Thread: Wood to vented gas log set conversion

I ran across a fireplace that had been converted from wood to a vented gas log set. The fireplace still had the fire brick with a clay liner (no metal liner) and the damper had not been mechanically "fixed" to restrict closing it less than 1". I have always called out any gas appliance that was exhausting into an unlined flue...but maybe I'm wrong here. Question? Is there a code or any published "rule" that I can get a copy of where it spells out what must be done with this type of conversion with respect to the metal liner necessity?

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Dave,

What do you mean by a "vented gas log set"? Is it a gas insert, or a gas log? Based on your description, it sounds like a log not an insert. In either case, get the manufacturer's name and then recommend that the gas log be installed to the manufacturer's specifications by a qualified chimney sweep or gas fire place installer. You are correct that if this log has a pilot burner, the damper should be modified so that it will not fully close. Installation of the metal liner will depend on what the manufacturer requires. Typically a gas log would not require a liner.

I often discuss the disadvantages of gas logs with my clients and discourage their use. They typically just suck heat out of the house. I encourage conversions to true gas inserts.

Dave,
A vented or " yellow flame " log set will require a fixed damper or the damper may have to be removed per the manufacturers instructions. If the log set is vent free the damper may be closed assuming the log set is installed per the manufacturers instructions as long as that is approved by the AHJ. Vented gas logs are beautiful but a net loss when heating a home. Vent Free logs in the USA are equipped with an oxygen depletion system of some sort and are 99% efficient and can add a fair amount of heat and ambiance to a room. Direct vent gas inserts are the best but are quite a bit more $$ than gas logs.

Jack

It sounds like you are describing a proper masonry fireplace with a fireclay flue lining. If so, that should be ideal for the vented gas logs provided the fireplace/chimney is in good condition and sized properly for the appliance (gas log set). Check the gas log installation instructions for sizing requirements of the firebox and flue, and also the damper opening requirement. The 1" opening requirement that is often referred to is, as far as I can tell, an urban legend. I have never seen that in print, and most instructions state a specific minimum square inch opening of the damper with the most common requirement being 50 square inches of opening for the damper and flue.

Bottom line is the answers to your questions are in the appliance installation instructions, and the building codes avoid the specific requirements and refer you to the instructions.

Jack,

Minnesota does not permit unvented gas appliances (other than gas kitchen stoves) to be installed. Unfortunately, it is legal to sell them. We sometime see them in big box stores where they are marketed as garage heaters. Not legal in the garage either.

Roger - Great to see you on this forum. Thanks for the info everybody.

One other thing if there is a metal liner installed, doesn't it have to extend 6" or so past the top of the clay tile?

I never worry about the specific dimension. It needs to extend up enough to be visible from the ground. That permits verification that it is present. 6" is usually enough for the liner to be visible.