Collection: Polar Air Ducted Fan Coils

The PDWA is available in 3R, 3R+1, 3R+2, 4R, 4R+2, and 6R coil configurations. Increasing the number of rows expands coil surface area, which improves heat transfer and allows the unit to achieve higher capacities in the same footprint. More rows also enhance latent performance, providing better humidity control in demanding climates. For projects using low-temperature heat sources such as heat pumps or solar thermal systems, additional coil rows improve efficiency by increasing the contact time between air and water, ensuring effective output at lower water temperatures.

ESP stands for External Static Pressure. A ducted ESP fan coil is designed to handle specific levels of resistance in the ductwork, ensuring efficient airflow and optimal performance. For example, the PDWA Medium ESP Ducted is designed explicitly for medium cooling capacities at lower external static pressures. It makes the PDWA suitable for installations with short runs and limited bends, where airflow resistance is minimal.

External static pressure must be matched to the resistance created by ductwork, grilles, filters, and fittings. If ESP is oversized (for example, using a high ESP unit on a short, straight duct run), the fan will push more air than required. This can cause excess noise, drafts at supply outlets, and wasted fan energy. In some cases, it may also lead to premature wear of system components. If ESP is undersized (for example, choosing a low ESP unit for a layout with long ducts and multiple bends), the fan may not overcome the resistance in the system. Airflow will drop, rooms at the end of the duct may not receive enough conditioned air, and overall cooling or heating performance will suffer. The result is uneven comfort and inefficient operation. Correctly selecting ESP ensures the fan operates within its designed range, balancing airflow delivery, noise, and energy use.

Yes, medium ESP fan coils can be integrated into variable airflow or zoning systems if the total duct resistance remains within their operating range, typically 50–130 Pa (0.2–0.5 in.wg). These units are often specified in projects where one fan coil serves several rooms, with zone dampers used to balance distribution. In real-world conditions, zoning adds pressure as dampers close and open. Medium ESP provides enough fan power to handle moderate changes without the energy consumption or noise of high ESP units. However, in systems with extensive zoning, complex ductwork, or high resistance from filters and accessories, a high ESP fan coil like the Polar Air PDWC may be more appropriate.

Yes. Medium ESP fan coils are commonly used with low-temperature heat sources, including heat pumps, district energy systems, and solar thermal collectors. Unlike conventional boiler systems, which may supply hot water at 70–80°C, low-temperature sources often operate at 35–55°C. To maintain output at these lower temperatures, fan coils often require additional coil rows or larger surface areas. More rows increase air-to-water contact time, improving heat transfer and allowing the unit to provide adequate heating and cooling even when supply water temperatures are lower. This makes medium ESP fan coils well-suited to modern energy-efficient systems, where lower supply temperatures reduce energy consumption and align with building decarbonisation goals.

Polar Air are a global leader in providing high-performance hydronic fan coil solutions with decades of HVAC expertise. Headquartered in Murcia, Spain and with a presence in North America, Polar Air are poised to support clients globally with their large range (over 1,800 configurations) of fan coil products that are sold in 28 countries worldwide.