When you’re running an air compressor for the first time, it makes sense to look into all its various features and capabilities. How many amps does an air compressor use? Can you plug your new air compressor into your home’s main power outlets and be safe to do so?
RPM generally dictates the speed of your air compressor. It stands for rotations per minute, and you will normally find older air compressor models have these statistics listed alongside horsepower (HP).
On the whole, however, you’re more likely to find that air compressor manufacturers tell you how fast their models run based on CFM, or cubic feet per minute.
How fast an air compressor should run depends on what you want it to do, and how much energy you wish to use. Therefore, there is never likely to be an exact answer!
However, as always at Renovation Dojo, we’ll do our best for you – keep reading, and we’ll take you through why RPM and CFM can make a difference to your air compressor projects, and why it’s worth keeping these details in mind.
What RPM should an air compressor run at?
There are a variety of different answers to this question, but to get a good idea of what industry professionals use, it is working to the standard of between 800 and 900 RPM. However, you will also need to keep your air compressor’s HP in mind, too – a little more on that below.
The slower the RPM, the quieter the motor. What’s more, an air compressor running at a lower RPM is likely to generate much less heat, and therefore, you won’t have to deal with humidity and moisture in the air. It’s a misconception that the faster the RPM, the more effective the compressor is. That’s because, again, HP comes into play. RPM is a measure of part rotation speed – not a measure of power!
That’s why you may find that some air compressors run at the same RPM, but at different rates of HP. 3HP, for example, tends to be the upper limit for most home air compressors.
You should also keep in mind that you can slow down RPM, or use a slower model if your air compressor is unable to run motors expressing more than 3HP. It is, as always, a bit of a learning exercise!
You’ll also need to keep in mind the pulleys used in the motor you wish to connect to your air compressor. There’s an interesting calculation that will likely help you, and again, we’ve listed this below.
Experts also suggest that most air compressors never actually reach their maximum RPM listed during operation. Even the best air compressors – and the best value air compressors – will likely hold back on the max ratings you’re advised of before you buy.
What’s the difference between RPM and HP?
Crucially, RPM is the speed at which a moving part in your air compressor will run per minute – it’s all about the rotations. HP, or horsepower, is a figure related to maximum power capacity.
For example, 1HP, in general, should have the power to pull up to 30,000lbs in weight by a foot’s distance in less than one minute. As you can imagine, that’s a lot of force!
Both HP and RPM are figures you will need to keep in mind when looking for a new air compressor. That’s because you’ll need to know how energy efficient these systems can be, and whether or not they are likely to keep up to the demands of the motors you wish to run.
You can actually work out the HP of a motor or device with RPM – however, you’ll also need to know the figure for torque, too. Torque is normally measured in imperial hefty and potential capability, so generally in pounds and feet.
The HP you need is generally calculated by multiplying your torque by the available RPM. This means that for an engine or machine to run at a higher power, it’s going to need a faster RPM or to build more torque – simple when you know how!
How to calculate air compressor RPM
Knowing how to calculate air compressor RPM, however, is a slightly different problem. Many experts have many different ways of calculating this exactly. Using a calculation is likely to be useful if you are using an older air compressor without access to the exact figures and statistics.
That said, there seems to be more worth in calculating or looking into the CFM of your air compressor. The general rule of thumb is that you’ll get around 3 to 4 CFM for each HP your air compressor runs at. That’s based on 90 PSI, or pounds per square inch.
Luckily, many manufacturers and air compressor brands will likely give you the information you need to know without you having to do much of the hard work yourself. The exact RPM or CFM you’ll need to run a specific motor or machine will depend on pulleys, weight involved, and the efficiency you’d like to power your machine at.
Is it worth looking for low RPM / CFM air compressors?
In many ways, it’s certainly worth considering switching to a lower RPM for air compression. That’s because you’re likely to save energy in doing so (and ergo money and risk of blowout). As mentioned, a slower RPM is also likely to work better with motor demands at higher HPs.
Therefore, it’s a misconception that you are going to need a very fast RPM to handle a particularly demanding motor or machine. If you’re unsure whether or not an air compressor is right for you in this regard, always make sure to consult with the manufacturer, in an available manual, or with your salesperson.
As you can see, RPM, CFM, PSI and HP are all points you need to consider when investing and setting up an air compressor. You don’t have to purely consider how many watts an air compressor uses!
Don’t worry – it is getting easier than ever to buy and set up air compressors in the modern age. Innovations in new technology mean that these systems are working harder for us than ever before, too!