Author: Tim Elliott
Company: Walchem, Iwaki America
Title: Regional Sales Manager
This guide walks you through the steps to troubleshoot persistently low glycol levels in a closed loop system equipped with a glycol auto-fill unit. It is intended for water treatment professionals and technicians working with HVAC, chilled water, or hydronic heating systems where maintaining proper system pressure is critical.
This guide assumes the following:
- The system is a closed-loop system that utilizes a glycol solution.
- A glycol auto-fill unit is present and intended to maintain system pressure automatically.
- The system is experiencing low pressure, and the auto-fill unit appears unable to maintain it.
¶ ✅ Step 1: Identify the Fill Unit and Confirm It’s Connected
- Locate the glycol fill unit associated with the affected loop.
- Trace the tubing or piping from the unit to the system to ensure it is properly plumbed.
- Confirm you are working on the correct equipment.
¶ ✅ Step 2: Verify Power and Valve Positions
- Ensure the auto-fill unit has power. If not, restore power before proceeding.
- Identify and verify the isolation valve between the fill unit and the system is open. If closed:
- Open it slowly.
- Observe the system pressure; it should begin to rise toward normal levels.
¶ ✅ Step 3: Check Glycol Tank Level and Alarms
- Inspect the glycol tank inside the fill unit:
- Look for a low-level indicator light or alarm condition.
- Check the mechanical float or low-level sensor for sticking or false readings.
- If the tank is empty or low:
- Refill with the correct glycol type and concentration.
- Review the customer’s maintenance procedures to prevent future dry runs.
- Look for a Hand/Off/Auto (HOA) switch on the fill unit.
- If set to Off, switch to Auto.
- In Auto, the system should activate the pump automatically when pressure is low.
Most glycol fill units use one of the following methods to sense system pressure:
- View the digital pressure reading on the controller.
- Compare it to a manual gauge on the system to confirm accuracy.
- If discrepancies exist:
- Attempt calibration.
- If calibration fails, recommend replacing the pressure transducer.
- Verify that the cut-in and cut-out pressures on the controller match system requirements.
- Locate the mechanical switch and inspect the cut-in and cut-out pressure settings.
- Compare them to system specs.
- Adjust only after consulting documentation and customer approval.
Tip: Pumps will only activate when system pressure falls below the cut-in threshold.
Always follow site safety protocols. De-energize circuits before touching components unless properly trained and authorized.
- Open the control panel and inspect:
- Wire connections between the pressure sensors, the controller, and the pump.
- Look for loose or disconnected wires.
- Check for a blown fuse or tripped breaker for the glycol pump.
- Replace/reset as necessary according to specs.
If the system pressure is below the cut-in and the pump still won’t run:
- Measure voltage across the pump motor’s Hot and Neutral.
- If the voltage is outside specs, the issue may lie in the control circuitry. Recommend calling a licensed technician.
- If the voltage is correct but the pump isn’t running, the pump motor may be faulty.
If the glycol feed unit fails to maintain pressure even after these checks:
- Please make sure to document all findings.
- Recommend service or replacement of the glycol pump or related components.
- Provide guidance on preventive maintenance:
- Regular level checks.
- Functional tests of pressure sensing.
- Clear documentation of setpoints and calibration routines.