Plans, Specifications, Documentation, and Site Review
Plans, specifications, and site review turn Code requirements into verifiable work. Permit drawings should show the HVAC system layout, equipment schedule, capacities, duct sizes and routing, ventilation and exhaust equipment, combustion-air provisions, venting, clearances, controls, and fire-protection details. Load calculations and duct design should be available even if not all are drawn on the permit set. Specifications should identify the referenced standards and the manufacturer's instructions that govern installation.
Site review is where many failures are caught. Before concealment, verify duct sealing, insulation, supports, firestopping, fire dampers, vent slopes, combustion-air openings, and equipment clearances. After start-up, verify airflow, temperature rise, refrigerant charge where applicable, and controls. Record deviations and obtain approval for changes. Good documentation includes inspection requests, site instructions, photos of concealed work, and commissioning records.
Traps: submitting a drawing marked 'HVAC by others' with no capacities or clearances; making field changes without a revision; covering ducts before the rough-in inspection; and failing to show how combustion air enters the room.
Worked example: an inspector finds a furnace vent passing through a wall with a clearance smaller than the listed clearance. The fix is not to add a random shield; use the listed clearance or an approved, listed method, revise the drawing if the layout changes, and have the corrected work inspected. A useful rule of thumb is: if it will be hidden, it must be shown, checked, and recorded before concealment.