What to look for in an air compressor
The best way to choose an air compressor is to already have in mind the air tools you plan on using it with as different air tools place different demands on the machine. Once you have identified the equipment it will be ‘powering’, you are then in a position to identify the parameters needed on the air compressor to have those air tools work properly. The two overriding characteristics of an air compressor to pay attention to are the maximum air pressure it can produce, and the free air delivery or air flow at the outlet that it is able to sustain.
For the air pressure (and to keep things as simple as possible), you can assume that all air tools operate at either of two air pressures. They either need an air pressure of around 40 pounds per square inch (psi), such as for spray painting guns, or air tools like air nailers require a pressure of around 90 psi to operate (most air tool categories operate in the higher 90 psi range). In general, air compressors come with an air pressure regulator to regulate the air pressure at the outlet so that you can use air tools with different air pressure requirements – but check this to make sure!
Free Air Delivery (Air Flow)
Most workshop air compressors can reach the higher air pressures required to operate the majority of air tools, so arguably, a more important characteristic to concentrate on when choosing an air compressor is its ability to maintain a specific free air delivery (FAD) or air flow. This should not be confused with the free air displacement of the compressor pump which is often advertised (albeit slightly disingenuously as it is always higher then the FAD) by air compressor retailers as it does not correspond to the air flow requirements of air tools. If you are confronted with an air displacement value only, then you can assume that the free air delivery of the air compressor at the nozzle outlet will be approximately one third less than its air displacement value. The unit of measure that is commonly used for enumerating free air delivery (and displacement) is cubic feet per minute (cfm), but here in the UK, we also sometimes use litres per minute (l/min).
Different types of air tools have different types of FAD requirements. Some, like air sanders, need an almost continuous flow of air while others, like air nailers, only need air in short bursts. As a result, air tool manufacturers have often had to make certain assumptions on how active their tool will be in the hands of the eventual user in order to derive a free air delivery rating for their tool. So for air nailers for instance, manufacturers usually assume an operating frequency of 30 nails discharged within the space of a minute, or for air impact wrenches, it is usually taken that they will be consuming air for only 12-15 seconds per minute. Therefore, in order to account for higher than average levels of your own air tool use, it is always best to increase the free air delivery that you need from the air compressor by 20-50% before looking for one that can produce this sort of air flow. The table below provides a guide to the typical air flow requirements of different air tools, but it is also important to determine the exact air flow required for the actual air tool you plan to use as they can vary significantly.
|Air staple gun|
|Air impact wrench|
|Air angle grinder|
Air Receiver (Air Tank) Size
This is the measure of the volume of the tank that holds the compressed air. Compressors sometimes come with more than one tank connected together but the number of tanks is actually irrelevant since the total volume is what counts. The bigger the air tank size, the less often the compressor motor will need to switch on to refill it. In addition, working away from a source of electrical power can be extended when using an air compressor with a larger air receiver.
Motor Horsepower Rating
This is the measure of the power of the compressor motor. Essentially, the higher the horsepower, the faster the compressed air tank is refilled. In general, the more horsepower, the better, but go for too high a horsepower and the compressor will need to be connected to a dedicated high amperage electrical circuit to avoid tripping circuit breakers.
Most Popular Air Compressors in the UK
|Air Compressor||Free Air Delivery|
|Max Working Pressure|
|Air Receiver (L)||Power (hp)||Weight (kg)|
|Wolf Air Dakota||9.4 ***||150||90||3||80|
|SIP 06242 Airmate TN3.0/50-D||9.5||130||50||3||45|
|Wolf Air Sioux||6.4 ***||116||50||2.5||35|
|Wolf Air Cheyenne||9.4 ***||150||50||3||44|
|SGS SC24H||6.4 ***||115||24||2.5||30|
SIP 06242 Airmate TN3.0/50-D (our favourite)
The SIP Airmate TN3.0/50-D compressor is a powerful machine that can generate up to 130 psi of pressure. Together with its 50L air receiver and relatively high Free Air Delivery of 9.5 cfm (air displacement of 14 cfm), it is a compressor that is capable of running the majority of air tools out there. Unlike some of its competitor products in its category and even though it has a powerful 3 hp motor, it is still able to safely operate off a normal 13A household plug. Some of that electrical efficiency comes from the twin, V-shaped pump motor design that it uses. SIP Industrial is a very reputable British company that has a history of manufacturing tools for both industrial and domestic users, and has been making air compressors of its own since the 1980’s. Today the company is involved in producing a variety of different machinery and power tools for a variety of different industries including the consumer market. So if you are a professional tradesman or just an over-active DIY-er and you have the money to spare for this quality product, then it definitely gets our vote!
Wolf Power Tools
Wolf is a power tool company whose products are marketed through a number of online outlets including Amazon, the UK Home shopping network, and SportsDirect.com, to mention a few. Their range of tools also includes a range of air compressors for the home and professional user which have become very popular with both DIY enthusiasts and tradesmen alike due to their relatively high specifications at an affordable price. In addition, their range of air compressors on offer caters to a wide range of requirements. As a result, several of their air compressors are positioned in the top ranks of air compressors popular in the UK.
Wolf Air Dakota
Currently, this is our all-round favourite in this category of air compressor based on overall value. This is a large capacity machine that is more suited to the professional or semi-professional who uses air tools regularly. With a 90L air receiver (air tank), the compressor is suited to operating the majority of air tools. The one downside to having such a powerful compressor is that it requires having a dedicated high amperage circuit to operate it. If used on a normal household ring main, the compressor will risk tripping the circuit breaker each time it switches on to refill the tank which can be several times during a job. It is quite a simple job for an electrician to add a dedicated high amperage circuit addition to the common household RCB, so this is not such a deal-breaker even for the home garage or DIY user. The unit displaces 14 cfm or 397 litres/min of air, which equates to a Free Air Delivery (FAD) of between 9 and 10 cfm – a metric that is more relevant to deciding which air tools it is capable of operating, and this FAD is more than enough for the majority of air tools. The unit comes fitted with an air outlet pressure regulator and twin outlet quick release couplers although check that the connectors on your air tools are compatible as not all quick connectors are the same. Another point to consider is that the machine is pretty weighty coming in at 80 kg (for comparison, that’s close to the average weight of a man), and although the wheels do make it somewhat portable, don’t plan on lugging this around too much!
Wolf Air Cheyenne
For the user that needs the high air pressure (150 psi) but not as much air capacity as the Dakota, Wolf has produced a model with a tank that is approximately half the size of its bigger sibling. In addition, it uses a different V-shaped motor allowing the device to be more efficient. Together, this makes the Wolf Cheyenne almost half the weight of the Dakota which some might find appealing if they plan on moving the compressor around somewhat. Once again as with the Dakota, the Wolf Cheyenne also needs to be operated off a dedicated high amperage circuit and not via a regular household ring main if you don’t want to keep resetting the circuit breakers on your mains circuit board on a regular basis. As with other Wolf compressors, the Cheyenne comes with Wolf-branded Uni Hi-flow Quick Release couplers that are not universally compatible with all air tool connections, so you may need to opt for alternative fittings for compatibility.
Wolf Air Sioux
Not everybody needs the high air pressures possible with the Wolf Dakota and the Wolf Cheyenne, so to cater to those individuals with lower requirements, Wolf has a couple of compressors with lower maximum working pressures in the form of the Wolf Sioux 50 and the Wolf Sioux 25. These air compressors have a smaller 2.5 hp motor that can produce a maximum working pressure of 116 psi, and the compressed air is stored in either a 50L or 24L air tank, respectively. However, even with the lower air pressures, one is not greatly limited on which air tools can be used with the Wolf Sioux which can still produce a Free Air Delivery rating of greater than 6 cfm, well within the range of most air tool requirements. One notable advantage of a less demanding motor is that these machines can be operated from a regular household circuit without the worry of tripping the circuit breaker on the mains circuit board.
SGS Engineering – SC24H
The SGS SC24H air compressor is suited to the average consumer with more modest needs. Here, you are paying more for the quality of the machine than you are for its specification. Similar to other compressors in its category, it can deliver 116 psi of compressed air but from a relatively small 24 litre air receiver tank that can put a limit on the type of air tools and the size of the job for which the compressor can be used for. The compressor is a good buy for small jobs and for air tools that don’t have high air flow requirements such as tyre inflating, finish nailing, and stapling, but it will struggle with most air impact wrenches, sanders and grinders. But for the household user, such high intensity DIY work might not be important, rather the fact that the unit can easily run off a normal household socket might be of more significant value. SGS Engineering itself is a reputable British company that makes a wide range of high-quality engineering tools, and this hand-built air compressor is no different. Once again, you are buying quality here rather then ‘quantity’, and as the company is located in the UK, you can also rest assured that spare parts, oil and oil filters are all easily available, further prolonging the life of the machine.
We all know the Hyundai corporation as the car manufacturer. But did you know they make other products as well? Well now you do. In fact they make an assortment of other machinery and tools as well as a line of air compressors targeted at the regular consumer and professionals. The HY2550 is one of their smaller ones in their product range providing a Free Air Delivery of 5.19 cfm or 147 litres / min at a working pressure of 115 psi, not dissimilar to other competitor air compressors in this category. The HY2550 has a 50L air tank which makes it capable of handling air tools with more needy air flow requirements. It also has 2 air outlets so that two air tools can be connected simultaneously.