Thread: Oil to gas conversion and the chimney liner

On a recent inspection, I called out a clay chimney liner that was not relined after the heating system had been switched from oil to gas. The town official was called and he stated (according to an agent) that no liner was needed because this was an interior chimney and had it been an exterior chimney then the liner would have been required. This is a new one on me. Can any of you fine individuals shed some light on this subject? For now, I have not changed my opinion that a liner is warranted.

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Tom, when you switch fuels that should trigger an NFPA 211 Level II inspection as does sale or transfer of property or operational problems. I can guarantee you that a proper inspection will reveal the need for a chimney liner regardless of whether interior or exterior wall. There is a bunch of bad info. flying around about liners only being needed for exterior chimneys, which is dead wrong. If the chimney is not suitable for the class of service then it must be repaired or rebuilt. Get the level II report and show it to Hector the Inspector and ask him what he thinks when the report indicates failed mortar joints, cracks and deterioration of the clay flue lining. He doesn't know his you know what from his you know where and needs to quit reading those comic books.

FYI, you cannot install an aluminum liner in a chimney that has served oil or coal. Even if you sweep the heck out of it, it will eat up an aluminum liner in a few months.

Should is a funny word. If no one required them (ie the town), then it would suggest the heating contractor should have done it but again - should comes into play. Is it REQUIRED or just good NFPA advice that should be followed? I do not hear of many level 2 inspections happening. Also, if the aluminum will not last long term, and rebuilding chimneys does seem to be happening all over the place, what are most chimney owners doing and part 2, what should they be doing? Thank you for your input.

Originally Posted by Tom King

Should is a funny word. If no one required them (ie the town), then it would suggest the heating contractor should have done it but again - should comes into play. Is it REQUIRED or just good NFPA advice that should be followed? I do not hear of many level 2 inspections happening. Also, if the aluminum will not last long term, and rebuilding chimneys does seem to be happening all over the place, what are most chimney owners doing and part 2, what should they be doing? Thank you for your input.

You're right Tom, it is a funny word but it is why I could use "shall" as a code imperative. You *should* follow NFPA 211 because it is the industry std held up in courts in most states, whether voted into law as an actual code or not. In some States like De., it is law, not under the building code but through the Fire Marshal's office and was held up in a Superior Court 2 yrs ago.

A lot of aluminum liners are being replaced with stainless or they are going high efficiency and doing away with the chimney altogether. Aluminum is suitable for a CAT I draft hood equipped appliance and then only if you can install it without damaging it and never in a flue previously serving oil or coal. The mfrs. don't care about disclaiming these conditions in their warranties because these liners are so cheap they don't care and seldom does anybody file a warranty claim on a beer can liner. They throw it out and replace it with stainless or go high efficiency. In my humble opinion, aluminum liners are allowed not to solve actual problems but prolong the problem while massaging someone's fears over a slight feeling of guilt or responsibility. It is not a permanent solution to the problem and often makes it worse.

Originally Posted by Bob Harper

Tom, when you switch fuels that should trigger an NFPA 211 Level II inspection as does sale or transfer of property or operational problems. I can guarantee you that a proper inspection will reveal the need for a chimney liner regardless of whether interior or exterior wall. There is a bunch of bad info. flying around about liners only being needed for exterior chimneys, which is dead wrong. If the chimney is not suitable for the class of service then it must be repaired or rebuilt. Get the level II report and show it to Hector the Inspector and ask him what he thinks when the report indicates failed mortar joints, cracks and deterioration of the clay flue lining. He doesn't know his you know what from his you know where and needs to quit reading those comic books.

FYI, you cannot install an aluminum liner in a chimney that has served oil or coal. Even if you sweep the heck out of it, it will eat up an aluminum liner in a few months.

Are you saying that an interior chimney with a clay liner is never suitable for venting a gas furnace? Or only when converting from oil? Or every clay liner is defective? Also, I am on vacation and do not have a copy of the IRC handy, but I don't think it references NFPA 211 as a required standard. If not, then you can reference the NFPA 211 standard all you want, but that does not meet that you must comply with it. In some cases I think that standard goes overboard regarding chimney relining (or maybe its just the interpretation of the standard).

Originally Posted by Mark Reinmiller

Are you saying that an interior chimney with a clay liner is never suitable for venting a gas furnace? Or only when converting from oil? Or every clay liner is defective? Also, I am on vacation and do not have a copy of the IRC handy, but I don't think it references NFPA 211 as a required standard. If not, then you can reference the NFPA 211 standard all you want, but that does not meet that you must comply with it. In some cases I think that standard goes overboard regarding chimney relining (or maybe its just the interpretation of the standard).

Mark, from the 2009 IRC; Chapter 24 titled Fuel Gas, under the Masonry chimneys heading, G2427.5.2. "Masonry chimneys shall be built and installed in accordance with NFPA 211 and shall be lined with approved clay flue lining, a listed chimney lining system or other approved material that will resist corrosion, erosion, softening, or cracking from vent gases at temperatures up to 1,800 degrees F."

There is an Exception;
Masonry chimney flues serving listed gas appliances with draft hoods. Category 1 appliances and other gas appliances listed for use with Type B vents shall be permitted to be lined with a chimney lining system specifically listed for use only with such appliances. The liner shall be installed in accordance with the liner manufacturer's installation instructions. A permanent identifying label shall be attached at the point where the connection isto be made to the liner. The label shall read: "This chimney liner is for appliances that burn gas only. Do not connect to solid or liquid-fuel burning appliances or incinerators."

G2427.5.5.3 titled Unsafe chimneys says; Where inspection reveals that an existing chimney is not safe for the intended application, it shall be repaired, rebuilt, lined, or relined or replaced with a vent or chimney to conform to NFPA 211 and it shall be suitable for the appliances to be vented.

I believe that confirms what Bob Harper has stated.

Ashley Eldridge
CSIA Director of Education
Chimney Safety Institute of America (CSIA) | Plainfield, IN

Originally Posted by Ashley Eldridge

Mark, from the 2009 IRC; Chapter 24 titled Fuel Gas, under the Masonry chimneys heading, G2427.5.2. "Masonry chimneys shall be built and installed in accordance with NFPA 211 and shall be lined with approved clay flue lining, a listed chimney lining system or other approved material that will resist corrosion, erosion, softening, or cracking from vent gases at temperatures up to 1,800 degrees F."

There is an Exception;
Masonry chimney flues serving listed gas appliances with draft hoods. Category 1 appliances and other gas appliances listed for use with Type B vents shall be permitted to be lined with a chimney lining system specifically listed for use only with such appliances. The liner shall be installed in accordance with the liner manufacturer's installation instructions. A permanent identifying label shall be attached at the point where the connection isto be made to the liner. The label shall read: "This chimney liner is for appliances that burn gas only. Do not connect to solid or liquid-fuel burning appliances or incinerators."

G2427.5.5.3 titled Unsafe chimneys says; Where inspection reveals that an existing chimney is not safe for the intended application, it shall be repaired, rebuilt, lined, or relined or replaced with a vent or chimney to conform to NFPA 211 and it shall be suitable for the appliances to be vented.

I believe that confirms what Bob Harper has stated.

Ashley Eldridge
CSIA Director of Education
Chimney Safety Institute of America (CSIA) | Plainfield, IN

My original concern was whether someone was saying you can never vent gas-fired equipment into an existing chimney with a fired clay liner. I believe there are situations where you can. G2427.5.5.1 states that chimneys shall be lined in accordance with NFPA 211. The there is an exception:

Where an existing chimney complies with Sections G2427.5.5 through G24275.5.3 and its sizing is in accordance with Section G2427.5.4 its continued use shall be allowed where the appliance vented by that chimney is replaced by an appliance of similar type, input rating and efficiency.

My point is that not every chimney with a fired clay liner must be relined. I agree that many do need new liners because of deterioration or not complying with other requirements.

Originally Posted by Mark Reinmiller

My original concern was whether someone was saying you can never vent gas-fired equipment into an existing chimney with a fired clay liner. I believe there are situations where you can. G2427.5.5.1 states that chimneys shall be lined in accordance with NFPA 211. The there is an exception:

Where an existing chimney complies with Sections G2427.5.5 through G24275.5.3 and its sizing is in accordance with Section G2427.5.4 its continued use shall be allowed where the appliance vented by that chimney is replaced by an appliance of similar type, input rating and efficiency.

My point is that not every chimney with a fired clay liner must be relined. I agree that many do need new liners because of deterioration or not complying with other requirements.

The exception you cite is N/A to the OP nor the discussion.

The clay-tile lined masonry chimney MUST be relined because of the CHANGE from Oil-fired appliance service to GAS fired appliances.

As Bob H. explained, it doesn't matter how 'clean' one thinks the chimney was, the chemical 'attack' due to the exposure/products of combustion (and incomplete combustion) as well as the increased water vapor componant will attack even the most ideally constructed former oil-service or combined service clay-lined chimney when converted to gas-fired-only duty, Interior or exposed, its only a matter of time being used and weather pattern swings before the mortar and tile itself will be failing. The same residues, reactions, and conditions will likewise compromise aluminium in a formerly oil-fired tile lined masonry chimney, in short order.

From the OP:

On a recent inspection, I called out a clay chimney liner that was not relined after the heating system had been switched from oil to gas.

Oil fired is not gas fired. The "Gas Code Section" exception does NOT apply to the circumstance. Coal or other solid-fuel is not the same fuel as gas (propane, 'refined' natural gas, etc.) A change in fuel type burner or overall appliance negates the exception.

A true Level II inspection most often reveals defects in most every clay-tile lined masonry chimney with some (usage years) age on it (esp. long enough to have had appliance(s) replaced (or added/subtracted) and/or duty/cycles altered!). Lack of maintenance, construction technique, Changes in the quality and refining standards (& additives) for the fuel over the years, seasonal changes (DHW vs. heating season; weather patterns) etc. Which is the POINT. Somethiing as simple as adding a modulating function where there was none can be enough to knock out the exception, it depends. Hence the code requirements, and the pertaining manufacturers' instructions envoking ANSI standards, including fuel codes so designated, which may or may not be the local "law", and when not directly, have been incorporated by the manufacturer's instructions in addition to the standards, and therefore a part of the local code/laws applicable.

This topic keeps getting made complex when in actuality it is quite simple:
-A chimney or vent must be suitable for the class of service-period.

-It is constantly incumbent upon the chimney or vent to remain suitable for a class of service once installed, even if "unchanged" for 30 years.

-Changes to a structure can and do change the suitability of chimneys and vents for intended applications

-you can theoretically construct a masonry chimney perfectly to the code (though I've never seen one in the wild. Maybe on Animal Planet they'll do an series on documenting their existence). However, if the conditions of use or performance of the appliance are such that there is venting failure meaning significant flue gas spillage or operational problems such as improper combustion, then it is still a problem and must be corrected.

-Appliances cannot read code books and are under no legal obligation to perform in any specified manner other than the laws of physics, which cannot be repealed.

-The use of combustion appliances results in wear and tear on venting systems even under optimal conditions.

-You have sufficient support in the codes, standards and appliance IOM instructions to call out virtually any masonry chimney for a level II inspection at any time.

-Instead of looking for reasons to dismiss calling out a masonry chimney you should be struggling to find a reason NOT to call for a level II, relining and repairs. I'm still waiting to find a single chimney I am not able to find anything wrong with. Moreover, for professional inspectors who have been properly trained and certified, they, too will not be able to report a single "perfect" chimney. It is not a question of if something is wrong but what. From there, you can refer back to the ANSI stds. for safety alerts in your hazard communication with your clients: note; caution; warning; danger with their attending escalation in probability and nature of damage or injury.

HTH