When your AC system isn’t working at full capacity, there are plenty of potential culprits. Two of the usual suspects are the evaporator coil and the condenser coil, but most homeowners aren’t sure which is which or what each one does. Here’s what you need to know.
Evaporator vs Condenser at a Glance
| Evaporator Coil | Condenser Coil | |
|---|---|---|
| Location | Indoor unit (in the plenum) | Outdoor unit (with the compressor) |
| Job | Extracts heat from indoor air | Releases that heat outside |
| Refrigerant state | Liquid in, gas out | Gas in, liquid out |
| Common issues | Corrosion, mold, dust buildup | Dirt and debris, rust, bent fins |
How Does an Evaporator Coil Work?
The evaporator coil lives in your indoor unit inside a box called the plenum, which is the metal chamber where air gets pulled in before it’s cooled. The coil itself is a set of copper tubes bent into U-shapes, often with thin metal fins attached so more air touches the surface.
Your AC doesn’t actually pump cold air into your house. It pulls heat out, and what’s left feels cool by comparison. The evaporator coil is filled with refrigerant, and as warm air from your home blows across the cold copper tubes, the heat from the air soaks into the refrigerant.
The refrigerant, which is now warm from carrying all that household heat, flows out through a pipe to the outdoor unit, where it can release the heat outside. That outdoor half is where the condenser takes over.
3 Common Evaporator Problems
Even with the shielding it gets indoors, the evaporator coil still hits snags that can drag down cooling performance. The usual offenders include:
- Corrosion. Copper tubes corrode as harsh chemicals in the refrigerant course through them, creating microscopic holes that breed refrigerant leaks.
- Mold, mildew, and moss. The plenum is scantily lit and damp, which makes it a breeding spot for biological hazards. Growth inside can block airflow through the evaporator unit.
- Dust buildup. Dust layers act as insulators that reduce heat absorption efficiency. Dust also piles on the coils and fins over time, despite the air blowing over them.
How Does the Condenser Coil Work?
The condenser coil does the opposite job of the evaporator. It’s part of the outdoor unit and works alongside the compressor.
By the time the refrigerant reaches the condenser, it’s a hot gas carrying all the heat it just pulled out of your home. The compressor squeezes that gas under high pressure, which is what gets it to release the heat. The outdoor fan blows that heat off the coils and out into the open air.
Once the heat is gone, the refrigerant settles back into a liquid and flows indoors through a small opening to grab another round of heat. That loop runs over and over the whole time your AC is on.
3 Common Condenser Problems
Because the condenser lives outside, it comes with a different set of problems than the evaporator. The most common condenser issues include:
- Dirt and debris. Dirt and natural debris in the outdoor unit can block the condenser coils.
- Rust and corrosion. Rust and corrosion in the pipes disrupt heat dissipation and shorten the life of the unit.
- Bent fins. Lawn debris, weed trimmers, and stray rocks can flatten fins and cut airflow over the coil.
Condenser and Evaporator Upkeep Tips
Good airflow is essential for an efficient air conditioning system. Check the fins routinely for debris or dust, and use a stiff brush or cloth to wipe them down. If the unit is clean but airflow is still weak, check for frost layers too. Ice build-up signifies an underlying problem in the tubes, such as a vent blockage causing frosting on the fins.
Is It Time to Schedule Your AC Maintenance?
Scheduling regular checkups for your air conditioning system is the best way to ensure your evaporator and condenser coils (and the rest of your unit!) continue to work hand in hand. We recommend scheduling a maintenance inspection at least once a year to improve your system’s efficiency, extend its lifespan, and prevent unexpected breakdowns.
The PlumbPRO Service Partner Plan includes annual tune-ups for your AC, furnace or boiler, and plumbing system, plus a sewer lateral check. Members also get dispatch fees waived (normally $59 per call), 5% off all services, priority scheduling, and extended warranties.
Let PlumbPRO Services Handle the Job
Your AC works hard all summer long, and it deserves a little TLC. Whether something’s already gone sideways and you’re in need of AC repair, or you just want a professional set of eyes on your system before the next heat wave, PlumbPRO Services has you covered.
Reach out today, and we’ll send one of our techs out to take a look.