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What Size Generator for 5HP Motor

Sizing a generator is a crucial step in making sure you’re buying a unit that can run your load without any problems. You want to make sure you don’t buy a model that can handle the amount of power your motor draws without overloading, as that can cause problems to both the load and the generator. So, what size generator is ideal for a 5HP motor?

First, you need to get your motor’s power draw (3730 watts) to get the rated watts. With this, you can estimate its starting watts by doubling the value (7460 watts). So, the ideal generator for running a 5HP motor must deliver at least 3730 running watts and 7460 starting watts and is compatible with the motor’s rated frequency and voltage.

And that is as simple as it can get. However, as you can see, there are few numbers involved. I have included the simple process I used to come up with these numbers. I’ve also included a simple buying guide to help you buy the best generator for your 5HP motor.

How to Size a Generator to Run 5HP Motor

When sizing a generator to run your motor, you need to know how much power the motor draws and then check the size generator ideal for running it.

Get the Motor’s Wattage (Running and Starting Watts)

As a reactive load, a motor will draw a high amount of power when starting up and draw less to keep it running. That means your 5HP motor has running and starting power, which you’ll need to get to size the generator to run it efficiently. Where do you start? There are two ways you can get these wattage ratings:

a) Use the Motor Voltage and Amp

The easiest way to calculate the size of a generator to run a 5HP motor or any other load is to use the already-available power ratings normally found on the unit’s manual or a tag/nameplate on the load case the motor back cover.

Here you can find the rated voltage and amperage. With these two, it’s pretty easy to calculate the wattage. All you need is to multiply the two and get VoltAmps, which is the same as rated wattage. And to get the starting wattage, multiply the running by two.

So, if your 5HP motor’s rated amperage is 17amp and runs on a 230-volt system, you get its wattage by multiplying the two valves to get:

16.23 amps x 230 volts = 3732.9 watts (VoltAmps)

That is the rated wattage. You want to multiply the rated wattage by two to get the starting watts, as I mentioned before. So, your motor needs at least 7465.8 watts (3910 x 2) to start and 3910 watts to keep it running.

b) Convert Horsepower to Wattage

If the amperage and voltage rating isn’t available, you can convert the horsepower, which you already have to wattage. Typically,

1HP = 746 Watts

So, take your motor’s horsepower and multiply it with 745.6 watts to get the rated watts.

5 HP x 746 Watts = 3730 running watts, and if you double this, you get 7460 starting watts.

So, what size generator is ideal for running a 5HP motor?

The perfect generator for running your 5HP motor must deliver 20% more of the motor’s rated watts and surge watts.

That means you need a generator that can produce 4500 running watts and 9000 starting watts. Your most concern here would be the starting watts. Most generators that provide this amount of power can deliver at least 5000 watts. But that doesn’t mean you should confirm it.

Remember to factor in other appliances or devices you might want to hook up to the generator. If there are many, you will want to invest in a standby-sized generator enough to run the appliances, including your 5HP motor.

How to choose a generator for a 5HP motor

The best approach to finding the right generator for your 5HP motor is to understand the factors that affect this choice.

1. Wattage

This is the first and most critical factor while choosing a generator. It refers to the power consumed by the motor. So to choose a generator for the 5HP motor, you need a unit sufficient of delivering its wattage requirement, which is around 4500 running watts and 9000 starting watts.

2. Generator Runtime

Running time refers to the amount of time an appliance or tool would run on one full tank of gas. This means that if you are running your 5HP motor for 6 hours continuously, then you need at least a 6-hour generator.

It is recommended that you start with a more significant wattage rating than required because it will keep the engine load down and the engine life up. Finally, note that a generator should not be chosen based on its maximum power consumption but rather on its continuous rating.

3. Fuel Type

Most generators run on gas as their primary fuel, but some can also run on propane. In addition to the type of fuel the generator runs on, you should also consider what kind of gas is available at your workplace or home. If you have a propane tank at your office or home, then choosing a unit that runs on propane would be more economical and convenient for you.

4. Noise Level

Noise is unavoidable with a portable generator because an internal combustion engine powers it. Noise levels may range from 55 dB (A) for units with low noise levels to 80+ dB (A) for extremely noisy units with higher power consumption levels.

For example, running the 5HP motor will be noisier than when you hook up another load like a circular saw. The noise level depends on the size, type, and power of the generator. Higher watt generators are usually noisier due to higher engine revolutions for producing that much power.

5. Portability

Portability is also an essential factor to consider if you need portable power. Generally, it refers to how easy moving around and transport the unit from one place to another without much hassle. Higher-end units come equipped with wheels and handles that make moving them easier.

6. Generator Type (Convectional or Inverter generator)

Conventional generators are cheaper and easier to repair, but they operate at a much lower efficiency than inverter generators. This inefficiency increases the conventional generator’s cost over time through higher fuel consumption and maintenance costs.

Converter generators run at around 85-90% power conversion efficiency. If the load changes, the engine adjusts its RPM automatically to meet the required wattage level. They can handle loads from about 50% up to 100%.

So when you need more watts for your tool, an inverter generator will adjust immediately without making noise or hampering performance in any way.

Inverters tend to be better with sensitive electronics such as laptops because their output is immaculate and free from spikes and fluctuations that may damage electronics equipment.

Inverter generators have another edge over conventional generators regarding portability and convenience because they are designed to be lighter than their conventional counterparts. This makes them easier to carry, which is especially beneficial for people who need to move the generator frequently.

You can read more on how to select a generator here.

Related Questions

Can you run a 110 motor on 220?

The short answer is yes; you can run a 110 motor on 220. A 220-volt line will work fine for running a 110V motor at half speed. The longer answer comes in when you realize that running at ten amps, the motor will get very hot very fast and potentially burn out or cause damage to itself or surrounding components.

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Sharif Gen

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