Dual Air Compressors

[X1 Mike]

I am needing more CFM than I currently have so I'm looking at running another compressor into my current one as a temporary fix.

Two compressors into one line should give me the CFM I need. I just need to add a couple check valves to keep each tank from filling each other up.

My question is how can I set these up so that they never start pumping at the same time? If I can delay them it shouldn't overload the circuit.



p.s. I'm well aware that the proper fix is a compressor large enough to do the job, I'm currently trying to ascertain my requirements. I don't want to spend money now on something I will have to substantially upgrade in 6 months.

 

[DeeKay]

If you don't want both pumps running at the same time I don't think you're going to benefit from having two compressors outside of a little more capacity with the second tank.
What kind of power do you have available and what kind of compressors do you have?

 

[redmondjp]

That's easy; you just ensure that your on-off pressure ranges are set differently. For example, you may have one compressor that turns back on at 90psi. Then adjust the pressure switch so that the other compressor turns on at at least 5psi different from that. You likely have to remove the cover from your pressure switch in order to adjust it - also note that some low-budget controls may not have an adjustment for this.

 

[u2slow]

We use dual setups at work. The pressure switches are set at different levels. (i.e. one has a lower cut-in) Tanks each have a hand valve. Air is drawn/filled based on what tanks are open.

 

[engineer2]

You can use an alternating relay. Your compressors will operate alternately: A-B-A-B-....
It'll work for compressors with a magnetic starter since they only have 10 amp contacts.
https://www.grainger.com/product/6MPN9
That one is cross-wired so, if you upgrade your electric, you can set it up to run them both at the same time if the pressure gets too low.
This way you can pipe the tanks together and have more air reserve plus you don't have to screw with pressure switch settings.

 

[dogdog]

That's easy; you just ensure that your on-off pressure ranges are set differently. For example, you may have one compressor that turns back on at 90psi. Then adjust the pressure switch so that the other compressor turns on at at least 5psi different from that. You likely have to remove the cover from your pressure switch in order to adjust it - also note that some low-budget controls may not have an adjustment for this.

^^^this
Adjust the cut-in pressure for them at different PSI..still no guarantee though, you might hit a sweet spot that they would have a chance just come on at the same time... you might be better to put the compressor in different circuit.

would be easier to pipe both compressor at a regulated psi say 90 PSI output on both to a aux tank. (in my case I have a 16gal horizontal craftsman that went bad).. using combination of a ball valve and T fittings.

 

[X1 Mike]

If you don't want both pumps running at the same time I don't think you're going to benefit from having two compressors outside of a little more capacity with the second tank.
What kind of power do you have available and what kind of compressors do you have?

i want them running the same time I just don't want them starting the same time.

I think setting the pressure switch is what I was looking for. Like most things the simplest is the right answer. Thanks

 

[The Cobbler]

as mentioned, different cut in pressures on each compressor . they are probably different enough as it is . the start up is when they take more current. forgo added check valves . some ( most) regulators have a bleed function, they will bleed air off if the regulated side is higher than the reg is set for. use only 1 regulator, feed one compressor (unregulated air) into the other before the regulator and you're all set

 

[Monza Harry]

I would also like to add that the circuits that the 2 compressors are running on should tied together and clearly marked! Too easy to get hurt if only one is turned off and someone starts working on something. This applies if the breaker you are worrying about tripping feeds the two separate circuit/plugs [ie; 30Amp main and two 1 HP compressors on two separate 15Amp circuits] if these will both run on a 15 or 20Amp plug they are pretty small units. if your pressure switch has a bleeder then check valves will be required to prevent the one starting first isn't bleeding or worse yet causing back pressure that will throw the breaker every time. Harry

 

[DeeKay]

i want them running the same time I just don't want them starting the same time.

I think setting the pressure switch is what I was looking for. Like most things the simplest is the right answer. Thanks

Ah I misunderstood, that makes sense then.

 

[theoldwizard1]

My question is how can I set these up so that they never start pumping at the same time? If I can delay them it shouldn't overload the circuit.

Put them on separate circuits and skip the check valves. Worked perfect for sandblasting a brick wall when one 2hp compressor was not enough.

 

[X1 Mike]

Put them on separate circuits and skip the check valves. Worked perfect for sandblasting a brick wall when one 2hp compressor was not enough.

Why no check valves? I would assume that it would be needed to keep one compressor from pumping the other tank.

 

[Lucid Moments]

I think redmondjp hit on the best answer but just because my mind works in weird ways sometimes I wonder if you could get a single pressure switch that could handle the power requirements for both motors and possible have it tee'd into the plumbing after you join the air from the two compressors together.

Certainly not a suggestion on how to deal with OP's issue, just a weird question.

 

[u2slow]

Why no check valves? I would assume that it would be needed to keep one compressor from pumping the other tank.

Our check valves are on the compressor outlet before the tank. Both comps charge both tanks... unless you isolate one.

 

[Citation]

So long as both compressors have compatible pressure ranges just connect the two tanks together and make sure there is some difference in cut in pressure as others mentioned. One pump filling both tanks is fine since this is a limited use setup. The extra wear is just occasional. I would put a ball valve between the two tanks so you can cut one compressor out of the system when demand is lower.

Btw, compatible pressure ranges means the tank blow off valves need to be similar, both above the maximum working pressure of either compressor and both below the rated tank pressure of either tank. Ideally the blow off valves will have the same rating.

 

[TonyJ]

I think I would wire them up with both compressors set at the same on and off point and wire a delay switch up inline with one of them so you can control the amount of delay. If both tanks are plumbed together and one switch is set a little different than the other then the pump that comes on first will raise the pressure above the cut on point of the second one unless you are really really using air and are out working the first pump