HVAC-R system involves heat transfer. A condenser unit is a device or unit used to condense a gaseous refrigerant into a liquid state through lowering its temperature (cooling) by a rotating condenser fan.
Condenser coils are normally made of soft copper tubing with aluminum fins. Nowadays more and more condenser coils are made of aluminum tubing to reduce material cost. Both copper and aluminum have thermal conductivity that can efficiently transfer heat. To let heat transferring more efficient aluminum fins are put around coil tubing which increases the surface area of condenser coil. Condenser fan pulls air flow through fins and takes heat away from condenser coil and fins and lowers refrigerant temperature.
Cleaning the condenser coil and fins is essential to ensure an HVAC-R system works efficiently. Dirt and debris in the air flowing through fins are collected on the surfaces of coil and fins, which will block air flow and prevent heat transfer.