Difference between a precision air conditioner and a comfort air conditioner
Office or home air conditioners are designed for human comfort; they run at certain hours of the day and also remove part of the air's moisture. Servers and electronic equipment, on the other hand, mainly produce sensible heat and run day and night. Precision air conditioners are designed with high airflow, a high sensible heat ratio and continuous operation in mind to meet this load.
| Comfort air conditioner | Precision air conditioning | |
|---|---|---|
| Working time | Seasonal, certain hours of the day | Every day of the year, uninterrupted |
| Check | Temperature only | Temperature and humidity, narrow tolerance |
| Airflow rate | Low to medium | High |
| Redundancy | Generally none | N+1 or more |
| Monitoring | Control | Alarm, BMS and remote monitoring |
Precision air conditioner types
- Room type DX precision air conditioner (CRAC): has its own compressor and rejects heat to an outdoor condenser.
- Chilled water precision air conditioner (CRAH): runs on chilled water from a chiller; common in large data centers.
- In-row precision air conditioner: is placed between rows of cabinets and removes heat close to its source.
- Free cooling types: save energy by running the compressor less when outdoor air is cold.
- Cabinet air conditioners: small-capacity units for electrical panels and individual cabinets.
Let's evaluate your server room's cooling together
Tell us the unit brand, quantity and room load; we will get back to you for a maintenance plan or capacity check.
What range are temperature and humidity kept in?
The common reference in data centers is the ranges recommended by ASHRAE; the recommended temperature range for server inlet air is generally taken as 18-27 °C. If humidity gets too low, there is a risk of static electricity; if too high, a risk of condensation. Exact values are determined according to the equipment manufacturer's and the facility's conditions. We covered humidity management in our article precision air conditioner humidity control.
Why is redundancy a must?
In a server room, the shutdown of a single air conditioner can trigger a temperature alarm within minutes. That is why at least one more unit than needed (N+1) is installed and the units are run in rotation. Details: N+1 redundant operation.
Precision air conditioner brands
The brands we encounter most often in the field include Liebert (Vertiv), Stulz, Uniflair (Schneider Electric), CIAT, Hiross, Rittal, Huawei, Airedale and Emicon. We provide maintenance and repair for these brands as an independent technical service: Liebert precision air conditioner service, Stulz precision air conditioner service, Uniflair, CIAT precision air conditioner service.
Precision air conditioner maintenance
During maintenance, the alarm history is read, sensors are compared with a reference measurement, and filters, fans, humidifier and drain are checked; on DX units the refrigerant circuit is checked, and on chilled water units the valve and water flow are measured. For the scope, see our precision air conditioner service page and the maintenance form.
Frequently asked questions
What does precision air conditioner mean?
It is an air conditioner designed to control temperature and humidity within a narrow range, without interruption, every day of the year. It is also referred to as a close control or CRAC unit.
Can a normal split air conditioner be installed in a server room?
It can be used as a temporary solution in small rooms; however, split air conditioners are not designed for continuous operation, humidity control and redundancy. A precision air conditioner is recommended for critical rooms.
What is the difference between CRAC and CRAH?
A CRAC is a direct expansion unit with its own compressor. A CRAH has no compressor and runs on chilled water from a chiller.
How often is precision air conditioner maintenance done?
For units that run continuously, a periodic check every three months and comprehensive maintenance once a year are generally recommended.
Which precision air conditioner brands do you service?
We provide maintenance and repair as an independent technical service for Liebert (Vertiv), Stulz, Uniflair, CIAT, Hiross, Rittal, Huawei, Airedale and other brands.