Ductwork Seal Classes

Overview

Engineering reference data for Ductwork Seal Classes in HVAC systems.

Key Formulas

Sensible Heat

$Q = \dot{m} c_p \Delta T$

Heat causing temperature change.

Latent Heat

$Q = \dot{m} h_{fg} \Delta\omega$

Heat causing moisture change.

COP (Cooling)

$COP = Q_c / W$

Coefficient of performance.

Variables

Symbol	Description	Unit
$Q$	Heat transfer	W
$\dot{m}$	Mass flow rate	kg/s
$c_p$	Specific heat of air	J/(kg·K)
$\Delta T$	Temperature difference	K

Seal Class Definitions

Duct sealing requirements are defined by ASHRAE and SMACNA standards, which classify systems into three primary seal classes. These classifications dictate which joints and seams must be sealed and set maximum allowable system leakage rates.

Practical Implications

The selection of a seal class is a direct trade-off between installation cost and long-term energy efficiency. Seal Class A represents the highest integrity, suitable for critical applications or high-pressure systems, while Seal Class C is a minimum standard for many general applications. Unsealed systems experience significant energy loss and should be avoided in conditioned spaces.

References

• Original Source