Furnace Flue, Boiler Flue & Hot Water Heater Flue Sizing
How to Use Category I Appliance Flue Chart
- Measure the length of the chimney flue
- Determine the total BTU output of the appliance(s) that is being vented
- Determine which type output the appliance(s) are venting (natural draft or fan assisted draft)
- Use the above chart to find the proper size chimney liner.
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- Flexi-liner systems are UL/ULC Listed for relining existing masonry or factory built chimneys and vents serving Category 1 natural gas or propane fired appliances.
- Venting gas fired appliances into masonry chimneys is prohibited unless a “Listed” liner (i.e. Flexi-Liner) or a tile liner conforming to CODE is utilized. Oversized, misaligned and/or cracked tiles DO NOT constitute a “code” liner.
- The air space around an installed Flexi-Liner System must not be used to vent other appliances.
- Insulating of Flexi-Liner Systems is a benefit to the installation but not always essential to effective operation of this venting system. Consult the Flexi-Sleeve installation instructions for insulation guidelines.
- A Flexi0Liner System venting more than one appliance shall not be smaller in diameter than the outlet of the largest appliance being serviced.
- The Flexi-Liner System may be smaller in diameter than the outlet of the appliance being served provided:
- The vent height is at least 10 feet
- The liner size is not more than one size smaller
- The “FAN MAX” is reduced by 10% if the appliance is “fan assisted”
- The outlet is larger than 4” if the appliance is natural draft
- If the vent system contains more than two 90º elbows, the maximum capacity shall be reduced by 10% for each additional 90º elbow or equivalent offset(s).