QIYUE FAN / CENTRIFUGAL FAN ARCHITECTURE

Housed Centrifugal Fan vs Plug or Plenum Fan

A centrifugal impeller is not the whole air-moving system. Before comparing offers, establish whether the fan includes its own housing or depends on the surrounding chamber as part of the installation.

Discuss the required architecture and package scope with the supplier before comparing configurations.

Where does the fan package end?

Conceptual diagrams of equipment and chamber boundaries, not to scale.

Plug and plenum describe an installation, not a universal replacement

ASHRAE’s fan chapter describes unhoused impellers used as industrial circulators, including heat-treatment ovens, as plug fans. It describes an unhoused wheel within a chamber with a connected inlet as a plenum arrangement. The same chapter notes that surrounding space and inlet conditions can affect performance.

Therefore, a request to “remove the casing to save space” is a system redesign question. Do not assume an existing housed fan’s curve, discharge arrangement or installation approval remains valid after changing its enclosure.

Use the pressure basis for the actual arrangement

ASHRAE identifies fan static pressure as the selection basis for the plug/plenum configurations it describes because usable outlet velocity pressure is not available in the same way as for a housed discharge. Use the rating basis specified for the proposed installation.

The static versus total pressure guide explains the terminology. Keep the curve, tested/rated installation and proposed site arrangement together during the review.

A real housing is visible; its rating is not

Compare the complete installation

For a housed package, review the casing, inlet/discharge interfaces and complete motor/drive envelope. For an unhoused proposal, identify which party designs and supplies the surrounding chamber, inlet arrangement, access and integration details.

A similar wheel diameter or motor rating does not prove interchangeable performance or mounting. Confirm the proposed assembly rather than identifying a replacement from appearance.

Three situations that deserve an early design review

• An oven circulation retrofit: distinguish chamber circulation from a separate moisture-exhaust duty. Do not treat an exhaust fan as equivalent merely because both move hot air.
• A constrained equipment enclosure: show the real space around the inlet and wheel, the access route and neighboring components. Request an arrangement-specific review rather than assuming a bare wheel solves the space problem.
• A housing-to-unhoused substitution: require a revised performance basis and integration scope. Keep safety, guarding, structural support and commissioning responsibilities explicit.

For process context, see the drying oven air-path guide. It separates circulation, exhaust and makeup roles without prescribing a particular fan architecture.

Decide from the system, not the silhouette

Compare proposals only after confirming the required duty, gas condition, pressure definition, arrangement-specific curve, mechanical envelope and integration responsibilities. Resolve missing scope before comparing price or assuming a drop-in replacement.

Start with centrifugal fan fundamentals if the component terminology is new, or send the existing arrangement and required duty for a project review.