Welcome to the Closed Loop Troubleshooting Guide — your field-ready resource for diagnosing and resolving issues in glycol-based closed loop systems.
Closed loop systems are a critical component in hydronic heating, chilled water, process cooling, and HVAC infrastructure. When these systems underperform — especially due to low pressure, glycol level fluctuations, or fill unit malfunctions — fast, accurate troubleshooting is essential to maintain system integrity and prevent costly downtime.
This guide is designed for field technicians, water treatment professionals, and facility managers, and aims to provide:
Clear, actionable checklists to help identify and resolve common issues — from faulty fill units to pressure switch misconfigurations.
Understand the role and function of glycol fill units, pressure transducers, isolation valves, and control panels.
Learn how to interpret common alarm states and panel indicators, and how to respond effectively.
Tips to prevent future issues — including tank refill protocols, sensor calibration, and routine system checks.
This guide is most useful for:
Before diving into troubleshooting: