Check the simple things first
Before anyone opens a panel, look at what the building can tell you. Is the chiller getting power, and are the disconnects on? Did the chilled-water setpoint get changed? Is the building automation system showing an alarm code — and did someone silence it without writing it down? Are the chilled-water and condenser-water pumps actually running? A chiller that is locked out on a flow safety looks exactly like a dead chiller, and the fix is a pump or a clogged strainer, not the machine itself.
The failures we actually find
When it is the chiller, a handful of causes account for most no-cool calls: low refrigerant charge from a slow leak, fouled condenser tubes or dirty air-cooled coils driving head pressure into a safety trip, failed flow switches, seized or grounded compressor motors, and control or sensor faults that feed the machine bad data. On older machines, capacity control problems — slide valves, inlet vanes, unloaders — often masquerade as a refrigerant problem.
Stop resetting it
The most expensive habit in chiller ownership is clearing a safety trip repeatedly until the machine stays running. Safeties trip for a reason. A chiller that locks out on high head pressure or low oil pressure and gets reset five times in an afternoon is a chiller being driven toward a compressor failure that can cost more than some machines are worth. One reset to see if the fault was transient is reasonable. After the second trip, stop and make the call.
What the service call looks like
Our technician arrives, pulls the fault history, tests the machine, and gives you a written diagnosis with a price before any repair begins — the trip and diagnostics fee for commercial equipment is $149. Central plant repairs are quoted per machine, and if the honest answer is that the chiller is at the end of its economic life, we will tell you that and price both paths.
Most of these calls are preventable
Nearly every chiller emergency we see traces back to something a maintenance visit would have caught: condenser fouling, a drifting sensor, a slow leak, a pump on its way out. If your chiller has no PM program — or a PM program that has never included eddy-current tube testing or oil analysis — that is the real problem to fix once the machine is running again.