We know that choosing an air compressor can be a daunting task. There are so many to choose from, and the technical terminology can be confusing if you don’t know what to look out for. So how do you choose the right air compressor for your needs?
This comprehensive air compressor buying guide will help. It covers how air compressors work, their uses and their features. It explains what CFM requirements are and looks at the different air compressor fitting types. It lists what size air compressors are required for different jobs and highlights some key things to consider when buying an air compressor. Finally, it answers some frequently asked questions. You can view our range of air compressors here.
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An air compressor is a machine that converts atmospheric air into energy that’s then used to power a variety of tools and devices. Its main components are a motor, pump and air storage tank.
An air compressor works by sucking in air through the pump, which then forces it into the storage tank, compressing it as it goes. Once the tank reaches capacity, the air compressor shuts off. The stored compressed air can then be used as power by attaching an air hose and air tool to the tank. When the trigger on the tool is pressed, pressurised air is released to power the tool.
- Belt drive vs direct drive air compressor
Belt drive air compressors have a belt that connects the pump to the motor, which turns when the motor is running. The size of the belt determines the pressure and speed the air compressor can reach. The main advantage of belt-drive air compressors is that the pressure and speed can be varied by adjusting or changing the belt, making them more flexible in terms of the tools they can power. They are also quieter than direct drive air compressors and require less maintenance, although the tension in the belt does have to be constantly monitored. This type of air compressor comes with a large storage tank and is designed for heavy-duty workshop and industrial use.
Direct drive air compressors are simpler in design, with their pump connected directly to the motor. They are more energy-efficient and reliable than belt drive models, but they are noisier and more expensive to buy. This type of air compressor has a small tank and is designed for home and semi-professional use.
- What is a magnetic starter on an air compressor?
A magnetic starter is an electromagnetically operated switch that’s typically found on powerful air compressors (5HP or above). It’s a safety device that stops electricity from powering the motor if it detects an overload, preventing the main pressure switch from burning out. Powerful air compressors without this device may frequently need their main pressure switch to be replaced.
- What is a reed valve air compressor?
A reed valve air compressor has a valve located in the pump called a reed valve. It’s there to ensure that airflow only goes in one direction. A faulty reed valve results in loss of power and air pressure build-up.
- What is a tandem type air compressor?
A tandem type air compressor is also known as a two-stage air compressor. This is because it compresses the air twice, rather than once, for double the pressure. It’s best used for heavy-duty industrial work where frequent and prolonged use is required.
- How does an oil-less air compressor work?
All air compressors require lubrication to their moving parts to moderate heat, friction and wear and tear. An oiled air compressor uses oil as lubrication, while an oil-less air compressor doesn’t. Instead, the parts are coated in a friction-reducing, self-lubricating chemical.
Oil-less air compressors are lighter, quieter and require less maintenance than oiled models. And their biggest benefit is that the lack of oil means no contaminants are transferred into the pressurised air. For this reason, they are ideal for spray painting and in clinical settings.
On the other hand, Oiled air compressors require less maintenance, but the oil contaminates the air. They are best used for professional, heavy-duty work where prolonged use is required.
The most important factor to consider when choosing an air compressor is what tools and tasks you will use it for. That will then determine the CFM (cubic feet per minute) requirement to power the tools (see more detail in the next section).
You’ll also need to consider how frequently and how long you’ll use it to determine what air storage tank capacity you need. For example, you’ll only need a small tank for occasional DIY use, but a large tank will be better for professional or prolonged use.
Other considerations include whether it needs to be portable, and therefore whether you need a corded or cordless model, and if you need a brushed or brushless motor or an oiled or oil-less model.
- Corded or cordless?
Corded air compressors are plugged into the electricity to supply power to the motor, which means they must be used near a power socket. For this reason, corded air compressors are best suited for use in factories and workshops where portability isn’t required.
On the other hand, cordless air compressors are powered by petrol or diesel. The absence of a cord means they can be used anywhere and are much easier to move around.
- Brushed or brushless?
Brushed air compressors have a motor that’s driven by small metal brushes. Whereas brushless air compressors have a motor with an electronic circuit board and sensor. The absence of brushes on a brushless motor means reduced friction and heat build-up and, therefore, less wear and tear, which gives them a long lifespan. Brushless motors are also more efficient to run than brushed motors.
- Oiled or oil-less?
As explained in the section above, an oiled air compressor has moving parts that are lubricated by oil. In contrast, an oil-less air compressor’s components have a special self-lubricating coating. Choosing between the types can be decided by considering how much the air compressor will be used and whether non-contamination of the air is important. For example, if the air compressor will be used for long hours daily in a factory, an oiled model will be best. Whereas an oil-less model is better for infrequent or DIY use. And if the air compressor will be used for spray painting or in a clinical setting, an oil-less model will supply non-contaminated air.
- Tank capacity
Air compressors come in various tank sizes, measured in litres, ranging from 4L to 100L. Generally, the larger the tank, the longer you can run the air compressor at a consistent power. However, the tank size you need will also depend on the tool you plan to use it with. All tools require a minimum airflow, measured in cubic feet per minute (CFM). To determine what tank capacity you need for a tool, multiply the tool’s standard cubic feet per minute (SCFM) by 6.
When referring to air compressor size, we refer to the airflow rate it can deliver, measured in cubic feet per minute (CFM). The rate you need will depend on the task you are carrying out and your tools.
This section of the air compressor selection guide covers some of the most common uses for an air compressor and recommends the size of air compressor you need for the task. However, you should always check the manufacturer's instructions for your tools for exact compatible air compressor sizes.
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- What size air compressor for the garage?
You will likely use a range of tools in a garage, so you should choose an air compressor size suited to the tool that needs the highest SCFM rate to work. For example, paint spray guns usually have the highest CFM requirements, needing an air compressor that delivers around 22 CFM.
- What size air compressor do I need for a plasma cutter?
For most plasma cutters, you'll need an air compressor with a minimum of 6 CFM.
- What size air compressor for framing nailer?
Most framing nailers need an air compressor with a minimum of 2.4 CFM.
- What size air compressor for nail guns?
Most nail guns need an air compressor with a minimum of 1.2 CFM.
- What size air compressor is needed for spray painting?
Spray gun CFM requirements vary greatly. Depending on your type, you'll need an air compressor with a minimum CFM of between 7.2 and 21.6.
Thanks in large part due to their versatility and low cost, piston compressors are among the most common air compressors being used today. They are the right choice for a wide range of applications, from DIY to workshops to dentists.
Once you have concluded that a piston compressor also meets your needs best, there is one more decision to make: aluminum versus cast iron.
If you have used our guide on what type of air compressor to choose, then you will know that the first step in selecting the right material for your compressor (which in this case means the pump, cylinders, flywheel and valves) is to figure out how you want to use your new compressor.
When you know, the choice may be easier than you think – even for a layperson.
Because both materials have distinct advantages, it’s impossible to say which one is better. Ultimately, you have to decide which one is better for you.
However, here is a rule of thumb: If you need a small, flexible compressor, especially for non-stationary use, then aluminum is often the material of choice.
But if durability is most important to you and/or your compressor has to function reliably in tough conditions, then you will probably prefer a cast iron model.
One final note, which is less important for Atlas Copco compressors because of their outstanding durability but should be mentioned in a world in which sustainability is increasingly important: Of the two materials, aluminum is much easier to recycle.
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