Quick answer: Yes, in many cases. Shasta Vent All-Fuel HT is listed to UL 103 HT for natural-draft stoves, fireplaces, furnaces and boilers burning wood, coal, oil or gas that call for a UL 103 or UL 103 HT chimney. Your furnace or boiler's installation manual has the final word. It sets the required chimney type, diameter and height, and the chimney must match it.
Check your appliance manual first
Before you order anything, find these four things in the furnace or boiler manual:
- Chimney type. Look for wording like "UL 103 HT," "factory-built chimney," "Class A" or "all-fuel chimney."
- Flue diameter. Never use a chimney with a smaller inside diameter than the appliance outlet unless the manufacturer specifically allows it.
- Draft type. Shasta Vent All-Fuel HT is for natural-draft appliances.
- Minimum chimney height and any limits on offsets or horizontal runs.
If the manual calls for a UL 103 HT chimney in 6" or 8", Shasta Vent is built for that job.
Which fuels and appliances are covered
| Appliance | Shasta Vent All-Fuel HT |
|---|---|
| Wood furnace or wood boiler (natural draft) | Yes, when the appliance calls for a UL 103 or UL 103 HT chimney |
| Coal furnace or stove | Yes. Burn low-sulfur coal (see maintenance below). |
| Oil furnace or boiler (natural draft) | Yes, when the appliance calls for this chimney type |
| Gas appliance that requires a UL 103 chimney | Yes. Follow the appliance's venting instructions. |
| Pellet stove | Not a listed application. See the Pellet Stove Venting Guide. |
| Appliance needing a flue smaller than 6" or larger than 8" | Not available. Shasta Vent makes 6" and 8" only. |
For more on the rating, see What Is All-Fuel Chimney Pipe? UL 103 HT Explained.
6" or 8" for a furnace?
Use the diameter in the appliance manual. Many larger furnaces and boilers call for 8". Shop 6" and 8" Class A chimney pipe, or start with a complete kit:
For help choosing, see 6 Inch vs 8 Inch Chimney Pipe.
Common furnace and boiler chimney routes
- Out through the wall and up the outside. A wall thimble passes through the wall above grade, a tee with cleanout cap turns the chimney upward, and a tee support carries the weight. Use wall brackets at least every 10 ft. See Planning a Through-the-Wall Installation.
- Straight up through the house. A ceiling support box carries the chimney above the appliance. Add a firestop radiation shield at each additional floor and an attic insulation shield in the attic. Where the chimney passes through closets, storage areas or rooms where people could touch it, enclose it.
- Exterior runs in cold climates. An exterior chimney inside a chase enclosure stays warmer, drafts better and builds up less creosote and condensation. See the Chimney Chase Guide.
Rules that still apply
- 2" air space to combustibles around the chimney. The appliance and its connector pipe have their own clearances, set in the appliance manual.
- The 3-2-10 rule: at least 3 ft above the roof penetration, and 2 ft higher than anything within 10 ft. See the 3-2-10 rule.
- Offsets: 15° or 30° elbows only, with a maximum of four elbows, and each offset supported by an elbow support bracket. See How Many Elbows Can a Chimney Have?
- Tall chimneys: the ceiling support box or a tee support each carry up to 50 ft of chimney. Add another tee support for taller runs.
- Above the roof: brace the chimney if it stands more than 5 ft above the roof, using an extended roof bracket.
- One chimney, one appliance unless your appliance manual and local code clearly allow otherwise. Ask your inspector before connecting more than one appliance.
Maintenance by fuel
- Wood: check for creosote at least every 2 months during the heating season, and have the chimney professionally inspected and cleaned at least once a year. See How to Clean Class A Chimney Pipe.
- Coal: use low-sulfur coal (1% sulfur or less, such as anthracite), because sulfur is corrosive to metal chimneys. Have the chimney professionally cleaned within 48 hours of the last burn of the season so residue doesn't sit all summer.
- Oil: an oil appliance that isn't burning efficiently can leave soot and dye residue that may stain the chimney or roof. Keep the burner serviced.
- All fuels: check the cap's spark arrestor screen every 2–4 weeks in season, and never use chemical chimney cleaners on stainless pipe.
Frequently asked questions
Can I use Class A chimney pipe for an outdoor wood boiler?
Many outdoor boilers come with their own stack. If yours calls for a separate UL 103 HT chimney in 6" or 8", Shasta Vent can work. Follow the boiler manufacturer's venting instructions.
Is a furnace chimney different from a wood stove chimney?
The chimney system is the same. The difference is that the furnace or boiler manual sets the diameter, height and connection requirements, so start there.
Can I replace an old furnace chimney with Shasta Vent?
If the old chimney is a factory-built metal chimney, replace the whole run with one brand. Listed systems can't be mixed. See Repair or Replace Chimney Pipe? If you're venting into an existing masonry chimney, see Do You Need a Chimney Liner?
Does a wood furnace chimney need a cleanout?
In a through-the-wall install, the tee's cleanout cap is the access point for inspection and cleaning. See Chimney Tees and Cleanouts.
Venting a furnace or boiler? Shop Class A chimney pipe and complete kits, or use our chimney planning guide.
Disclaimer: Shasta Vent blog articles share general information and common practices in the chimney and hearth industry. They are not installation instructions for your specific project, and they don't replace professional advice. Building codes, appliance requirements and site conditions vary. Before you install, modify or repair a chimney, follow your appliance manufacturer's instructions and the installation instructions that come with your chimney, check with your local building department, and consult a qualified professional such as a CSIA-certified chimney sweep, NFI-certified specialist or licensed installer.
