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  1. #11

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    Quote Originally Posted by tbone1004 View Post
    no. If you run an e-ccr in parachute mode as most do in a cave because of the ups and downs you actually are doing a lot more manual input than you would with an mccr.
    But if the user is not paying attention, the unit will fire when pO2 drops below the low set point (at least that is what I thought the OP was asking)

    Jason Gulley

  2. #12
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    Quote Originally Posted by jason View Post
    But if the user is not paying attention, the unit will fire when pO2 drops below the low set point (at least that is what I thought the OP was asking)

    That's what I was asking


  3. #13
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    This seems to be answering some of my questions. My understanding was an e-ccr could be run in manual mode, so the goal with all training is to teach you manually to instil monitoring and pO2 control. That's why I was surprised to find quite a few "purists" that think people's first rb should be fully manual only. Then once you've gained experience, move to an e-rb. I really didn't understand that when it can be taught on either type of rb.


  4. #14

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    Quote Originally Posted by jason View Post
    But if the user is not paying attention, the unit will fire when pO2 drops below the low set point (at least that is what I thought the OP was asking)
    right, sorry I think I misread that.

    I think all of the current e-ccr's will only allow a low setpoint of 0.5. My meg allows .2

    @rddvet
    to the other comment about shutting things off. You don't want to shut your parachute off, and the only active way to do that is to shut your O2 off on an eccr. Shutting the ADV off if you have one is something many do after they get to depth

    the advantage of the mccrs is usually cost and you aren't tempted to just let the solenoid do all of the work. On some units *meg, xccr etc.* the cost advantage of something like a KISS is very much still there. Against something like the Liberty, it really isn't there, especially if you have an upcoming need for a trimix analyzer.


  5. #15
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    Quote Originally Posted by tbone1004 View Post
    @rddvet
    t Shutting the ADV off if you have one is something many do after they get to depth

    Why? To keep the loop volume fairly constant?


  6. #16

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    Quote Originally Posted by rddvet View Post
    Why? To keep the loop volume fairly constant?
    others more experienced may have different reasons, but here is why I shut mine off.

    I use the mav to maintain loop volume as they flow enough to breathe in "open loop mode", so you inhale until you feel min loop, then hit the mav while inhaling until you have a comfortable loop volume. The ADV's are great for when you need/want a hands free descent though. A lot of the diaphragm ones are prone to leaking mainly when they activate when you don't want them to. On a dpv, in high current, wrong body position, etc will get a lot of them to go. Mine is a plunger style and is quite stiff so it's uncomfortable to breathe against so it just stays shut off.

    I have an iBov with adv coming though and much prefer the concept of ADV built into the bov vs. having it in the t-piece or in the counterlung. I'll still probably turn it over to "loop only" mode since I imagine I'll have it tuned quite light, but it's great that it's an option. The Poseidon is the other bov that has that built in but you can't disable it. It's on the Xstream though which is not prone to freeflowing so that helps. There is a technique for this with normal bovs as well just have to have a delicate touch with it


  7. #17
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    A set point of 0.2 and shutting off the ADV at depth?
    Oh my, what is the point of even trying to justify any of that?

    Sent from my SM-G955F using Tapatalk


  8. #18
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    Quote Originally Posted by rddvet View Post
    I haven't really seen anyone ever express an opinion here, and since we'd be doing the majority of our rb dives in caves (after appropriate training), I thought this would be the place to ask.
    You best option is probably to test dive as many different units as you can and learn about them. How they work and what their pros and cons are.
    A very difficult task since owners and instructors/dealers will likely tell you their unit is the best invention since sliced bread.

    Eccr vs. Mccr is just one decision you need to make and there are so many more.
    I went mccr because I was told a broken solenoid could execute me without warning.
    While that is certainly true, now I know that there are many ways an mccr can fail with the exact same result.
    I would not consider either safer than the other.

    There are pros and cons to everything and most units have some flaws and shortcomings that may or may not be obvious.
    I would try and see what works best for you.
    Getting trimmed out properly and feeling comfortable with the unit is a good foundation, then try to figure out how well it works for you compared to the other models out there.




    Sent from my SM-G955F using Tapatalk


  9. #19

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    I started on an E-CCR, and I don't think there's anything wrong with that. As said above, my class was run fully in manual mode with a low pO2 parachute, with the idea that if something breaks, you are diving it in manual mode, so you better know how to do it.

    Since then, I've done a mix of letting the rebreather fly the pO2 with the solenoid, and running it manually at depth. Typically, I let it run when I'm on a scooter, as it just makes life easier, but occasionally I force myself to run it manually while scootering just to keep the muscle memory up. Even if you let the solenoid control your oxygen addition, it's easy to keep track of what it's doing, since it's easy to hear the solenoid injecting without the bubbles making so much noise.

    As far as turning off the ADV at depth...The ADV on my SF2 fires when the counterlung bottoms out. It's VERY sensitive, and it's relatively easy for the ADV to flow a small amount of gas without the click of the solenoid to tell you it happened. (If you are descending and it fires a large amount, though, it's very obvious.) It's really nice when there's lots of ups and downs to deal with, but I usually turn mine off when depth is stable, even if I am letting the solenoid run the pO2 setpoint. This is because I usually run a hypoxic dil, and if the loop volume drops because you are using up the O2 in the loop, adding dil to make up that volume via the ADV will drop the loop pO2, and then the solenoid still needs to add O2 to balance it out, making it harder to maintain a min loop volume. If I were running a dil that was closer to 1.2 at depth, however, I wouldn't bother closing the ADV.

    I wouldn't use a low setpoint of 0.2 other than at the surface prior to getting in the water. The SF2 lets you set 0.19 to keep the solenoid from firing at ambient O2. When I get on the loop, even while at the surface, I turn of the ADV (to keep out hypoxic dil), flush the unit with O2 to verify the pO2 is staying up where it belongs, then set the pO2 to the low setpoint of 0.7 while gearing up to keep myself from doing anything stupid. If I hear the solenoid fire while I'm gearing up, it let's me know something isn't working right...

    When I start the dive, if I'm running the unit manually, I typically set the high setpoint 0.2 below where I plan to run the unit for the duration of the dive. You COULD leave it at 0.7, but honestly, if you're aiming for 1.2 and it fires at 1.0, you're preventing yourself from racking up unnecessary deco due to your inattention. And frankly, if I let it drop to 0.7 while aiming for a 1.2, I probably needed the reminder from the solenoid well before then to tell me I'm not paying enough attention. I always swap to the high setpoint at 30ish feet, since that's where I double check that my cells can show a 1.6 without any apparent limiting, and usually pop on my ADV around there, too, just to help make life easier while descending.


  10. #20

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    Quote Originally Posted by nakatomi View Post
    I went mccr because I was told a broken solenoid could execute me without warning.
    On that note, I did have an issue with an oxygen 1st stage that had IP creep, which caused my solenoid to slowly inject O2 without clicking. It didn't add quickly, and it never spiked my pO2, but it did make the O2 not drop as quickly as it usually does, which is how I came to find the issue - it was weird not needing to click the O2 MAV with the right frequency. If there was a rapid flow of O2 going into your unit, I would suspect you'd likely hear it - that's what your BOOM drills are for. Otherwise, as long as you are monitoring your pO2 frequently, changes don't tend to happen super rapidly, and you shouldn't really be surprised by your pO2 numbers, even if something isn't working quite right



 

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