🔍 Key Concepts

• Look at whether the system sends out two separate air streams (hot and cold) from the main air handling unit or just one supply duct. • Check if there is a mixing box at the room/zone where hot and cold air are blended under control of a room thermostat. • Compare this with a terminal reheat layout, where air is generally cooled centrally and then reheated only at the terminal, versus systems where both hot and cold ducts run through the space.

💭 Think About

• Follow the airflow from the coils to the room: Do you see distinct hot and cold ducts leaving the central unit, or a single conditioned air stream? • At the space served, is the thermostat controlling a mixing device that blends two ducts, or only a reheat coil on a single duct? • Ask yourself which of the four listed system types is specifically known for using separate hot and cold trunks that are mixed at each zone.

✅ Before You Answer

• Verify in the legend what the symbol M (Dual Duct Air Mixing Unit) represents and where it is located in the diagram. • Confirm whether the diagram shows both a cooling coil and a separate reheater coil feeding different ducts that then run toward the rooms. • Before choosing, rule out options that would normally have only one main supply duct or only local reheat at the terminal rather than central hot and cold ducts.