Venting below an overhang (sidewall snorkel)

What is going on

Sidewall snorkel venting under an overhang on an NTI TRX is the one that gets installers in trouble. The exhaust has to drop below the overhang by a set amount, and the terminations need proper spacing and snow clearance, or the boiler will recirculate exhaust or ice up. Local codes can be stricter than the manual, so check them first.

Likely causes

• Exhaust not low enough below the overhang
• Intake and exhaust terminations too close together
• Termination too close to grade or snow level
• Exhaust not extended far enough past the building

Check in this order

1. For every 1 in of overhang, place the exhaust 1 in vertically below the overhang, with 12 in minimum
2. Keep the minimum separation between exhaust and intake sidewall terminations required by local codes
3. Keep at least 12 in above the highest expected snow level or grade, whichever is higher
4. Extend the exhaust 12 to 24 in beyond the building
5. Have the installation checked against local code before commissioning

More boiler guides

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• Burner not running on a call for heat