2 compressors on 1 tank???

[oldeerslayer]

Has anyone tried putting 2 small single stage 2-3 HP compressors on one 80 gallon horizontal tank? Sounds like a cheap way to get lots of volume. Especially for someone who already has the big tank.
My old (really old) Challenge 5HP 2 stage is starting to use oil and parts for a 50's era pump are getting hard to find and expensive.
I keep seeing these Craftsman and other brands of similar compressor with a 3hp pump and single stage twin cylinder pumps in the $1-200 range ($50 if they never drained the tank and it now has a hole). They put out 6-7 SCFM@90psi. Why not mount 2 completely separate systems on my 80 gallon tank. I'll pull the 50 amp double pole breaker and replace it with a pair of single pole 20's which would be on the opposite legs of my power supply.
Maybe stagger the on & off pressures so that only one would kick in during light usage, but still have the ability to generate 12-14 SCFM when needed?

I'm sure some tool genius has already figured out how to or why not to - please enlighten me.

 

[theoldwizard1]

Really big ones do exactly that ! Couple of 5-10 hp motors and pumps on a couple hundred gallon tank.

I think they run off of a common pressure switch/contactor.

 

[Heavymetalmechanic]

Generally called a duplex compressor setup, often see them in bigger shops.

 

[phil du jour]

it's just a question of whether or not the tank can handle the increased volume. i have seen industrial setups that have six 300 HP compressors feeding one gigantic tank the size of a garage (can't tell you the exact size). if you can get it hooked up and the tank can handle it, i don't see why not.

 

[May Pop]

Also standard on HVAC compressors. Mine is over 30 years old. Quincy still going strong.

 

[CNGsaves]

Yes, you can run 2 compressors on one tank.

. . . But about giving up on 5 HP Challenger pump . . No, NO, NO !!!

Repair the workhorse 5 HP 80 gal 2 stage Challenger . . . . it's just like overhauling a little lawnmower . . . just BIGGER cylinders !!

Tie in your little Craftsman to big tank while you're overhauling the Challenger, and hope the C-man keeps running.

Your comment about not wanting to work on Challenger compressor since it's blowing a little oil is troubling . . . . seems to sound like you'd rather be using a Crapsman than the Challenger ??

 

[oldeerslayer]

Glad to hear that it sounds like a possible way to go.
Any suggestions as to whether or not the on and off pressure should be staggered or the same. I suspect trying to get them both to turn on at the same time might be tricky due to variations in pressure switch accuracy, even if I used two identical switches. Is there such a thing as a double throw pressure switch? Could I use the original 230 volt switch and run one off each side without completely combining the 2 electrical systems?
My gut reaction is to set it up with one coming on at 100 and the other at 95psi and turning off at say 125 and the other at 130. Most of these inexpensive compressors seem to top out around 135. Looks like no simple way around both starting together on an empty tank short of turning them on one after the other. Which could work since it would only be an occasional occurrence. I'd be sure each had an outlet check valve to prevent any problems with back pressure.
I'm sure most of the wiring diagrams, etc. for the super sized commercial setups would be irrelevant as they are like 3 phase or bigger.

 

[oldeerslayer]

Repair the workhorse 5 HP 80 gal 2 stage Challenger

Any suggestions on where to locate the necessary parts? I haven't had much luck finding them that old.
I'd much rather overhaul the old girl. She chugs along around 600-700 rpm's and would last another 50 years. It seems I read somewhere they were built for 50,000 hours. Unlike these new ones in the big box stores that howl at 1400-1500 and are meant to last a couple thousand hours.

 

[oldeerslayer]

Just found this on Chicago CL:

QUINCY DUPLEX AIR COMPRESSOR - $600 (ORLAND PARK)
MODEL 108 3 X 2 1/2 POWERED BY 1 1/2 HP BALDOR 1725 RPM
MODEL 106 2 1/2 X 2 1/2 POWERED BY 3/4 HP DAYTON 1725 RPM
2 NEW BELTS 60 GAL TANK 1989 200 PSI RATED NEW MOTOR PULLEYS
FRESH SYNTHETIC OIL NEW FILTERS NO CHEAP STUFF SPARED NO EXPENSE
COMPRESSORS BOTH SPIN ABOUT 750 RPM LOADLESS START SET UP 4 115 VOLT
BUT WILL RUN 220V

 

[volleyball]

I thought HF is selling a 2 stage now. Maybe get that and then save the original for the long task of rebuilding. For a home shop, it should last a long time, which may be needed if you cannot find parts. Or they are too expensive.

 

[Mooky]

As said, common industrial set up, duplex compressor. An "alternating relay" or "lead-lag" controller is used to control both motors, alternating their operation to equalize run time.

The lead-lag controls will start the second compressor when the pressure drops to a certain point. It can also switch compressors to equalize run time.

Alternating relay:

http://www.hubbell-icd.com/icd/components/ac5247.asp

A Google search will likely find some DIY controllers, the industrial versions I'm familiar with are used on much larger machines and very expensive.

Search for "duplex compressor controller" or similar.

 

[May Pop]

That is an older HVAC compressor. Very similar to what I have. The only problem with it is it is still not as powerful (CFM) as a similar sized 2 stage unit. Its very nice to hear them start with no load then when the oil pressure comes up they start pumping.
Seems that 600 is a little high priced for that unit but it does look like it has a newer compressor on one side.

 

[Kev442]

I have planned out exactly what OP stated. I picked up two Cman compressors from the 70's for $50 each with weak tanks. I also picked up a 60 gallon tank from a dead oilless. Funny thing, I put one on the tank and never got around to plumbing the second one in yet as I haven't needed to blast at that location.
Initial fill up is slightly slower than normal at about 9-10 minutes, but recovery is pretty dam good. Someday I'll plumb the second one, but not a priority.

 

[oldeerslayer]

I picked up two Cman compressors from the 70's for $50 each with weak tanks

Funny I'm also from WI and that's what I paid for the one I have which also had a pin hole in the tank. I just pulled the top plug and put in a bolt with rubber and steel washers on both the inside and outside. Been running a couple years like that.
Does anyone know if the older Craftsman were made in the USA. We weren't doing much trading with mainland China back in the Nixon era. They may have even been made by a good name company back then, to Sears specs.

May go a different route as I got a lead on a Speedaire 3Z180, which after a little investigation on Google turns out to be Graingers house brand for a Champion R15B. It's under $400 complete with 5HP single phase and good tank. Be a lot quicker than rebuilding my antique and in my little garage 21-23 SCFM @ 175 would be plenty. Should it need repair, parts seem to be a lot easier to find.
If the deal goes through I might even dig out my HF sandblasting box and try to figure out a way to hook up some sort of dust collector to it so I can actually blast with enough air and be able to see what I'm doing.

 

[volleyball]

Years ago I got a 30 gal single stage that had a pinhole in the tank. With no money, I just used some old lead solder I had and soldered it up. 5 years later and it still held with no leaks. I had used a putty knife to force some solder into the hole creating a plug.

 

[Packard V8]

There's a reason those cheapo toy compressors from the big box stores come with small tanks. Put them to work continuously trying to supply real volume, such as a blast cabinet or air tools and they'll soon die a hot, noisy death.

So yes, easy to gang them, but be gathering several and using quick-disconnects, because they'll be like popcorn.

My old (really old) Challenge 5HP 2 stage is starting to use oil and parts for a 50's era pump are getting hard to find and expensive.

There's also a reason big volume compressors are made with lots of iron and cost lots of money to buy new.

One more vote to rebuild the Challenger. No, parts aren't really hard to find. Yes, they'll cost a bit more initially than picking up junk, but done once, done right, done for your lifetime.

jack vines

 

[sb7979]

it's just a question of whether or not the tank can handle the increased volume.

???? Not sure what that statement means.