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So you’ve got two compressors and one compressor tank, and you are wondering how to plumb them up?
While this is a compressor issue that most folks won’t have to deal with, some folks with smaller compressors, like those used for air brush painting, might want to add a tank to a couple of compressors that don’t come with tanks.
Most compressors come with some sort of pressure switch to shut them off when the tank pressure reaches the cut out set point. You have to ensure that your air compressors both have pressure switches that will shut them down when the pressure reaches cut out, and preferably, have adjustable pressures switches if you are trying to plumb two compressors together.
Note that your compressor(s) may run longer than normal due to the fact that they have to fill a tank to the cut off pressure before the compressor stops.This has ramifications for compressor duty cycle.
What is the compressor duty cycle?
Some compressors have a true 100% duty cycle, meaning that they can run and run, and not overheat and cause damage to the motor. Some compressors have limited duty cycle, meaning that if you run them too long, they can be damaged due to heat buildup.
Not sure about the duty cycle of your compressor? If you are not sure, then only run your air compressor in ten minute segments, at which point, you shut the compressor down, and then wait at least ten minutes more before starting it up for the next usage period.
If you don’t pay attention to duty cycle, then you can damage your compressors.
And, if you are trying to plumb two compressors and one compressor tank together, knowing that the compressors will run longer than normal may have an affect on them!
Plumbing two compressors and one compressor tank
Here is how we would plumb two compressors and one compressor tank.
The air compressors each will come equipped with a discharge coupler. This is the plug into which you insert the air line connector to get air to flow from the compressor to the air line.
Both compressors are to be plumbed with a line from their discharge coupler. Each of those lines run through a check valve so that air can flow out of that compressor but not back towards it.
Both lines then connect to a Tee with the outlet from the Tee connecting to the tank.
The tank will have its own discharge coupler into which you would plumb the air line for your air brush spray gun or air tool.
Both compressors on at the same time?
Do you want both air compressors to run at the same time? We wouldn’t. If both compressors have the same cut in and cut out settings however, this is what will happen.
What we would do is set the pressure switch on compressor A to, for example, cut in at 90 PSI. The cut out might be 120 PSI on compressor A.
On compressor B we would set the cut in pressure setting to, for example, 85 PSI with the cut out also at 120 PSI.
Then, as long as air compressor A could keep up with the compressed air demand of the air tool, air compressor B will not cut in.
If air demand exceeds the output capacity of compressor A, the tank pressure will continue to drop until it hits 85 PSI, at which point compressor B would then kick in, adding its capacity to the tank.
If the demand for compressed air exceeded the capacity of both compressors, the tank pressure would continue to drop, and both compressors would continue to run.
You might consider swapping out the settings on compressor A and compressor B from time to time, otherwise, compressor A would always be doing the bulk of the work and this has ramifications for compressor maintenance.
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