how to plumb two air compressors together
 

I'm upgrading from a Craftsman 30 Gal oilless to a 5 Hp 60 Gal upright. I was going to try to sell the Craftsman in the local paper, but figured since it still works, I could just plum it together with the new one and have even more air.

I'm concerned about having both compressors tied to the same air line though as I don't want the smaller one fighting the larger one, or does that not matter? If it does, I was thinking about using a check valve, but haven't been able to find any for air line.

I also considered having just an isolation valve, allow the Craftsman to run long enough to charge the tank with the valve closed, and then turn it off with the valve open and use it as a reservoir running just the 60 Gal compressor.

I also have a small 13 gallon compressor with a bad motor. I was going to plumb that one in as well just to have the extra reservoir volume.

Any ideas on a good and safe way to plumb these together?

I've already read through all the threads regarding air line construction, ie, black pipe or copper (NOT PVC!), and routing issues such as up to the ceiling and back down with a trap/drain and filter/oiler, etc, etc.

The question is more along the lines of if I need check valves, etc to control air flow amongst the two running compressors.

I wouldn't use the old one for anything more than the tank. Is the new one oilless as well? They usually run high rpms and are really loud. I'd take you're 13 gallon tank, and mount it on the wall next to where you're going to mount your compressor, plumb it directly into the output line on the new compressor, and then plumb your shop lines into the 13 gallon tank. Don't forget to put a dryer on the line before the shop lines.

I don't think either of the compressors will be able to figure out where the extra air is coming from - they're not that smart. Nor would they care. They would both go on and of depending on what they are set to. Just make sure they are capable of and set to similar pressures. Just plumb them together the ar will equalize in the two tanks.

However, I'm with pfogle - discontinue use of the oilless unit, and just use the tank. They're way to noisy, and prone to failure, IMHO.

As far as actually hooking them up... "I've already read through all the threads regarding air line construction, ie, black pipe or copper (NOT PVC!), and routing issues such as up to the ceiling and back down with a trap/drain and filter/oiler, etc, etc." ...you already know.

Thanks guys. The 60 gal is a 220V motor, cast iron oiled pump.

If you hook them both together for extra air capacity set the pressure switches so that the second compressor comes on 5-10psi lower than the first. Most of the time only one compressor will come on and the second compressor will only come on when you are using a lot of air.

Of course... it's always nice to have a backup compressor if you need it! I had mine get repaired and that's when you need air the most. If it's still running, I would tuck it away.

rclarke is exactly right! You need to have a lead and a lag compressor. Set the lead compressor for what ever system pressure you want and set the lag compressor to 10 psi lower than what the lead will switch on at. 2 compressors, a 13 gal reciever tank... you must plan on using lots of air!

I've linked a 80gal 2 stage ingersol to a second 60gal tank, I did not retain the second motor or pump, just the tank.
I used a hydraulic hose and flare fittings to link the two tanks together and Isolate the vibration from the rest of the black pipe air plumbing to the shop.

I've not yet figured out how to link the IR auto drain valve to both tanks, so I have a manual drain valve on the aux tank.

More air is GOOD! especially if you have a sandblaster!

yep, I have a blasting cabinet and pressure pot, both really suck the air!! The Craftsman actually was a great compressor for everything else, did fine for all the air tools and I painted my 78 F-150 with it, but it just couldn't keep up with the blasting.

Its to the point now where my time is more valuable and worth the investment to not have to wait for the compressor to catch up.

Thats what I'd do. When starting from zero pressure the little one will help build it up. Most of the time the "good" compressor will do all the work. The old one will be a backup and much better than nothing if the "good" one quits. Just pipe the tanks together.

Cool, thanks for the info guys.

Next question...

I need to free up some space in the garage and want to put the two smaller compressors in the attic. Obviously the smallest will be air storage only, but the middle one still works. I'm thinking if I put it in the attic, I can put in a dedicated 20A breaker for it, and either turning it on and off with the breaker (breaker box is in the garage) or wiring in a separate switch in the garage for it so I can just leave the actual switch on the compressor on all the time.

So, the question is, how do I mount the compressor in the attic so that it doesn't vibrate the ceiling apart, or if I put it up there, should I just use it for air storage only?

Only options I can think of is put it on some thick rubber mounts with it sitting on the ceiling joists, or suspend it somehow from the roof joists so its not touching the ceiling at all. Only thing is, its kind of heavy...

hocky pucks for thick runner mounts

I have a similar set up a loud, obnoxious oiless and an older jacuzzi twin cast. They are hooked together with sim pressure and it drives all my tools very well. I have less than $100 invested and the capacity of an expensive unit. I'm going to put the loud one outside in a dog house I'm thinkin- man those are horrible!

HI SIGT... Great project....My reservations are safty related. If your second floor is 2x4 trusses, they are not intended for storage loads, much less the vibrating loads. Second , the age off the tanks are critical,even more so if they were not originally pressure tested. not all consumer tanks are rated for long life, will crack and explode due to internal rust, etc. How to change the air intake filters, not forgeting to drain the pipes, oil changes, etc. If you come up with a vibration isolation system , please post. When hanging the compresser, I would ask on the hvac forums , since a lot of homes have the ac, fan units under the roof....and sound is always an issue for them...I have great luck blasting with 1/8 nozzels and six cfm...anything more I would just rent a larger gasoline compresser, 30$ a day and 10 cfm...or a tow behind disel unit that can blast a frame in an hour....good luck..http://campaigns.ford-trucks.net/for...ons/icon14.gif

I like RClarke's idea, (fifth in thread.)

Couple of thoughts. When you plumb the tanks together use as large a line as you can.

I have made a pretty fair noise reduction by mounting an upright compressor on a pallette using motor mounts. The pallette set on a rubber mat.

It is good to build a cabinet around it, but remember it needs ventilation. Line the cabinet with "soundboard" from you building supply.

If you use the oilless only as a resevoir, in the ceiling would be good just for space considerations, but I believe that if it is running, the vibrations will be transmitted all through your framing.

Do you have space for an outdoor cabinet to set both your secondary units in?