System Design
Brief provides recommendations to help engineers improve the
efficiency of large HVAC systems. It focuses on built-up
variable-air-volume (VAV) systems in multistory office buildings.
The recommended measures promote efficient, practical designs that
advance standard practice, achieve cost-effective energy savings,
and can be implemented using current technology. Here are some of
the key recommendations:
- Reduce design system static pressure
- Employ demand-based static pressure reset
- Use low-pressure plenum returns/relief fans
- Employ demand-based, supply temperature reset to reduce reheat
energy and extend economizer effectiveness
- Design fan systems to turn down and stage efficiently
- Size terminal units to balance energy impacts of pressure drop
and minimum airflow control
- Set terminal unit minimums as low as required for ventilation
and use intelligent VAV box control schemes to prevent
stratification
- Employ demand-based ventilation controls for high-density
occupancies
- Design conference rooms to provide ventilation without
excessive fan energy or reheat
Of all the recommendations in this Design Brief, VAV box control
and supply air pressure reset often have the largest impact on
system efficiency. Design engineers are encouraged to pay
particular attention to these two issues.
The first edition of this design brief was prepared for Energy
Design Resources in 2002. Between January and April of 2010, an
engineering review of this document was conducted to update
passages affected by recent changes in the California Building
Energy Efficiency Standards (Title 24 2008). The original content
creator was not actively involved in this engineering review, and
therefore is not responsible for the updates to the affected
passages.
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