Jul 12
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How to buy an air compressor
What air compressor should I buy?
If you have never owned one you may be very well asking yourself how to buy an air compressor as the variety available is huge! What size do you need? How big a tank is right for your job? Will it be very noisy? Does it have enough power? Will I be able to carry it? Is it suitable to use on site? How long will it take to inflate my tires and a host of other questions that will come to mind.
Far too often people will buy an air compressor without any thought as to the use that they will put it to and are then disappointed that it cannot do what they want, they then leave a review of the product saying how poor it is even though the problem is often themselves! My first compressor that I purchased was an impulse buy in a store and was vastly underpowered for what I needed as I am a very keen DIYer and like to mess with my car and other projects. The unmissable bargain that I had purchased was really a waste of my money but it led me to read up on and learn about them before my next purchase.
This article will run through the various aspects of air compressors and what you should look for when buying one.
Air Compressor Portability
If you need to move your compressor around from place to place then you need to buy yourself a portable air compressor, but peoples definition of portable varies considerably as do their needs from their compressor.
If you need a small air compressor for cleaning, inflating tires, air brushing or firing a small nail / staple / or brad gun for upholstery or small carpentry works then a lightweight compressor that can be carried from place to place will be sufficient. These can weigh as little as 20lbs with convenient carrying handles to make life very easy. Small air compressors however are exactly that, they will not power more substantial tools so don’t buy them expecting huge volumes of air!
If you need a larger compressor that can power a more substantial finishing gun or framing gun then you can still find compressors that can be carried weighing up to 50lbs which is about as much as most people can carry around comfortably for short distances. These compressors are also still small enough to put in the trunk of your car to use away from home. In addition to those that can be carried you will also see small wheeled versions that can be moved like a small trolley or wheelbarrow making life even easier.
If you need a more substantial compressor that can supply more air for running multiple nailers or for ratchets and impact drivers for mechanical work then the compressors you buy will need to be wheeled to enable you to move them around. Consider also whether you can get them into your vehicle should you need to use them as anything other than a home air compressor.
Gas Powered air compressors generally are wheeled as they are designed to be used on site and moved around to where the work has to be done, however most are too large to fit into a standard saloon car and will need a pickup truck to be taken to site.
Air Compressor Noise
An air compressor consists of a motor and a pump to compress air into a tank to provide power, these are invariably noisy and vibrate considerably! That being said it is possible to buy quiet air compressors and some are surprisingly powerful despite the lack of noise.
If you are going to use a compressor in a residential area or you like to do your work into the night then you should consider investing in as silent a model as you can afford. It is also better to buy quiet models if you are going to be using in a confined space as you do not want to be damaging your hearing.
You should use hearing protection if you are going to use one in a confined space for any length of time. Look at this hub on decibel levels if you need to see how loud a compressor really is in comparison to other items.
Air Pressure.
An air compressor pumps air into a tank called a receiver under pressure and the tank stores that pressurized air for your use. Tanks come in a variety of sizes and pressure.
Most tools require less than 100PSI (pounds per square inch) to be operated, there are some exceptions to this such as high powered framing nailers that are powerful enough to drive a nail into concrete
Most air compressors pressurize tanks to around 125PSI although some will pressurize to 150 or even 200PSI which means that you have a larger volume of air in a smaller tank. A smaller tank therefore at a higher pressure can be the equivalent of a larger tank at lower pressure.
A higher pressure will mean that you can use your air tools for longer before the compressor has to work to refill the tank with air, this will help minimize the wear and tear on your compressor and any interruptions to your work whilst the tank pressurizes.
An air regulator is used to reduce the pressure of air coming from the tank into your airline and to your tool so that your tool can be run at its optimum pressure.
Tank Size
Generally speaking the bigger the tank the larger the volume of air that can be supplier for air tools and the longer that you can run tools before the compressor has to refill the tank. Where possible use as big a tank as you can get, if you have to make allowances for portability and space then try to get a higher pressure model as this will make up for the smaller size.
You run your air tools from the tank not direct from the air compressor, the tank is your buffer and power storage facility, it will slowly empty until it hits a predetermined pressure at which point it will refill by switching on the compressor. As long as your tank is of adequate size for your tools the compressor will not be on a lot of the time.
Many people buy small compressors expecting them to refill their car or truck tires rapidly like the air supply at the local garage, buying a low pressure compressor with only a one gallon tank will not do the job that quickly although it will be many times quicker than one of the 12V tire inflaters that you keep in your trunk for emergencies.
Power Supply
Most of the smaller compressors will run off of a standard power socket at 120V or 240V in some countries and will be quite OK with a normal extension lead to get power to them. However when you start to move up to the larger compressors you may need a dedicated circuit as they pull too many amps, especially on start up. So if a compressor requires 13 amps or more you may want to think about where and how you will power it.
Look at the reviews on the various sites as you may see many comments about some air compressors throwing circuit breakers every time they start up, if this is the case then you will have to invest in a dedicated circuit for the compressor for your garage air compressor.
Also check the voltage that it runs at as not all run at just 120V or even single phase etc.
Motor HP
How powerful a motor should you use? Well anything above 2HP is likely to blow a 15amp circuit at 120V so it is unlikely that you will be using a motor more powerful than this unless you wish to wire a specific circuit for your air compressor.
If a manufacturer claims that the engine size is several HP but it runs on a standard circuit then they are likely inflating their HP rating considerably and many do even though it is illegal to do so!
A compressor can supply about 4 CFM per HP (horse power) to refill the air tanks so obviously a compressor with a lower power although able to run on a standard circuit will take more time to refill the tanks so if you use “thirsty” tools you are likely to have interruptions to your work whilst the tanks are replenished.
What size Air Compressor?
Most air compressors pressurize tanks to around 125PSI although some will pressurize to 150 or even 200PSI which means that you have a larger volume of air in a smaller tank. A smaller tank therefore at a higher pressure can be the equivalent of a larger tank at lower pressure.A higher pressure will mean that you can use your air tools for longer before the compressor has to work to refill the tank with air, this will help minimize the wear and tear on your compressor and any interruptions to your work whilst the tank pressurizes.
An air regulator is used to reduce the pressure of air coming from the tank into your airline and to your tool so that your tool can be run at its optimum pressure.
CFM or SCFM
The volume of air a compressor can supply is a very important factor when considering how to buy an air compressor. Cubic feet per Minute(CFM) or Standard cubic feet per minute (SCFM) is how the volume of air that a compressor supplies is measured. This is normally quoted at two different pressures, 90PSI and 40PSI. Every air tool has a requirement for volume of air to provide it with the power that it needs at a specific pressure, the following table will give a little guidance as to how big the CFM needs to be for a specific type of tool.
If your compressor cannot supply the required CFM for a tool then the tool will either not work at all or it will work very poorly. It is best to buy an air compressor that is capable of providing at least 25% more CFM than the biggest tool that you want to use.
An option here if you are worried about getting the right air compressor for the tools is to buy Air compressor combo kits with the tools included in with the compressor.
CFM Required for Air Tool
|
Tool
|
CFM Required
|
|
|---|---|---|
|
Nailer
|
1 CFM
|
|
|
3/8 Ratchet
|
3 CFM
|
|
|
Air Hammer/Chisel
|
4 CFM
|
|
|
Air Drill
|
4 CFM
|
|
|
1/2 Impact Wrench
|
5 CFM
|
|
|
Angle Grinder
|
6 CFM
|
|
|
Spray Gun
|
6 CFM
|
Reliability
No manufacturer is perfect but some have fewer quality problems than others; manufacturers such as dewalt have gone through a period of poor quality that many blame on their outsourcing of components to china, but to be honest many manufacturers have done the same.
When deciding how to buy an air compressor and which one you need it is best to read reviews so that you get an idea of what experience other users have had. But don’t just be guided by stars, read the reviews as many negative reviews are more to do with the reviewers misplaced expectations than a failure of the actual compressor.
Most sales sites have reviews so look at all of the reviews if there are any and search forums such as the industrial air compressor forum to see if there are any reported problems.
Buying an air compressor
I hope that this answers any questions you may have had about how to buy an air compressor, if you have any more questions or wish to add anything please leave it in the area below.
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