FAQs - UPS Sizes - 1kVA
Typical questions clients ask before buying a 1kVA UPS (1000VA uninterruptible power supply) to protect their computers, server rooms and IT networks. A 1kVA UPS may also be refered to as a 1kW UPS (1000W) if the UPS is rated at unity power factor.
A 1kVA uninterruptible power supply will have a built-in battery pack and the amount of runtime the UPS can provide when there is a mains power outage is dependent on the load connected. At 80% load a typical 1kVA/1kW UPS can provide 5-10 minutes of battery runtime. This can be extended by adding plug-in battery packs if the UPS has this facility or oversizing the uninterruptible power supply. For long runtimes, in excess of 7hours, standby power generators can be more cost-effective than a large battery set.
Online 1kVA UPS are also referred to as double-conversion or even triple-conversion UPS systems. This refers to the AC-DC-AC or AC-DC-DC-AC operation of the UPS as it converts the mains AC (alternating current) into DC direct current via the rectifier charger assembly and then converts the DC back to AC via the online inverter. The inverter generates a digital sinewave without a break in supply whether powered from the mains power supply or battery set. In a line interactive UPS an automatic voltage regulator (AVR) powers the load when mains power is present and an inverter ‘cuts-in’ during a power outage. The break in supply is minimal (2-4milliseconds) and most modern switch mode power supplies (SMPS) – used to power electronics, computers, servers and network devices – can work with a line interactive UPS. The principle benefit of an on-line UPS, aside from its superior waveform and no-break supply, is a built-in automatic bypass. If the UPS has an internal fault or is overloaded the connected load is automatically transferred to the mains power supply without a break in supply.
Most 1kVA/1kW UPS use a valve regulated lead acid (VRLA) maintenance free battery with a 5year design life. Some 1kVA UPS are available with lithium-ion batteries with a 10year design life. Lead acid batteries are the most commonly used as a lead acid battery is the most suitable for standby operation, as required by uninterruptible power supplies. Lithium-ion batteries provide greater energy storage density, faster cycling and are less susceptible to heat and can therefore be used in warmer operating environments. For some server rooms and data centres, the use of lithium-ion UPS batteries allows savings to be made in air conditioning and cooling systems.
Lead acid batteries in a 1kVA UPS will recharge within 4-8 hours up to 80% capacity. The amount of time that it takes to recharge a uninterruptible power supply battery is dependent upon the total size of the UPS charger (measured in Amps – A) and the size of the battery (Ampere-hour – Ah). A guide for long runtime UPS is to achieve a recharge of 80% within 24hours. Lithium-ion UPS will recharge quicker within 2hours
How long UPS batteries will last is dependent upon several factors including their design life, type, the number of charge/discharge cycles they are put through and the ambient temperature of the room they are working within.
Lead acid VRLA UPS batteries can be of the 5year or 10year design life type. These will require replacement within 3-4 or 7-8 years respectively. In terms of room ambient, the recommendation for lead acid UPS batteries is 20-25°C. For each 1degree rise above 30°C the design life halves. Lithium-ion UPS batteries have a longer design life from 10years or longer but have a higher cost than lead acid types.
When you purchase a 1kVA UPS, the product warranty will generally include the batteries for the warranty period. Some UPS manufacturers limit the warranty to that provided by their battery supplier, and this may be on a pro-rata basis i.e. 100% warranty cover in year 1, 80% in year so and so on. Some UPS companies will offer extended battery warranties and battery cover including testing and replacement as part of their UPS maintenance contracts.
A rackmount or rack UPS is designed for installation in a 19inch server rack or cabinet. Care should be taken to make sure that the internal depth of the server rack is sufficient for the depth of the UPS and its rear panel connections.
A rackmount UPS is supplied with sliding rails that are attached to the supporting structs in the server rack and then UPS is then attached to the rails. The UPS is also secured to the front of the UPS using M6 bolts and cage nuts. Rackmount UPS battery packs are also installed in a similar way if their weight can be supported by suitable sliding rails. If not, a heavy-duty shelf may be used. Rackmount UPS bypasses are also available for installation in a server rack or cabinet and plug-in ones will offer power distribution outlets.
A standalone or Tower UPS is designed for floor standing installation. Matching plug-in battery packs can be used for to provide extended runtimes. If a UPS maintenance bypass is required, a tower 1kVA UPS can use a wall mounted maintenance bypass. The bypass allows the UPS to be maintained or removed from a single-phase supply without interruption to the load.
A single phase 1kVA or 1kW UPS designed to connect to a single-phase electrical supply. It is sometimes called a single-phase UPS for a 1/1 (single phase in and single phase out) installation. The UK electrical supply voltage is 230Vac 50Hz and a 1000VA UPS will be supplied with a power cord with a BS1363 3-square pin plug to plug into a wall socket. Power from the UPS is provided typically by IEC320 C13 outlet sockets on the rear of the UPS or via a UPS maintenance bypass or a a power distribution unit (PDU) if either of these are also installed.