Heating Equipment Inspection and Installation Review
Read the nameplate first
Every inspection starts with the nameplate: input and output ratings, gas type, vent category, clearances, and required combustion air. Vent category drives material and pressure: Category I appliances vent under negative pressure with listed metal vent, while condensing Category IV appliances use positive pressure and often PVC or CPVC. Single-wall connectors need greater clearance to combustibles than listed double-wall B-vent, and the connector must rise toward the chimney, commonly 1/4 inch per foot, with a short, direct run.
Combustion air comes from the room, from outdoors through sized openings, or from a listed direct-vent arrangement. Gas piping needs a shutoff, a sediment trap on the appliance side, and proper sizing for pressure drop and connected load. Heat exchangers must be inspected for cracks, corrosion, and flue-gas recirculation; safeties such as flame sensors, rollout switches, limit switches, and pressure switches must be functional. Hydronic systems add expansion tanks, relief valves, low-water cutoffs, circulators, and air elimination.
Traps
- Reducing clearances or substituting materials without manufacturer approval.
- Using PVC on a Category I appliance or sharing a connector improperly.
- Installing a sediment trap in the wrong orientation or omitting a drip leg.
- Treating a code minimum as a substitute for the installation manual.
Worked example
A furnace rated for a 40–70°F temperature rise is running 85°F rise; that is an airflow problem, not a gas-pressure problem. Check the filter, blower speed, and duct static pressure before adjusting gas input. Rule of thumb: correct airflow to the nameplate rise rather than masking it with a lower manifold pressure.