You are called to a commercial building with a multi-zone hydronic heating system. The owner reports that one zone (Zone B) is not heating, even though the zone valve appears to be open and the circulator pump for the main loop is running. Upon inspection, you find that the supply and return pipes for Zone B are cold. What is the next logical step in your troubleshooting process?

Question: You are called to a commercial building with a multi-zone hydronic heating system. The owner reports that one zone (Zone B) is not heating, even though the zone valve appears to be open and the circulator pump for the main loop is running. Upon inspection, you find that the supply and return pipes for Zone B are cold. What is the next logical step in your troubleshooting process?

Answer options: ✅ Check the operation of the dedicated circulator pump for Zone B, if present, or measure differential pressure across the zone.

• Purge the entire hydronic system of air, starting from the boiler.
• Increase the boiler's operating temperature to compensate for the cold zone.
• Inspect the main system's expansion tank for proper pre-charge.

Correct answer: Check the operation of the dedicated circulator pump for Zone B, if present, or measure differential pressure across the zone.

Explanation: If the zone valve is open and the supply/return are cold for a specific zone, the issue is likely a lack of flow to or through that zone. This is often caused by a malfunctioning zone pump (if it's a pumped zone) or insufficient differential pressure across the zone. Purging the entire system might be needed later, but focusing on the specific zone's flow is the priority. Increasing boiler temperature or checking the expansion tank wouldn't directly address a lack of flow to a specific zone.