High Static Fan Coil Unit: When You Need Extra Duct Length
Standard ductable FCUs are built for short, simple duct runs. Once a design needs longer ductwork, more diffusers, or ducted return air paths, the fan needs to push air against more resistance — that’s what a high static Fan Coil Unit is built for. Jaideo Automation supplies the High Static Fan Coil Unit.
What Is Static Pressure, and Why Does It Matter?
Static pressure is the resistance air encounters as it moves through ductwork, grilles, filters, and diffusers. A standard low or medium static FCU is designed for short, direct duct runs. As duct length increases, or more diffusers and turns are added, resistance builds up — and a fan that isn’t rated for that resistance will deliver less airflow than the design requires, undercooling the space.
What Makes a High Static FCU Different
- A higher-rated fan and motor capable of pushing air against greater duct resistance
- Maintains design airflow across longer duct runs than a standard static FCU
- Often paired with ducted return air paths as well as ducted supply, adding further resistance the fan must overcome
When You Need a High Static FCU
- Long duct runs between the FCU and supply diffusers
- Multiple diffusers served from a single FCU
- Ducted return air, rather than a simple open return grille
- Large open-plan spaces where air needs to travel further from the unit
When Standard Static Is Enough
For short duct runs with one or two nearby diffusers — the typical case for a single room served by a ductable ceiling concealed FCU — standard low or medium static pressure is usually sufficient, and costs less.
Getting This Right at Design Stage
Static pressure requirements should be calculated during ductwork design, not assumed. Specifying too low a static rating results in underperforming air distribution once ducts are installed; specifying too high wastes fan energy and adds unnecessary noise. Jaideo Automation can help match static pressure requirements to your duct design. For the format comparison, see Ceiling Exposed vs Ductable FCU and the standard Ductable Ceiling Concealed FCU; to size airflow first, use the FCU Sizing Guide. Where the air handling side is larger than an FCU can serve, see the Standard Air Handling Unit.
Frequently Asked Questions
What is a high static fan coil unit?
A high static fan coil unit uses a higher-rated fan and motor to maintain design airflow across longer duct runs, more diffusers, or ducted return air paths than a standard FCU can handle.
When do I need a high static FCU instead of a standard one?
A high static FCU is needed when duct runs are long, multiple diffusers are served from one unit, or ducted return air adds resistance beyond what a standard static FCU is rated for.
What happens if static pressure is undersized for the ductwork?
If static pressure is undersized, the FCU delivers less airflow than the design requires once resistance builds up through the ductwork, resulting in undercooled spaces.