What is the difference between Line Interactive, Online, and Standby topology UPS systems?

UPS topologies are defined by how power moves through the unit:

Online (Double Conversion) UPS—Online UPS systems, such as the Vertiv™ Liebert® GXT5 or APS, deliver continuous high-quality AC power to equipment with no break in output when transferring to battery. AC input power is converted to DC, then back to AC, supplying the load with continuous pure sinewave output. This provides power conditioning, zero transfer time to battery, tight output voltage regulation and better transient suppression than line-interactive units. Because these systems are more complex, they typically cost more than their Line Interactive counterparts. They are well suited for all IT applications, but really shine in applications with poor quality input power or highly sensitive loads.

Line Interactive UPS— A Line Interactive UPS, such as the Vertiv™ Liebert® PSI5, interacts with the incoming power by filtering noise, providing surge protection, and adjusting the voltage when necessary. Using a simple and highly reliable design, the line interactive UPS can handle most power issues in online mode. It will switch to battery when needed which results in a 4-6 millisecond break in power during the transfer. This break in power is called the “transfer time”. Typical IT loads have no issues with this duration and the transfer to battery will appear seamless. This technology is particularly effective in areas where outages are rare, but power fluctuations are common. They are a great cost-effective choice for most IT applications

Standby (offline) UPS—A standby UPS, such as the Vertiv™ Liebert® PST5, is a cost-effective choice for basic power protection. They provide basic filtering and surge protection. In the event of an over voltage, brown out, or black out situation they will switch to battery power until the event resolves. This results in a 6-8 millisecond transfer time, which is typically well tolerated by computer loads. Due to their basic design these units are smaller and less expensive that other types of UPS units, allowing the user to have backup power wherever they need it. They are a good choice for home applications such as desktop PC’s and modems, or business applications such as POS terminals and electronic sign controllers.

Are the Batteries in my Vertiv UPS system “Hot Swappable”?

Yes. The battery modules in all PSI5, GXT5, and APS UPS systems are “hot swappable” and user replaceable. This means that you can replace batteries on the fly without needing to schedule downtown. Please note that should a power outage occur during the brief time the UPS has no batteries installed, you would not have any battery backup available. Refer to the user manual of your specific model for more details.

What is typical battery life?

Battery life depends on several variables, including number of deep discharges, amount of time spent on battery, and (most importantly) temperature.

There are two different types of batteries used in Vertiv UPS products. Traditionally UPS units have used VRLA (Valve Regulated Lead Acid) batteries. This is the same technology as a car battery. They are reliable, affordable, and reasonably durable. The tradeoff is that they are bulky, extremely heavy, and have a limited temperature range.  The latest technology in UPS products is Lithium Ion batteries. This battery type can be found in cell phones, laptops, and some electric cars. Lithium Ion batteries are smaller, lighter, and longer lasting than VRLA. If your UPS is not specifically labeled as Lithium Ion, you can assume it has a VRLA battery.

VRLA batteries typically last 3-5 years in a 20-25°C (68-77°F) environment. Each 8°C (15°F) increase in temperature will reduce the lifespan of the battery by approximately 50%. This means that a battery might have a 4-year lifespan at 22°C (72°F), but less than 2 years at 32°C (90°F).

Lithium-ion batteries typically last about 10 years up to 25°C (77°F), and about 7 years while operating at 40°C (77°F). This makes them a much better choice for applications where cooling is less than ideal.

It is important to remember that the temperature inside the UPS will be warmer than the ambient temperature, and that heat can increase rapidly if there is a lack of cooling or air circulation. If you find that your batteries are not lasting as expected, check the temperature where the UPS is installed. You may find a need for additional cooling or ventilation.

What is bypass and what is the difference between internal bypass and maintenance bypass?

Bypass is a mode of operation in which the input power bypass the UPS electronics and is passed directly to the load. Typically, this would be used during configuration, testing, or addressing a systems issue. There are two distinct types of bypass:

Internal Bypass: This means that power is still flowing through the UPS, but it is bypassing the power processing electronics, effectively passing directly from the input to the output of the UPS.

External Maintenance Bypass: This is an external piece of hardware. It either mounts to the UPS or is an entirely separate box. When a unit is in external bypass there is no power flowing in or out of the UPS. It is entirely separated from the load and electrical system. This allows you to service, upgrade, or replace the UPS with no effect on the attached load.

What is a reasonable amount of IT load to connect to a UPS?

When a piece of IT equipment is first powered on, it typically takes a big gulp of electricity to get its power supply up and running. This is called inrush current. Once the equipment is fully powered up the power draw will drop down significantly to its steady state draw. Because of this you need to allow for a certain amount of excess capacity on your UPS to allow for the typical load as well as the inrush. If you do not have this excess buffer you may run into issues where the UPS is overloaded every time you try to turn on the attached load. This can result in dropped loads, which is exactly what we are trying to prevent.

We recommend that your UPS unit not be loaded to more than 80% capacity. This provides ample headroom for inrush current in typical IT applications. If you are selecting a UPS for a new install, we would recommend sizing it at around 50-60% capacity. This allows for potential inrush as well as any unexpected system expansion if you need to add another server or switch in the future.

For further assistance in selecting a Vertiv UPS, consult our product selector page:


What is UPS Redundancy?

A modular redundant UPS, such as the Vertiv Liebert APS, is comprised of Power, Battery, and Control modules. Each APS Power Module has a capacity of 5kVA. If the system has more power modules than necessary to support the load, a module can be taken offline for replacement without affecting the attached load. When we discuss levels of redundancy, we refer to the power capacity needed as “N”. A UPS solution with 1 more power module than needed to support the load would be referred to as “N+1” redundancy, 2 more power modules that needed would be “N+2”, etc. Customers seeking the highest level of redundancy may specify a “2N” solution, which would be a full duplicate system. In addition to providing redundancy for service, a modular UPS solution also allows you to add additional power and battery modules and scale the capacity of the system as your needs grow.

Will a larger UPS have a longer runtime for the same load?

Not necessarily. UPS capacity refers to the total amount of load that can be supported by the UPS, not the runtime. Typically, larger capacity UPS units have larger batteries, but not always. If you need an extended runtime, the best solution is a UPS that supports external battery cabinets, such as the PSI5 “RT” models, GXT5, or APS series. Refer to the product page for your specific model UPS to determine how many external battery packs are supported and the expected runtime for your specific load.  

Note: Lithium Ion PSI5 units do not support external battery cabinets at this time.

What is the highest capacity UPS I can use with a standard household 3 prong (NEMA 5-15) outlet?

1500 VA is the largest UPS with a standard household style 3 prong plug. Anything larger than this will have something else, even if it is a 120v model. Typically, 2-2.2kVA 120v models will have an L5-20 input plug and 3kVA 120v units will have an L5-30 input plug. Refer to the product page for your specific model UPS for details.

How can I configure a graceful shutdown of my connected equipment?

Vertiv offers 2 different applications for graceful shutdown:

Vertiv™ Power Assist

Vertiv™ Power Assist is free software used to gracefully shutdown an IT device when the UPS battery backup experiences a threatening condition. It communicates with your Vertiv UPS using USB communication.

Vertiv™ Power Insight

Vertiv™ Power Insight is free software that provides system monitoring and graceful shutdown using a network connection. It is for use with Vertiv UPS systems equipped with the Vertiv™ Liebert® IntelliSlot RDU101 Communications Card.

Does Vertiv offer a UPS solution with OSHPD compliance?

Does Vertiv offer a UPS solution with OSHPD compliance?

Are Vertiv UPS products UL Listed?

Yes, All PSI5, GXT5, and APS units are UL1778 Listed. For additional compliance information, refer to the Guide Specification document or product brochures found on the product pages for your specific UPS.

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