It is very difficult to come across two existing building that are built and occupied in identical fashions with the exception of their HVAC system – one utilizes a VAV Box approach and another utilizes a VAV Diffuser approach. However, there is a study in India where this is being done. Acutherm has received verbal confirmation of 15% energy savings by the VAV Diffuser approach. The VAV diffusers being used are Therma-Fuser™ diffusers. A written report has been requested by Acutherm.
The “dual maximum” control strategy is one of the exceptions to the rules covering reheat in the prescriptive approach to Title 24 (140.4(d)). There are several ways to meet Title 24 with Therma-Fuser™ diffusers:
- Follow the performance approach to Title 24 compliance. 140.4(d) is only required in the prescriptive approach.
- Avoid reheat as 140.4(d) is only applicable to reheat systems. A building design that uses multiple AHUs to provide the necessary zoning for heating is one example of a system that does not use reheat.
- Use T-Series thermally-powered Therma-Fuser diffusers. The “dual maximum” control strategy is only required for systems with DDC to the zone (140.4(d)A). T-Series Therma-Fuser diffusers with a built in thermostat and VAV damper provide a zone of control, but are not DDC and thus fall under 140.4(d)B.
Pressure control directly affects noise and air volume; the latter is very important in the diffusers’ decision on what to do next.