There are sometimes great reasons why you might want to connect two air compressors. While a single air compressor may not offer enough flow to supply a higher demand air tool and another, single air compressor, can have the same problem with that same air tool, if you connect two air compressors into one line to the air tool, you may have enough airflow from the two to use that higher demand air tool.
This article will provide you with the necessary information on connecting 2 air compressors together, how to do it, and the most important considerations!
How Compressors Run to Generate Air
A quick review of how compressors work (also covered in detail on a page on this site) is that they have an air tank into which air is pumped. When the tank pressure reaches the cut-out setting of the pressure switch, the pump stops, and nothing else happens until you begin to use the compressed air that’s stored in the compressor tank.
As you use air, the tank air pressure drops. When the tank pressure drops to the pressure switch cut-in level, the pump will start, and add more air to the tank until the tank reaches the cut-out pressure setting, and the pump stops.
What Does Connecting Two Air Compressors Together Achieve?
However, if your air tool has a greater demand for compressed air than the compressor can deliver you will use air in the tool at a greater rate than the compressor can supply it, and even though the compressor is running, since it cannot keep up with the demand of the air tool, the tank pressure will keep dropping until there is not enough compressed air to run the air tool.
To use a higher-demand air tool you will need a bigger compressor. Or, connecting two air compressors to the same airline to the tool, if you have a couple of small air compressors around, this might work.
In this situation where your air tool requires a greater demand of air at a greater rate than the compressor is capable of supplying, by adding a second air compressor and feeding both into the same line, you will have greater CFM to provide the tool.
Let’s say we have a second air compressor that has the same CFM rating as the first and is the same brand and model, we could double the current CFM rating of the system without any additional control complexities. This is how to connect 2 air compressors together in parallel, or just run 2 air compressors in tandem!
This method for connecting two air compressors together for more CFM pumping capabilities, while also providing a higher CFM at the outlet of the compressors, available for use with your tools.
Here’s a YouTube example of the methods being used!
In some cases, it will also be possible to connect two different make and model air compressors, with different CFM ratings. For instance, you could connect a 5 CFM air compressor with a 10 CFM air compressor and have 15 CFM available!
Here’s a YouTube demonstration that explains this method in more detail!
How to Connect Two Air Compressors Together
If you have two air compressors, select which will be the primary air compressor and plumb a tee into the discharge coupler on that one. At your discretion, you can consider removing the regulator from the line so that the flow to the tee is full pressure.
The tee is set up as: one leg of that tee is the supply from the primary air compressor, one leg of this tee is the supply from the secondary air compressor, and the last leg is where you install the airline to your air tools.
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If both air compressor tanks are full of compressed air when you start using your air tool, compressed air will be drawn from both tanks… at least, in theory. The reality is, compressed air always flows through the easiest path from high pressure to low.
As air is drawn from the two compressor tanks to the air tool, compressed air from one tank will flow into the other tank and vice-versa, rather than all of it flowing down the airline to the tool.
By installing a check valve in the line between the secondary air compressor and the tee of the primary compressor. This will prevent air from the main tank and compressor from flowing back into the secondary tank and, if the secondary compressor is not running, air could be lost from that compressor’s unloader valve.
The installation of check valves will be easy as they typically have arrows on them which depict the flow direction! Your setup should have both compressor’s outputs connected to check valves via hoses and then into a t-manifold which then has a hose on its output where you can connect your pneumatic tools.
Once the pressure in the hose to the air tool drops due to air use and the primary compressor tank no longer keeps up, air will be drawn from the secondary tank as well, helping maintain the flow and pressure to the air tool.
If the regulator(s) are removed at the compressor, a regulator should be installed at the point of using the joined supply so that the air tool can be operated at its best efficiency and minimum air use.
As just touched on, check valves are an important component to consider attaching when connecting two compressors for more CFM. When the secondary air is flowing, once again, air from that second tank could flow back towards the tank of the primary air compressor rather than down the line to the air tool, as air will always flow the path of least resistance.
Solution? Another non-passing valve before the tee in the discharge coupler of the primary compressor, allowing air out of the tank, but not back into it from the other compressor.
The image above is of a simple, in-line, check valve for compressed air. It’s also known as a non-passing valve. If you Google air check valve you will find many sources with a variety of attachment options.
With the male thread on either end of the check valve in the image, installation is not complex. Note the arrow on the body. That shows the direction that the compressed air can flow through this valve. Take care not to install it backward!
Setting up the two compressors to feed one line will enable work to be performed more successfully with a high-demand air tool but, if the air tool exceeds the capacity of the two air compressors, then it would be time to consider a larger compressor for increased airflow if that tool is to be used a great deal.
Running 2 air compressors in tandem is a great idea for continuous air tool applications as the combined air system now has a higher CFM. It is also suitable for intermittent uses, in cases where specific air tools require a greater CFM than your singular air compressor is capable of providing.
Though, with that being said, connecting two air compressors together with each other for intermittent use only maybe a tad radical. It’s probably worth just buying an additional air tank rather than a full compressor, given that you’re demanding only very short periods of continuous use.
It may also be that buying a new compressor that is a suitable size for your air tools and can deliver the correct CFM may be more cost-effective. This depends significantly on each case, you may have a neighbor who has an air compressor that you can borrow with ease whenever you need the additional CFM, and so, that would be a more cost-effective method.
Duty cycle is another important consideration that you must understand so that if you’re obtaining a second compressor, it has the same duty cycle like the current one, ensuring neither exceeds its rating and overheats, causing damage and premature wear of components.
After obtaining a second air compressor, and you’ve connected it using the method described in this article, you will need to adjust the pressure switches to ensure that the gap between them is not too big. If that is the case, one of your air compressors will be doing the majority of the work, starting and stopping far more frequently.
This will lead to premature wear on the compressor working extra, meaning you will need to conduct additional maintenance, and undoubtedly this will have a shorter life span. In an ideal situation, to achieve the full potential CFM of the combined air compressors, both cut-in and cut-out pressures should be the same.
But, it’s likely that you won’t always need the full potential of the system so it can instead be recommended that you have one of the compressors cutting in and cutting out at pressures 5 PSI lower than the other.
This results in you having primary and secondary air compressors. And, an important consideration here, is that some air tools may only draw air from one compressor (the primary), and so, it is recommended to periodically adjust the pressure switches of the compressors so that one is not always doing ALL the work!
If you have air compressors that are the same make, model, and size, then it’s almost guaranteed that the two compressors will have the same cut-in and cut-out pressures already, so you have no synchronizing issues to deal with! In theory, both air compressors should work approximately the same amount, depending on the tool requirements.
FAQs (Frequently Asked Questions)
The best way to connect air compressors together is by connecting each compressor output to a manifold (typically a tee). It’s crucial that check valves are installed between the outputs and the tee to ensure that air does not flow back into either compressor from the other.
Yes, piggybacking two air compressors together by connecting them to the same line via a tee, will allow you to provide greater amounts of airflow to meet higher demands.
It’s not recommended to try daisy chain air compressors as this involves taking the output of a compressor and running it into the input of another air compressor. It’s better to connect both air compressor’s outputs to a comment tee and then have a hose connected to the output of the tee.
In general terms, the easiest way to manage multiple compressors is to manually set the cut-in and cut-out pressures in a cascade arrangement. All the pressure bands should be the same but they may be offset slightly.
Yes, by adding a second air compressor you now have the addition of two air compressors CFM ratings. If the compressors were the same rating, you would have double the CFM. It may be that you have an 8 CFM air compressor and you add a 5 CFM air compressor, so you’re resulting combined CFM will equal 13 CFM (8 + 5).
If you have any questions about connecting 2 compressors together, please leave a comment below, so that someone can help you!