Cat vs non-Cat & Chimney Choice for Weekend Burning

[yurij]

Hi - I am going to install a high-efficiency wood-burning fireplace (with an OAK) in a weekend home in the casktill moutians of NY. the installation is on an interior wall with the chimney snaking up various closet areas. this is really a 1.5 story building so there is no attic to speak of. i am concerned that when the unit is not working, that the cold air will come down the flue, can cause the fireplace/chimney to act like a giant cooling unit. The fireplace doors will be closed, so the cold air will not physically leak into the house, but the unit and chimney will "probably" get very cold and hence cool the house.
So how is this related to cat vs non-cat? I believe most cat's use a damper-like device to force the combustion gases to go through the cat, which is a much more difficult path for the air to traverse (if i open the fireplace doors with the cat engaged all the smoke comes out, whereas this does not happen is the cat is not engaged). so, i am thinking that when i am away, i should leave the cat engaged, and that should significantly diminish the amount of air that is moving through the OAK-fireplace-chimney system and hence not cool off the house as much.
the equivalent thing for a non-cat is to close the air-supply as much as possible, but i read that some units won't let you do that completely, and it still leaves the entire firebox full of cold air, i.e. more surface area for the cold to exchange with the interior of the house.
it seems to me that the cat will do a better job at preventing the house from getting colder while the unit is not used. does this sounds reasonable?
a similar concern about the the chimney. i have narrowed down my choice to the BIS Tradition/Lennox Montecito Estate with their insulated pipe or the VC Sequoia II cat which uses their triple wall air cooled pipe. the insulated pipe "should" conduct less cold into the house simply because its 11" diameter whereas the VC pipe is 13" diameter (the VC pipe has 18% more surface area for conduction).
i don't want the fireplace to act as a "air-conditioner" in the winter when its not being used. i have read (or heard) of some fireplaces where the cold air is pouring out of the fireplace vents when its not used and the people have to cover it with a blanket!
thx -yurij

 

[webbie]

My experience is that the packed pipe units will radiate less. This may be somewhat changed by current designs, but when the units are not in use, the cold air often dumps down the outer pipe and makes the unit and chase bottom cold. Might be fine for temperate and warmer climes, but not for cold ones. I guess what I am saying is that I personally (living in new england now) would use a packed pipe model.

 

[seaken]

Yes, you are right to be concerned with cold air infiltration. Cold air infiltration usually will come from three sources.

Most common complaint comes from a poorly built exterior chase that has not been insulated properly. You should be able to avoid that with your interior location. Use a firestop at the first 8 foot level and insulate it.

Second, the outside air supply. Most OSA kits do not allow for shutting off the air supply when not wanted. The OAK is usually just a duct pipe and a exterior hood. You will need some sort of shut-off to minimize cold air infiltration through this air duct.

Third, the chimney system. Air-cooled systems will be far more likely to allow cold air infiltration and condensation. For a weekend house I would avoid the air cooled systems. Packed insulated systems will also allow cold air into the firebox but will be less of a problem with condensation. If there is a damper in the appliance the packed insulated systems will be less likely to fill the firebox with cold air while not in use. They will also heat up faster when you come up for the weekend and want to get the fireplace started. You will still have to prime the flue but the packed insulated chimney will be easier to work with.

The BIS Tradition is a non-cat (same as Lennox Mendicito Estate) and does not have a flue damper. However, the inlet air is pretty tightly controlled. With the doors closed there will be little problem from the OSA duct. Security uses a "boost" control for start ups and the air flow is limited without heat to establish draft.

The Sequoia (the large version, not the smaller Sequoia II) uses a catalytic and has a by-pass damper. But it only supports the air-cooled chimney. Much more likely to be a problem for weekenders. The Sequoia II uses the Everburn system non-cat, but also supports only the air-cooled chimney. The outside air supply on these stoves are also not as tightly controlled as the Security/Lennox units.

I would suggest the BIS Tradition with the GSX packed insulated chimney system.

If you are close enough I may be able to help. We're on the far east side of the Catskills. Bear in mind that I don't have a very good setup for do-it-yourselfers. But we have been hired to install several of these types of units over the years. If you are looking for a BIS dealer we may be able to help.

 

[yurij]

thx. but VC says that the triple wall pipe does not allow ANY of the cooling air out into the chase. This pipe has 3 zones, the outer zone has cooling air, the middlw zone has cooling air, and the interour zone is the flue. I don't know how they do it, but where the pipe attaches to the fireplace, it allows the outer zone air to cross into the middle zone, effectively creating a circuit so that air can enter the top of the chimney in the outerzone, get drawn down to the bottom cross into the middle zone and then travel up and out of the chimney. so no spillage. as opposed to double wall air-cooled which evidentaly spills out onto the fireplace. makes sense, but the triple wall still has alot more area for regular condution

 

[yurij]

seam - thx for the info. i will be in the area saturday (to check on the "taking forever" construction) and will stop by. and yes, i meant the Sequoia cat version, not the non-cat II. so you think that the cat damper does not add any appreciable "insulation" when its closed and i am away vs the OAK shutoff?
btw, have you seen the tradition in action? i want to "see" the flames (maybe the secondary burn). and if i can't really then i will run it most of the time with the doors open, which would be sad considering the $$ spent to get the high-efficiency.

 

[seaken]

thx. but VC says that the triple wall pipe does not allow ANY of the cooling air out into the chase. This pipe has 3 zones, the outer zone has cooling air, the middlw zone has cooling air, and the interour zone is the flue. I don't know how they do it, but where the pipe attaches to the fireplace, it allows the outer zone air to cross into the middle zone, effectively creating a circuit so that air can enter the top of the chimney in the outerzone, get drawn down to the bottom cross into the middle zone and then travel up and out of the chimney. so no spillage. as opposed to double wall air-cooled which evidentaly spills out onto the fireplace. makes sense, but the triple wall still has alot more area for regular condution

This is generally true, and if I had to choose an air-cooled system I would choose triple-wall. However, condensation will still be a problem and the quality of the pipe cannot withstand any corrosive environment. The chase must be properly ventilated to control condensation. I still think the packed insulated pipe is better.

 

[seaken]

seam - thx for the info. i will be in the area saturday (to check on the "taking forever" construction) and will stop by. and yes, i meant the Sequoia cat version, not the non-cat II. so you think that the cat damper does not add any appreciable "insulation" when its closed and i am away vs the OAK shutoff?
btw, have you seen the tradition in action? i want to "see" the flames (maybe the secondary burn). and if i can't really then i will run it most of the time with the doors open, which would be sad considering the $$ spent to get the high-efficiency.

No, the damper is not a sealed damper system. It is a bypass. The flue is not completely shut off.

You will have to decide if flame viewing is more important than efficiency. Ultimately, all these high-efficiency fireplaces will not give you your familiar flame view fire. But, in general, the non-cat baffle types (such as the Tradition) are more pleasing to watch. The catalytic and Everburn models tend to be less visibly active.

Yes, I have seen the Tradition burning. It is very similar to a large non-cat stove like a Lopi Liberty, etc. I do not have one in my showroom. I have a Panorama in my store, but we do not burn it. I recently finished an install of a Tradition and the customer said he really likes it.

But if you are more interested in flame view you may to reconsider. The Tradition is a lot of money to spend when you're not going to use it as a heater as much as an open fireplace.

 

[yurij]

sean - its almost impossible to find somenoe who has a tradition on display, never mind seeing it burn. i was hoping that people on this forum would comment in my other posts concerning the tradition, but looks like tradition owners do not visit here. i will use the unit for heat whenever i can, but when i want to sit and look at the fireplace, i want to see the fire. and of course when i am not there, the unit will not be producing any heat.
i am thinking of using the gravity duct to heat another room, will this backfire on me when i am not there and the unit is cold, i.e. will the other room get colder as a result of the cold fireplace venting cold air into the other room?

 

[seaken]

sean - its almost impossible to find somenoe who has a tradition on display, never mind seeing it burn. i was hoping that people on this forum would comment in my other posts concerning the tradition, but looks like tradition owners do not visit here. i will use the unit for heat whenever i can, but when i want to sit and look at the fireplace, i want to see the fire. and of course when i am not there, the unit will not be producing any heat.
i am thinking of using the gravity duct to heat another room, will this backfire on me when i am not there and the unit is cold, i.e. will the other room get colder as a result of the cold fireplace venting cold air into the other room?

Sorry, I've been away from the forum for awhile. Yes, it's hard to display a lot of fireplaces. There are only a few shops around that are large enough to display more than a couple wood fireplaces. And none of them are Security/Lennox dealers.

Not sure how to answer the gravity duct question. I would guess that there should not be any dramatic exchange of cold air. The gravity system is outside of the firebox and chimney system and should be static at room temperature.

Sean

 

[builderbob]

Another thought on cold air infiltration from the outside air ducts. At least for the BIS Tradition and the Kozyheat Z42, the OAK's 4" ducts route the cold air so there is a section where the duct
goes "up". Cold air "sinks" rather than go "up". (I think Quadrafire 7100 uses two 6" cold air ducts?)

The Z42 has the inlet on the unit a foot or 1-1/2 ft. up from the bottom. So the inlet is higher on the unit than on the outside wall inlet. The Bis Tradition has the duct attach at the bottom outside of the unit, but there is a section of duct inside the unit that goes up before ending at the firebox inside. Again this means the unit inlet is higher than the outside wall duct inlet.

Also, to make, one could route the OAK duct "under the floor" from the outside wall then come up through the floor to the fireplace chase cavity to connect to the fireplace unit.

Another thing, use insulated duct with OAK. Not sure about the Kozyheat Z42, but BIS Tradition supplies insulated duct with OAK.

Tape seal the duct at outside wall end and at fireplace attachment, and cold-air infiltration should be minimized from the OAK source.

 

[yurij]

Thanks for the info. I am going with the VC Sequoia Cat. This unit requires 2 OAK's. The people at the fireplace store I am purchasing this from said they:
1) never heard of using insulated pipe for the OAK pipe
2) never heard of putting in a "trap" (like an inverse drain trap) to trap the cold air from easily traversing the pipe from the OAK openning up to the chimney.
the insualted pipe for the OAK makes alot of sense (where do I get some since the store does not carry it), and the trap makes sense also, but is it really effective, and how high should the trap be to be usefull? thx again

 

[builderbob]

Here is info on cold air infiltration and cold air wants "to fall down". Also about insulating cold air ducts. (It is in relation to bathroom exhaust fans, but is very instructive on "cold air" and minimizing its infiltration.)

http://www.askthebuilder.com/594_Bathroom_Exhaust_Fan_Leaks_Cold_Air.shtml


Try other fireplace stores for insulated duct. Or I believe I have read in this forum that insulated 4" (assuming 4" is what you need for your model) dryer vent ducting is used. Any hardware store, Lowes or Home Depot for that.

 

[builderbob]

Thanks for the info. I am going with the VC Sequoia Cat. This unit requires 2 OAK's. The people at the fireplace store I am purchasing this from said they:
1) never heard of using insulated pipe for the OAK pipe
2) never heard of putting in a "trap" (like an inverse drain trap) to trap the cold air from easily traversing the pipe from the OAK openning up to the chimney.
the insualted pipe for the OAK makes alot of sense (where do I get some since the store does not carry it), and the trap makes sense also, but is it really effective, and how high should the trap be to be usefull? thx again

For more info on combustion cold air ducts installation, see Kozyheat Z42 manual pages 6 and 7 for illustrations.

(broken link removed to http://www.kozyheat.com/pdf_files/z42.pdf)

You mention "trap", but it may be as simple as having the cold air duct inlet at the outside house wall be below the bottom of the fireplace. Or at least below where the cold air duct attached to the fireplace. If the outside house wall inlet was even 1 foot lower, then by necessity there would be two 90 degree angles getting it to stove.

 

[builderbob]

the insualted pipe for the OAK makes alot of sense (where do I get some since the store does not carry it), and the trap makes sense also, but is it really effective, and how high should the trap be to be usefull? thx again

Does it really work? Well Lowes, Home Depot, etal sell "insulated dryer vent ducting" to connect dryers to house wall outlets.

Why insulated for this application? I guess cause folks don't want cold air infiltrating into the home.

 

[yurij]

BTB - yes, the OAK will terminate about 2-3 feet beneath the fireplace, so I think that should handle the trap aspect, the cold air will just not make it up the pipe. Excellent point. I'll use the insulated pipe to prevent the pipe from cooling the conditioned air space that will it run through. it will go beneath the floor to the heated basement and run out the side of the house. Its just making sure the pipe is on-hand when the installers come.

 

[builderbob]

BTB - yes, the OAK will terminate about 2-3 feet beneath the fireplace, so I think that should handle the trap aspect, the cold air will just not make it up the pipe. Excellent point. I'll use the insulated pipe to prevent the pipe from cooling the conditioned air space that will it run through. it will go beneath the floor to the heated basement and run out the side of the house. Its just making sure the pipe is on-hand when the installers come.

Depending on how long the duct is, I don't know how much heat/cool transfer there would actually be. I doubt any hearth company or shop has ever run actual tests on this aspect. If your duct is only 5 or 8 feet long or so, it may be no big deal. Someone like me (and maybe you?) might figure, well if I can do anything to minimize what might have a tiny chance of being a problem, and can minimize it cheap--why not, just for good measure.

Another thought too, since the Security BIS Ultima, Tradition etc (and the Lennox clones) fireplaces come with insulated outside air ducts, if there is either a BIS dealer or Lennox fireplace dealer around, you might get the insulated duct from them.

Link to BIS Ultima manual, see page 20 on details of BIS outside air duct install instructions, and illustrations. They say same thing for BIS Tradition model and lennox for Montecito Estate model.

(broken link removed)

Be nice to see pictures of you fireplace once you get it in! And maybe pictures of it going in too.

 

[yurij]

BTB - Good idea about the BIS/Lennox supply. I believe there is a dealer so I'll see if they have some on hand.
I was thinking I could wrap the non-insulated pipe with some appropriate insulation, foil faced bubble wrap or whatever is appropriate for insulating heating ducts. That certainly should be adequate.

 

[builderbob]

BTB - Good idea about the BIS/Lennox supply. I believe there is a dealer so I'll see if they have some on hand.
I was thinking I could wrap the non-insulated pipe with some appropriate insulation, foil faced bubble wrap or whatever is appropriate for insulating heating ducts. That certainly should be adequate.

In case you haven't got the VC Sequia owner's manual yet, here is link. See pages 11 and 12 re outside air ducts. It says the they are not supplied with the unit and are optional. Says if you do use the outside air supply you need two OAK kits and "Class 1" 4" duct to use with them.

I did see where they say "in New York" you MUST use metal non-combustible ducts. You could call you local building inspection dept and ask them if certain types of duct (and any insulation you want to wrap it in) you can find locally satisfy that code N.Y. requirement.


(broken link removed to http://www.vermontcastings.com/catalog/elements/files/2007/20005167_EWF36A.pdf)

 

[builderbob]

I did see where they say "in New York" you MUST use metal non-combustible ducts. You could call you local building inspection dept and ask them if certain types of duct (and any insulation you want to wrap it in) you can find locally satisfy that code N.Y. requirement.


(broken link removed to http://www.vermontcastings.com/catalog/elements/files/2007/20005167_EWF36A.pdf)

Actually for NY, it said "only aluminum, noncombustable flexible, or type "O" duct material may be used." So when I said "metal" I was too restrictive. Your local building code folks would be most helpfull, maybe even tell you where you can get the duct that meets NY code.

 

[yurij]

BTB - In NY, I am required to use the OAK (2 of them). The local inspector has told me that the only way he will sign off on the fireplace installation is if:
1) he observes the entire process (highly unlikely since it takes the entire day) so that he can observe it was constructed as per the specification
2) or that the qualified installer signs a document saying it was installed as per manufacturer's spec.
According to him, a qualified installer is someone who has alot of liability insurance for this sort of thing. He does not want the town to have any liability in case there is a fire and its traced back to an improper fireplace installation, which he eventually approved. He wants someone else's insurance to take the fall. Whatever the merit to his reasoning, that is what he told me.
The installers have installed several sequoia's (as well as lots of other brands) and its really up to them to agree that whatever they put in there is ok since they must produce this document. They told me that they have never installed the Sequoia with insulated OAK pipe, but they do think it's a decent idea.

 

[builderbob]

BTB - In NY, I am required to use the OAK (2 of them). The local inspector has told me that the only way he will sign off on the fireplace installation is if:
1) he observes the entire process (highly unlikely since it takes the entire day) so that he can observe it was constructed as per the specification
2) or that the qualified installer signs a document saying it was installed as per manufacturer's spec.
According to him, a qualified installer is someone who has alot of liability insurance for this sort of thing. He does not want the town to have any liability in case there is a fire and its traced back to an improper fireplace installation, which he eventually approved. He wants someone else's insurance to take the fall. Whatever the merit to his reasoning, that is what he told me.
The installers have installed several sequoia's (as well as lots of other brands) and its really up to them to agree that whatever they put in there is ok since they must produce this document. They told me that they have never installed the Sequoia with insulated OAK pipe, but they do think it's a decent idea.

Sounds like you have been covering all the bases. I would expect you will have a good install to your satisfaction as well as the installers and the inspector. Bodes well for many years of happy, warm, enjoyable fires!