Abstract
This paper presents the monitoring results for the HVAC systems installed in a university building, which prove that oversizing is a real problem with existing systems. In our study, how the zones served by systems are grouped is a major cause of oversizing. This is particularly obvious when monitoring the systems serving the zones on a single facade; monitoring those in zones situated on two facades shows that additional reasons must also be considered as well. The monitoring presented in the paper is carried out on four systems, two serving zones on a single facade and two others serving zones located on two facades. Following the processing of the ensuing data, the results obtained show that the systems mostly function at between 55 and 65% of their design capacity. An analysis of these results indicates that a better design approach could reduce the total airflow rate of HVAC systems, reduce building energy consumption, and promote better systems operation.
Highlights
IntroductionHVAC (heating, ventilation and air conditioning) systems are generally designed to ensure occupants’ comfort
HVAC systems are generally designed to ensure occupants’ comfort
HVAC systems which are sized to meet design loads operate mostly at partial loads, with the fan airflow rate often being close to 50%, which, in effect means close to the minimum recommended by ASHRAE [1]
Summary
HVAC (heating, ventilation and air conditioning) systems are generally designed to ensure occupants’ comfort. The design objectives in our context include, for example: (i) ensuring appropriate system capacity to meet building loads for design operation conditions, (ii) energy efficiency to reduce annual operating costs, and (iii) minimum life cycle costs The first of these objectives always leads to system oversizing, with the two going in the opposite direction. HVAC systems which are sized to meet design loads operate mostly at partial loads, with the fan airflow rate often being close to 50%, which, in effect means close to the minimum recommended by ASHRAE [1] In these conditions, the air supply temperature must be adjusted, and if zone loads are diversified, may result in over-cooling or overheating of some zones: this may in turn have an impact on occupants’ comfort. We end with an analysis of the results obtained, followed by conclusions
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