Answer:
When a rooftop unit equipped with an economizer starts, it typically follows a specific sequence of operations to optimize energy efficiency and indoor air quality. Here's a general sequence of actions for a rooftop unit with an economizer:
Startup: The unit begins by going through its startup sequence, which includes system checks and diagnostics to ensure all components are functioning correctly.
Initial Operation: Initially, the unit may operate in a standard mode, using mechanical cooling (compressor) or heating as needed to maintain the desired indoor temperature.
Monitoring Outdoor Conditions: Simultaneously, the economizer controller monitors outdoor air conditions, such as temperature and humidity.
Economizer Control: If the outdoor air conditions are favorable (e.g., cool and dry), the economizer damper is modulated to allow a controlled amount of outdoor air to enter the building. This can help cool or ventilate the indoor space without relying solely on mechanical cooling.
Mixed Air Temperature: The unit measures the temperature of the mixed air, which is a combination of outdoor air and return air from the building.
Cooling or Heating Decision: Based on the mixed air temperature, the unit's control system decides whether to continue using the economizer (free cooling) or switch to mechanical cooling or heating.
Optimization: The economizer controller continually optimizes the mix of outdoor and return air to maintain the desired indoor conditions efficiently. It may adjust damper positions and compressor operation accordingly.
Ventilation: The economizer also ensures that outdoor air is supplied for ventilation purposes to maintain indoor air quality.
Shutdown: When the unit is no longer in use, it goes through a shutdown sequence, which may include closing dampers, turning off fans, and shutting down the compressor or heating elements.
The goal of an economizer is to reduce energy consumption by utilizing free cooling when outdoor conditions are suitable, improving indoor air quality, and maintaining comfort. The specific operation of a rooftop unit with an economizer may vary based on the equipment's design and control system.
Step-by-step explanation: