🔍 Key Concepts

• Outside air duct thermostat location in the diagram relative to dampers and outside air stream • Difference between sensing outside air temperature vs. inside air temperature in winter operation • Purpose of closing vs. opening outside and exhaust air dampers during very cold weather to protect coils and maintain heating efficiency

💭 Think About

• In the illustration, trace the control line from the thermostat labeled "Winter" and see which pneumatic dampers it actually operates and whether they are shown as N.O. (normally open) or N.C. (normally closed). • Think about what you want the system to do if the outside air becomes much colder than the room air—would you want more outside air or less, and what would that mean for both the outside air and exhaust dampers? • Ask yourself whether a duct thermostat located in the outside air duct would logically be sensing outside air temperature or inside air temperature, and which answer choices are therefore inconsistent with the diagram.

✅ Before You Answer

• Verify which thermostat in the outside air duct is specifically labeled "Winter" and that it is in the outside air stream, not in the room or return air. • Confirm whether the control action driven by the winter thermostat causes the dampers to close to reduce extremely cold intake or to open to bring in more outside air. • Double‑check if the statement mentions the thermostat sensing inside air temperature while being drawn in the outside air duct—those options should conflict with the illustration.