Quick answer: To assess your data centre’s power distribution needs, start with each circuit’s capacity (volts × amps), then apply the 80% safe-load rule to find usable wattage. Divide that by each server’s expected draw, checking both watts and amps and using whichever gives the lower server count. Then add non-IT loads like cooling, UPS, generators, fire suppression and alarms, and leave headroom for growth. A managed service provider can validate your numbers before you commit to a facility or expansion.
For a step-by-step worked example of the calculation, dive into the full article below.
The lifeblood of a data centre is the power it has and the power available for expansion – without electric power, a data centre is useless.
The data centre that is just opening looks beautiful. It is immaculate, equipment gleams, and racks of equipment fill the data center floors. Servers that move faster than lightning strikes fill the racks, and entry to the facility at every access point requires a biometric scan to open the doors.
But the lifeblood of a data centre is the power it has and the power available for expansion – without electric power, a data centre is useless.
About the Power Needs of a Data Centre
Electricity comes in two flavours – traditional power is Alternating Current (AC) that operates at 120 volts or 240 volts. Direct current (DC) is harder to label as to volts, it is a constant flow that never changes direction; qualities not found in AC. DC power is sometimes used to power things such as telecommunications equipment. Accordingly, it is not unusual to find both types of power used in a data center.
How Power is Used in a Data Centre
The data centre, let’s call it DCF for Data Centre Facility, draws power from the local utility company. The power flows into the Uninterruptible Power Source (UPS) that runs on AC power. The power is distributed to the circuit breakers in DCF. The breakers work with 30 amps and 208 volts. This means that each circuit breaker can handle a maximum load of 6240 watts. However, best practices allow for 80% of the power to be used to stay in an 80% or lower safety zone. This means you have 4992 watts available.
If each of your servers is anticipated to run using 600 watts, the maximum number of servers you can run from a single circuit breaker is 8 (600*8 = 4800).
The servers are plugged into rack mounted power strips. Each server is pulling 3.3 amps. Using amps as a measurement metric suggests the proper number of servers a circuit breaker can handle is 7.
Best practices say to err on the side of caution and use the lower number of servers; in this case, the company can only use 7 servers per circuit breaker.
Some of the power that flows to the UPS is converted and stored as DC power in case of an outage.
More Than Servers
The power supply to the DCF powers more than servers and computer equipment, power is mission critical for the DCF and its substantial facility load that includes besides servers:
- Heating, ventilation, and air conditioning (HVAC)
- Alarm systems
- Generators and UPS systems
- Alarm systems
- Fire suppression systems
There is a great deal of information and formulae concerning calculating power distribution needs for data centres. This article’s intent is to give you enough information so that you can discuss your data center’s power needs and for the future with a Managed Service Provider MSP). Including your MSP in determining the electrical capacity of the data centre brings you an expert’s perspective.
If you are considering using a vendor-supplied data centre and want expert advice, contact Steadfast Solutions, an experienced provider of IT managed services. We are available and can be reached at 1300 739 335 or hello@steadfastsolutions.com.au.