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Air Compressor Buying Guide

Posted by Kyle on

Buying an air compressor is something that you will only do once every decade or two, so it is important that you choose the right one. The customer must identify the tools or equipment that will consume the most amount of air at the highest pressure. The automotive equipment experts at Irish Garage Equipment have the knowledge to help our customers make the correct buying decision.

Many retailers sell compressors on the assumption that the bigger the tank or the motor the better, a big tank is useless if your pump is too small.

Generally you should always buy more air compressor than you need.

What is CFM?

CFM stands for Cubic Feet per Minute of air delivered by a compressor and is the single most important number for you take into account when buying a compressor.

Note that CFM will increase when the pressure (PSI) decreases, and the CFM will decrease when the pressure (PSI) increases.

Each tool in your workshop will have an air consumption rating in CFM at a certain pressure, you must find the CFM of each tool that are in use at the same time and add them together. You can use this CFM consumption rating when shopping for an air compressor.

Below is an estimate of the consumption of certain air tools, so you can make calculations.

1.1 Air consumption:

1/2" impact wrench5cfm
1"impact wrench9-11cfm
Paint spray gun6cfm
Tyre changer5cfm

1.2 CFM output of IGE air compressors:

50 Litre 2.5hp9cfm
100 Litre 4hp16cfm
200 Litre 4hp16cfm
300 Litre 6hp (3hp + 3hp)28cfm
150 Ltr 6.5hp16cfm

What size of a MOTOR do I need?

The size of the motor is not important when buying a compressor, it is all about the pump and the displacement of it. The manufacturers of the compressor will fit a motor sufficient enough to run the pump on the compressor. The EU have regulated this with the requirement of CE certificates on all consumer electrical goods.

The PHASE of the motor is an important aspect, as you will need to take into consideration the power available in your work shop, single phase is the standard power available throughout Ireland with the standard 3 pin 13amp plug. The larger blue socket is also single phase with higher amps, either 16 or 32 amp. Three phase power is for industrial applications it has a larger red plug and socket, available in 5 or 7 pin depending on amps. A three phase power supply is only necessary for motors of 5 horse power or larger. Although all our compressors at IGE use a single phase supply compressors with a single motor greater than 4hp require a 3 phase supply.

What size air TANK do I need?

The receiver tank stores the air that the pump compresses. The air compressor goes into standby when the pressure (PSI) in the tank reaches the factory set pressure (normally 120psi), this is determined by the setting on the pressure control switch. When the air pressure in tank drops below the preset pressure (normally 60psi) the compressor starts automatically and the process begins again.

Air power tools that operate on small bursts of air only need a small tank volume to meet their demands, tools like sand blasters and orbital sanders that have a greater consumption will require a larger volume of air and a larger tank.

As the air rests in the tank it settles and cools; cool air holds less moisture so the moisture falls out of the air and accumulates in the bottom of the tank, this is why their is a drain bung at the bottom of the tank. This rest period also allows the pump and motor to rest and cool down, thus prolonging the life span of the compressor.

For additional information contact us on 01 257 21 71 or email

You can see a selection of our air compressor by clicking here.

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