What size UPS system? There are many factors to consider when buying your UPS system and what size by kVA is one of the hurdles we are here to help you with now.
Let's get straight into it!
Understanding the terminology is important so you get the correct amount power.
Systems are typically sized by a kW (kilowatts) and/or a kVA (kilo-volt-amperes) rating. For example, a 1 kVA UPS means its circuitry can handle 1,000 volt-amperes.
The basics for AC power is that “watts = volts x amps.” So a 1,000VA UPS should be able to handle 1,000 watts, right?
No UPS is 100% efficient, power is usually lost in the transformers and circuitry of the backup system. This is called reactance. The solution to this is that most UPS manufacturers will list a “power factor” to use and calculate the maximum wattage a UPS system can handle. This means that the formula for watts = volts x amps x power factor.
For example, 1kVA UPS from N1C has the capacity to power 900 watts of connected equipment. This means the UPS has a “power factor” of 0.9.
Putting 900 watts through on a 1 kVA UPS means the UPS is operating at 100% load capacity which is not recommended. Going over that may cause the UPS to short circuit and fail which makes owning a UPS pointless because it is backup power for short circuits and power outages etc. Using less wattage on a UPS, say 450 watts on the 1kVA UPS, means it is running at 50% power. This will lengthen the battery runtime of the UPS when the power goes out also lengthening the life of the UPS so less work is needed during maintenance and repairs
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Every device you are connecting to your UPS should have a maximum wattage rating on its label. From there you must add up their watt usage. This will help you determine the maximum load capacity on what you are connecting to your UPS system.
Once you have the maximum load you are going to put through the UPS system there must be at least 20% room for marginal error. This means that you should only run the UPS system around 80% of what you have calculated. This will allow you to have a ceiling whenever you reach peak conditions. Starting some electrical devices will cause a spike in watts used. This gives the UPS some leeway so you don’t overload it. (For Example, the initial startup of a hair dryer uses more watts than when the hair dryer is operating normally a few moments later.)
If you think you need a full 900 watts to put through a UPS System, it would be wise to get a 2kVA system to run it at 50% load capacity so there is room for a potential maximum load with extra room. There would be no wiggle room if you bought a 1kVA system with a 900-watt load. You’d be at 100% capacity from the start which will cause you to stress very early on.
Our next factor we consider is to think about is your battery runtime requirements.
If you’re connecting equipment that is on a different floor or wing of your office complex or is in an offsite location, you may need more time for the UPS to protect your load and keep devices running. If you know your building’s generator will kick in right away during an outage you might be able to get away with less runtime.
For example, the 1kVA UPS from N1 Critical Technologies offers 11 minutes of runtime at 100% load (900 watts). If your load was 900 watts and you used a 2kVA UPS from N1 Critical, you’d be running at 50% load and would get 24 minutes of runtime. If you ran 900 watts on a 3kVA UPS from N1C, you’d be running at 33%, getting more than 30 minutes of runtime and so forth.
Lithium-Ion UPS systems have a longer runtime when compared to similar lead-acid. The chemistry of lithium-ion battery packs — like those inside N1 Critical UPS systems — store more power in a smaller space, making them capable of providing extended runtime in the same size UPS unit.
This gives users additional flexibility to “wait out” an outage for a little longer, or provide extra travel time to an off-site location during a power outage. These extra minutes can be critical and that’s why lithium-ion batteries are becoming the future of energy storage in UPS applications.