Seasonal HVAC Maintenance

Regular maintenance stops small problems from becoming no-cool or no-heat emergencies. A good visit is not a quick filter change. It is an ordered set of checks, each with a number you can write down. Those records let the next technician see what has changed. This guide gives a standard order for cooling and heating visits. Follow the manufacturer's service schedule when it says something different.

What You Will Be Able to Do

• Carry out a cooling-season visit in a logical order.
• Carry out a heating-season visit on a gas furnace in order.
• Decide which readings to record.
• Recognize findings that mean you should stop and call a qualified technician.

Getting Ready

1. Talk with the customer. Ask about noises, odors, comfort problems and any CO alarm events.
2. Read the data plates, and note model, serial number and refrigerant.
3. Pull the last service record if there is one.
4. Set up floor protection and tools.

Warning: Turn off and lock out the power before you open panels or put your hands near fans or belts. Verify zero volts with a meter, and discharge capacitors before you touch them.

Cooling-Season Visit

Outdoor unit

1. Lock out the power and verify it is off.
2. Clear leaves and debris from around the unit. Keep the recommended clearance.
3. Clean the condenser coil with water at low pressure from the inside out, using coil cleaner if needed. High-pressure water bends fins.
4. Straighten bent fins with a fin comb.
5. Check the contactor for pitting and burn marks.
6. Test the capacitor against its rating.
7. Check electrical connections for looseness, heat damage and bad insulation.
8. Inspect the line set insulation.

Indoor unit

1. Replace or clean the filter.
2. Inspect the evaporator coil. Clean it if it is dirty and accessible.
3. Clean the drain pan and drain line, and test the float switch if there is one.
4. Check the blower wheel for dirt.
5. Measure static pressure.

Running checks

1. Restore power and start the system. Let it run at least 15 minutes.
2. Measure compressor and blower amps, and compare them with the nameplate.
3. Measure temperature split.
4. Trained, EPA-certified technicians can check superheat and subcooling. Connect gauges only if the readings point to a problem or the visit calls for it. Each connection can lose a little refrigerant.

Do not add refrigerant unless measurements prove a low charge, and find the leak if they do.

Heating-Season Visit on a Gas Furnace

Gas furnace work is for trained, qualified technicians.

1. Replace or clean the filter.
2. Inspect the vent and flue for rust, gaps, proper slope and blockages.
3. Inspect the burners for dirt and rust, and vacuum the burner compartment.
4. Inspect the heat exchanger with a strong light and a mirror or camera.
5. Clean the flame sensor with a light abrasive pad or fine steel wool if its signal is low.
6. Check the ignitor for cracks, without touching the element.
7. Inspect the pressure switch tubing, and clear any condensate.
8. On a condensing furnace, clean the condensate trap and test the drain.
9. Test the gas lines near the unit for leaks with a suitable detector or a leak solution.
10. Measure gas pressure.
11. Run a combustion test, and record oxygen, air-free CO and stack temperature.
12. Measure temperature rise, and compare it with the rating plate.
13. Check that CO alarms in the home are present and working.

Heat Pump Winter Checks

Add these to a heat pump's visit:

1. Clear snow and ice from around the outdoor unit.
2. Check the defrost board and sensors. Force a defrost if the manual allows, and watch the sequence.
3. Check backup heat amps.
4. Confirm the thermostat's O/B setting and emergency heat setting.

What to Record

When to Stop

Do not leave equipment running if you find any of these:

• A crack or hole in a heat exchanger.
• High CO in the flue, or any CO in the living space above a safe level.
• A strong gas smell or a leak.
• Flame rollout.
• A blocked or disconnected vent.
• A burned wire or a melted connection.

Follow your company's process. Shut the unit off, tag it and tell the customer clearly and in writing why it is off.

Common Mistakes

Check Your Understanding

A coil is dirty and a technician picks up a pressure washer. What is the problem? High-pressure water bends fins. Use low pressure from the inside out.

The capacitor reads inside its tolerance, but it is near the bottom and the last visit read much higher. What should you do? Record it and let the customer know. Replacing a weak capacitor now can prevent a failure.

Combustion testing shows high CO. Do you finish the tune-up and leave? No. Find the cause, and shut the unit down if it is not safe.

A customer wants their system "topped off" during a spring visit, and it has never been checked for a leak. What should you do? Measure first. If the charge is low, there is a leak that needs to be found.

Key Takeaways

• Follow a fixed order so you do not skip anything.
• Lock out the power and verify it before you open a panel.
• Record numbers, not just "OK."
• Only add refrigerant after measurements prove the system is low, and look for the leak.
• Do not leave a furnace running if you find a safety hazard.