FCU Plenum Boxes — Supply & Return

Smart Ventilation Systems fabricates custom plenum boxes for fan coil units to order in galvanised steel. Choose your FCU manufacturer and model — Daikin, Samsung, Mitsubishi Electric and more — or enter the connection size from the unit drawing, and build the plenum around it in our interactive 3D configurator.

Built to your fan coil unit

  • Supply and return air — discharge plenums with spigots to diffusers, or return plenums with optional filter sections
  • Stepped or tapered body — flat step plate to keep the box short, or a gradual taper where space allows
  • Acoustic lining — 6mm or 12mm internal foam lining to cut noise breakout
  • Spigots anywhere — click any face in the 3D view to place circular spigots exactly where the drawing calls for them

Priced individually

Every plenum is custom made, so we price each one on application. Configure the box, add it to your quote and send it over — our team responds with a price, usually the same working day.

FCU plenum box FAQs

What is an FCU plenum box?

A plenum box (or plenum chamber) connects a fan coil unit to the ductwork. On the supply side it distributes air from the FCU outlet into circular spigots feeding diffusers; on the return side it collects air back to the unit, often through a filter section.

Can you make a plenum to suit my fan coil unit?

Yes — every plenum is made to order to match your unit's connection size. Pick your manufacturer and model in the configurator and we'll build the plenum around it, or enter the connection size yourself from the unit drawing.

What is the difference between a stepped and tapered plenum?

A stepped plenum changes size with a flat step plate, which keeps the box short. A tapered plenum transitions gradually, which is gentler on airflow where space allows. Both can be made with a flat top or flat bottom to suit ceiling void constraints.

Do you line plenum boxes acoustically?

Yes — we can line the inside of the box with 6mm or 12mm acoustic foam to reduce noise breakout from the fan coil unit.

How much does an FCU plenum box cost?

Plenums are custom made, so we price each one individually. Configure what you need, add it to your quote and send it over — our team will come back to you with a price, usually the same working day.

See also our FCU plenums overview and FCU ductwork packages, or send us your FCU schedule to price the full set. Call 07710 984 957 — Mon–Fri, 8am–5pm.