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The UK is in that time of the year when weather events can lead to momentary power outages or even complete mains power supply failures. High winds, heavy snow and even flooding can lead to brownouts (lower mains voltages), surge voltages, short breaks in the electrical supply and even substations going offline. Whilst server rooms and data centres have uninterruptible power supplies, home workers can find their home PCs and networks exposed to power problems. So, ‘what is the best UPS’ for home workers?
Uninterruptible power supplies use stored energy to provide backup power to the loads connected to them. In the event of loss of mains power, the battery powers the inverter section of the UPS which converts the DC (direct current) from the battery to an AC (alternating current) waveform to supply the load. When the mains power supply is present, a small charging circuit, recharges the battery. The most supplied battery type is a Valve Regulated Lead Acid (VRLA). In a small UPS system, the battery should be user-replaceable and will require replacement within 3-4 years of installation.
Alternative UPS battery types include lithium-ion but small UPS power supplies with this type of battery tend to cost up to 30% more than a lead acid battery UPS and tend not to be user-replaceable.
There are 3-types of UPS, and they differ in how they use their inverter sections, their surge protection and how the quality of their outputs. A standby or off-line UPS has a filtering circuit to provide protection from spikes and electrical noise. If the mains voltage fluctuates or fails, the ‘off-line’ inverter switches on and powers the load. There is a short break in supply and the inverter waveform may be a step-wave or square-wave. This may be different to AC sinewave you would expect from a mains power supply 13A socket in a home, but the supply is suitable for most electronic equipment with switch mode power supplies (SMPS), including the type of PCs, workstations and consoles used by home workers, students, and gamers.
A standby/off-line UPS provides basic power protection and as such will retail at a very budget friendly price. A basics standby ups, the CertaUPS C60 1000VA for example retails for less than £97.50 excluding VAT.
The next level of UPS is similar in topology to a standby/off-line system and is referred to as a ‘line interactive’ uninterruptible power supply. This type of UPS functions in a comparable way and have an inverter that provides either a step-wave or sinewave output. As well as a superior waveform output, the UPS will have greater brownout, surge, and transient voltage protection. This is due to the UPS having a built-in automatic voltage regulator (AVR).
When the mains supply is present, the AVR stabilise the incoming voltage inside a set window. This window range from 162-290Vac during which the UPS can protect its load(s) without using battery power. The AVR ‘bucks’ or ‘boosts’ the incoming mains supply voltage. This provides ideal protection from brownouts and voltage surges. This type of UPS can also feature a filtering circuit to provide protection form higher voltage surges and transients from nearby lightning strikes.
In a line interactive UPS, the inverter section is powered-up and can connect to the load(s) faster than a standby/off-line UPS in the event of a power problem, than a standby/off-line UPS. Whilst an oscilloscope may show a small distortion in the output waveform, to most home and office electronic equipment, the change to or from ups battery power is negligible when the mains power supply fails or restored.
A line interactive UPS provides intermediate power protection and a system such as the CertaUPS C200 1kVA for example sells for less than £140.00 excluding VAT.
A double-conversion online UPS provides the ultimate level of protection. In this type of UPS, the inverter section is running continuously and powers the load. There is no-break when transferring from and to battery power. When mains power is present a filtering circuit and the AC-DC-AC conversion process ensures a clean and stable electrical supply from the inverter. A rectifier/charger circuit provides voltage stabilisation, over a wide input voltage range and charges the battery set. An online UPS also features an automatic bypass allowing the load(s) to be safely transferred to the mains power supply if there is a UPS overload condition.
A double conversion online UPS provides the ultimate power protection such as the CertaUPS C400 1kVA for example sells for less than £215.00 excluding VAT.
Home workers require several pieces of IT and electronic equipment to perform their jobs. Typical examples include a desktop PC and/or laptop, computer screen, webcam, printer, and broadband router.
Not all this equipment will require power backup for general day-to-day work, video conferencing or connection to an organisation’s VPN (virtual private network). However, it is good practice to ensure the critical items are UPS protected. A momentary power outage can disrupt file transfers to a remote server room or cloud storage location, interrupt an important conference call or lead to corrupt data.
More info: https://www.theguardian.com/technology/2020/mar/21/working-from-home-tech-self-isolation
To calculate the UPS size required, list the devices, and assess the Amps they draw and then multiply by 230Vac (the UK mains supply single phase voltage).
UPS load = 230V x Total Amps = VA or divided by 1000 kVA
Amperages can be taken from equipment rating labels, datasheets and in manuals or through a Google search. Where only the Watts value is provided, simply take this as the total VA required for that device. At this size of the application, the difference between actual Watts and VA will be negligible. Printer protection should be considered carefully. A home office printer may be use inkjet or laser technology. Laser printers can draw significant amounts of power and are not usually connected to a UPS as they can lead to a significant UPS oversizing.
Most home users will have around 250-500VA of electrical load that require uninterruptible power and UPS in this size range tend to offer up to 5minutes runtime when fully loaded. This can be increased by oversizing the UPS so that the load is say 50% lower than the UPS rating.
For example, a 500VA load on a 1kVA UPS can provide up to 10minutes runtime at half load. The table below shows the pricing for CertaUPS rated at 1000VA (1kVA).
|UPS Type||UPS Model||Price ^||Typical Applications|
|Standby/Off-line||C60 1000VA||£97.50||Alarm panels, CCTV DVRs, desktop PCs, EPoS terminals, gaming consoles, routers, satellite TVs, NAS storage, workstations|
|Line Interactive||C200 1000VA||£140.00||Desktop PCs, gaming consoles, NAS storage, workstations|
|Online||C400 1000VA||£215.00||High-end workstations, file servers, NAS/SAN storage|
^ Excluding VAT, delivery extra
UPS in this range are available from stock for next working day delivery.
The 3 UPS types offer distinct levels of protection. For home users and remote workers, a line interactive UPS offers the best all-round price v performance package. The protection level when mains power is present is superior to that of an off-line UPS and the output waveform from the inverter is more akin to that of an online UPS system.
If a longer battery runtime is required, plug-in battery packs can be used with some types of line interactive and almost all online UPS. A typical example is the line interactive sinewave output CertaUPS C300R 1kVA. This smart line UPS is both a tower and 19inch rackmount type system and retails for approximately £280 excluding VAT.
Ensuring the computers and IT equipment used by home workers has uninterruptible power can be just as important as proving UPS for a comms room, server room or data centre. Power interruptions can damage hardware, reduce productivity and lead to downtime and data corruptions. For a limited outlay, off-line/standby UPS can protect home workers’ computing equipment with basic power protection. A line interactive UPS is the best UPS for those with a slightly larger budget as this type of UPS will provide superior electrical protection and performance. Online UPS provide additional protection including an automatic bypass for overload and short-circuit conditions.