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Electric vs Gasoline Compressor

Discussion in 'Compressors, Boosters and Blending Systems' started by mmcmah, Sep 12, 2020.

  1. mmcmah

    mmcmah ScubaBoard Supporter ScubaBoard Supporter

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    I want to get a compressor so that I don't have to worry about where to get my tanks filled.

    I've already narrowed down the options and likely looking for a used Bauer Junior II or a new L&W 100.

    What I am trying to figure out is whether to just get a lower-maintenance and lower running cost (?) electric motor which will be tethered somewhere in my home, or get a higher maintenance and higher running cost (?) gasoline engine which would allow me to throw it in the back when driving so that I could refill tanks as needed.

    I live in Denver, so most of my diving is a car ride away, and I'm contemplating having to go on multi-hour trips to even get to a dive site, which is why I keep coming back to the question of portability.

    Thanks in advance for your advice.
     
  2. a878bob

    a878bob Manta Ray

    # of Dives: 1,000 - 2,499
    Location: Michigan
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    I decided on electric after considering the same question. I have enough cylinders to get me through a weekend if needed. It's worked out great.
     
  3. mmcmah

    mmcmah ScubaBoard Supporter ScubaBoard Supporter

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    Thanks. That is a good idea as well. Certainly one of my thoughts was the possible danger of having an expensive compressor sitting in the back of the vehicle while diving. Plenty of cylinders would certainly obviate the problem and they probably wouldn't be as attractive for someone to take.

    I realize that gasoline compressors have the added expense and maintenance associated with using gasoline, but is there any circumstance in which you've found yourself wishing you'd had a more portable gas unit?
     
  4. Miyaru

    Miyaru Tec Instructor ScubaBoard Sponsor

    # of Dives: 2,500 - 4,999
    Location: EU
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    As long as you're filling just one tank, a Bauer Junior is just fine. Most versions have a 2.2kW electric engine and require a slow fuse (rated C, the usual household automatic breakers are B). Not something you'd easily find near a campsite or where ever you're going.

    If you need to fill doubles, forget about a Junior. It's not designed to run continuously.

    K14, powered by 8HP Briggs&Stratton, at work near a cave site:
    WhatsApp Image 2020-07-18 at 08.46.36.jpeg
     
    rob.mwpropane likes this.
  5. mmcmah

    mmcmah ScubaBoard Supporter ScubaBoard Supporter

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    Thanks for the advice and for the picture. I suppose I didn't consider "continuous" running to include needing to fill doubles. Given the time needed to fill one HP tank, wouldn't it take about an hour to fill a set of doubles? Does that count as continuous running?

    If so, then the Juniir definitely won't work as I definitely want to be able to fill doubles... Would the Oceanus work, unless I can find a K14?

    From you picture I assume you favor the gasoline engine?
     
  6. RayfromTX

    RayfromTX Student Of Gas Mixology Staff Member ScubaBoard Sponsor

    # of Dives: 200 - 499
    Location: Hill Country of Central TX
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    More tanks are easier than toting around a compressor unless you are going for a long time.
     
    couv and grf88 like this.
  7. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
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    more tanks are cheaper and easier than toting a pump around. I recommend getting electric. If you find that you need/want it to go with you, then you probably need a trailer anyway and at that point the investment in a generator is usually worthwhile.
    On the fuse discussion, you can get a soft start for about $100 and it calms them down during startup and shutdown which makes everything happier.
     
    Dark Wolf and couv like this.
  8. broncobowsher

    broncobowsher Solo Diver

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    Own enough tanks to do the day's worth of diving. Maybe a weekend if you play that way.
    If you need to fill at home, electric.
     
    RyanT likes this.
  9. Miyaru

    Miyaru Tec Instructor ScubaBoard Sponsor

    # of Dives: 2,500 - 4,999
    Location: EU
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    Filling doubles is simply filling 2 tanks. The Junior block runs fast, I think it's around 2400rpm. Fast running compressors were never meant for more than 1 tank. They'd overheat eventually. A Junior fills around 75 liters per minute, pushing 5000 liters into a D12 would take over an hour.

    I don't favor the gasoline engine. It's noisy, requires driving out of town because of the noise and you have to monitor wind direction all the time. Also, as an extra precaution, hopcalite should be added to the filtration.

    The compressor in the picture is a Bauer K14, fill rate 125 liters per minute, runs only 1000rpm. Still takes a long time to fill all the doubles which are interconnected with decanting hoses, on the other hand the tanks won't get hot.

    If you really want to get a compressor that will last forever, get a 4 stage compressor. The one in the picture is from 1967 and still runs without issues, I only added a filtration system to meet todays air quality standards. I favor the Bauer K14 series (anything older than 1990 was built to last).
    I tried this compressor with a 3.7kW 3-phase electric engine on several generators. Without a softstarter, the breaker would trip immediately, with a softstarter the generator started to moan and the compressor refused to start. The generator that finally managed to do the job, was the size of a trailer.

    If it's possible to bring enough tanks, it's for sure the easiest and cheapest solution. Having a fill station in the neighborhood is even easier. But if you're with a group of 10 divers, cave diving during four days, no fill station around.... mobile compressor.
     
    happy-diver and RayfromTX like this.
  10. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
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    @Miyaru

    Of note when sizing generators and big electric motors like this. The K14 is likely a 5hp motor, which you would expect would be around 3.7kw because that's what the math says. The problem is that assumes the motor is 100% efficient which it most certainly is not. The data plates on the new 5hp motors claim 85% efficiency, so to run the K14 you would need a >4.5kw generator. The rule of thumb that I use is 1kw/hp. It's a smidgen over reality, but it saves the generators from running balls to the wall the whole time and it's usually splitting hairs cost wise. I.e.

    The Junior II that @mmcmah mentioned is 3hp motor as the L&W will likely have as well. A >3kw generator will be required.
    Quick look at Home Depot says a Generac 3.6kw is $460 and the 5.5kw version is $690. Sure it's $250, but it's not egregious by any means and it's also more than enough to run most of your house in a power outage.
     
    rjack321 and Bob DBF like this.

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