BS/EN 50600-4-2-2016 pdf download.Information technology Data centre facilities and infrastructures Part 4-2: Power Usage Effectiveness.
By definition, the calculated PUE is always greater than 1.
Where the only energy source is from the electrical utility, then EDC is determined by the location of the utility meter. PUE may be applied in mixed use buildings that allow of the differentiation between the energy used for the data centre and that for other functions. Alternatively, the derivative partial PUE (pPUE) may be applied (see Annex C).
EIT includes but is not limited to:
a) IT equipment (e.g. storage, processing and transport equipment);
b) supplemental equipment (e,g, keyboard/video/mouse (KVM) switches, monitors, and workstations/laptops used to monitor, manage, and/or control the data centre).
EDC includes EIT plus all the energy that is consumed to support the following infrastructures:
1) power delivery – including UPS systems, switchgear, generators, power distribution units (PDUs), batteries, and distribution losses external to the IT equipment;
2) cooling system – including chillers, cooling towers, pumps, computer room air handling units (CRAHs), computer room air conditioning units (CRACs), and direct expansion air handler (DX) units;
3) others including data centre lighting, elevator, security system, and fire detection/suppression system.
5.2 Total data centre energy consumption
The data centre under consideration shall be viewed at as a system defined by interfaces through which energy flows.
The following forms of energy shall be metered at the interfaces:
a) electricity;
b) gaseous fuel;
c) fluid fuel;
d) fluids for cooling (comprising water usage when returned fluid and not evaporated).
The following forms of energy are not required be metered at these interfaces:
1) air for cooling;
2) water from natural sources (i.e. requiring no energy consumption in its provision).
If technical subsystems, e.g. on-site co-generation of heat and electricity, have meters at their output, they are considered external to the system. If technical subsystems have meters at their input or only have partial metering at their outputs, they are considered internal to the system.
5.3 Total data centre energy consumption in mixed-use buildings
The total data centre energy consumption for data centres in mixed-used buildings shall be calculated on the energy use of the data centre as system only if metering of all shared technical subsystems allows separation of energy usage.
If energy use of shared technical subsystems cannot be separated, total data centre energy usage shall comprise the building in total. The impact on PUE should be counteracted by implementing the necessary meters for separation.
6 Measurement of Power Usage Effectiveness
6.1 Measuring energy consumption
6.1.1 General
In order to calculate PUE, it is necessary to measure EDC and EIT. This is not a trivial task, especially within existing data centres which can require the installation of instrumentation to collect the data.
Although measurement of EDC and EIT are adequate to calculate PUE for the defined equipment and supporting infrastructure, more monitoring data of logical subsets is necessary to assess areas for potential improvements and to evaluate the resulting improvements to PUE across the data centre.
6.1,2 Measurement period and frequency
The calculation of PUE requires the recording and documenting of EDC and EIT over a coincident period of 12 months. This standard does not specify the frequency of measurements of EDC and EIT, since PUE is calculated on an annual timeframe. However, the frequency of measurement employed will determine the timing of subsequent PUE calculations on a rolling annua’ basis.
6.1.3 Meter and measurement requirements
Measurement of EDC and EIT shall be undertaken using either:
a) “watt meters with the capability to report energy usage, or;
b) kilowatt-hour (kWh) meters that report the actual energy usage (true r.m.s). via the simultaneous measurement of the voltage, current, and power factor over time.BS/EN 50600-4-2-2016 pdf download.