10 Things You Need to Know When Buying a Reciprocating Air Compressor

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Are you thinking about buying a reciprocating air compressor for your workshop, garage or business? There are some things you should know before buying one!

An air compressor is a huge investment, so take your time to learn about air compressors and the different models and options.

Buying the wrong air compressor will not only get you disappointed (in terms of usefulness or power or air output), but can also set you up for huge maintenance bills in the future.

Here are 10 things to think about BEFORE you go to the store to buy a reciprocating air compressor.

1. Compressor type

There are basically 3 types of reciprocating air compressors:

  • Single stage compressors
  • Two stage compressors
  • Twin compressors
    Single stage units compress the air in one stroke, from ambient to end pressure. They typically go up to 20 CFM (cubic foot per minute) at a pressure of 125 psi

For more power, you will need a two stage compressor. A two stage compressor uses two stages to compress the air to the end pressure. This means your compressor will have two cylinders/pistons.

The big cylinder is the low pressure stage, while the small cylinder is the high stage. In between the stages the air is cooled.

Two stage air compressors go up to about 50 CFM capacity at about 175 psi.

Whether you need a single or two stage compressor ultimately depends on the amount of capacity (cubic foot per minute) you need.

2. Capacity and pressure

The capacity (CFM) and the pressure of the air compressor are the two most important specifications.

To find out the capacity that you need, simply add up the air consumption of all the air tools that you will use.

Small tools like nailers use only a little air, while big tools like sanders and grinder use lots of compressed air!

To find out the pressure that you need, check again the specifications of the air tools that you plan to use. The highest required pressure dictates the pressure that you need.

It’s always smart to buy a compressor that is capable to deliver more than you need. You will probably add more tools in the future, and almost all compressed air systems will have a leaking hose or coupling somewhere!

3. Horse power

You DON’T need to know the horsepower of the air compressor.

The horsepower is a result of the required pressure and capacity that you need, not the other way around.

Don’t look at horsepower. Look at capacity (CFM) and pressure (psi).

4. Electrical connections

You wouldn’t be the first happy new compressor owner that comes home with an air compressor that he is unable to wire up!

Know the voltage that you have at home. Know the maximum current that your wiring can handle. Do you have single phase or 3 phase power?

Installing extra electrical wiring (or even having 3 phase power installed at your home!) can be more expensive than the air compressor itself!

5. Noise

Do you plan to install the compressor inside or outside?

A reciprocating compressor makes a lot of noise. Always check the noise level of the compressor before buying one. If you are buying a compressor in a shop, ask them to run it, so you can hear what is sounds like.

To reduce the noise, you can make an enclosure around the compressor. Make sure you add enough ventilation holes (and a fan if necessary). An air compressor creates a lot of heat, so adequate cooling is required!

6. Tank size

Most reciprocating compressors come with a 40 – 80 gallon tank, which is fine.

A larger tank size is always better. A bigger tank means that there is a bigger compressed air buffer.

A bigger compressed air buffer is useful when you use big tools that use more air than the capacity of your compressor. Pressure will drop more slowly with a bigger air tank.

7. Compressed air filters

How clean do you need your compressed air?

Compressed air is hot, wet and dirty. Depending on your application, you need to filter it and remove water and oil.

If you use compressed air for paint-spraying, you don’t want oil, water or dust in your compressed air, the air needs to be very clean.

If you only use it for powering air tools, you don’t want water in your compressed air but you don’t really care about oil.

There are filters available to remove water (droplets), oil, and dust. For even dryer compressed air, you need to get a compressed air dryer.

8. Other options and extra’s

There is a list of options you should thing about. Do you really need them, or are they optional?

Pressure regulators – to regulate the tank pressure back to a stable, lower pressure
Size and number of air connections
Vertical or horizontal tank
Manual or automatic drains

9. Weight

Most (online) stores will drop your new air compressor on your drive way. You will need to bring it into your garage or wherever you want to place it yourself.

Your new air compressor will probably come on a wooden pallet. You can choose to keep it on the pallet, or remove the pallet.

Think about how you will bring your 600 lbs air compressor to its place before you buy it!

10. Duty cycle

Last, but definitely not least!

The duty cycle is the percentage of time your compressor can run.

Most single stage compressor have a duty cycle of only 50%. This means that when you run your compressor for 5 minutes, it needs 5 minutes to cool down.

Most dual stage compressors have a duty cycle of 100%. They can run 24 hours per day when needed.

If a compressor has a 100% duty cycle, it is often advertised. Beware when the duty cycle is not mentioned.. it is probably only 50%!

Conclusions

As you can see, there are lots of things to think about when buying an new air compressor. The above list will help you make a good decision. If you can’t choose between two models, always pick the bigger unit.

There is a lot more information in the air compressor buying guides on my website: thediyhubby.com