Cooling
A precision cooling unit runs every hour of the year, so its maintenance has to keep it efficient and catch the faults that would stop it. A visit covers the parts every unit shares, such as filters, belts and sensors, and the parts that depend on the type: refrigerant and condenser coils on a CRAC, the chilled water valve on a CRAH, humidifiers and drains wherever they are fitted.
Because it is a different machine doing a harder job. Vertiv's paper on the service side of precision cooling states that precision systems have very different service and maintenance needs from building air conditioning designed for comfort, and that they run around the clock. LBNL's master list adds the efficiency case: regular maintenance of cooling units helps ensure they keep operating efficiently, which shows up directly in the energy bill and in PUE.
These items come from LBNL's table of cooling unit maintenance and Vertiv's service paper; the manufacturer's schedule for the specific unit sets the intervals.
The refrigeration circuit. LBNL lists refrigerant charge and the condenser coil for CRACs and air conditioning units, which carry their own compressors. Vertiv stresses that the service provider must know the oils and refrigerants used in the precision units, and that people untrained on the equipment can cause cooling systems to fail while adjusting them. For the difference between the two unit types, see CRAC vs CRAH.
The chilled water side. LBNL lists the chilled water valve actuator for CRAHs and air handlers; a valve that sticks or drifts starves the coil of water and the room of cooling even though the unit's fans keep running. The chiller plant behind the CRAHs has its own maintenance, and because several CRAHs depend on it, its condition decides the room's.
Because they are the parts most likely to put water where it should not be. Vertiv notes that a unit with a humidifier may need more frequent maintenance to avoid condensate drain problems that could flood the computer room, that a plugged evaporator coil drain can spill water, and that steam humidifier drainage must be maintained.
In a room where the UPS, its batteries and their cabling sit on or under a raised floor, a condensate leak is a power-path hazard as well as a cooling one. Leak detection around each cooling unit, as described in the server room monitoring guide, is the backstop.
They save the most energy and need the most checking. LBNL notes that airside economizers need regular service to work properly: the outside air temperature sensors that decide when they open must stay calibrated, the actuators and linkages on the louvers must be lubricated and adjusted, and the whole economizer system should be tested at least once a year.
It catches what a visit cannot: the slow drift and the sudden failure. Temperature at the rack inlets, humidity in the cold aisle and leak rope around each cooling unit are the basic room sensors described in the server room monitoring guide, and Schneider Electric notes that alerting on the rate of temperature change gives a quicker indication of failure than a snapshot value. Cooling unit alarms should reach the same people as the UPS alarms, so that whoever answers knows both what the room is doing and what the UPS is carrying.
Between visits, a log of unit run hours and alarms also tells the next visit where to look, in the same way a UPS event log does.
Because the UPS room depends on it. ASHRAE's power equipment paper notes that UPS modules are cooled by forced air and that a UPS battery room must be held within the narrow temperature range the battery maker specifies, because battery life is very sensitive to temperature; it gives 25 °C as the ideal for lead-acid batteries and roughly halves their life for every 8 to 10 °C above it. It also notes that when the HVAC fails, IT equipment draws more power as its fans speed up, raising the UPS load as the room warms.
Timing the cooling visit alongside UPS maintenance lets both teams check the same room: temperatures at the UPS and the battery string, airflow at the UPS intakes, and whether any cooling work will need the UPS room cooled by other means while it happens. Cooling design, installation and maintenance are delivered through specialist cooling subcontractors. For the UPS side, what a preventive UPS visit includes and UPS battery testing and replacement service cover the power equipment.
To the manufacturer's schedule for that unit. LBNL lists the items, and adds that airside economizers should be tested at least once a year.
Air filters, fan belts where fitted, and sensor calibration, per LBNL's cooling unit maintenance table.
Mostly from condensate and humidifier drains. Vertiv notes that a plugged evaporator coil drain can spill water and that humidifier drainage needs maintaining.
It can. The UPS and batteries need their temperature held during the work, so the visit should be planned with the UPS room in mind.
Cooling design, installation and maintenance are delivered through specialist cooling subcontractors.
Sources, checked 2026-10-04:
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