Around a thousand staff are accommodated in open-plan offices at high density, 6 m2 per person, so air conditioning was essential. The high energy performance of these FCUs helped designers at Jacobs of Cardiff to develop a low-energy solution for the project.
Both buildings were stripped out to leave only the original walls and floor, and high levels of insulation were installed.
Heating and cooling are provided by over 200 Actionair EHW 230 fan-coil units located horizontally in the ceiling voids. These units are designed to operate at constant volume against pressures from 10 to 60 Pa. The volume can be set at the factory using a potentiometer which transmits a constant voltage to the fan controller. Commissioning time is greatly reduced as the only requirement is to balance airflow through each branch.
A 0 to 10 V DC output to a DDC controller offers further energy-saving benefits Until the room load is met, the FCU runs at the selected speed and duty and related noise level. The unit then throttles back by automatically reducing fan speed in response to a ‘ramp’ signal from the controller. If the room temperature varies too much from the setpoint, the controller will put the fan into auto-boost mode for quick recovery.
