Commercial chiller repair and service

How a chiller system fits together

The chiller makes cold water. Pumps push that water through coils in the air handlers or through the jackets and plates of process equipment, where it picks up heat, and back to the chiller. The chiller then dumps that heat outdoors: through its own condenser fans on an air-cooled machine, or through condenser water and a cooling tower on a water-cooled one. A fault anywhere in that loop shows up as the same complaint: "the chiller is down."

That is why we look at the whole loop on a chiller call, not just the box. A dirty tower, a failed pump seal or a stuck valve will trip a perfectly healthy chiller.

Chiller faults we find most

What you see	What is usually behind it
High head pressure trip	Dirty condenser coil or fouled condenser tubes, a failed condenser fan, low condenser water flow, or a cooling tower that is not rejecting heat.
Low pressure or freeze alarm	Low chilled water flow from a pump, strainer or valve problem, low refrigerant charge, or a bad sensor reading.
Flow switch alarm	A pump that is off, cavitating or losing its seal, air in the loop, or a clogged strainer.
Compressor will not start or trips on overload	Contactors, starters, a failed motor winding, oil problems or a compressor safety doing its job.
Water not getting cold enough	Lost capacity from a compressor down, a staging or setpoint problem in the controls, or more load than the machine was sized for.

We write down the alarm history before anyone resets anything. The controller usually knows what happened first, and the first alarm is the one that matters.

Air-cooled and water-cooled

Air-cooled chillers sit outside, often on a roof or a pad, and reject heat through condenser coils and fans, like a big rooftop unit that happens to make water. Their weak points are the condenser coils, fan motors and the heat of a Middle Tennessee July, when every degree of coil fouling shows up as head pressure.

Water-cooled chillers sit in a mechanical room and send their heat to a cooling tower through condenser water. They are more efficient, and more dependent on clean tubes, good water treatment and a tower that works. Hard water scale on condenser tubes robs capacity quietly until the machine starts tripping on hot afternoons.

What chiller maintenance covers

• Operating log: pressures, temperatures, amps and approach temperatures, compared with the last visit
• Condenser coil cleaning on air-cooled machines; condenser and evaporator tube condition on water-cooled ones
• Refrigerant leak check and charge verification
• Oil level and condition, compressor starts and run hours
• Electrical: contactors, starters, connections and motor amp draw
• Flow switches, safeties and sensors tested, not assumed
• Chilled and condenser water pumps, strainers and valves on the loop

Chillers are usually the most expensive single piece of equipment in a building, and they are almost always on a maintenance agreement for that reason. Catching a fouled condenser or a slow leak in April costs far less than a trip in August.

Process chillers and critical cooling

Manufacturing equipment is often cooled with chilled water: molds, presses, welders, lasers and the hydraulics that drive them. When that chiller goes down, production goes down with it. We have also serviced the smaller chillers that cool MRI machines, where the chiller is the difference between scanning patients and rescheduling them.

On process and medical systems we plan any shutdown with your team first, and on an emergency call the first job is keeping the load cool by whatever safe means are available until the repair is finished. We cover process and critical cooling from the Clarksville industrial parks to the refrigerated food plants in Murfreesboro. That keep-it-cool-first approach is how a TV station stayed on the air with garden soaker hoses on its condenser coil while a fan motor was on its way.

Repair or replace a chiller?

ASHRAE's median service life estimates put reciprocating chillers at about 20 years and centrifugal machines at about 23, and plenty run well past that with good care. We repair chillers until repairing them stops making economic sense. When a machine reaches that point, usually after a compressor failure on an old refrigerant, a leaking heat exchanger or repeated major repairs, we lay out the numbers and help you plan an equipment replacement on your schedule.

Chiller questions