Rumford Technical Discussion

Rumford Technical Discussion
Venting Fireplaces with Gas Logs
10/14/14

The National Fuel Gas Code as well as all gas log manufacturers require gas logs to be installed only in code-compliant fireplaces.
There are three good reasons:
1) Open fireplaces take about 30 times as much "dilution air" through the face of the fireplace as is needed for stoichiometric combustion. The area of the flue needs to be about one tenth of the area of the fireplace opening, as required by code, or the fireplace won't draw the products of combustion which, with gas logs, is laced with carbon monoxide.
2) Gas logs generally are not listed nor tested so the manufactures simply specify that they must be installed only in code-compliant fireplaces.
3) Twenty-five years from now, if it looks like a real fireplace, someone may think the fireplace really is a real fireplace and try to burn wood in it. So it better be a real fireplace.

The Authority and the Code

Date: Fri, 1 Jun 2007
From: "Cabot, Paul"
To: buckley@rumford.com
Cc: "Ranfone, Jim"
Mr. Buckley,
Mr. Ranfone forwarded your question to me.
The National Fuel Gas Code (NFGC) in section 12.6.1.3 (attached) requires masonry fireplaces be constructed in accordance with NFPA 211. Listed gas log sets (listed to standard ANSI Z21.60) are specifically intended for installation in solid fuel burning fireplaces, therefore, a fireplace so constructed to NFPA 211 is sufficient for the installation of a Z21.60 gas log.
Section 10.6 (attached) covers the installation of decorative appliances (including Z21.60) and would require the flue to be constructed of non combustible materials and requires that you follow the gas log manufacturer's instructions which would include sizing (for listed appliances). The NFGC does contain a sizing table for unlisted (attached).
Regarding the use of b-vents. Section 12.6.1.3 requires the lining of a masonry chimney to be constructed of clay, listed lining system or materials that do not degrade at temperatures up to 1800 degrees F. Type B vents do not meet this criteria.
ANSI Z21.60 gas log sets are purely decorative and there are no federal minimum efficiency standards.
No need to buy the Code.
I hope this helps.
Paul Cabot
Administrator National Fuel Gas Code
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See also Why Gas Logs are not Certified by Rett Rasmussen

A Required Dangerous Situation

Some officials, in an overzealous attempt to control wood-burning emissions, allow gas logs only if the flue size is reduced to prevent wood-burning. This, of course, violated the National Fuel Gas Code, the manufactruer's installation instructions and guarantees that the fireplace will spill carbon monoxide. See an example.

Discussion

1/8/04
I have had custom Rumford fireplaces in two homes we built in Maine. I love the way they look and how well they draw and reflect heat. Now we live in the Memphis area and are just beginning to build a new home. I want a gas Rumford and do not want the expense of a brick or masonry chimney. What do you recommend for a Rumford design and kit that would transition to low-cost gas venting system? Do such systems exist?
Thanks,
Michael

Michael,
Your very logical sounding proposal is a violation of the National Fuel Gas Code as well as counter to any gas log manufacturer's installation instructions for three good reasons:

1) Open fireplaces take about 30 times as much "dilution air" through the face of the fireplace as is needed for stoichiometric combustion. The area of the flue needs to be about one tenth of the area of the fireplace opening, as required by code, or the fireplace won't draw the products of combustion which, with gas logs, is laced with carbon monoxide.
2) Gas logs generally are not listed nor tested so the manufactures simply specify that they must be installed only in code-compliant fireplaces.
3) Twenty-five years from now someone may think your fireplace that looks like a real fireplace really is a real fireplace and try to burn wood in it. So it better be a real fireplace.

You may use a Class A "all fuel" metal chimney as specified at http://www.rumford.com/metalchimneydetail.gif but it may be less expensive (and certainly will last longer) to build a masonry chimney.
My recommendation is to build a masonry chimney. I think, with good planning and the right materials, you can build the chimney inexpensively. Send me a plan and I will make some cost-cutting suggestions and you will end up with a safe, legal and functional chimney.
Best,
Jim Buckley