Second compressor for more capacity

[pepo1]

I need more air to run my spray gun. Pressure dies out pretty quickly with the current setup - about 13 cfm, 100 litres, 125 psi. So, I'm looking for the best way to connect two horizontal style air compressors for more capacity while only running one of the compressors if possible. Or if running both compressors is better, then the best way to go about it. Both compressors are same brand, about 13 cfm and 100 litres each.

The goal is to get better capacity but also less moisture in the airlines. So, I'm thinking of the second compressor as being a settlement tank, like an auxilliary or header tank, but in the form of a complete compressor.

The devil is always in the details. Tons of videos on YouTube of people combining compressors, all with some difference or other, some more dangerous setups than others. I just want a clean simple way to give my gun more air for longer using the two compressors I already have.

 

[The Cobbler]

it is totally doable
I would suggest you plumb the auxiliary compressor into the main compressor before the pressure regulator as most tend to bleed off excess air pressure , and it is difficult to get them set tot eh exact same pressure .
in other words use only 1 regulator for the 2 tanks , take the aux tank pressure before the regulator and tie it in to the main compressor before the regulator .
this is from my past experience when we had a compressor go down @ work when we were stapling underlay for flooring and had to tie 2 smaller compressors together to get enough volume to run 2 staplers going almost steady

 

[engineer2]

Sounds like you have the electrical capacity to run both at the same time. If that is the case, and they have a magnetic contactor starter, you can use what called a "cross-wired alternating relay". It will alternate the running of the compressors to even out the run time. The "cross-wire" feature allows both to run at the same time if one can't keep up.

Moisture removal is another matter. At minimum you can set up an aftercooler and an in-line desiccant filter. The better way to go is a refrigerated air dryer. Don't know about NZ, but here they come up for sale now and then locally.

 

[PoorUB]

I would just tee the tank outputs together and rig up a water separator. Then set one pressure switch 5 PSI below the other.

If you are concerned of equal run time, just shut off one of the compressors and make the other run in the times where you don't need a lot of air.

 

[theoldwizard1]

I don't understand the issue ? My nephew had some SERIOUS sand blasting to do. One 2HP compressor could not keep up. Just plumbed 2 of them together. Each require their own 240V 20A circuit.

 

[iagsxr]

The second compressor tank won't act as a moisture trap if A. Both compressors are running. B. You just tee into the outlet on the second tank.

The way a second tank does act as a moisture trap is if it's just a holding tank and fills from an inlet separate from the outlet. Gives the air time to cool.

Just tee into the outlet on the second tank. Put your regulator/moisture trap after the tee. If you don't want them both to run unplug or flip the breaker on one. You'll still have twice the storage capacity. Tank pressures will equalize.

I plan to do this exact thing, feed a smaller compressor with a larger one for sandblasting in an outbuilding. I may regulate the air from the larger compressor only because it's 175psi and the working pressure on the other tank is 140psi.

I've watched YouTube videos where people have put in one-way check valves in the lines. I don't see the point.

 

[nadogail]

I use a tee fitting with two male ******* and one female connector to use both my compressors at once.
Each compressor feeds a hose and the two hoses are connected to the tee and the output feeds the combined air load.

 

[Stelzer]

This is a subject that has always intrigued me. If anyone has pics of their setup or at least a reference pic of what they're describing, it'd be most appreciated.

 

[Leaflessshadetree]

IMO it won't make a huge difference in how you connect them. If the dryer has the capacity you can put it after the Tee or run a dryer on each.
There are little details like equalizing run time or minimizing it on one compressor, are you really doing enough for this to matter.
When sandblasting I've connected the hoses from 3 different compressors (a 5 HP 80 gallon (18 CFM), a 2HP 25 gallon (3? CFM) and a 6 (advertised) HP oilless 33 gallon compressor (5-6 CFM?). Each with it's own regulator.
Start blasting with all tanks full, each compressor kicks on when the pressure in it's tank drops to that compressors set point, each turn off when pressure increases to it's set point.
If I blast for a long time with a large nozzle all 3 will be running and pressure will drop to a point where I need to let them catch up.
My estimate is that performance is similar to what I'd get with a 25-27 CFM compressor.

 

[Metal-Marc]

Just buy a bigger compressor?

 

[pepo1]

Just buy a bigger compressor?

Here in NZ, you have to go 3-phase to get anything bigger than what I have.

 

[pepo1]

The second compressor tank won't act as a moisture trap if A. Both compressors are running. B. You just tee into the outlet on the second tank.

The way a second tank does act as a moisture trap is if it's just a holding tank and fills from an inlet separate from the outlet. Gives the air time to cool.

Just tee into the outlet on the second tank. Put your regulator/moisture trap after the tee. If you don't want them both to run unplug or flip the breaker on one. You'll still have twice the storage capacity. Tank pressures will equalize.

I plan to do this exact thing, feed a smaller compressor with a larger one for sandblasting in an outbuilding. I may regulate the air from the larger compressor only because it's 175psi and the working pressure on the other tank is 140psi.

I've watched YouTube videos where people have put in one-way check valves in the lines. I don't see the point.

Thanks for the input, you and everyone. When you say "tee into the outlet on the second tank", I'm guessing you mean after the pressure switch. See attachment yellow circle. What about just teeing into that **** plug (for want of a better term) circled in green. In fact there's one of those on either end of my compressors. Just plugs not a connection as in the image. I think this would essentially turn it into the holding tank scenario I was after for less moisture, but does this still provide the additional capacity the gun needs? Still getting my head around it all.

 

[dchawk81]

Thanks for the input, you and everyone. When you say "tee into the outlet on the second tank", I'm guessing you mean after the pressure switch. See attachment yellow circle. What about just teeing into that **** plug (for want of a better term) circled in green. In fact there's one of those on either end of my compressors. Just plugs not a connection as in the image. I think this would essentially turn it into the holding tank scenario I was after for less moisture, but does this still provide the additional capacity the gun needs? Still getting my head around it all.

As long as you don't need to regulate the air pressure you can run it directly out of the tank like that. That's what I'd do. It's also where my 60 gallon is ran, with a regulator/spinner separator.

As long as you don't tee into your drain port. So you can, you know, still drain it.

 

[pepo1]

@dchawk81

I was thinking of running air from the first compressor INTO the second compressor at that point where I've circled green. Then just plugging the tools into the existing regulated outlet on the second compressor (where I've circled yellow). That air should have settled somewhat by the time it gets into the hose. I can add a water separator and whatever as necessary.

So, in summary:
1) First compressor keeps running till it fills itself and the second compressor tank, pressure equalized across the two.
2) Sprayer runs off second compressor, plugged into the regulated outlet after the pressure switch

Would there be any safety issues with one compressor pumping up a second compressor tank? If the second compressor isn't running, it won't automatically shut off at the set pressure, so the system would be relying on the first compressor's pressure switch to keep everything safe across the whole system. I guess that's fine.

 

[dchawk81]

@dchawk81

I was thinking of running air from the first compressor INTO the second compressor at that point where I've circled green. Then just plugging the tools into the existing regulated outlet on the second compressor (where I've circled yellow). That air should have settled somewhat by the time it gets into the hose. I can add a water separator and whatever as necessary.

So, in summary:
1) First compressor keeps running till it fills itself and the second compressor tank, pressure equalized across the two.
2) Sprayer runs off second compressor, plugged into the regulated outlet after the pressure switch

Would there be any safety issues with one compressor pumping up a second compressor tank? If the second compressor isn't running, it won't automatically shut off at the set pressure, so the system would be relying on the first compressor's pressure switch to keep everything safe across the whole system. I guess that's fine.

It'll just take longer to fill up.

The only real issue will be possibly exceeding the duty cycle of the compressor and/or motor. Depending how often you use it to make it cycle. Since it's going to be running twice as long from empty, but it'll be emptying half as fast since you doubled the capacity. Might be moot.

Most compressors aren't designed to run continuously so if you're basically running this thing all day every day it won't last. That's why bigger compressors have bigger pumps and motors and the industrial ones have longer duty cycle ratings.

 

[iagsxr]

Thanks for the input, you and everyone. When you say "tee into the outlet on the second tank", I'm guessing you mean after the pressure switch. See attachment yellow circle. What about just teeing into that **** plug (for want of a better term) circled in green. In fact there's one of those on either end of my compressors. Just plugs not a connection as in the image. I think this would essentially turn it into the holding tank scenario I was after for less moisture, but does this still provide the additional capacity the gun needs? Still getting my head around it all.

Yes, going in the circled green would be perfect for what you're trying to accomplish. In my mind going in the one farthest away from the pressure regulator outlet would be best but that's splitting hairs.

As someone else mentioned, the only thing you have to watch for just running on one compressor is exceeding it's duty cycle. Once you have this set up you can time it's run time and know. Either run them both or put a shutoff valve between the two if it becomes an issue.

 

[Rt jam]

Running 2 tanks or a larger tank does not change the CFM. It will only change the cycle time and how long the compressor runs for between the min and max settings.

Are you using a HVLP spray gun?

 

[Moss]

I have had this setup for about 10 years. Joining two compressors does combine the cfm of both units and it works very well. Follow the blue hose in this picture. The cut in pressure on the blue compressor is slightly lower than the green one so the only time the blue one really comes on is if I am sandblasting or some other intensive task.

I often just leave the blue one unplugged and it just acts as extra storage. It's very noticeable when I am blasting and they are both pumping air compared to just the larger green one.

Side note: I purchased the blue compressor when I was younger about 23 years ago and as time went on it didn't meet my needs so I got the bigger one and combined them. They both have been good but the old blue made in USA unit is bullet proof!

 

[pepo1]

Running 2 tanks or a larger tank does not change the CFM. It will only change the cycle time and how long the compressor runs for between the min and max settings.

Are you using a HVLP spray gun?

Yes, HVLP is what I'm stuck with at the moment. LVLP might be the solution.
I find that if the compressor is not running when I start spraying, then the pressure at the gun drops off within a few seconds of the trigger pull, but it still takes a while before compressor kicks back on again. By that time, the gun is useless. However, if I start spraying with the compressor running, the pressure seems to hold up enough to get stuff done. Probably because the compressor is actively replenishing the air instead of waiting for the air pressure to drop to 80psi before it starts working.

 

[pepo1]

I have had this setup for about 10 years. Joining two compressors does combine the cfm of both units and it works very well. Follow the blue hose in this picture. The cut in pressure on the blue compressor is slightly lower than the green one so the only time the blue one really comes on is if I am sandblasting or some other intensive task.

I often just leave the blue one unplugged and it just acts as extra storage. It's very noticeable when I am blasting and they are both pumping air compared to just the larger green one.

Side note: I purchased the blue compressor when I was younger about 23 years ago and as time went on it didn't meet my needs so I got the bigger one and combined them. They both have been good but the old blue made in USA unit is bullet proof!

That looks clean. The only reason I was against running both compressors is perceived complications with pressure setting offsets between the two and the need for dedicated 20A circuits. It sounds like in general you just need one compressor at a slightly lower pressure than the other and Bob's your uncle.

 

[dchawk81]

That looks clean. The only reason I was against running both compressors is perceived complications with pressure setting offsets between the two and the need for dedicated 20A circuits. It sounds like in general you just need one compressor at a slightly lower pressure than the other and Bob's your uncle.

Or, as MAC would say, R.B.R.T.

 

[pepo1]

I use a tee fitting with two male ******* and one female connector to use both my compressors at once.
Each compressor feeds a hose and the two hoses are connected to the tee and the output feeds the combined air load.

Any chance of a photo of your setup? Where is the "tee" located? Is it just dangling in the air?

 

[Moss]

That looks clean. The only reason I was against running both compressors is perceived complications with pressure setting offsets between the two and the need for dedicated 20A circuits. It sounds like in general you just need one compressor at a slightly lower pressure than the other and Bob's your uncle.

I have never had any issues with the pressure settings. I turned the screw on the smaller compressor years ago to get it to kick in at around 88psi. I don't remember the exact spread but if I am really using a lot of air the delay isn't long. It's just enough so both motors don't surge at same time - which I wanted. The larger one kicks in at it's factory settings I think around 90psi

Yes you need to have dedicated circuits which for me was simple because they are right beside the electrical panel. If your panel is far that's certainly more work.

 

[pepo1]

IMO it won't make a huge difference in how you connect them. If the dryer has the capacity you can put it after the Tee or run a dryer on each.
There are little details like equalizing run time or minimizing it on one compressor, are you really doing enough for this to matter.
When sandblasting I've connected the hoses from 3 different compressors (a 5 HP 80 gallon (18 CFM), a 2HP 25 gallon (3? CFM) and a 6 (advertised) HP oilless 33 gallon compressor (5-6 CFM?). Each with it's own regulator.
Start blasting with all tanks full, each compressor kicks on when the pressure in it's tank drops to that compressors set point, each turn off when pressure increases to it's set point.
If I blast for a long time with a large nozzle all 3 will be running and pressure will drop to a point where I need to let them catch up.
My estimate is that performance is similar to what I'd get with a 25-27 CFM compressor.

Sounds simple. As you say, I'm not doing this enough for it to really matter. How did you connect your three compressors?

 

[GrayFlattop]

2 compressors plumbed together should be no issue. I would want to have each stand alone with respect to controls. Ideally run them both into another (third) tank, but it doesn't matter that much.

At work we have 5 of them (the smallest is 150hp). We have it set-up so three of them run almost continuously and the rest cascade with demand.