HVAC Preventive Maintenance Checklist: A Complete Guide
Below you will find our definitive checklist for preventative HVAC maintenance.
1. Schedule Overview
Twice-Yearly Service
• Early spring (before the cooling season) and early fall (before the heating season) cover all major components before peak use.
Monthly and Quarterly Checks
• Monthly: Inspect air filters.
• Quarterly: Visually inspect thermostat and outdoor unit.
2. Air Filter Inspection & Replacement
- Locate and Identify
- Filter slot in the furnace/air handler or return grille.
- Note MERV rating (we recommend MERV 8–11 for homes).
- Inspect
- Remove the filter and hold it to light. If the light does not pass through most of it, replace or clean it.
- Replace or Clean
- Disposable Filters: Install a filter of the same size and rating.
- Washable/Electrostatic Filters: Rinse under lukewarm water and let dry thoroughly before reinstalling.
- Reinstall
- Ensure the airflow arrow points toward the blower.
- Mark the date and plan the next check-in in 30–90 days (depending on the pets, smoking, or allergies).
3. Thermostat Check & Calibration
- Determine Thermostat Type
- Mechanical (bimetallic/mercury), digital non-programmable, or programmable/smart.
- Verify Accuracy
- Place a reliable thermometer next to the thermostat sensor.
- If readings differ by more than ±1 °F, adjust the thermostat calibration according to the manufacturer's instructions.
- Test Operation
- Cycle heating and cooling: listen for the outdoor fan when switching to cooling and for furnace ignition when switching to heat.
- Replace batteries annually to prevent erratic behavior.
4. Ductwork Inspection & Sealing
- Inspect Visible Runs
- Check-in basements, attics, or crawlspaces for loose seams, tears, or disconnected sections.
- Seal Leaks
- Mastic Sealant: Brush on gaps and seams (remains flexible).
- UL-181 Foil Tape: Use only on joints and seams—press firmly to adhere.
- Check Insulation
- Ensure wrap-style (fiberglass) insulation is intact (R-6 or R-8 in unconditioned spaces).
- Repair torn insulation with mastic or foil tape.
- Balance Airflow
- Use a smoke pencil or anemometer at each register to confirm even airflow. Adjust dampers as needed.
5. Coil Cleaning (Condenser & Evaporator)
- Outdoor Condenser Coil
- Power Off: Shut off at the disconnect or breaker.
- Remove Debris: Clear leaves, grass, and ice; maintain a clearance of at least 2 feet.
- Straighten Fins: Use a fin comb to correct bent fins.
- Clean: Apply a non-acidic coil cleaner, wait 5–10 minutes, then rinse gently from top to bottom.
- Indoor Evaporator Coil
- Power Off: Turn off the air handler or furnace.
- Inspect Drain Pan and Line: Clear debris; flush the condensate line with a 1:1 bleach-water solution.
- Spray No-Rinse Coil Cleaner: Apply evenly; cleaner drains through the pan. For heavy buildup, brush the fins first.
6. Refrigerant Level & Leak Inspection
- Measure Pressures
- Connect gauges to suction (low-side) and liquid (high-side) ports. Compare to the manufacturer's specifications for your refrigerant (e.g., R-410A).
- Check Subcooling & Superheat
- Subcooling: Measure liquid line temperature 12 in. from the service port, subtract from saturation temperature. Aim for 8–12 °F.
- Superheat: Measure the suction line temperature near the evaporator and subtract it from the saturation temperature. Aim for 8–15 °F.
- Locate Leaks
- Use an electronic leak detector along refrigerant lines and fittings.
- Apply a soap-bubble solution to suspect spots and watch for bubbles.
- Repair & Recharge
- Fix leaks (braze or replace components), evacuate to at least 500 microns, and then recharge with the correct amount of refrigerant.
7. Electrical Connections & Safety Controls
- Power Off
- Shut off power at the outdoor unit disconnect and the air handler/furnace breaker.
- Tighten Connections
- Check terminal screws and lugs on contactors, motors, transformers, and control boards. Torque control wiring to 20–35 in-lb and line-voltage terminals to 90–95 in-lb.
- Inspect Capacitors & Contactors
- Capacitors: Look for bulging or leaking; test capacitance—replace if off by more than ±6 µF.
- Contactors: Check for pitting or carbon buildup; verify air gap (0.022–0.026 in. per contact pair). Replace if worn.
- Test Safety Switches
- High-Pressure Switch: Briefly blocks condenser airflow—confirm it opens and shuts off the compressor.
- Low-Pressure Switch: Slightly pinch the suction line—verify it trips.
- Flame Rollout Switch (Gas Furnace): Lift the flame sensor—confirm it shuts off the gas valve.
- Verify Control Voltage
- Measure 24 VAC between R and C on the transformer; it should read 24 VAC ± 10 %. Lower voltage indicates a problem.
8. Supplemental Checks
- Blower Assembly
• Clean the blower wheel and inspect the belts for wear or improper tension.
- Flue & Venting (Gas Furnaces)
• Inspect the flue pipe for corrosion and ensure it has a proper slope (¼ inch per foot). Use a smoke pencil to confirm the draft.
- Cabinet Seals
• Ensure access panels and seams seal tightly to prevent air leaks.
- Condensate Drain
• Confirm that there is no standing water in the primary pan; check the secondary pan and test the overflow switch. Clear slow drains with compressed air or a wet/dry vacuum.
- System Cycling & Noise
• Run a complete cycle; listen for unusual sounds (humming, rattling, grinding) indicating loose parts or bearing wear.
9. Wasatch Front Seasonal Notes
- Spring (Cooling Prep)
• Remove winter debris and ice from the outdoor unit.
• Check suction-line insulation for UV damage.
- Summer (Peak Cooling)
• Inspect condensate lines monthly (high humidity).
• Set the thermostat to approximately 78 °F when the space is occupied to reduce energy consumption.
- Fall (Heating Prep)
• Switch to heat; check burner flame (steady blue).
• Test heat pump defrost cycle—ensure reversing valve shifts properly.
- Winter (Peak Heating)
• Inspect the heat exchanger for cracks or rust (carbon-monoxide risk).
• Test electric heat strips on heat pumps or electric furnaces (listen for clicks when engaging).
10. Documentation & Record Keeping
- Log All Maintenance
Record dates, tasks completed, filter size/type, refrigerant pressures, thermostat offsets, and electrical measurements. Document any repairs.
- Provide a Homeowner/Occupant Checklist
Offer a simple sheet for monthly filter checks, battery replacements, and visual inspections. Highlight warning signs such as unusual noises, temperature swings, or water leaks.
By completing these tasks, homeowners and landlords on the Wasatch Front can keep HVAC systems running reliably and efficiently. Whenever a task exceeds your comfort level, or you discover an issue, contact Salt City Plumbing, Heating & Air for professional service.
Stay comfortable year-round—schedule expert HVAC maintenance with Salt City Plumbing, Heating & Air.