Factors for Comparison of Centralised Systems vs. Direct Heat Recovery Units
Centralised Systems require extensive ductwork / dampers, and the fan power to keep all building air in circulation is considerable. AirMaster air handling units with heat recovery have virtually no ductwork, so that specific fan power is kept low. EC (electronic commutation) drive motors also help to reduce power consumption.
The commissioning of centralised mechanical ventilation systems requires extensive balancing of dampers throughout the distribution ductwork, which is labour intensive. AirMaster direct ventilation units have no such requirement.
Duct penetrations between fire containment areas of a centralised system require rapid occlusion measures at each containment boundary. Heat Recovery Ventilation units do not face this issue.
In operation, centralised systems are usually unable to reduce flow to any room left unoccupied, unless it is provided with sophisticated actuated dampers. In practice, the likely scenario is that ventilation will continue to those spaces without any specific need, which wastes energy. Heat recovery ventilation units which are provided with either PIR or CO₂ sensors will shut down or drop to base load according to room usage.
For very large spaces, (e.g. conference halls, cinemas etc) centralised systems will remain the preferred choice by the building services designer. For the smaller and even medium sized projects, direct heat recovery ventilation can be expected to become increasingly important in the search for ventilation solutions which are energy efficient, compact and simple to operate.