Combining two small 50ltr compressors

[ProjectBobcat]

My main compressor is a 50litre 2hp 14cfm unit. It's been great but the tank is too small so it ends up running continuously when sand blasting in particular. The manufacturers do the same compressor in a 100ltr version, but I couldnt stretch to the extra money at the time I bought it. I just picked up another 50 litre 2hp 8.5cfm compressor cheaply. Is it possible to reliably daisychain the two compressors in a temporary way so that I can have the extra capacity when needed?

If it is possible then how do I calculate the cfm of the combined units running together?

Thanks

 

[isb cornbinder]

Do not over think or complicate this otherwise simple situation. Run the compressors as two separate units. Connect the tanks to your air system. It is not necessary to connect the compressors. Larger storage does not give you more air. The upper limit of your system is the combined CFM of both compressor pump units. You could have both pumps on a 1000 liter tank and the output will be the same, when averaged over time.
My spell-check wants to change pump to pimp.

 

[sparky 1971]

I have a 60 and 30 gallon compressor tied together. I just used a 1/2" black iron T fitting. I also used a check valve at each compressor so they don't fill each other.

 

[ProjectBobcat]

Run the compressors as two separate units. Connect the tanks to your air system. It is not necessary to connect the compressors. Larger storage does not give you more air. The upper limit of your system is the combined CFM of both compressor pump units. You could have both pumps on a 1000 liter tank and the output will be the same, when averaged over time.

Thank you. Am I understanding it correctly that if I connect up both compressors, and my tool requires 10cfm, i could run both at 5cfm (or any other combination adding up to 10)?

 

[stonesfan68]

You should have no issue plumbing the two compressors together.

 

[isb cornbinder]

Thank you. Am I understanding it correctly that if I connect up both compressors, and my tool requires 10cfm, i could run both at 5cfm (or any other combination adding up to 10)?

 

[ProjectBobcat]

Thank you all for the help!

 

[GeoBruin]

It sounds like you've got it mostly figured out but just a couple extra considerations...

- If you don't have check valves installed as discussed above (and perhaps even if you do) make sure the max cut off pressure for one pump or the other doesn't exceed the maximum rating of the the other compressor's tank. For example, if you plumb a two-stage 175 psi compressor to a single stage (140? psi) compressor, the latter's tank may not be rated for the former's pressure.

-if both compressors are on the same circuit, and if they have similar cut-in pressures, you might consider goosing one or the other up or down so both compressors aren't cutting in at the same time, causing a large current draw.

 

[PoorUB]

My main compressor is a 50litre 2hp 14cfm unit. It's been great but the tank is too small so it ends up running continuously when sand blasting in particular. The manufacturers do the same compressor in a 100ltr version, but I couldnt stretch to the extra money at the time I bought it. I just picked up another 50 litre 2hp 8.5cfm compressor cheaply. Is it possible to reliably daisychain the two compressors in a temporary way so that I can have the extra capacity when needed?

If it is possible then how do I calculate the cfm of the combined units running together?

Thanks

Sorry, but 2 HP and 14 CFM? and why is the second 2 HP 8.5 CFM? which seems more realistic! And also the tank is not too small if it runs constantly, the pump is. The tank has nothing to do with continuous output. It just lets you draw a bit of air now and then with out running. Hook up a sand blaster to most compressors and they will run all the time unless they have some serious HP.

But yes, just connect them to your air system, or if no system, just run an air hose out of each compressor, into a tee fitting and out with one line. Chances are one will start much sooner than the other and do the bulk of the work. There is nothing mysterious that needs to be done, and yeas yu will get what ever the added CFM of each comes up too.

 

[Jland]

I have a 5hp 20 gal devilbis and bought an 21 gal upright tank only for 20 bucks that I set up as an auxiliary tank while I can’t sandblast continually the extra air does make a difference. Nice thing for me is I have the option of running both in a series or just wheeling the aux tank down to the livestock pen to do work and not stretch a hundred feet of 10ga cord... I’m to old to lug that heavy **** around anymore

 

[Citation]

It sounds like you've got it mostly figured out but just a couple extra considerations...

- If you don't have check valves installed as discussed above (and perhaps even if you do) make sure the max cut off pressure for one pump or the other doesn't exceed the maximum rating of the the other compressor's tank. For example, if you plumb a two-stage 175 psi compressor to a single stage (140? psi) compressor, the latter's tank may not be rated for the former's pressure.

-if both compressors are on the same circuit, and if they have similar cut-in pressures, you might consider goosing one or the other up or down so both compressors aren't cutting in at the same time, causing a large current draw.

OP, for short term use, the above is really all you need to worry about. In general I would want them both on separate breakers and ideally with slightly different cut in pressures so they will never try to both start at the same time. I played with tying my 4 gallon roofing compressor to my 26 gallon belt drive unit. It should give me around 9 CFM. My larger compressor has two female couplers, one without a regulator. I run a hose from the roofing compressor and connect via a male-ball valve-male adapter. My garage has two circuits so they can run at the same time. It's useful if I want to use my cut off wheel a lot but mostly I tried it out because I had the parts around.

 

[The Cobbler]

I would suggest you tie the compressors together before the pressure regulators . most regulators are pressure balancing, so if the pressure in one is higher than the other it will bleed off air trying to balance the pressure in the hose .

 

[sparky 1971]

I would suggest you tie the compressors together before the pressure regulators . most regulators are pressure balancing, so if the pressure in one is higher than the other it will bleed off air trying to balance the pressure in the hose .

Another reason for check valves. My 60 gallon shuts off at 155 psi and the 30 gallon at 125. While at this time I am running both of them without any regulators whatsoever, when the smaller comp had a regulator, there was no bleeding anything off. The larger compressor holds the check valve of the smaller compressor closed until the pressure drops to 125 or below. Then they take turns feeding air depending on which has the higher pressure.

 

[ProjectBobcat]

Sorry, but 2 HP and 14 CFM? and why is the second 2 HP 8.5 CFM? which seems more realistic!

Well spotted, typo on my part, my main compressor is 3HP 14cfm, not 2HP.