TABLE OF CONTENTS The control and optimization of temperatures in the occupied zone and the amount of thermal stratification (during cooling operation) is crucial to system design and sizing, energy-efficient operation, and comfort performance of UFAD and TAC systems. This section presents and discusses (1) recommended control strategies for effective system operation, (2) incorporation of individual control, particularly with TAC systems, to allow occupants to fine-tune their local environment, and (3) operations and maintenance (O & M) issues that differ from issues in conventional system operation. The discussion does not cover all possible control scenarios but is intended to introduce some of the key control strategies that have been frequently used in previously completed projects and explain how they differ from those typically used in overhead mixing-type systems.
This section presents control strategies that have been developed and applied in underfloor air distribution (UFAD) installations, the large majority of which have been pressurized plenum designs.
As described in Chapter 1, since air is supplied directly into the occupied zone near floor level, minimum supply outlet temperatures should be maintained in the range of 61 65 F (16 18 C) to avoid over-cooling nearby occupants. For TAC supply outlets located closer to the occupants and used to provide velocity cooling, even warmer minimum supply air temperatures may be advisable.
A common control method for interior zones maintains constant static pressure in the underfloor plenum to ensure constant volume airflow from each diffuser (similar model...
