Airside Economizers and ASHRAE Standard 90.1-2013
This newsletter discusses the requirements for airside economizers in comfort cooling applications according to ASHRAE Standard 90.1-2013.
Economizer Requirements
Airside or waterside economizers are required for individual fan-cooling units greater than 54,000 Btu/hr (4.5 tons, 15.8 kW) for all climate zones except 1A and 1B.
Economizer Control Types
Standard 90.1 describes four allowable control types: fixed dry-bulb temperature, differential dry-bulb temperature, fixed enthalpy with fixed dry-bulb temperature, and differential enthalpy with fixed dry-bulb temperature.
Economizer Exceptions
There are several exceptions to the economizer requirement, including systems with a cooling capacity less than 54,000 Btu/hr, systems that require non-particulate air cleaning, and systems that operate less than 20 hours per week.
Sensor Accuracy
The standard prescriptively requires outdoor-air, return-air, mixed-air, and supply-air sensors to be calibrated to specific accuracies to ensure proper operation of the airside economizer.
Manual:
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