Combining two compressors?

Lil Foot

Well-known member
Lifetime Member

Equipment
1979 B7100DT Gear, Nissan Hanix N150-2 Excavator
May 19, 2011
7,609
2,679
113
Peoria, AZ
Anybody out there ever tried to run two compressors teed together feeding one air tool? Would I need one way check valves to keep them from back feeding each other? Or would that even matter?
I have an older 30gal, 6.3cuft @90psi unit, and someone wants to give me a similar output compressor with a 20 gal tank. Most of the time mine is adequate, but sometimes, when running tools that need a lot of cuft, it falls behind. I was wondering if I could tee their hoses together & use their combined output for more cubic feet per minute.
Thoughts?
 

bradmond

New member

Equipment
BX25D
Mar 14, 2015
46
0
0
SeaTac, Wa
Can't imagine why it wouldn't work. Shouldn't need check valves either, just connect them together.
 

dandeman

Member

Equipment
BX2230, LA211 FEL, RCK60B Mower, GCK60BX Bagger; Ford 4000, bush hog, blade, etc
Aug 9, 2013
166
2
18
Chapel Hill, NC
www.dan-de-man.net
I've done it on a temporary basis to boost CFM... No need for check valves as long as both designed more or less to handle the max air pressure...
 

85Hokie

Moderator
Staff member
Lifetime Member

Equipment
BX-25D ,PTB. Under Armor, '90&'92-B7100HST's, '06 BX1850 FEL
Jul 13, 2013
10,790
2,600
113
Bedford - VA
Lil Foot,

It can be done - but think about water for a second, air and water share some of the same properties. A water hose hooked to a house, stretch out 50 feet you have "x" flow and "x" pressure - streeeeetch that hose out 200 feet, even though the static pressure is the same, the flowing pressure and volume will both go down.

I say all that because if you need volume, a hose will only produce a certain about of volume at a certain pressure - once the limit of the hose is reached, the pressure can no longer help the volume due to the friction of the air in the hose itself.

I larger tank will hold more pressure for more time, thats a fact - but you will need for one of the two or both of the compressors to run for a while to get to that point of cut off pressure. Once there, the amount of pressure you have available will be the same, the time it takes to drop will be increased, but the CFM will stay the same!! Now - will it last a longer period of time? Yes, but until the hose sizes change, there will be little increase in CFM.

Join the two together - INCREASE the hose if you can, I bet you are running 1/4"??? I do, but if you run 3/8" at least to the tank and to the device, you will increase the CFM by.....

check this table and you'll see that a larger hose will allow the flow that you need!

http://www.gates.com/catalogs-and-resources/resources/repository/calculator/air-flow-calculator

use .375 D , 100 psi , 50 ft and 5 cfs .....the amount of friction loss is 10 times less than .25 D hose.

A larger storage tank does hold more air, but once the pressure drops, there will be a much longer wait until it gets back up - unless you can sync them together allowing them to kick on at the same time!;):)
 

Wbk

New member
Feb 20, 2013
307
0
0
St Adolphe Manitoba Canada
Anybody out there ever tried to run two compressors teed together feeding one air tool? Would I need one way check valves to keep them from back feeding each other? Or would that even matter?
I have an older 30gal, 6.3cuft @90psi unit, and someone wants to give me a similar output compressor with a 20 gal tank. Most of the time mine is adequate, but sometimes, when running tools that need a lot of cuft, it falls behind. I was wondering if I could tee their hoses together & use their combined output for more cubic feet per minute.
Thoughts?
When I had my shop we ran two 15hp compressors together, one control operated both of them and we never had any problems.
 

North Idaho Wolfman

Moderator
Staff member
Lifetime Member

Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Jun 9, 2013
31,003
6,992
113
Sandpoint, ID
It will help, I used 3 pancake compressors tied together to keep up with a spray gun when my big compressor took a dive and had to be replaced. ;)
 

dandeman

Member

Equipment
BX2230, LA211 FEL, RCK60B Mower, GCK60BX Bagger; Ford 4000, bush hog, blade, etc
Aug 9, 2013
166
2
18
Chapel Hill, NC
www.dan-de-man.net
Re: Air Hose pressure drop...

I used to use my air compressor and an approx 16' long 3/4" copper pipe with an air jet directed downward to clean out my gutters. To get the air volume I needed over the long run of hose to get around the house, I used 100psi rated 3/4" dia. garden water hose as my air hose.

The compressor tank has a ball valve (low restriction when fully open) with water hose fitting that the hose connects to.
 

Lil Foot

Well-known member
Lifetime Member

Equipment
1979 B7100DT Gear, Nissan Hanix N150-2 Excavator
May 19, 2011
7,609
2,679
113
Peoria, AZ
Thanks guys, kinda confirmed what I was thinking, that it should help some.
But today I saw the other compressor, and it might be the filthiest power tool I've ever seen. Must be at least a 1/4" of dust & dirt on it. Hope the air filter is somewhat clean. Well, that's what pressure washers are for, I guess. Maybe I'll like it more when I can see it.:rolleyes:
 

Tooljunkie

Well-known member
Lifetime Member

Equipment
L1501,home built carry all, mini plow blade.
May 13, 2014
4,150
33
48
60
Lac Du Bonnet, Manitoba,Canada
We used two compressors to keep up for painting cars , including an extra tank. The volume difference between 1/4&3/8" air hose is quite significant. Fittings also play a part in restriction.
I now run a 5 hp 60 gallon in my shop,3/8" air hose. Upped my pressure a little and its like two different impacts. 3/4" impact still suckholes but i rarely need it. You will accomplish more if the joined compressors run a bigger hose,simply for the less restrictive fittings.
Have seen one compressor with two pumps on one motor. It made air!!

No matter what, it will be an improvement.
 

ipz2222

Active member

Equipment
L235, bx2670
May 30, 2009
1,927
32
38
chickamauga ga usa
Ck your fittings. Haveing a half inch hose with a one quarter inch fitting won't get you the air flow. I take all my male fittings and drill them out to get a little more flow. Allmost have to have a lathe to do that.
 

Lil Foot

Well-known member
Lifetime Member

Equipment
1979 B7100DT Gear, Nissan Hanix N150-2 Excavator
May 19, 2011
7,609
2,679
113
Peoria, AZ
I'm pretty sure line restriction is not my problem. If it was, the tool would run out of air before the tank got low enough to start the compressor. The opposite is true. My highest cfm tool is a cold gun-
http://www.exair.com/en-US/Primary ...ystems/Pages/Cold Gun Aircoolant Systems.aspx
and it will run fine for about 3-9 minutes, depending on pressure, then the compressor kicks on and stays on and never catches up. It will continue to run until flow gets so low that I have to shut off the cold gun until the compressor recovers & shuts off. By hooking two together, I'm just hoping to extend my run time. At least until I can afford a large enough compressor for my needs. (lottery?:D)
 

olthumpa

Active member
Lifetime Member

Equipment
L275
May 25, 2011
1,501
3
38
Maine
Is it possible to increase your psi switch to a higher cut in pressure setting and a higher cut off setting or are you already at the designed limits? My compressor came set with a 145 cut in psi and a 175 cut out psi and per the factory, I can increase both by 30psi.

Could you add a large slave tank to increase your storage capacity before you run out of air.

Is it possible to install a Air Compressor Unloader to eliminate the lag in startup before the psi has dropped to the cut in psi?

http://www.ebay.com/itm/like/270710543911?lpid=82&chn=ps&ul_noapp=true
 

Lil Foot

Well-known member
Lifetime Member

Equipment
1979 B7100DT Gear, Nissan Hanix N150-2 Excavator
May 19, 2011
7,609
2,679
113
Peoria, AZ
It was originally set to 75psi cut in & 100 psi cut out; I have reset it to 95 & 120 respectively. A big reserve tank would work great, but by the time I spend the money for one, I may as well spend a little more & get a bigger compressor.
I don't think the unloader valve would gain me much, if anything. I think I'm just going to have to bite the bullet & buy a big compressor/tank setup.