Commercial Chiller Shutting Down in Austin, TX: Two Faults, Two Causes

August 26, 2026 — Austin, TX

When a commercial chiller trips offline, the first repair rarely tells the whole story. A 90-ton air-cooled chiller at a commercial facility in southeast Austin shut down twice in late August. Each shutdown had a different cause. Here is what Setpoint found, what we fixed, and what operators can learn from it.

The Equipment and the Complaint

The unit is a Trane Series R air-cooled chiller rated at 90 tons, with two compressors (A and B) supplying chilled water to the facility. The operator reported intermittent shutdowns. The chiller would run, trip, and need a reset, with no obvious pattern.

The controller had logged a Starter Transition – Compressor A fault. That gave us a starting point.

Shutdown One: The Compressor Starter Circuit

On large chillers like this one, a compressor doesn’t simply switch on. It starts through a staged contactor sequence and then transitions to full run. The controller watches auxiliary contacts on those contactors to confirm each step actually happened. If the confirmation doesn’t arrive in time, the controller assumes something is wrong and shuts the compressor down to protect it.

Our tech traced the Compressor A starter circuit and found the auxiliary contacts weren’t reliably reporting the transition. The work performed:

• Diagnosed the Compressor A starter and contactor transition sequence
• Replaced all four auxiliary contacts in the starter sequence
• Restarted the chiller and confirmed Compressor A started and transitioned normally through repeated testing

The starter-transition fault did not return.

Chiller or rooftop unit down after hours? Call 512-992-5537. Setpoint runs 24/7 emergency commercial HVAC service across Austin and the surrounding area. See our emergency commercial HVAC and refrigeration repair page for details.

Shutdown Two: The Chilled-Water Flow Interlock

Later, the chiller tripped offline again, this time after hours. Setpoint returned on an emergency call. The obvious assumption was that the starter repair hadn’t held. The diagnostics said otherwise: the starter circuit was fine, and the second shutdown came from the chilled-water flow interlock.

Every chiller has to prove water is flowing through its evaporator before it’s allowed to run. If flow stops, refrigerant can freeze the water inside the evaporator and crack it, which is one of the most expensive failures a chiller can have. So the moment the flow signal drops, the chiller shuts itself down. That’s the system protecting itself. But a bad signal looks exactly like a real loss of flow.

Testing the flow-monitoring relay and sensor circuit revealed an intermittent wire-break condition. The pumps and water flow were fine; the wiring that reports flow kept dropping out. The work performed:

• Tested the flow-monitoring relay and flow-sensor circuit
• Inspected and serviced the flow-sensor connector and pins
• Reseated and tightened the threaded connection
• Restarted the chiller and monitored both compressors running normally as chilled water pulled toward its 44°F setpoint

The flow fault did not return during testing. Intermittent wiring faults can be stubborn, though. If this one comes back, the next step is replacing the flow sensor, connector, or cable rather than servicing them again.

What Austin Operators Should Take From This

Intermittent chiller shutdowns are some of the hardest calls in commercial HVAC. The unit often runs fine by the time a tech arrives. A few habits make a real difference:

• Write down the fault before you reset. The diagnostic code on the controller is the most valuable clue a tech has. A reset can bury it.
• Note the time and conditions. Time of day, outdoor temperature, and building load all help separate an electrical fault from a capacity or flow problem.
• Don’t assume a second trip is the first problem returning. In this case the two shutdowns had nothing to do with each other.
• Don’t keep resetting a safety. Flow and pressure safeties exist to prevent evaporator and compressor damage. Repeated resets without a diagnosis risk turning a wiring repair into a major one.
• Schedule regular service. Routine commercial HVAC maintenance includes checking contactors, terminals, and safety circuits before they start causing nuisance trips.

For the field notes from this job, see the 90-ton commercial chiller repair check-in. Setpoint services water chillers, process chillers, glycol systems, and rooftop units. Learn more on our water chiller repair and commercial HVAC repair pages.

Call Setpoint for Commercial Chiller and HVAC Repair

If your chiller is tripping offline, logging faults, or struggling to hold setpoint, call 512-992-5537. We’ll find the actual cause, not just the one that looks most likely.

Setpoint Services LLC — Texas TACLA00116720C. Commercial HVAC, chiller, and refrigeration service for Austin, Pflugerville, Round Rock, Georgetown, Cedar Park, Leander, Hutto, Taylor, Kyle, Buda, Jarrell, Temple, Belton, and surrounding Austin Area communities.