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Suggestions on a tankless compressor to drive small booster

Discussion in 'Compressors, Boosters and Blending Systems' started by Reku, May 8, 2019.

  1. tbone1004

    tbone1004 ScubaBoard Supporter ScubaBoard Supporter

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    @Reku I wouldn't bother with it. IIRC those are only rated at like 1.5cfm. The key with the boosters is cooling the gas off, not necessarily running them slow. They cool themselves with adiabatic cooling when they cycle. Now the bottles you're filling will get warm obviously, but the booster doesn't really care.

    To keep the booster happy you need dry and clean air, Grade D. The only difference with E is a tighter fO2 requirement and they put a VOC limit of 25ppm on there. The booster doesn't care about that, and no there is no bypass into the HP chamber. You can get Grade D with no chemicals on a normal compressor, you need chemicals for Grade E and OCA. If you use an oil-less compressor, you can get away without chemical filtration.
    You can do that before or after a HP regulator with after being considerably cheaper, but you'll be pumping all of that stuff through said regulator and a scuba regulator probably won't like that.

    Where you are going to hit a wall is the 23:1 compression ratio on your booster.

    Since you said price is no concern. This will work. Thomas makes one as well which is 2755TE48/40 .
    71R (TWIN CYL - HIGH PRESS)
    It is probably going to run you about $800 *from my last quotes from both companies*, you'll still need to get a capacitor and housing, regulator, auto shutoff switch with unloader *very important to have the unloader*, etc etc so you'll be in for over a grand and it certainly isn't a "package" deal. The picture of my system above took a stock California Air Tools 6010LFC and gutted it. The switch with the unloader was on the pump, the capacitor and cover was on there as well so all I did was move the unloading valve under the regulator and get a 3/8npt to 1/4npt reducer. With the pump above you will have to source all of that which isn't that bad, but it's work to figure it all out.

    Unfortunately as the pressure increases it causes a squared increase in power consumption which is why the Gast is only rated at 2cfm. That is essentially the max you can get on a normal wall outlet with the 3/4hp motor. Up to 2k fill pressure it will probably spit out around 3cfm, then slow itself down as pressure builds. To get 5cfm would take 2.5x that amount of power. You can run a 1.5hp motor on a standard wall circuit, but that's the max rating of a normal 15a circuit so you have to have a dedicated circuit for it or you'll be blowing breakers which is why you don't see them very often. I have one on my Rix, but it has a VFD to slow it down if there is other demand on the circuit.

    These boosters cycle as soon as the outletpressure/23=fill pressure so if the filling tank is down to like 1500psi, as soon as the pump hits 65psi it will cycle. You'll see the LP system pressure drop down a lot as soon as it cycles. The LP system won't stay at 150psi and won't get to 150psi until the outlet pressure gets to 3450 and then it will stall.

    Now, why do I mention all of that. The Gast is going to be the same CFM at the same pressure as the Cornelius and with proper filtration you are going to be into it for maybe $2k. It weighs about 20lbs so that is considerably lighter, it has a 3/4hp motor instead of 1.5hp so it will cost you half as much in electricity to run. A water separator and filter for the Cornelius with the adapters to a scuba regulator *assuming no cost for the reg since you can run it off of a normal inflator hose* you're going to be in for about the same amount of money.

    Edit, just found this one. 150psi, about 2cfm at max pressure, but gets you 5cfm at lower pressures. 15020c is the full system that uses this pump so it'll have the capacitor, start switch, check valve etc. You can remove all of that for your portable system, then put QD's on the tank so you have a buffer if you need the compressor for any power tools or at home use since your filters will appreciate the extra capacity so they don't cycle quite as hard. These compressors like mine do get quite hot during use so if you have a box fan it doesn't hurt to have it pointed at the heads. I haven't really found that they do much which is why I abandoned putting computer case fans on mine, but when I'm pumping gas in my garage i put a box fan over it to blow on it especially since it is in the pelican case and has limited air flow around the motor
    https://www.amazon.com/California-A...t=&hvlocphy=9052807&hvtargid=pla-570018120417
     
  2. Reku

    Reku Solo Diver

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    @tbone1004

    All of that makes sense. Looks like I will be using a shop compressor after all!

    Is it worth doing anything with that Cornelius? It was free. It does build pressure and the separator is working. Could become an interesting side project.

    Thanks for the info.
     
  3. tbone1004

    tbone1004 ScubaBoard Supporter ScubaBoard Supporter

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    @Reku It's a good conversation piece and it's a robust compressor so if you have any use for up to 1500psi tanks then sure, but I wouldn't personally bother investing money in it unless it has sentimental value
     
  4. Reku

    Reku Solo Diver

    # of Dives: 5,000 - ∞
    Location: Great Lakes + Northern Florida + Marsh Harbor
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    @tbone1004

    Interestingly enough despite it's name it does have a discharge air pressure rating of 3,000 psi, once you hit 3350 it will vent the relief valve and reseal at 3200. The manual says don't push it past 3500 psi. I'll do some testing and see. I agree though if it maxes out or fails to build pressure past 1500 psi I wouldn't have too much use for it. I've got a few bottles that are full at 2015psi but they are so small that transfilling works well from an hp set of doubles.

    I'll dig for some more information and see what I find. if all else fails I'll just take it apart and put it back together for the experience.
     
  5. tbone1004

    tbone1004 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: I'm a Fish!
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    @Reku oh, I thought I'd seen the cornelius with 3500 in the model number for the higher pressure ratings. If that's the case I'd just get your banks filled to 3k or whatever you're comfortable running it and if you need it boosted higher just run it through the booster. They don't care about high pressure, it's the big differences between inlet and outlet pressures they get really inefficient.
    If you can get a couple of HP cascade bottles and at least one LP cascade you can get a pretty solid fill station setup going.
     

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