CCS Flue Liner Types & Installation 3 — Questions and Answers
Question 1: What is the minimum clearance typically required between a UL-listed metal liner and combustible framing in a masonry chimney chase?
- 0 inches — no clearance required within a masonry chimney (Correct answer)
- 1 inch on all sides
- 2 inches on all sides
- 6 inches on all sides
Correct 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.
Question 2: Which type of mortar is recommended for repointing terra cotta flue tile joints?
- Type S Portland cement mortar
- Refractory mortar rated for high-temperature use (Correct answer)
- Standard exterior mortar mix
- Hydraulic lime mortar only
Correct 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.
Question 3: When installing an aluminum liner, which appliance type is it approved for use with?
- Wood stoves and fireplaces
- Oil-fired appliances
- Category I gas appliances only (Correct answer)
- Pellet stoves only
Correct 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.
Question 4: What is the function of an insulation blanket or poured insulation fill around a flexible stainless liner?
- It prevents galvanic corrosion between the liner and masonry
- It raises flue gas temperature to improve draft and reduce condensation (Correct answer)
- It satisfies UL listing requirements for the liner alone
- It eliminates the need for a chimney cap
Correct 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.
Question 5: 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?
- Seal the offset with high-temp caulk and continue inspection
- Install a flexible liner to navigate the offset (Correct answer)
- Reduce the appliance firing rate to compensate
- Document the offset and re-inspect in 6 months
Correct 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.
Question 6: What does UL 1777 specifically cover in relation to chimney liners?
- Masonry fireplace construction standards
- Chimney liner systems for gas and oil appliances (Correct answer)
- Factory-built chimney system assemblies
- Solid fuel-burning appliance clearances
Correct 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.
Question 7: Which condition would require a chimney sweep to recommend full liner replacement rather than repair of a clay tile liner?
- Minor efflorescence on the exterior of the chimney
- A single hairline crack in one tile with no separation
- Multiple tiles with open separations allowing flue gas bypass (Correct answer)
- Slight color variation between adjacent tile sections
Correct 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.
CCS Flue Liner Types & Installation 3
What is the minimum clearance typically required between a UL-listed metal liner and combustible framing in a masonry chimney chase?