Outdoor reset of hot water temperature for heating gives hottest water during which weather?

• A. hottest water during milder weather
• B. hottest water during the coldest weather
• C. night setback
• D. hottest water only in the morning

Answer: (B)

Outdoor reset adjusts the heating water temperature based on outdoor air temperature. The colder it is outside, the higher the supply water temperature must be to compensate for greater heat loss and to maintain the indoor setpoint. So the system delivers its hottest water when the outdoor temperature is at its coldest. When it’s milder outside, the curve lowers the supply temperature to save energy and avoid overheating. Night setback can reduce temperatures during the night, but the peak hot water occurs with the coldest outdoor conditions.