How will being dirty affect the outdoor coil?

expert EXPERT April 26, 2007

The outdoor coil sees unfiltered air pass through it when the system is working. Many modern systems draw air in through the sides and discharge through the top. Other intake and discharge arrangements are possible.

It's very common for some or all of the coil to be matted over with dirt and debris. The fan pulls relatively dirty air through the coil and dirt will accumulate on the upstream side. This is typically visible looking at the coil from outside the cabinet. Grass clippings discharged by lawn mowers can clog a condenser coil quickly. Leaves and wind-blown debris can also get stuck on the coil.

Restriction of air flow through the coil leads to poor heat transfer between the coil and the outdoor air. This means the refrigerant leaving the condenser coil will be warmer than it should be. This means that less heat can be removed from the system. Comfort will suffer and energy costs will be high. Over the long term, compressor damage may result.

The condenser coil should be inspected at least from the outside of the condenser cabinet. Use a light to ensure that there is free air passage through the coils. Where there is dirt on the coils, cleaning should be recommended as regular maintenance.