There are two fundamentals to cover when designing server room in terms of critical infrastructure. The first is cooling and the sizing of an air conditioning system to remove heat generated by the servers and provide a suitable working ambient. The second is the choice and sizing of a suitable uninterruptible power supply.
A UPS system is designed to provide battery backup when the mains power supply fails. The battery is usually an internal one or may be housed in an external cabinet or tray for a rack mount UPS system. There are several aspects to consider when selecting the right uninterruptible power supply to protect your server room or datacentre environment.
These are the basic of choosing an uninterruptible power supply for a server room environment: load size and matching to the mains power supply characteristics, the battery runtime required, and type of UPS topology preferred. Once this assessment has been made other considerations can be made.
The next step is growth and resilience level required. It is considered best practice to add 20% to the load profile for future expansion. This applies to mono block UPS. If more expansion is required, then then a mono block UPS must be oversized, or one chosen that can be installed with the capability of parallel expansion for N+x resilience.
In an on-line UPS system, the built-in automatic bypass provides protection from a single point of failure. If the UPS suffers an overload or fault condition, the critical load is transferred to the bypass supply without a break in supply and downtime. In a resilient UPS installation, two or more UPS systems are installed to share the load, with the potential capacity to support the entire load if one of the UPS systems suffers a fault condition or is taken out of circuit.
Modular UPS systems tackle both future expansion and resilience by design. A modular UPS uses standard frame sizes, housing several standard-sized UPS modules. For example a 20kW frame using 10kW modules, a 180kW UPS frame using multiple of 30kW modules or a 300kW frame using 50kW modules. The UPS can be installed with one or two or more modules from day-one, with additional modules added as required.
Modular UPS tend to use a tower format matching that of server rack cabinets. They provide a way to make the most of the floor space within a server room or datacentre can are designed to scale vertically. Additional modular UPS frames can be installed in parallel to scale the installation horizontally. Modular UPS also tend to be designed for three phase and higher power ratings. Smaller single phase (1/1 and 3/1) formats are available. Some smaller modular UPS systems are also available with self-contained frames that can be installed within an existing server cabinet.
Space availability is therefore one of the other key considerations for a UPS installation. Smaller UPS systems may be installed alongside a server rack as a floor standing tower or within the rack as a rack mount cabinet. The larger the uninterruptible power supply, the greater the space required and this space increases as more battery runtime is required. For large datacentre applications, the UPS system may require a separate UPS and battery room(s) and a centralised rather than a decentralised approach.
It is relatively easy to size and select an uninterruptible power supply and battery for a server room or datacentre environment. There is little difference in the basics other than scale and the complexity of the overall installation. Thought should also be given to maintenance provision in the form of a UPS maintenance bypass switch and preventative maintenance contracts in order to ensure that whichever type of system is installed is inspected and maintained at least once a year and without downtime to the connected loads.
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