Retrofit Catalytic Converter for ZC Fireplace

[MidwestWoodBurner]

Hello all,

I was unsuccessful at finding user reviews for either of the EPA-qualified catalytic retrofit devices approved for fireplaces (both masonry and zero-clearance). Is there anyone who owns one, and would like to provide some feedback?

Here are links to the two products currently available:

http://earthsflame.com/features-of-earths-flame/
http://healthyhearth.net/healthyhearth.html

Both claim to reduce particulate matter by up to 90% (when above 300*F) and to increase the heating efficiency of the fireplace.

I am concerned that extra heat from the secondary combustion might warp the flue damper. Any thoughts on either product would be appreciated.

 

[begreen]

These units may improve combustion efficiency, but I wonder about maintaining them and cat life. Also, it's hard to see how it would improve heating efficiency greatly, which makes the value debatable. I think an EPA insert in the fireplace would outperform one easily, on both scores.

 

[bholler]

I am concerned that extra heat from the secondary combustion might warp the flue damper. Any thoughts on either product would be appreciated.

I think they would both be wastes of money.

 

[MidwestWoodBurner]

I've considered a new unit, but I'd like to tinker a bit (safely) before I give up on it. I am new to stove design principles, so help me understand why a cat would not improve heating efficiency greatly. It seems that the more I dug, I was able to find old threads on here where people rigged up baffles and secondary combustion tubes to improve their ancient stoves. Wouldn't either of these cat products act as both a baffle and a secondary combustion device, thus increasing heat output?

 

[rwhite]

I w

I've considered a new unit, but I'd like to tinker a bit (safely) before I give up on it. I am new to stove design principles, so help me understand why a cat would not improve heating efficiency greatly. It seems that the more I dug, I was able to find old threads on here where people rigged up baffles and secondary combustion tubes to improve their ancient stoves. Wouldn't either of these cat products act as both a baffle and a secondary combustion device, thus increasing heat output?

I would question what they mean in terms of efficiency. Less particulates out the chimney? Maybe? More heat transferred to the room? I doubt it. I went through something similar about 15 years ago trying to improve the heat from my fireplace. Basically just a bunch of gadgets that may have helped a bit but probably nothing measurable. And when the fire burns down in 2 hours you still have a big cold air hole in the house pulling all the warm air out. Believe me you will kick yourself when you spend all that money ( that could have been spent on a proper stove) and it doesn't work.

 

[MidwestWoodBurner]

I w

I would question what they mean in terms of efficiency. Less particulates out the chimney? Maybe? More heat transferred to the room? I doubt it. I went through something similar about 15 years ago trying to improve the heat from my fireplace. Basically just a bunch of gadgets that may have helped a bit but probably nothing measurable. And when the fire burns down in 2 hours you still have a big cold air hole in the house pulling all the warm air out. Believe me you will kick yourself when you spend all that money ( that could have been spent on a proper stove) and it doesn't work.

So help me out here, since I'm new to stove design principles. I understand that there are major differences between wood stoves and wood fireplaces, and that a stove is a superior heating device. What in particular is it about wood stoves that gives them the edge over wood fireplaces?

 

[jetsam]

So help me out here, since I'm new to stove design principles. I understand that there are major differences between wood stoves and wood fireplaces, and that a stove is a superior heating device. What in particular is it about wood stoves that gives them the edge over wood fireplaces?

One is a big metal box that feeds combustion with a metered amount of house air, and exhausts it up a flue pipe. The amount of warm air taken from the house is the amount used for combustion (or perhaps much less, if you install an outside air kit).

The other is a large hole in your house that you can sometimes light a fire in. A fraction of the warm air that is whooshing out of your house full time is used for combustion. The best you can hope for is that it has a fairly airtight door and some kind of fan rig to try to get some heat out into the room it's in.

Both deliver some IR heat to the room via the window. A freestanding stove sends tremendous radiant heat to the room just by virtue of being a big metal box with a fire in it. An insert stove usually has a little of that going on (it sticks out a bit), but relies on a convection deck and blower fans to make up for its lack of surface area.

EPA stoves take it a step further and reburn the airborne organic goodies to make a lot more heat. If you do this in a wind tunnel, the extra heat goes up the wind tunnel. If you do it in a metal box with lower airflow, the extra heat makes the metal box hotter.

All of this is is a bit like comparing the virtues of sharpened rocks and chainsaws though- they're different steps on the ladder of technology. I'm not here to tell you that you can't cut down a tree with a properly chipped flint axe, but common sense says that a bad stove will probably outheat a great fireplace any day of the week.

 

[cjw8]

Fireplaces range from -15% to +15% efficiency. EPA and Cat woodstove can go as high as +85% efficiency.

 

[rwhite]

Fireplaces range from -15% to +15% efficiency. EPA and Cat woodstove can go as high as +85% efficiency.

There again, depending on the sales pitch, what are we meaning by efficiency? If we're talking heating efficiency (heat produced vs heat loss) then I would say a fireplace is WAY in the negatives due to the times it's not operating but still drawing off heat. But there's no comparison in burning efficiency between the 2.

 

[begreen]

I've considered a new unit, but I'd like to tinker a bit (safely) before I give up on it. I am new to stove design principles, so help me understand why a cat would not improve heating efficiency greatly. It seems that the more I dug, I was able to find old threads on here where people rigged up baffles and secondary combustion tubes to improve their ancient stoves. Wouldn't either of these cat products act as both a baffle and a secondary combustion device, thus increasing heat output?

Increasing heating efficiency in a closed steel box is very different from cleaning up the smoke going out of an open fireplace. The difference is between heating efficiency and combustion efficiency. There is much more air (10x) being sucked out of the room and up the chimney than there is in a wood stove. And much less heat stays in the room that a wood stove.

An insert will work much better because the fire is completely contained within a steel cabinet that has an outer convection jacket that is independent of the firebox inside the stove. The heat from the firebox is transferred to the to the convection air chamber. Air is pulled in a the bottom of the convection chamber and blown out the top into the room. That brings about much better heating efficiency than an open fireplace.

 

[MidwestWoodBurner]

Increasing heating efficiency in a closed steel box is very different from cleaning up the smoke going out of an open fireplace. The difference is between heating efficiency and combustion efficiency. There is much more air (10x) being sucked out of the room and up the chimney than there is in a wood stove. And much less heat stays in the room that a wood stove.

An insert will work much better because the fire is completely contained within a steel cabinet that has an outer convection jacket that is independent of the firebox inside the stove. The heat from the firebox is transferred to the to the convection air chamber. Air is pulled in a the bottom of the convection chamber and blown out the top into the room. That brings about much better heating efficiency than an open fireplace.

Good info, but let me clarify. I own a prefab that incorporates both of those features, namely a convection chamber (with fan) and gasketed doors (though not air tight). I am assuming, perhaps incorrectly, that most of the combustion air is being drawn from the outside air passage, and a small amount (maybe around 10%) is drawn in through the gap in the doors, which have a cabinet-style closure. Considering these three design features, what other concepts are involved in say a Travis Industries Elite model or Heat n Glo Northstar that make them superior to what I have?

 

[ddddddden]

I've had a cat stove for about 5 years now. Before getting the new stove, I had ideas similar to yours for adding secondary combustion to the old insert...now glad I did not waste time with that project. Not all catalytic stoves are known as top performers, especially early designs that just slap a cat in the flue. IMO, top performance results from a whole lotta R&D. Trying to get similar results by modifying an old stove or fireplace is like trying to make an F1 car out of an old Chevy... and then you have to find a good supply of high-octane fuel for it. My stove is widely regarded as a very good performer, but this does not happen with wood that is not nice and dry. Soooo, for me, keeping up a supply of good fuel is enough trouble, without worrying about tweaking my stove design.

 

[ddddddden]

...what other concepts are involved in say a Travis Industries Elite model or Heat n Glo Northstar that make them superior to what I have?

The concepts may be identical.

The difference is in testing and refining for performance and usability, IMO.

 

[bholler]

Good info, but let me clarify. I own a prefab that incorporates both of those features, namely a convection chamber (with fan) and gasketed doors (though not air tight). I am assuming, perhaps incorrectly, that most of the combustion air is being drawn from the outside air passage, and a small amount (maybe around 10%) is drawn in through the gap in the doors, which have a cabinet-style closure. Considering these three design features, what other concepts are involved in say a Travis Industries Elite model or Heat n Glo Northstar that make them superior to what I have?

Well for starters with your zc unit if you did put that cat in there it would void the ul listing and make your fireplace nolonger code compliant. We really would need to know the make and model of your fireplace but i would bet that it is more like 10% coming from the outside air supply and the rest from your house. Then you have no control over that air the fire just burns as fast as it wants And the vast majority of that heat goes up the flue and out

 

[begreen]

Good info, but let me clarify. I own a prefab that incorporates both of those features, namely a convection chamber (with fan) and gasketed doors (though not air tight). I am assuming, perhaps incorrectly, that most of the combustion air is being drawn from the outside air passage, and a small amount (maybe around 10%) is drawn in through the gap in the doors, which have a cabinet-style closure. Considering these three design features, what other concepts are involved in say a Travis Industries Elite model or Heat n Glo Northstar that make them superior to what I have?

There is a lot of design engineering that goes into a finished product like those mentioned to optimize heat recovery and combustion efficiency. A good EPA ZC fireplace is designed for a hotter fire in the firebox and 24/7 burning. Many older units are not. Your concern about heat damage is appropriate. Though one of the shortcomings of these devices is that they are add-on and not integral to the heat recovery system of a good ZC fireplace. The Earth's Flame looks like a simple baffle holder. I see it also has a gas log starter. Do you need this and would it be approved for your fireplace? "The HearthCAT™ Wood Burning Fireplace System is sold as an emission control device ONLY."

What make and model ZC fireplace? All that I have looked at would consider adding this device to their fireplace as a modification that voids the UL testing. That becomes a liability issue if there damage or injury done. Another caveat, some ZC fireplaces have a drop down damper that could be right in the flame path.

 

[MidwestWoodBurner]

It is a Heatilator Accelerator 36 C, and has a butterfly-style damper.

 

[bholler]

It is a Heatilator Accelerator 36 C, and has a butterfly-style damper.

This is copied from the manual for your fireplace page 7 they say you cant do it pretty clearly

3
Important Safety and Operating Information WARNING! Risk of Fire! Hearth & Home Technologies disclaims any responsibility for, and the warranty and agency listing will be voided by the following actions.
DO NOT
:
• operate damaged fireplace
• modify fireplace
• overfire
• install any unvented gas log set
• install any component not approved by Hearth & Home Technologies
• install parts or components not Listed or approved
• operate the fireplace without fully assembling all components
Improper installation, adjustment, alteration, service or
maintenance can cause injury or property damage

 

[mellow]

A baffle in an old pre-epa thick steel Fisher is quite different than putting one in a thin metal ZC fireplace, they are not built for that kind of heat retention.

 

[MidwestWoodBurner]

I'm wondering if an insert is even acceptable.

 

[jetsam]

I just looked at the two products listed in the original post too. One of them is a piece of refractory board and a steel frame to hold it up at an angle. There is no cat. I think the ad copy contains some valid info but is a bit disingenuous; $1 worth of cement board does not turn a fireplace into a tube stove. You could potentially see some improvement with this device (which you could replicate with a few feet of wire rope, four eyelets, and a piece of cement board).

The other product actually is a cat, but it fits into the flue, so you will see a 0% increase in heat output unless you go sit on the roof (I know this sounds great, but waking from a sound sleep to find that your sofa is unexpectedly doing 40 MPH downhill can be rather disconcerting).

 

[bholler]

I'm wondering if an insert is even acceptable.

Your fireplace is one of the few that actually allow an insert to be installed in it. It is on page 34

 

[begreen]

I'm wondering if an insert is even acceptable.

In this case yes, (thx bholler for checking) and properly installed it will certainly provide more heat.

 

[MidwestWoodBurner]

Thank you, all. I'm learning...