Facility health and audit tests should be used to assess the health of your server room to help detect conditions that may lead to temperature and humidity related equipment failures.

Whilst you are not mandated to run Server Room Facility Health & Audit tests on a continuous basis, you should consider this kind of testing on a regular basis. When you undertake this testing, ensure that the test is repeatable. Repeatable tests and therefore test data sets give you the ability to spot trends over the course of multiple test runs.

The ASHRAE publication Thermal Guidelines for Data Processing Environments contains specific advice and recommendations for data equipment environmental monitoring. If you want more in-depth information about equipment installation verification testing, I strongly recommend you buy the publication.

Aisle Measurement Locations

Place your temperature and humidity sensors in each aisle that has equipment air inlets. If you are not able to test using automated environment monitors then manual measurement and recording of ambient temperature and humidity will do the job.

Use the following guidelines to establish locations for measuring aisle ambient temperature and humidity. You may mark the points permanently on the floor so you are able to repeat the tests at a later date.

• establish a measurement location at least every 3 - 9m of aisle or every fourth cabinet (see Figure 1)
• locate measurement locations midway along the aisle, centred between equipment rows
• only locate measurement locations in the cold aisle of a server room with a hot aisle / cold aisle configuration

Figure 1: Measurement locations in aisle

Measurement locations should be representative of the ambient temperature and humidity of that aisle. Telcordia GR-63-CORE (2021) suggests measuring aisle temperature 1.5m above floor level. Lacking a more elaborate measurement system, this is considered the minimum measurement.

The objective of these measurements is to ensure that the aisle temperature and humidity levels are all being maintained within the recommended operating conditions of the class environment.

HVAC Operational Status

Measure and record the following status points at all HVAC AC units as applicable:

• Operating status of unit: ON / OFF
• Supply fan: status ON / OFF and fan speed if variable
• Temperature: supply air temperature, return air temperature
• Humidity: supply air humidity, return air humidity

Automatic logging of HVAC equipment parameters can provide valuable insight into operational trends and will make data collection less error prone. The objective of the measurements is to confirm your HVAC AC units are working correctly.

Figure 2: Location to measure air flow on air conditioner

Evaluation

Aisle Temperature and Humidity Levels

The temperature and/or humidity of any aisle with equipment inlets that is found to be outside the recommended range for the class environment should be investigated and the resolution fully documented. The investigation should involve identification of the source of the out-of-range condition and a possible corrective action. The corrective action could be as simple as minor air balancing or more complex involving major rework of the cooling system. A decision to take no action must be made with the recognition that prolonged operation outside of the recommended operation ranges can result in decreased equipment reliability and longevity.

HVAC Unit Operation

Temperature and humidity levels at the HVAC unit should be consistent with design values. Return air temperatures significantly below room ambient temperatures could indicate short circuiting of supply air. Short circuiting is a pathway that allows cold supply air to bypass equipment and return directly to the HVAC unit. Short circuiting can be very expensive as you are paying to cool air that is not being used to cool your equipment. The cause of any short-circuiting should be investigated and evaluated for corrective action.

Figure 3: Air short circuiting from air outlet to inlet

Summary

Facility health and audit testing should be carried out on a regular basis to ensure that the inlet temperature for your equipment is within the recommended range for that equpment environment class. You should mark your measurement locations so that you are able to reliably repeat the testing. The sensor data should be recorded, stored and analysed so that future trends can be spotted and corrected as necessary.

References

Thermal Guidelines for Data Processing Environments Fifth Edition (2021) ASHRAE Datacom Series

Telcordia GR-63-CORE (2021)

• Data Center