UPS Not Working On Generator Power

UPS battery backups can be lifesavers in a wide variety of situations. While many people use them to keep critical devices powered in homes or offices, some use them in places where generator power is the only option. The power is essentially the same, so why would a UPS not work on generator power?

A UPS will not work on generator power if that power is unstable, with fluctuations in frequency, voltage, and more. Besides that, the UPS’ sensitivity settings might be too high, causing it to switch to battery power when experiencing minor electrical fluctuations. Lastly, the generator fuel type and UPS topology can also affect their compatibility and cause the UPS not to work on generator power.

Understanding UPS compatibility with generators can be pretty challenging to understand at first. But don’t worry. This guide will show you everything you need to know!

Why Is My UPS Not Working On Generator Power?

A generator will give your UPS the power it needs to function correctly. Unfortunately, there are significant differences between power from a generator and a standard wall socket.

Here are the reasons your UPS is not working on generator power and how you can deal with them:

Generator Power Instability

What it means: The first thing you must understand is that UPS units are picky about the incoming power it accepts.

Regardless of whether the unit gets power from a wall socket or generator, it will only accept it if the current is stable. That means the current should not have too many fluctuations in terms of current, voltage, and other characteristics.

Each UPS unit has various circuits that monitor the incoming power supply. When the unit senses that the incoming power is unstable, it will stop accepting it, and the UPS will stop working.

What it does: The first reason your UPS is not working on generator power is that the power is unstable. Unfortunately, a generator can’t always provide a stable power supply. So, it’s normal for there to be drops or spikes in voltage, for example.

As mentioned above, those fluctuations will trigger the UPS to reject the power and stop working. Unfortunately, that means the UPS can’t run on generator power and won’t recharge its battery.

Generators rely on mechanical components to produce electrical power. So if its output is unstable, there’s likely a mechanical problem like varying engine speed, clogs, or others that need to be fixed.

How to fix it: Generally, the solution to this problem is to fix the generator’s mechanical problem. Doing that will allow the generator to run smoothly and produce a stable output that the UPS will accept.

Common mechanical issues in generators include dirty filters, dirty fuels, clogs, and more.

Read: Why Ups (Battery Backup) Is Beeping Continuously?

UPS Sensitivity Settings

What it means: A stable flow of electricity is crucial for a UPS to function correctly. That’s why it has built-in circuits that sense any current fluctuations. When those fluctuations happen, the internal circuits protect the UPS by disconnecting incoming power and going to battery mode.

Many UPS models also allow you to control their sensitivity towards those fluctuations. So, for example, if your power source is prone to some instability (like a generator), you can lower the sensitivity settings.

As a result, the UPS won’t switch over to battery power so quickly.

What it does: Another reason your UPS is not working on generator power is that the UPS sensitivity settings are too high. That will cause the UPS to stop working when experiencing minor fluctuations in the generator power supply.

How to fix it: You can solve this problem by changing your UPS sensitivity settings to something lower. That way, the UPS will continue working even when the generator experiences trouble trying to maintain a stable power supply.

Read: How To Check UPS Battery Health?

Generator Fuel Source

What it means: Generators come in all sorts of shapes and sizes. But, more importantly, they also come with plenty of different options for fuel sources.

For example, you can buy generators that run on propane, diesel, or even natural gas.

All of them are useful for generating electricity. However, each of them will affect the generator’s performance quite differently.

What it does: At this point, it should be clear that generators can sometimes struggle to maintain a stable output. When that happens, the UPS will sense that unstable power and stop working.

Another deciding factor in the generator’s output stability is the type of fuel it uses. For example, your gas or propane generator will take slightly longer to respond to fluctuations. That can disrupt the generator’s power supply to the UPS and stop it from working.

On the other hand, diesel is the preferred fuel source among generator owners. That is because diesel generators tend to provide a more stable output despite being more expensive to run.

How to fix it: The only way to fix this issue is to be more mindful when matching a generator with your UPS. If possible, you should use a diesel generator to provide a more stable output.

But let’s say that propane or gas generators are your only option. In that case, you’ll have to get a generator that’s much larger than your UPS needs. That’s because larger generators can handle fluctuations better and maintain a stable power output for your UPS.

Read: How To Troubleshoot UPS Battery?

Type Of UPS System

What it means: UPS systems come in several types, also known as ‘topologies’. There are standby, line-interactive, and online double-conversion UPS models available on the market today.

Standby and line-interactive UPS systems are less compatible with generator power. That’s unlike online double-conversion types that work well with generators as power sources.

What it does: The difference between UPS topologies is in how they handle changes in the incoming electrical frequency.

If your UPS is a standby or line-interactive type, that could explain why the unit fails to work on generator power. These types of UPS units manage frequency variations by using their battery power. 

In simple terms, the UPS will stop working on generator power and switch to battery mode instead.

However, an online double-conversion UPS is much better equipped to handle unstable generator power that fluctuates in frequency and voltage.

How to fix it: The solution to this issue is to change UPS types. As you read above, online double-conversion UPS models are much more compatible with generators because of how they respond to unstable incoming power.

Therefore, if you have to rely on generator power in the long term, investing in that kind of UPS would be wise.

Read: Can A UPS Last For 3 Hours?

Frequently Asked Questions (FAQs)

Here are a few more questions and answers to help you troubleshoot your UPS:

Can I Use UPS On Generator?

Yes, you can run your UPS on generator power. UPS models can accept incoming power from generator outlets as they do with standard wall sockets in your home or office.

Read: What Happens When UPS Battery Fails?

How Do I Size A UPS Generator?

The generator you choose for your UPS should be between 1.25 to 2 times higher in capacity than the UPS. That is because larger generators will handle current fluctuations more effectively than if the generator was smaller or closely matched with the UPS.

What Are The Four Types Of Fuel Used In Generators?

When choosing a generator to use with your UPS, you can select a generator that runs on diesel, propane, gasoline, or natural gas. Although costlier to operate, diesel generators are the best choice for their excellent performance and output. 

What Is Electrical Frequency, And Why Does It Matter?

Electrical frequency is the rate at which electrical current changes each second, and it’s measured in hertz (Hz). Therefore, a generator’s electrical frequency fluctuations can prevent it from working well with a UPS.

What Are The Names Of The Three 3 Main UPS Topologies?

The 3 UPS topologies are standby (or ‘offline’), line-interactive, and online. Online UPS systems are much better suited for generator power than standby and line-interactive types.