Does Coil Coating Affect EER and COP Ratings?
Key facts
| Factor | Effect on efficiency |
|---|---|
| Thin film (5–15 μm) | Small; PG-S1 tested at up to 1.8% heat-transfer loss |
| Thick film (20–40 μm and above) | Larger; test on a comparable coil |
| Bridged fins | Lower airflow and capacity; the largest effect |
| Uncoated coil corroding in service | Efficiency falls as fins corrode and foul |
Where efficiency is lost
EER and COP compare cooling or heating output with power input. A coating can lower output by adding thermal resistance and raise power by increasing fan pressure drop. With a thin film both effects are small.
Ratings and coated units
Efficiency ratings are measured under standard conditions on the unit the manufacturer submits. A coating added afterwards is not part of that test. Some manufacturers publish derating guidance for coated coils; ask before relying on rated values in energy calculations.
Over the life of the unit
An uncoated coil in a corrosive site loses capacity as fins corrode, loosen and foul. Over several years that loss usually exceeds the initial effect of a thin coating.
What this means for your project
Specify a thin-film system and a film range, ask for heat-transfer data, and check the manufacturer’s position on coated units if rated efficiency is contractual.
