Compressors - Size Matters!

By Dean Bielanowki

When looking to purchase a compressor, you really need to know what you plan on using it for, because with compressors, size really does matter!

Certain pneumatic tools require much more air flow than others, and with a small compressor, these high volume air tools will simply not work very effectively. Let’s look at some examples.

We’ll start with air nail guns, which are perhaps the most common pneumatic tool used with portable air compressors. Now, nail guns use very little air in comparison to most air tools, because the air is used in very short pulses as each nail is driven by the nailer, so overall air volume required is comparatively small. Even a small 1-gallon air compressor will be able to run a large framing nailer. So if you only plan to use air nailers with a compressor, you can get away with the smaller tanks on the smaller units.

The difference in tank size is that the smaller the tank size, the more times the motor will have to kick over to refill the air storage tank. If you are a builder that constantly uses an air nailer with nailing in rapid succession, you might want to consider a 6 gallon tank compressor as minimum. For only occasional use by the home DIY enthusiast or renovator, a 3-gallon tank unit will work well. Smaller air nailers like pin nailers use even less air and so you can go to smaller compressors again.

Any other pneumatic tool that uses small short bursts of air can be put in this similar category. But then there is the other side of the coin - air tools that use compressed air constantly or in high volumes. These tools are typically spray guns (not including low volume airbrushes however), air sanders, air grinders, some heavier duty air drills, pneumatic wrenches and rattle guns. These tools can use air continuously and as such require larger storage tanks on compressors to deliver that amount of air without interruption. A 15 gallon or larger tank on a compressor bests suits these tools because the motor can cycle to keep the tank filled to a constant working pressure. Anything smaller and the compressor motors will tend to run continuously in an effort to maintain tank pressure, and many compressor motors are not rated for continuous work over long periods.

Usually an air tool will specify in its documentation what volume of air flow it uses. Compressors also will state what volume of air flow they can continuously produce. Matching the air tool’s required flow rate to the flow rate capability of the compressor you wish to use it with is vital.

Then there is the issue of oil vs oil-less compressors, and direct-drive vs belt-driven. Basically, these facts could be argued until the cows come home, but in my experience, oil compressors (i.e. ones that have an oil reservoir to lubricate moving motor parts) generally last longer than oil-less units and are generally quieter in operation too. Belt-driven motors are also often much quieter than direct drive models too. But there are also cost differences to consider. Belt-driven models are generally more expensive but possibly last longer and are certainly much friendlier to the user and their neighbors when it comes to noise output. Oil-less compressors are mostly “maintenance-free” meaning no oil-changes are required before each season of use.

Whatever you choose, my advice is to first think what type of air tools you plan to use in the future with your new compressor. If any continuous flow or high volume tools are to be used, you need to look at the larger models with larger motors and tanks. If only air nailers, airbrushes or low volume air tools are required, a smaller unit might just fit the bill. And then there is the portability aspect too… Larger compressors are heavy and hard to move around. Small ones can be easily carried.

So many things to consider! But spend the time to make the right choice now and you will not need to re-purchase later on down the track!