Many company server rooms are really a storage closet or small room with a standard split air conditioner. Everything is fine while the AC runs. But on a summer night when it fails, or does not restart after a power cut, the room heats up fast and the servers either shut themselves down or their components get damaged.
What Temperature Is Right?
What matters is the temperature of the air entering the front of the server (Inlet), not the temperature in the middle of the room or the number on the AC display. The widely used ASHRAE guidelines for IT equipment recommend an inlet temperature of roughly 18 to 27 °C. Overcooling the room usually brings no benefit and only raises the power bill.
Humidity matters too. Very dry air increases the risk of static electricity, and very humid air risks condensation and corrosion. Keep humidity within the range the equipment manufacturer recommends, and watch especially for water condensing on cold surfaces.
Manage the Airflow
Most servers and rack equipment draw air in from the front and exhaust it at the back. The goal is to get cold air to the front of the equipment and keep hot exhaust air from circling back to the intake.
- Hot and cold aisles: if you have several racks, arrange them so the fronts face each other (cold aisle) and the backs face each other (hot aisle).
- Blanking Panels: close empty rack spaces with these panels so hot air does not flow from the back to the front.
- Equipment orientation: install equipment with side-to-side airflow so it does not blow hot air into server intakes.
- AC airflow: aim the AC vents so cold air reaches the front of the rack, not the back.
Standard AC or Precision Cooling?
Standard split air conditioners are designed for human comfort, not for round-the-clock operation and precise humidity control. They may be enough for small rooms, provided that:
- You have at least two units, so if one fails the other can carry the load.
- Each unit restarts on its own after a power interruption (Auto Restart).
- The two units run in rotation so wear is shared between them.
- They are serviced regularly and their filters are cleaned.
For larger rooms and higher heat loads, Precision Cooling or In-Row cooling systems, which are designed for 24-hour operation and control of both temperature and humidity, are a better choice.
Never install an AC indoor unit or its pipes above a rack. Water dripping or condensing onto servers is one of the most expensive, and most preventable, server room incidents.
Monitoring and Alerts
- Install temperature and humidity sensors at the front of the rack at mid height, not next to the AC.
- Also monitor server inlet temperatures through management controllers such as iLO or iDRAC.
- Set up email or SMS alerts when temperature crosses a threshold, so someone knows before it reaches a dangerous level.
- Place water leak sensors on the floor, especially near the AC condensate drain.
Checklist
- Equipment inlet temperature is within roughly 18 to 27 degrees.
- Humidity is monitored and within an appropriate range.
- Empty rack spaces are closed with Blanking Panels.
- There are at least two cooling units with automatic restart.
- No AC unit or water pipe sits above the racks.
- Temperature and water leak alerts are active and tested.
ITPlus724 engineers can review the cooling and airflow in your server room and recommend the right solution for temperature monitoring and timely alerts.