A hydronic heating system is installed in a building at an elevation of 100 metres above sea level. The boiler is located in the basement, 3 metres below the lowest heating terminal. What is the minimum cold fill pressure (static pressure) required at the boiler to ensure adequate pressure at the highest point of the system?

Question: A hydronic heating system is installed in a building at an elevation of 100 metres above sea level. The boiler is located in the basement, 3 metres below the lowest heating terminal. What is the minimum cold fill pressure (static pressure) required at the boiler to ensure adequate pressure at the highest point of the system?

Answer options: ✅ 30 kPa (4.4 psi)

• 60 kPa (8.7 psi)
• 90 kPa (13.1 psi)
• 120 kPa (17.4 psi)

Correct answer: 30 kPa (4.4 psi)

Explanation: The minimum cold fill pressure must be sufficient to overcome the static head of the highest point in the system. For every 1 metre of height, approximately 10 kPa of pressure is required. Therefore, for a 3-metre static head, a minimum of 30 kPa (3m x 10kPa/m = 30 kPa) is needed. This ensures water reaches the top of the system and provides a slight positive pressure to prevent air ingress.