Chilled Water Reset
Many energy efficient HVAC control strategies have been incorporated into the new 2014 Florida Building Code and can be referenced in the 2014 Energy Conservation Volume Chapter 4. Two (2) control strategies have been implemented that require hydronic systems greater than or equal to 300,000 btuh (25-tons) be provided with part load controls which shall include:
- Automatic reset of the supply-water temperatures based on zone-return water temperature, building return water temperature, or outside air temperature as an indicator of building heating or cooling demand. The temperature shall be capable of being reset by at least 25 percent of the design supply-to-return water temperature difference; or
- Reduce system pump flow by at least 50 percent of design flow rate utilizing adjustable speed drive(s) on pump(s), or multiple-staged pumps where at least one-half of the total pump horsepower is capable of being automatically turned off or control valves designed to modulate or step down, and close, as a function of load.
The rule of thumb of raising the chilled water supply temperature one degree Fahrenheit (F) reduces chiller energy consumption roughly 2%. These energy savings typically result in payback times of less than one (1) year with larger chill water systems.
