The 'Like-for-Like' Furnace Swap
A single-family homeowner calls for a final inspection on a basement furnace changeout. The original unit was 80,000 Btu/h natural draft; the new one is a 120,000 Btu/h induced-draft Category I furnace in the same closet, and the contractor also cut in a new 14-inch return trunk. The contractor tells the inspector, 'It's a like-for-like replacement, so no permit was pulled-we just swapped the unit.' The homeowner then mentions that a handyman installed a bathroom exhaust fan last year and asks the inspector to 'sign off the whole house while you're here.' The closet door is a solid slab with no combustion air openings, and the old single-wall vent connector is still in place.
1. Was a permit required for the furnace and the new return duct? Distinguish a repair from an alteration.
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A permit was required. The administrative chapter requires a permit for the installation, alteration, replacement, or addition of mechanical equipment and systems. The exemptions are narrow-minor repairs and replacement of components that do not change the approval, listing, capacity, or characteristics of the appliance. Swapping an 80,000 Btu/h furnace for a 120,000 Btu/h unit is a 50 percent input increase; it changes combustion air demand, venting, and clearances, so it is an alteration, not a repair. The new return trunk is new ductwork and independently requires a permit. The inspector should reject the 'like-for-like' characterization, require a permit application and construction documents showing the new input, venting, and combustion air, and then inspect as new work.
2. How should the inspector handle the unpermitted bath fan the homeowner disclosed?
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The fan is existing unpermitted work and cannot be approved sight unseen. The code official has authority to require that unpermitted work be permitted and inspected, or removed, and to require exposure of concealed work to verify compliance. The inspector should document the fan (location, discharge point, duct material, termination, and whether it draws from a bathroom), issue a written correction, and require a separate permit and inspection. Signing it off as part of the furnace final would be approving work that was never inspected and would put the inspector's approval on an unknown installation.
3. Can the final inspection be approved as-is? What must be verified, and in what order?
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No. A final approval is a finding that the work complies, and several items are unresolved: the 120,000 Btu/h input requires a combustion air calculation (the solid closet door provides none), the existing single-wall connector must be checked for size, slope, and clearance, and the new return must be inspected before concealment. Proper order: approved permit and documents; rough-in inspection of duct, vent, and combustion air before concealment; then final. The inspector should fail the final with a written correction list rather than approve and revisit.