Fireplaces, Heating Stoves, Flues and Chimneys - Partially vented gas burner?

Hi. I'm new here and I would like to hear opinions on this situation:

I have a very old house with an unlined brick chimney. There are two small coal-burning fireplaces which vent into separate flues in the chimney. I do not use them. (edited to add: I live in the deep South FYI)

I would like to put small gas burners in the fireplaces, but I also would like to avoid lining the chimneys, since there are two flues, each about 40 feet high and that would run up some serious $$.

The Rasmussen company makes a small fake coal burning unit that runs on gas. This unit is rated for vented, unvented, or partially vented applications. Its gas consumption and output is quite small in relation to the rooms it would be serving, so ventilation should not be a huge problem if I blocked off the flues and used the burner in "unvented mode". Nevertheless, I am leery of an unvented unit.

Rasmussen's party line is that to use the burner in complete vented mode the chimney should be suitable for burning wood, i.e., lined.

What if I used it partially vented? Let out enough combustion products to be extra sure no one was going to die of CO, yet not so much that it created a huge condensation problem in the unlined chimney?

I wouldn't be using the fireplaces a lot and it would be mainly for ambience.

Summary: options with an unlined chimney and this unit would be:
1) Run unvented and hope that the unit really is safe unvented as they say, and that the large size of the rooms (plus the non-"tightness" of the house) will dilute any nasty gases that decide to show up anyway.

2) Run vented and hope the combustion products (water and CO2 = carbonic acid) don't dissolve the chimney bricks too much. (Then again, people burned coal all winter in it for 80+ years and it's still standing).


3) Run partially vented as a compromise.

What do you think? (Thanks for reading this long thing.)

It is either vented or unvented, there is no "partial" venting. These units are designed to be used in very specific applications. When you alter the installation, you alter the performance. Follow the owner's and install manual.
http://www.rasmussen.biz/logs/pdf/c9%20_SR_%207-04.pdf

Vent free gas fireplaces can be very safe IF properly installed, used and maintained. You need to find an installer that knows ventfrees to install and educate you in the proper use and maintainence requirements.
Check to see what your state/local codes allow.

Hi Rob,

Thanks for responding.
About partial venting, here is a quote directly from Rasmussen's website:

"... Chillbuster CoalFire has been certified to ANSI Z21.11.2, the national vent-free heater standard, which is the strictest of all gas appliance standards. ...

Chillbuster CoalFire is also certified to ANSI Z21.60, the national vented decorative appliance standard. With the two certifications, you can burn CoalFire with the damper open, closed or any place in between, depending on local jurisdiction requirements or consumer preference. "


Therefore it appears all three options (vented, unvented, partially vented) are indeed a possibility.

J


Edited to add website reference:

Chillbuster Coal-Fire Fireplace Heater (http://www.rasmussen.biz/Logs/CoalFire.html)

(quote is near the bottom of the page)

You left out some very important wording in your reply which could mislead and/or injure you or others.

Inquiries have been made as to the lack of randomness of the coal placement. Chillbuster CoalFire has been certified to ANSI Z21.11.2, the national vent-free heater standard, which is the strictest of all gas appliance standards. Patterns other than what we ultimately certified the product with would not have passed the rigorous testing that permits these units to be used with the damper closed, including the requirement that no soot can be produced. The overall effect and functionality of the finished CoalFire product are excellent.

Chillbuster CoalFire is also certified to ANSI Z21.60, the national vented decorative appliance standard. With the two certifications, you can burn CoalFire with the damper open, closed or any place in between, depending on local jurisdiction requirements or consumer preference.


This unit is designed to be used as a ventfree when the coals are placed in the exact position in which it received it's ventfree certification. If you decide to move the coals, it becomes a vented appliance. The install manual states that the damper must be fixed in the open position with at least 29 sq. inches.

Since you asked for opinions, here is mine. I would only use this appliance in the fully vented or fully ventfree manner and I am not fully comfortable with using it as a ventfree. Sure, it may be safe as a ventfree, but maybe it is not. I would not risk your or my life upon it.

??? I left out that particular wording because it was not relevant to the situation being discussed and therefore added unnecessary length to the post.

We were talking only about opening or closing the flue. Nowhere did I ever suggest fiddling with the coal placement. .:confused:


If you think unvented units are bad no matter what, fine, OK, thank you for your opinion... no need to start talking about altering the appliance configuration when that was never brought up.





You left out some very important wording in your reply which could mislead and/or injure you or others.

Inquiries have been made as to the lack of randomness of the coal placement. Chillbuster CoalFire has been certified to ANSI Z21.11.2, the national vent-free heater standard, which is the strictest of all gas appliance standards. Patterns other than what we ultimately certified the product with would not have passed the rigorous testing that permits these units to be used with the damper closed, including the requirement that no soot can be produced. The overall effect and functionality of the finished CoalFire product are excellent.

Chillbuster CoalFire is also certified to ANSI Z21.60, the national vented decorative appliance standard. With the two certifications, you can burn CoalFire with the damper open, closed or any place in between, depending on local jurisdiction requirements or consumer preference.


This unit is designed to be used as a ventfree when the coals are placed in the exact position in which it received it's ventfree certification. If you decide to move the coals, it becomes a vented appliance. The install manual states that the damper must be fixed in the open position with at least 29 sq. inches.

Since you asked for opinions, here is mine. I would only use this appliance in the fully vented or fully ventfree manner and I am not fully comfortable with using it as a ventfree. Sure, it may be safe as a ventfree, but maybe it is not. I would not risk your or my life upon it.

Another thing:

You left out some very important wording in your reply which could mislead and/or injure you or others.....
trimmed for length. (If anyone wants to read your whole post they can scroll up)

LOL If people actually want to install this thing, I doubt they're going to use an internet post as an instruction manual.

Another thing:

trimmed for length. (If anyone wants to read your whole post they can scroll up)

LOL If people actually want to install this thing, I doubt they're going to use an internet post as an instruction manual.


It is amazing how many people think that anything they read on the internet is fact and also may mistake something posted in a well written manner, like your post, as gospel. You came to the internet for advice on this product expecting an educated response didn't you? With the tort laws in this country like they are, we ALL must be careful. That is all I was doing here, trying to clairify the vented/ventfree options a little more.

Gas fireplaces, in general, are very safe. They have been tested for safe operation in very specific configurations and any change to those configurations effect the usage(vented vs. unvented), but the untrained DIY homeowner may not know the consequences of something as simple as the improper placement of the logs or coal pieces. Gas fireplaces are not a DIY item. You may get it right when installing/repairing them, but if you do not get it right, people can be injured and lives and or property lost.

Ventfree gas appliances can be a safe and efficient form of additional heat in a home. I have serviced/repaired several thousand ventfree gas fireplaces over the past 10 years and have never seen any serious health issues caused by them.

Jo500, I am just trying to help you here. Gas fireplaces are how I make my living and I must make sure that I inform those asking for my help/advice, free or paid for, to the best of my ability.

Feel free to ask any other questions you may have.

OK, maybe I took it wrong. Thanks for your input.

I am leaning towards using an unvented burner and having the flue blocked off. For the record, I am a fairly meticulous person who reads instructions and abides by them. I wasn't even considering installing a burner myself, but I do like to research things thoroughly so I can be sure I am getting what I want and need. In this far southern climate, we don't have many local fireplace experts to consult in person.


One other question, then: Peterson Real-Fyre has a ventless 16" gas log burner which *might* fit in my fireplace. (Apparently the fit depends on what control unit is used, so I emailed to ask but I haven't heard back.)
This 16" unit comes in two versions: one with 20,000 BTU output and another with 9500 BTU output.

It occurred to me that if I purchased the 9500 BTU unit I ought to be pretty safe from CO emissions. The smallest of the two fireplace rooms is 3000 cubic feet, which is way more than enough to define it as an "unconfined space" with a 9500 BTU burner (in fact it is over 6 times the required volume, if my calculations are correct).
But on the other hand, I wonder if that would be so small as to be rather pointless, heat-wise, in such a large space. I am looking mainly for ambiance in the fireplaces but a bit of heat would be welcome on chilly nights. What do you think? 9500 or 20,000 BTU? The room volume is three times as much as is needed for the room to be an "unconfined space" with a 20,000 BTU unit. Is 9500 "underkill"?

J



It is amazing how many people think that anything they read on the internet is fact and also may mistake something posted in a well written manner, like your post, as gospel. You came to the internet for advice on this product expecting an educated response didn't you? With the tort laws in this country like they are, we ALL must be careful. That is all I was doing here, trying to clairify the vented/ventfree options a little more.

Gas fireplaces, in general, are very safe. They have been tested for safe operation in very specific configurations and any change to those configurations effect the usage(vented vs. unvented), but the untrained DIY homeowner may not know the consequences of something as simple as the improper placement of the logs or coal pieces. Gas fireplaces are not a DIY item. You may get it right when installing/repairing them, but if you do not get it right, people can be injured and lives and or property lost.

Ventfree gas appliances can be a safe and efficient form of additional heat in a home. I have serviced/repaired several thousand ventfree gas fireplaces over the past 10 years and have never seen any serious health issues caused by them.

Jo500, I am just trying to help you here. Gas fireplaces are how I make my living and I must make sure that I inform those asking for my help/advice, free or paid for, to the best of my ability.

Feel free to ask any other questions you may have.

If CO is your major concern, then I wouldn't worry too much. Peterson is one of my favorite gas log companies and have very few problems with their gas logs. At every service call I perform I check for gas leaks and check the CO output and I have yet to have a problem with CO with the Peterson ventfree gas logs. Just make sure you get the refractory logs and not the ceramic fiber logs. I have seen odor issues with the fiber logs.

Where in the South do you live? Depending upon the Winter temperatures, 20k btus may be too much, but it will give you a better looking flame. If you can, I would go with the option of a thermostat remote. You can set the temperature and the fireplace will turn on and off to control the room temperature. Some will even regulate the flame height.

Also, you said it was an older home. Most older homes have pretty large mantles. Check the height above the fireplace and the distance it protrudes to make sure you can find an attractive hood that meets your fireplace's needs.

That's good to know about Peterson.

I'm in northern Florida. On any given winter day, it could be 80 degrees or it could be 20 degrees. An average winter day would have a high in the 60's and a low in the 30's. I expect we'd mostly be using the fireplaces in the evenings.

The mantel is indeed another issue I need to look at. The mantels project outward 5 1/2 inches and are 18 inches above the top of the firebox. I've looked at the manuals for both the Peterson logs and the Rasmussen coals. Without a hood, only the low BTU (9500 BTU) Peterson logs are acceptable for this configuration.

But the fireplaces do have a sort of hood on the existing surround. The trim projects out 3 1/2 inches from the wall in the center. Here is a link to photos of one of the fireplaces: Photo Albums: fireplace - Contents (http://pwp.att.net/p/s/community.dll?ep=331&folderid=298674&groupid=402038&folderview=thumbs&ck=)

Does that outward "bulge" of the copper trim over the firebox count as a hood?

(FYI I'm going to have the fireboxes cleaned and repaired before I go burning anything in them.)

J.


If CO is your major concern, then I wouldn't worry too much. Peterson is one of my favorite gas log companies and have very few problems with their gas logs. At every service call I perform I check for gas leaks and check the CO output and I have yet to have a problem with CO with the Peterson ventfree gas logs. Just make sure you get the refractory logs and not the ceramic fiber logs. I have seen odor issues with the fiber logs.

Where in the South do you live? Depending upon the Winter temperatures, 20k btus may be too much, but it will give you a better looking flame. If you can, I would go with the option of a thermostat remote. You can set the temperature and the fireplace will turn on and off to control the room temperature. Some will even regulate the flame height.

Also, you said it was an older home. Most older homes have pretty large mantles. Check the height above the fireplace and the distance it protrudes to make sure you can find an attractive hood that meets your fireplace's needs.