Learning Center
Preparing Your HVAC for Winter
A practical fall startup checklist for heat pumps, furnaces, and dual-fuel systems in NC — before the first cold snap arrives.
7 Steps Before Heating Season
Best timing: September–October. Steps 1–6 are homeowner tasks. Step 7 is professional service.
Replace the Air Filter
Start the heating season with a fresh filter — same logic as summer startup. Heating mode moves just as much air as cooling mode, and a clogged filter restricts airflow to the heat exchanger (gas furnace) or heat pump coil. Replace and set a reminder to check monthly through February.
NC winters are mild but variable. A filter that was fine in October may be significantly dirtier by January if the system ran heavily during a cold snap.
Test Heating Mode Before the First Cold Night
Switch the thermostat to HEAT and set it 5°F above current room temperature. For a heat pump, you should feel warm (not hot) air from vents — heat pumps produce 90–100°F air, compared to gas furnaces at 120–140°F. For a gas furnace or dual-fuel system, you may smell a brief burning odor as dust on the heat exchanger burns off — this is normal and should clear in 15–30 minutes.
NC cold snaps can arrive quickly in October–November. Test before the first cold night, not during it.
Verify Defrost Cycle Operation (Heat Pumps)
Heat pumps periodically enter defrost mode to melt ice from the outdoor coil. During defrost (5–15 minutes), the system reverses to cooling mode momentarily — you may see steam rising from the outdoor unit and the supplemental heat strips activate. This is completely normal. What's not normal: defrost running for more than 30 minutes, or the outdoor unit covered in thick ice that never clears.
Test Auxiliary Heat (Heat Pumps)
If your thermostat has an AUX HEAT indicator, test that it functions by setting the temperature 5–6°F above room temperature rapidly. AUX HEAT (electric resistance strips) should kick in when the heat pump alone can't keep up. It should show on the thermostat as AUX HEAT (normal) — not EM HEAT (emergency heat, bypasses the heat pump). Continuously running AUX above 40°F outdoor temp indicates a heat pump issue.
Check Insulation and Weatherstripping
Cold air infiltration around doors and windows dramatically increases heating load. Check weatherstripping on exterior doors — if you can feel a draft or see daylight, replace it. Check that attic access hatches are insulated. Ensure crawl space vents in NC homes are properly managed for winter — practices vary by construction type.
NC building codes allow crawl space approaches that vary from older construction. If your home has a vented crawl space, consult with a building professional about seasonal vent management.
Clear Outdoor Unit — But Don't Cover It
Clear leaves and debris from the outdoor unit before winter. Do NOT use a standard tarp or cover — heat pumps run in heating mode all winter and need airflow. Only use a cover specifically designed for heat pump tops (to block falling leaves/debris from above), not full covers that block all sides.
Schedule a Heating Tune-Up
September–October is the ideal time for a heating system tune-up — before peak demand and before the first real cold snap. For heat pumps: defrost cycle test, reversing valve check, refrigerant charge, electrical inspection. For gas furnaces or dual-fuel: heat exchanger inspection, burner check, igniter test, flue inspection — plus all the standard electrical and mechanical checks.
Call Before the Cold Snap If You Notice These
Gas furnace: no ignition after 2 attempts (pilot or electronic igniter not activating)
Heat pump blowing cool or room-temperature air in HEAT mode above 35°F outdoor temp
AUX HEAT running constantly on a mild (above 40°F) day
Outdoor heat pump unit in a solid block of ice that hasn't cleared in 2+ hours
Any burning smell that doesn't clear within 20–30 minutes
Gas smell near a gas furnace (evacuate, call gas company, don't reenter until cleared)
CO alarm activating while furnace is running (evacuate, call 911)
Book Your Fall Heating Tune-Up
September and October slots fill faster than homeowners expect. Don't wait for the first cold night. NC License #27258 · Serving the NC Foothills since 2003.