Arkansas HVACR NewsMagazine September 2025

ARHVACR NewsMagazine September 2025

S tate, National, Chapter News State national Chapter News

Kirk’s Corner Exhaust Done Right:

A Guide to Proper Venting for Natural Gas Furnaces t.pierce@summitutilities.com

When it comes to installing natural gas furnaces, one of the most critical — and frequently overlooked — components is the exhaust system. Improper venting doesn't just compromise furnace efficiency; it can lead to dangerous carbon monoxide buildup, fire hazards, and costly code violations. Whether you're retrofitting an older home or installing a high-efficiency system in new construction, knowing how to size, configure, and install the exhaust properly is essential to a safe and successful job. Exhaust systems are responsible for carrying combustion byproducts — mainly carbon monoxide, nitrogen dioxide, and water vapor — safely out of the building. A well-designed and properly installed vent prevents backdrafting, corrosion, and furnace damage. In high-efficiency (condensing) units, improper venting can even trigger error codes and shutdowns. Why Exhaust Venting Matters

Understanding Furnace Types and Venting Categories

Category I (Non-Condensing, Natural Draft or Induced Draft) • Uses metal flue (Type B vent) • Relies on a draft • Sensitive to negative pressure/backdrafting Category IV (Condensing Furnaces) • Uses PVC, CPVC, or polypropylene for venting

Requires both exhaust and intake piping (sealed combustion)

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Needs a proper slope for condensate drainage

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Understanding which category the furnace falls under is step one. Always refer to the manufacturer's installation manual — model-specific venting details override general rules.

Key Considerations for Proper Exhaust Installation

1. Material Matters Use only manufacturer-approved materials. For condensing units, avoid