Compressor Shopping

Discussion in 'The Tool Shed' started by Focker, Oct 2, 2017.

  1. Oct 2, 2017
    Focker

    Focker Rust Never Sleeps Staff Member Sponsor

    Tri-Cities WA
    Joined:
    Aug 18, 2014
    Messages:
    4,341
    I want a 2 stage compressor.

    While looking at used ones... How can I tell if it's 2 stage? Is the tell tale sign 2 different sized hard lines going into the tank?

    A 2 stage can have just one cylinder... Right?
     
  2. Oct 2, 2017
    45es

    45es Sponsor Sponsor

    Naches, WA
    Joined:
    Mar 31, 2007
    Messages:
    372
  3. Oct 3, 2017
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    18,218
    Andrew from New Mexico is the compressor expert. I don't recall his handle here - but he was active in the past few days at IFSJA. Failing that, the Garage Journal forum about tools may be able to help.

    Here he is - 1970CJ6

    If you are looking at a specific compressor that is not a current model, you could post up a pic on Garage Journal. I presume you want to be able to identify a well-priced 2-stage compressor so you can buy it on the spot rather than go away and research it. Can't help you there - but according to the Quincy article a 2-stage compressor must have two cylinders of different sizes (low pressure large and high pressure small). Some single stage compressors have two cylinders, but I presume they must be the same diameter, so that each does the same amount of work.

    I presume that a 2-stage has the two cylinders on the same shaft, driven by a single motor. The second stage is higher pressure and lower volume, so it must be smaller to equalize the work between the two cylinders. P1 V1 = P2 V2. Knowing this, you should be able to ID a 2-stage compressor if you can see the cylinder block.

    What do you have now? I get along fine with my single-stage 60 gallon Coleman-Powermate unit, bought on close-out from Lowes. I probably would need more air if I ran a blast cabinet or did outdoors blasting. For tools and painting, it's plenty.
     
    Last edited: Oct 3, 2017
  4. Oct 3, 2017
    Focker

    Focker Rust Never Sleeps Staff Member Sponsor

    Tri-Cities WA
    Joined:
    Aug 18, 2014
    Messages:
    4,341
    Thanks guys.

    Tim,
    I read the other compressor threads and looked at your Garage Journal links. As always (well mostly... Lol) good information.

    I currently have a 5hp 25gal DeVILBISS Pro Air II that I've been using for 21 years. My FIL went halves on it as long as I stored it at my house and used it to blow out his sprinklers every fall. I've kept up my end of the deal. I replaced the cylinder sleeve (piston kit) about 7 or 8 years ago...It's oilless and noisy.

    I want to upgrade. I "think" I want a 2 stage, but probably don't need it.
     
  5. Oct 3, 2017
    tarry99

    tarry99 Member Sponsor

    Northern California
    Joined:
    Oct 29, 2012
    Messages:
    3,143
    My old rule of thumb is , buy the biggest and highest rated CFM compressor you can afford that will fit in the space & electrical supply you have......................two stage are nice.........more CFM.
     
  6. Oct 3, 2017
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    18,218
    Just a comment - budget the installation costs along with the compressor. My compressor was cheap at $300, but I'm sure I spent that much on materials to install it. Pipe, flex coupling, valves, drier, regulator, safety valve, wire, conduit, circuit breaker, etc.

    You will need a 230 circuit for anything larger than a portable compressor.

    TP Tools has a helpful diagram for your installation. Modular Metal Piping Kits
     
  7. Oct 3, 2017
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
    Joined:
    Aug 13, 2015
    Messages:
    1,775
    Everybody needs a 2-stage compressor. :D

    That being said, I've been running air sanders and sprayers in a wood shop steadily for 12 years, and die grinders and air drills for years before that on my single cylinder upright that might be the same 28gal, 5hp, but oil-version of yours. I think I bought it in '99. It runs constantly; sometimes 8-10 hours a day. I keep synthetic oil in it, keep the tank empty of condensation, I modified the air intake to fit a square automotive-style air cleaner, and it just keeps going. I haven't noticed any performance loss over the years. Yes, it's on the verge of too small for my needs, but it was cheap, and more importantly, it's portable.

    The thing that really made mine bearable was the paper towel roll air drier that I made a few years ago. That's da'bomb.

    This is beside the point, but at this stage (pun intended), I think I'd almost rather get a second compressor of the similar type than a bigger single 2-stage compressor. I'd run them to an outside holding tank, and have the second compressor switched to kick on at a lower pressure, as a backup under heavy use. I'd have less into the whole setup than a big 2-stage that I couldn't move without a pallet jack or forklift.
     
    Walt Couch and Focker like this.
  8. Oct 3, 2017
    Focker

    Focker Rust Never Sleeps Staff Member Sponsor

    Tri-Cities WA
    Joined:
    Aug 18, 2014
    Messages:
    4,341
  9. Oct 3, 2017
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    18,218
    The 5.9CFM at 90 PSI is the limiting value for your air tools. Check that you can get by with that much air. A 2HP rating is impossible at 120V through a line cord (but the compressor manufacturers are known to lie about HP ratings). 2HP is 1500W at 12.5A with 100% efficiency. Typical efficiency is around 50%, so you really need something like 25A minimum to make 2HP at 120V - the most you can get from a 120V 3-prong domestic outlet is 20A. Your standard 3-prong lighting outlet is 15A. Also, I recall that the 29gal tank is popular for these portable compressors because 30 gallons or larger requires compliance with ASME standards, or something like that.

    If you need to stay within a budget, how about something like this? Porter-Cable Stationary Belt Drive Air Compressor, 60 gal. at Tractor Supply Co. A lot more compressor for another $130.
     
    Last edited: Oct 3, 2017
  10. Oct 3, 2017
    tarry99

    tarry99 Member Sponsor

    Northern California
    Joined:
    Oct 29, 2012
    Messages:
    3,143
  11. Oct 3, 2017
    Twin2

    Twin2 wasn't me Sponsor

    Virginia Beach, VA
    Joined:
    Apr 28, 2011
    Messages:
    3,201
    not to change subject . but you have my interest
     
  12. Oct 3, 2017
    Focker

    Focker Rust Never Sleeps Staff Member Sponsor

    Tri-Cities WA
    Joined:
    Aug 18, 2014
    Messages:
    4,341
    Yes
     
  13. Oct 3, 2017
    Focker

    Focker Rust Never Sleeps Staff Member Sponsor

    Tri-Cities WA
    Joined:
    Aug 18, 2014
    Messages:
    4,341
  14. Oct 3, 2017
    tarry99

    tarry99 Member Sponsor

    Northern California
    Joined:
    Oct 29, 2012
    Messages:
    3,143
    No hurry..........Save your $$$ and get something decent @ 220 volts with some CFM's ..................check Craigs list lots of nice compressors sitting in some old dudes garage.
     
  15. Oct 3, 2017
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    18,218
    Was that offered ... ironically? No possible way to get 4 HP from that 15A 120V plug. The spec writers invent weird metrics like "starting HP" so they can make ridiculous claims. Might be a nice portable compressor though. I expect it's on a par with the Harbor Freight one that gets such good reviews. Probably quieter than your oilless compressor. Put a big automotive air cleaner on the air intake and it should be a lot quieter.

    Anyway, my compressor is a Coleman, and it's been fine. No complaints.
     
  16. Oct 3, 2017
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
    Joined:
    Aug 13, 2015
    Messages:
    1,775
    Road trip to Spokane! $350
    If I had the cash right now, I'd probably steal this out from under you.

    60 gallon air compressor

    [​IMG]
     
  17. Oct 3, 2017
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    18,218
    Ya know, I thought I'd do that... watch Craig's list and pick up the compressor I wanted used. I watched for a couple of months, and all that showed up were portables like above, and huge industrial sized compressors that the sellers wanted too much money for. I could buy a 60 gal Quincy for that much.

    I don't remember if I got a tip somewhere or I was in Lowes and saw they were closing out the Kobalt compressors made by Coleman-Powermate. You want a 60 or 80 gallon upright stationary compressor that uses about 20A of 240V power. This should make 12-15 CFM of air at 90 psi, which is what you run your air tools at. I'd watch Lowes and Home Depot for a Kobalt or Husky after Christmas... maybe you'll find a bargain. Heck, the Kobalt that's roughly the same as the compressor I bought is only $500 without a sale: Shop Kobalt 60-Gallon Electric Vertical Air Compressor at Lowes.com 3.7 HP at 240V is less than 12A. You could wire a 20A 240V circuit easily using the yellow Romex. Basta.
     
  18. Oct 3, 2017
    timgr

    timgr Jeepin' Nerd Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    18,218
    I have that one except mine is black and the big sticker says Kobalt instead of Coleman... but it's otherwise clearly marked Coleman-Powermate. IMO $350 is high for that compressor ... but it's a good compressor.
     
    Last edited: Oct 3, 2017
  19. Oct 3, 2017
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
    Joined:
    Aug 13, 2015
    Messages:
    1,775
    It's a steal out here. The inland NW Craigslist tool market is ridiculous. People would rather pay over retail for used than just buy new.
    The motorcycle market is REALLY bad.
     
  20. Oct 3, 2017
    termin8ed

    termin8ed I didn't do it Staff Member Sponsor

    Mason, MI
    Joined:
    Dec 22, 2002
    Messages:
    2,145
    Thats kinda what we have at work. 2 compressors working on tandem. Apparently whoever wired them screwed up so they both are wired to the same pressure switch. Can turn number 2 off or 1 and 2. Cant turn 1 off by itself.
     

Share This Page

New Posts