Flue Liner Types & Installation Flashcards

What is the minimum clearance typically required between a UL-listed metal liner and combustible framing in a masonry chimney chase?

Answer: 0 inches — no clearance required within a masonry chimney

When a listed flexible liner is installed inside a masonry chimney, no additional clearance from the masonry is required because the masonry itself provides the separation.

Which type of mortar is recommended for repointing terra cotta flue tile joints?

Answer: Refractory mortar rated for high-temperature use

Refractory mortar is designed to withstand the high temperatures and thermal cycling inside a flue, unlike standard Portland cement mortars which can crack and fail.

When installing an aluminum liner, which appliance type is it approved for use with?

Answer: Category I gas appliances only

Aluminum liners are approved only for Category I (non-positive pressure, flue gas temperature above dew point) gas appliances due to their lower heat and corrosion resistance.

What is the function of an insulation blanket or poured insulation fill around a flexible stainless liner?

Answer: It raises flue gas temperature to improve draft and reduce condensation

Insulating the liner keeps flue gases hotter longer, improving draft and reducing the condensation that leads to creosote buildup and liner deterioration.

A chimney sweep discovers that a liner section junction has an offset of more than 30 degrees inside an existing masonry chimney. What is the correct course of action?

Answer: Install a flexible liner to navigate the offset

Flexible liners can navigate offsets that rigid sections cannot, making them the appropriate solution when significant angular changes exist in the flue path.

What does UL 1777 specifically cover in relation to chimney liners?

Answer: Chimney liner systems for gas and oil appliances

UL 1777 is the Standard for Chimney Liners, covering testing and performance requirements for liner systems used with gas and oil appliances.

Which condition would require a chimney sweep to recommend full liner replacement rather than repair of a clay tile liner?

Answer: Multiple tiles with open separations allowing flue gas bypass

Open separations between tiles allow combustion gases and heat to bypass the liner and contact combustible materials, creating a fire and CO hazard requiring full replacement.