointed out), and one would think that if the BTU reward was all that high, someone would've perfected a similar, but more firesafe/CO safe, design years ago. The old style heatilator fireplace design was not all that much different, but their ducting was a bit more seperate from the chimney. And, of course, they used convection to pull air up; JimT is forcing it downward with the fan.

 

[Todd]

Have you checked your chimney for creosote. That setup will cool your flue gas just like those creosote making stove pipe heat reclaimers.

 

[RedRanger]

To me,it looks like something that is eventually going to cook the op,sooner or later.

 

[Todd]

Have you checked your chimney for creosote. That setup will cool your flue gas just like those creosote making stove pipe heat reclaimers.

stove pipe heat reclaimer has scraper plate to knock off condensed creosote on tubes & fall into fire below.

Those heat reclaimers were made for the older non EPA stoves that run hotter stack temps. Newer EPA stoves run relatively lower stack temps and keep 70% or more of the heat in the stove. They need every bit of that 30% in the stack to maintain good draft and less chance of creosote build up. I've tried pipe reclaimers with EPA stoves and result was always too much creosote.

 

[swestall]

Where is our original poster and what does he think about all this?

 

[jimtmcdaniels]

Thank-you for all your feedback and concern!

You are all very loving spiritual guys or you wouldn't be on here helping people make life a bit nicer and warmer and less expensive.

I feel very safe with the installation at this point.

Thank-you for the compliaments I've gotten here and on another forum. I know many by the book people want to scold me for this setup but it's working great and I wanted to get the info out there for whoever is looking for trying to get more heat out of the inserts.

The liner is flexible corrigated one peice single walled. It was the slightly thicker one more ridgid one.
The chimney is brick with non portland cement mortar so it was easier to remove the bricks then it may have been.

In spite of discussions that a cold vent pipe can cause poor draft, I still have good draft.
Although I imagine the two story that I have (vrs a one story building - shorter chimney design) and the interior chimney I have (vrs exterior wall chimney design) helps with the draft.

The house was built in 1900 and I wanted to retain the mantel and the original look and it's not a large room so installing a stove was not an option.

The upstairs bedroom is now about 2 degrees cooler than the main floor adjoining room from the insert so it's a good balance. The fan seems to create a nice circular loop of air movement from blowing out just above the insert, then up the steps to the large bedroom where the vent is in the chimney then back down the chimney and out the top of the insert.

Hogwildz, you're by a Nuclear Power Plant, interesting. So which is true: that Nuclear Plants energy is extremely expensive when added in the fact that the metal fatigue forces the plants to close after 30 years and that the cost of storing the waste forever is cost prohibitive, that wall street won't back their building and that the oil industry is pushing for them because it's another energy that the consumer can't make for themselves, or is nuclear Power the short term answer to our Electricity shortage until a new energy source is found that others are declaring?

Hogwildz, I'm not so concerned with chimney fires because from what I've read they happen and it's no big deal especially with a liner instead of a no liner and a large chimney dimensions. I've read the liner steel won't melt below 2500 degrees.
I am concerned with an insert that has no extending above it metal lip to act as a shield. I put a peice of paper in the insert etc and flames can dance out the top. That's one of the reasons I added the metal lip I did. I am amazed what little the manufacturers have done over the centuries.

Moondoggy, I feel it's safe. If I have a leak in the one peice stainless steel, I have the CO sensors and I imagine I'll smell it unlike a leak in my natural gas heat exchanger where there is no odor to the exhaust gases.
How's Long Island, I hear the guys are Wild and HOT. I'm gonna make it to NY someday for a visit as soon as I take up my friend's offer who lives there.

Grandpajohn you're right, the motor does take more heat than normal but since I needed a setup where the air came down and I wanted everything in the fireplace it had to be. I've had it running for 2 months and gotten it as hot as I can with the insert glowing red some and the fan off or on, it has taken the heat. You're right, the only thing to burn - start a fire is the wiring and the motor windings insulation and I'm not to worried about a fire in the fireplace. The worse will be a burned plastic smell.
Also I did have the very same block off sheet metal plate installed before I thought of adding the blower motor and the heat was still trapped in the chimney.
The key to increasing the heat output was the vent in the chimney upper wall and the blower motor installation.
Yes there was a smell from the soot in the chimney and the blower circulating air through it, but the smell went away after a month and I no longer smell anything.

Think of the family, the little children that will burn up in the house on fire, think of the child sitting in the middle of that Michelin tire, there's so much riding on that tire.....
Well I don't have any children and never will. My cat has a cat door to get out of. I'm more concerned with my housemate who smokes in bed at times. No I don't want my house on fire but I have to be reasonable like we all do. I wouldn't have a fireplace in the first place if I wanted to be really scared of life.

I hope you all do realize that we are all dying and will be dead by around age 100 or a lot sooner for many.

This is not the real world, our home is heaven, we are only here for a brief trip down here that we chose, it gets boring in heaven.

This isn't the first challenge I've tackled outside the man made book and box.

It took I guess 200 years for the stove industry to add a cat or double burn chamber (so technical sounding but such a simiple design a caveman could have invented it) to where we have stoves that create 30 percent more heat and the only reason the stove industry did it was because the Government forced them to.

Well maybe in 200 years when the Government forces the industry, they'll make installations similar to mine...instead of letting all the heat go out the roof.

Why don't the stoves have a high temp limit shut off air so that stove someone filled full with wood and lite and walked away from that overburns an hour later glowing red meltdown is shut down automatically?

I wish the insert manufacturers would focus on all these things so consumers like me don't have to try something new and untested on their own. I've got a house to heat, not the outside, I don't need a very expensive box that just sits there and looks pretty, I'm not a millionaire, although I think the inserts make some, considering the mark-up I imagine for a metal box that seems it hasn't been redesigned since last time the Government forced them too.

 

[berlin]

he has no chimney fire concern, as i understand it he's burning anthracite coal.

 

[billb3]

particulates emissions, jimbob

 

[webbie]

Obviously our function is as a discussion board. We have folks building their own boilers over in the Boiler Room, fixing their own pellet stoves (and probably voiding the warranty in some cases), etc.

This particular installation aside, many of the general ideas are sound and have been promoted here before. For instance, we usually mention that an insert is more efficient when installed without panels or with loose fitting panels and a tight block off plate. Reason? Some heat can be reclaimed from the pipe and the insert top, rear and sides. I have also installed "hearth stoves" back in my fireplace and then taken a small fan and set it on the hearth blowing in - so that even more air would circulate around the unit.

In a free standing interior installation, the single wall pipe provides LOTS of additional heat and efficiency. Also, many interior masonry chimneys get warm and exchange heat into the house.

Lastly, some built in masonry units - like the Old Jotul System 8, used a similar setup where the space around the unit AND the flex connector from the unit to a chimney - was part of a convection chamber built around the entire firebox.

Of course I am not putting my blessing or curse on any experimentation or unsafe practices - but it is sometimes part of the human condition to attempt to build a better mousetrap!

Jim, you sound like an inventor.......but always keep in mind that a lot of people crashed and burned before the first flight flew. Still, I agree the smoking in bed and driving your car probably represent your biggest risks.

 

[webbie]

If Elk would have read that, his head would explode..

I checked with a local building official, and he said "computer says no".

 

[granpajohn]

It took I guess 200 years for the stove industry to add a cat or double burn chamber (so technical sounding but such a simiple design a caveman could have invented it) to where we have stoves that create 30 percent more heat and the only reason the stove industry did it was because the Government forced them to.

I think the secondary burn chamber was invented a long time ago. The Jotul Black Bear comes to mind. We used to call it a smoke chamber (or something like that), and it wasn't as good as they are now, but it probably hit the 30% you mentioned.

In looking at the new photos, I don't think the fan will fail catastrophically, in a ball of fire. But you may throw the switch one day and find that it won't work, leading to closer inspection and discovery that "the dang thing started to melt". Only time will tell. Could put that reflective tape on to protect from radiant energy. I don't know how much help that would be.

Story around Baltimore is that the guy that invented the residential bathtub heated the water by wrapping the piping around the (coal fire) chimney. It did fail, but not because of heat/fire. Back then all the pipe had to be cast iron; the tub was lined with lead. It was all so heavy that it collapsed much of the second floor. (Long story short.)

Reclaimation of lost BTUs always makes for an interesting thread. At least to those with inventive minds. Thanks for sharing.

 

[swestall]

OK, but you still might want to consider installing a fire stop damper in that opening just in case something did happen.

 

[NJPyro]

I put a deposit down on the Morso 1710 2 weeks ago...supposed to be installed this week...now after reading this I'm having second thoughts over whether I made the right choice...I made my decision assuming a stove company wouldn't sell something that did not work well...called the importer before I gave local installer a deposit and they assured me the convective heat coming out of this fanless insert was plenty...I have an old heatilator interior fireplace with about 10 feet of stone across and from floor to ceiling...now I'm wondering if I should try to capture some of those btu's through it...from what I read here it seems I should seal above the stove and keep the sheet metal surround loose...any other thoughts?

 

[webbie]

This holds true with most inserts - that a sheet metal block off plate and very loose (or no) front panels will result in better performance and more heat. It's just physics - heat trapped back in the fireplace will tend to be lost if the fireplace is partially exterior.

I'm sure you will get a lot of heat, but adding some is always nice also.

 

[Cath]

Perhaps I'm missing something. Did the OP actually cut a section of bricks out of his fireplace? If so, what if anything did he do to brace the bricks above the ones he removed?

Regarding the potential fire hazard, I'm all for thinking outside the box but I wouldn't want to be in that bedroom if something went wrong. It has been said on these boards before that you are most vulnerable when you are asleep. I can't help but think that this set up could significantly reduce the amount of time you have to get out of harms way.

~Cath