Which Type of UPS System Works Best with a Generator?

Do you have a generator to supply power during a lengthy blackout? You’ll get the most out of it if you connect your generator to a UPS system.

But there’s more than one kind of UPS – it’s important to choose the right type of system so it will play nicely with your generator power.

Generator and UPS System Compatibility

A generator typically produces inconsistencies and fluctuations in voltage and frequency ranges. If the range is wider than what the UPS is willing to accept, your load will continue to run off the UPS and eventually deplete the batteries.

This scenario would be typical with an off-line or line-interactive UPS system.

An on-line, double-conversion UPS system works differently and is the type of UPS we recommend for use with a generator.

 An on-line UPS continually converts incoming AC power – whether from the main power supply or a generator – into filtered DC power, and then reconverts it back into AC power with a pure sine wave. That’s the clean feed of power your sensitive equipment craves.

And as another benefit, an on-line UPS filters variations in frequency as part of its everyday operation, so battery life doesn’t shorten prematurely.

When it comes to Generator and UPS Compatibility, Size Does Matter

Your standby generator must provide computer-grade output power and be dedicated to run UPS protected IT applications only. Additionally, the continuous generator capacity rating must be at least twice the rated capacity of the UPS system used.

As connected equipment cycles on and off, inrush currents can cause the UPS to switch between AC, battery and bypass modes. Over-sizing the generator relative to the UPS capacity will help prevent this from happening.

Don’t Forget About Grounding

If you pull the plug on your UPS to move it from the utility power supply to the generator, you’re also pulling the plug on the electrical grounding.

A sudden loss of grounding on the UPS and all the equipment it powers could be a big problem: currents normally dissipated to ground through the UPS would find another path to get there, possibly through network cables, passing through other devices along the way.

Your in-house facilities manager or a local electrician should be consulted to make sure you have no safety or liability concerns. Your installation needs to maintain grounding, adhere to codes and minimize the chance of equipment damage, data loss and shock hazards.

Get Help Choosing the Right UPS to Work with Your Generator

If you are still unsure about which UPS system to buy, dayari technologies Interactive On-Line UPS Product Finder will guide you through the choices to help you select the right on-line system for use with your generator.

5 Questions to Consider When Choosing a UPS System

Choosing the right UPS System can be a daunting task for even the most knowledgeable IT professional. Here are five basic questions you should ask to give you peace of mind knowing you made the right decision.

1. Do I need a Network/Server UPS or a Desktop UPS?

Network/Server UPS Systems protect equipment in high-availability environments like data centers. Desktop UPS Systems protect computers, peripherals and other electronics in your home or office.

If you answer yes to any of these questions, you should choose a Network/Server UPS.

  • Will the UPS support mission-critical equipment?
  • Will the UPS support a load higher than 750 watts?
  • Will the UPS be installed in a rack or rack enclosure?
  • Does your equipment require pure sine wave power?
  • Do you want the UPS to have expandable runtime?
  • Will the UPS support high-voltage (200-250 VAC) loads?

2. How much UPS capacity do I need?

To estimate capacity requirements, add up the wattage of all the equipment you plan to connect. (Refer to the equipment manufacturer’s documentation to find the wattage.

 If it lists amps, multiply by the AC voltage to estimate wattage. If you can’t find documentation, refer to the equipment nameplate.) Check the UPS specifications to see which models will handle your requirements.

3. Which input and output power connections do I need?

Check the UPS specifications to make sure the UPS can connect to a compatible AC circuit/outlet in the installation location.

You also need to make sure the UPS system’s outlets match the plugs and voltage requirements of your equipment.

You can provide additional outlets, placement flexibility and management capabilities by connecting one or more PDUs to the UPS output.

4. How much battery backup runtime do the UPS provide?

With an 80% load, included UPS batteries typically provide five to ten minutes of runtime. That’s long enough to outlast most outages.

 If you need additional runtime, choose a UPS system that supports connecting external battery packs.

 Detailed runtime data for each UPS system, including external battery pack configurations, is available on our website. Go here for more information on sizing your UPS.

5. What other UPS features do I need?

Tripp Lite manufactures more than 250 different UPS systems with a wide range of features designed to satisfy any application or budget. Visit our online UPS Selector Guide to find the right model for your application.

Line-interactive vs On-line Network UPS Systems and Which Should You Choose?

The two main types of UPS operation (known as the UPS system’s topology) used in Network/Server UPS Systems are line-interactive and on-line.

 At the most basic level, line-interactive UPS systems are less expensive than on-line UPS systems (approximately 20 to 40% less, depending on the model and manufacturer), but they also provide less protection than on-line UPS systems.

It’s helpful to explore the differences between line-interactive and on-line models to understand the trade-offs involved.

 Note: If you need a UPS system larger than 5,000 VA (4,000 watts), an on-line UPS is your most likely choice.

Let’s consider four key UPS features and how line-interactive and on-line technology deliver each feature to connected equipment.

Voltage Regulation

Line-interactive UPS systems use automatic voltage regulation (AVR) to correct abnormal voltages without switching to battery.

(Regulating voltage by switching to battery drains your backup power and can cause batteries to wear out prematurely.)

The UPS detects when voltage crosses a preset low or high threshold value and uses transformers to boost or lower the voltage by a set amount to return it to the acceptable range.

On-line UPS systems use a more precise method of voltage regulation: they continuously convert incoming AC power to DC power and then convert the DC power to ideal AC output power.

This continuous double-conversion operation isolates connected equipment from problems on the AC line, including blackouts, brownouts, over-voltages, surges, line noise, harmonic distortion, electrical impulses and frequency variations.

In “line” mode (i.e. when not operating from battery), line-interactive UPS systems typically regulate output within ±8-15% of the nominal voltage (e.g. 120, 208, 230 or 240 volts). On-line UPS systems typically regulate voltage within ±2-3%.

Surge/Noise Protection

All Network/Server UPS Systems include surge suppression and line noise filtering components to shield your equipment from damage caused by lightning, surges and electromagnetic (EMI/RFI) line noise.

On-line UPS systems offer superior protection because the double-conversion operation isolates equipment from problems on the AC line.

Pure Sine Wave Output

When operating from battery power, a line-interactive UPS system generates the waveform of its AC output. An on-line UPS does this continuously. All on-line and many line-interactive UPS systems have pure sine wave output.

 Pure sine wave output provides maximum stability and superior compatibility with sensitive equipment.

Pure sine wave power is required by some equipment power supplies and prevents others from overheating, malfunctioning or failing prematurely.

Transfer Time to Battery

During an outage, line-interactive UPS systems typically transfer from line power to battery-derived power within two to four milliseconds, which is more than fast enough to keep all but a small percentage of the most power-sensitive equipment operating without interruption.

On-line UPS systems do not have a transfer time because the inverter is already supplying the connected equipment load when an outage occurs.