January 1, 2025

Proper winter chiller maintenance is crucial to prevent freeze damage and ensure reliable operation. Here’s a step-by-step guide:

1. Assess Operational Needs:

Continuous Operation: If the chiller runs year-round (e.g., for process cooling), protect it against freezing temperatures.

Seasonal Shutdown: If not needed, winterize and shut down the system.

2. Continuous Operation Protection:

Maintain Water Flow: Use a chiller bypass valve to circulate water through the evaporator even when cooling isn’t needed.

Set Anti-Freeze Thermostats: Configure controls to run the pump if water temp nears freezing (e.g., 40°F/4°C).

Glycol Solution: Add propylene glycol (typically 30-50% mix) to the chilled water loop. Test concentration annually with a refractometer.

Insulate Exposed Pipes: Wrap pipes, valves, and fittings in cold areas with closed-cell foam insulation.

Verify Freeze Stats: Ensure freeze protection thermostats and alarms are functional.

3. Full Winterization (Shutdown):

Drain ALL Water:

Evaporator, condenser, cooling tower sump, piping, pumps, strainers, and expansion tanks.

Open drain valves and remove drain plugs from low points.

Purge Residual Water:

Blow out pipes with compressed air (≤50 PSI).

Tilt pipes to eliminate pockets.

Cooling Tower Care:

Drain the basin and spray nozzles.

Cover to prevent debris/ice damage.

Protect the Chiller:

Drain evaporator/condenser barrels.

Install desiccant breathers on refrigerant openings.

Pump Maintenance:

Drain volutes and seal chambers.

Remove and store seals if needed.

4. Air-Cooled Chiller Specifics:

Fan Operation: Ensure fans cycle correctly to maintain head pressure.

Coil Protection: Keep coils clean to prevent ice buildup from trapped moisture.

Refrigerant Charge: Verify charge before winter; low charge risks freeze-ups.

5. Glycol System Checks:

Test concentration (target -10°F to -20°F below expected lows).

Check for leaks or degradation.

Ensure compatibility with gaskets/seals.

6. Building Heat:

Maintain ambient temps >40°F (4°C) in chiller rooms.

Use thermostatically controlled heaters if needed.

7. Documentation & Verification:

Log all maintenance steps.

Walk down the system after shutdown to confirm draining.

Label valves/pipes that were winterized.

Critical Risks to Avoid:

Freeze Damage: Ice expands and can crack pipes, heat exchangers, or compressors.

Undrained Water: Even small amounts in U-bends can cause ruptures.

Power Failures: Have backup power or emergency draining plans.

Pro Tip: Schedule maintenance in early fall to avoid cold-weather rushes.