HVAC SOP Example

Gas Furnace Changeout — 96% AFUE

Complete furnace replacement with PVC venting through side wall, new thermostat, and combustion analysis.

1. Shut down & make safe existing unitTurn off gas supply at the unit shut-off valve. Confirm gas is off with combustible gas detector — do not proceed if any reading is detected. Switch off electrical disconnect and tag out breaker at panel. Set thermostat to OFF. Allow 30 minutes for heat exchanger to cool before proceeding. Document existing wiring with photos before any disconnection.
2. Disconnect & remove old furnaceDisconnect gas line at union — immediately cap the building stub with an approved gas cap. Disconnect flue vent and cap the old penetration through the wall or chimney temporarily. Label and photograph all wiring terminals before disconnecting — take a second photo of any thermostat wiring at the stat. Disconnect supply and return air connections. Dolly old unit out and haul off site per local appliance disposal requirements.
3. Rough-in prep & gas line verificationInspect the existing gas supply line — verify line size meets new unit's BTU input requirements (80,000 BTU typically requires minimum 1/2" line). Confirm inlet pressure at the shutoff valve is within specified range (typically 7" WC for natural gas). Inspect supply and return air connections for leaks, damage, or disconnected duct sections. Clean installation area. Lay cardboard or drop cloth to protect flooring during installation.
4. Set new unit & route PVC ventingPosition new furnace on level pad — verify level in both axes with bubble level. Secure unit to pad per manufacturer requirements. Route 2-pipe PVC concentric vent kit through side wall — maintain proper slope (1/4" per foot toward the unit on the intake, and toward the termination on the exhaust). Maintain all clearances from windows, doors, gas meters, and electrical equipment per manufacturer spec and local code. Use approved PVC cement at all joints.
5. Gas, electrical & thermostat connectionsReconnect gas line with new dielectric union and approved pipe dope on all threaded joints (no Teflon tape on gas connections). Pressure test gas line at 1.5x working pressure — hold 15 minutes with manometer, no drop acceptable. Run and secure 24V thermostat wiring per wiring diagram — verify no crossed wires. Reconnect all electrical connections per diagram, ensuring ground is properly terminated.
6. Start-up, commissioning & documentationRestore gas supply slowly — check all new joints again with gas leak solution. Restore power and cycle thermostat to call for heat. Observe ignition sequence: induced draft, igniter glow, gas valve open, flame confirmed on sensor. Verify pressure switches make properly. Run unit through full heat cycle. Perform combustion analysis — CO must be below 100 ppm in the flue; CO₂ typically 8–10% for natural gas; flue temp within manufacturer range.
7. Airflow verification & customer handoverMeasure external static pressure across the unit with manometer. Verify blower CFM is within designed range for the ductwork system. Balance supply registers if significant imbalances are found. Confirm thermostat operation through full cycle. Photograph completed installation, all connections, and equipment label. Leave completed start-up sheet, warranty registration card, and user manual with homeowner. Explain filter maintenance schedule and thermostat operation.