Electronic vs manual CCR

[beto]

Hello,

As part of evaluating some CCR units I have tested both a MEG and a KISS. In both cases I only did manual control of the Po2 during this
test dives: The MEG test was on a pool, and the KISS test was on pool and a long ocean not too deep (60ft/18m). I found it relative easy to control ppO2 manually specially with the nice integrate O2 monitor on computer and/or HUDs.

So my question to the very experience people on this forums is: Why bother to have electronic controlling O2 vs just doing it manually by the diver?

It sounds like for remote locations the simple the system is kept the more chances of going diving on a giving day.

What am I missing?

Thanks for your input

Best,
Beto

 

[Dave Sutton]

Bear in mind that any rebreather can be flown manually. Leon at ISC (Meg Manufacturer) prefers to have divers fly manually with the solenoid as a backup. Any rig will have electronics, the only difference is that in one case you have a solenoid that you may or may not allow to work, and in the other case you do not.

Why would you dive one way or the other? There are as many answers as there are divers diving rebreathers. Some are good and well reasoned answers, and others are just rationalizations. Most serious RB divers these days are using eCCR systems, but there is a significant minority who still use the KISS type system, most notably these days on the manual version of the rEvo rebreather. The KISS rebreather itself is widely considered to be obselescent, but it still has a loyal following and has done many safe dives. Do a bunch of reading and research, and ask questions. The only bad question is the one you keep to yourself.


Dave

.

 

[DSix36]

I will throw my nickels worth into this discussion.

I started out with an eccr and found it to be a great and easy way to dive a rebreather. It took care of the PO2 for me and all I had to do was just check once in awhile to make sure that things were working properly.

I found myself stating to get a little complacent with checking my handsets often enough. I did an entire 4 hour cave dive without ever looking at my handsets and only using the HUD. I realized that his type of crap was going to get my arse dead one day decided that I needed to make a change.

I went and got myself a rEvo that was a hybrid unit. I run it manually and use the electronics (set lower) as a parachute in the event that I do something real stupid. I have found it nice to be able to switch the setpoint when task loaded and letting to run eccr for a moment to be an occasional benifit also.

Personally, I believe that I am much more "in tune" with my environment and PO2 changes this way.

IMHO - everybody should do their first 50 hours or so flying manually just to learn good and safe habits.

 

[kwinter]

Running manual on a full eCCR can be done, but it is a royal pain and not a good way to enjoy a dive. Unless you are fairly deep, you will have to manually add O2 every few breaths. That is a far cry from a mCCR with a CMF orifice or needle valve that leaks some O2 into the loop to virtually match your metabolic rate. In those cases, most find they are only manually adding a few times during the course of a dive.

To suggest that an eCCR without a leaky valve should be dived manually for the first 50 dives is nuts. It would turn folks off from RB diving. Too much work. But with mCCR or hybrid, I agree that it encourages awareness.

 

[Iain3]

Running manual on a full eCCR can be done, but it is a royal pain and not a good way to enjoy a dive. Unless you are fairly deep, you will have to manually add O2 every few breaths. That is a far cry from a mCCR with a CMF orifice or needle valve that leaks some O2 into the loop to virtually match your metabolic rate. In those cases, most find they are only manually adding a few times during the course of a dive.

To suggest that an eCCR without a leaky valve should be dived manually for the first 50 dives is nuts. It would turn folks off from RB diving. Too much work. But with mCCR or hybrid, I agree that it encourages awareness.

I've run almost an entire dive manually on an Inspo when the computers failed and it is certainly a pain in the arse.

Most people I know who do run eccr units manually with setpoint as a parachute have added a trickle valve in making it a hybrid unit.

 

[Clare]

Running manual on a full eCCR can be done, but it is a royal pain and not a good way to enjoy a dive. Unless you are fairly deep, you will have to manually add O2 every few breaths. That is a far cry from a mCCR with a CMF orifice or needle valve that leaks some O2 into the loop to virtually match your metabolic rate. In those cases, most find they are only manually adding a few times during the course of a dive.

To suggest that an eCCR without a leaky valve should be dived manually for the first 50 dives is nuts. It would turn folks off from RB diving. Too much work. But with mCCR or hybrid, I agree that it encourages awareness.

It's how I dive my JJ. O2 levels drop far more slowly than that - if you accept a .1 drop then I'm probably adding every couple of minutes. Really not that bad at all.

I have the solenoid set underneath at .7 in case a problem occurs which means I really am too busy for a bit to get involved.

Only pita is managing it on ascent. The delay in reading coming through led me to a couple of interestingly high po2 levels which then required flushing. I'm getting used to that though.

Why do it? Like the control and the fact it makes me watch more. My buddy doesn't do it.

 

[Packhorse]

When I started looking at CCR's I had decided I wanted to start with a mCCR and learn some good habits.
90 hours later Im more than happy to stick with mCCR.

One of the reasons I chose the rEvo was this simplicity of changing mCCR to hCCR.

 

[Iain3]

It's how I dive my JJ. O2 levels drop far more slowly than that - if you accept a .1 drop then I'm probably adding every couple of minutes. Really not that bad at all.

I have the solenoid set underneath at .7 in case a problem occurs which means I really am too busy for a bit to get involved.

Only pita is managing it on ascent. The delay in reading coming through led me to a couple of interestingly high po2 levels which then required flushing. I'm getting used to that though.

Why do it? Like the control and the fact it makes me watch more. My buddy doesn't do it.

Matt Partridge dives his like that but has fitted a Pelagian trickle valve or something like that onto his, so less frequent top-ups needed.

 

[cys]

With my mk15 I find it just about as easy to dive with the solenoid as without. If I'm in between solenoids, I'm still going diving. Been there, did it, not that long back on a multi-day boat trip.

 

[lizardland]

With my mk15 I find it just about as easy to dive with the solenoid as without. If I'm in between solenoids, I'm still going diving. Been there, did it, not that long back on a multi-day boat trip.

Did the same when my original pod died and I was looking for electronics options. I did a good few months of diving on just the o2 button most of which was 50m+ stuff. I wasnt looking forward to my first long deco but it was surprisingly easy. I did think about not replacing the electronic control at all.

Sent from my GT-I9100 using Tapatalk

 

[Ben Field]

As an MCCR diver I have only once found myself wishing for ECCR, I was on a long deco hang (90min) and the swell had picked up considerable since we jumped off the boat, it was a team dive so 12 on the station. The constant depth maintenance, associated PPO2 adjustment and rebuild got Very irritating.
However for the rest of my CCR dives I've never seen the need, its certainly more efficient and easier on ascent IMO.

My concern with running a Hybrid in Parachute mode would be that the ECCR element could fail unseen (as you are manually running the unit over the failure) and if you for whatever reason need the parachute it won't be there. On full ECCR or MCCR you'd notice your failure at a higher PPO2 and have time for an easy bail, I wouldn't want to rely on spotting issues below 0.6bar PPO2, thats a "low opening" parachute.

I don't think either E or MCCR is better, just different, I don't think there needs to be a "Vs"

 

[Peter L]

My concern with running a Hybrid in Parachute mode would be that the ECCR element could fail unseen (as you are manually running the unit over the failure) and if you for whatever reason need the parachute it won't be there. On full ECCR or MCCR you'd notice your failure at a higher PPO2 and have time for an easy bail, I wouldn't want to rely on spotting issues below 0.6bar PPO2, thats a "low opening" parachute.

What are the potential failures?
- Leaky valve blocked - O2 adds would be more frequent early before .7
- Solenoid fails - Controller would have already barfed at you..
- Low solenoid battery - Controller would have already had a moan..
- SP controller dies - you still have the leaky valve and alternate display..

I have had a mix of the failures above all were obvious, none of them ended the diving and flying manual is no bother and in some ways easier than having the solenoid fighting the PPO2 drop on the ascent.

 

[ccrdave]

I like mccr very much but I mean a trickle valve mccr not a button only job, that is a pain in the arse, especially on ascent you you may be busy doing other things
A few years ago an mccr was probably more reliable than an eccr, but now with the advent of controllers like the predator I think that is now not the case

so whats the difference? well solenoid v trickle valve, they can both fail shut, and they can both fail open. One is monitored by you only, the other is monitored by the electronics and you.
Also on ascent the eccr holds constant setpoint and thats why we get deco advantages on rebreathers, with mccr its more time consuming to emulate that

I one of the reasons I dive eccr is because when I am teaching I can give some more time to my students, and at mod 1 ascents can be busy!

if I didnt teach which would I dive....dont know!

 

[DSix36]

To suggest that an eCCR without a leaky valve should be dived manually for the first 50 dives is nuts. It would turn folks off from RB diving. Too much work. But with mCCR or hybrid, I agree that it encourages awareness.

Very valid point. It does suck to run an eccr manually. I would change my suggestion to be that every rebreather diver should start with a manual or hybrid unit then. I still think eccr breeds complancency.

 

[Ben Field]

What are the potential failures?
- Leaky valve blocked - O2 adds would be more frequent early before .7
- Solenoid fails - Controller would have already barfed at you..
- Low solenoid battery - Controller would have already had a moan..
- SP controller dies - you still have the leaky valve and alternate display..

I have had a mix of the failures above all were obvious, none of them ended the diving and flying manual is no bother and in some ways easier than having the solenoid fighting the PPO2 drop on the ascent.

I was only alluding to one possible scenario, when you run a low setpoint as parachute but dive MCCR above that (either with or without leaky orifice- although I have no idea why anyone would bother with MCCR without KISS style trickle O2 feed I have no idea?) if you need to abonadon the MCCR override and let PPO2 fall for the ECCR to catch it will being doing that at a much lower PPO2 than ECCR's are typically run at.
Combined with fast ascent/descent and whatever caused you to leave the MCCR element you might not notice another issue.

Probably not a real issue but IME people make more low PPO2 mistakes than high ones.

 

[Chris Kennedy]

Started on manual when I closed my Dolphin and fitted it with needle valve. Both my homebuilt's have needle's and after several hundred hour's manual on them and my rEvoII I have just fitted rEvo with Shearwater controller package I picked up from somebody who upgraded to rms. As I like Predator and use one on GAF the price made it a good buy. I still tend to fly the rEvo and have to agree that a basis in MCCR breeds good monitoring habits.

 

[Garspeed]

I dive a Vision in normal eCCR mode but when doing shallow training dives I almost always revert to doing what I did in my training which is running low SP and manually controlling O2 to a higher value. In this way, the good habits of constant ppO2 monitoring and manual control are refreshed and kept up to date should I need them for real due to failure. I also tend to run my shallow deco ppO2 above set point which also helps maintain my skills and can assist with bouyancy in shallow depths as the solenoid no longer fires when it likes.

There is no debate that eCCR can make you lazy, especially when using HUD's to ensure all is well but that doesn't mean you should move to mCCR. It just means you need to pay more attention to handset monitoring.

Cheers
Gar

 

[ccrdave]

Started on manual when I closed my Dolphin and fitted it with needle valve. Both my homebuilt's have needle's and after several hundred hour's manual on them and my rEvoII I have just fitted rEvo with Shearwater controller package I picked up from somebody who upgraded to rms. As I like Predator and use one on GAF the price made it a good buy. I still tend to fly the rEvo and have to agree that a basis in MCCR breeds good monitoring habits.

I agree my prototype inspiration started life as a MCCR and so did my prototype JJ-CCR a much keener sense of monitoring is established on mccr

 

[matt]

Full manual (MAV only) sounds a right faff - it's doable, I've done it, I'm grateful I only do it for practice.

mCCR with the orifice seems OK, with the exception that you have no fall-back "beeping" if you make a mistake. Perhaps hCCR is a decent compromise - but feels to me like buying the car and the bike and taking both for a spin.

For me the rebreather is a tool for a job and not the job itself. Hence I dive eCCR, and I always have and I've never tried mCCR or any other combination so there's nothing for me to compare to - but eCCR just works, for me at least. I'd give hCCR a go if I wanted to change unit and there was one at the same price-point as eCCR (there isn't one, is there?).

Perhaps I'm not in tune with the pO2 or something else, but that opinion is not particularly important to me. Watching the HUD is watching the SP, good enough. Having the deco built into the handset forces you (if force is needed and discipline is not an option) to look at SP every few minutes anyway.

That's my 1c's worth (2p).

Matt.

 

[jcook]

Running manual on a full eCCR can be done, but it is a royal pain and not a good way to enjoy a dive. Unless you are fairly deep, you will have to manually add O2 every few breaths.

Umm I have to disagree, I dive this way every time I go. It really isn't as complicated as you make it out to be. Do you constantly pay attention to the rpm's on a manual car or do you know about when to shift? Ya I know, not the best analogy. My SW HUD lets me know when I need to give a burst of O2 in the CL's. I may hit the add button into the exhale lung once or twice a minute. For the ascent, I haven't see any trouble with the PO2. That is unless I am doing a fast ascent for some reason (did once to see how to deal with it). Every time I exhale through my nose on ascent I add O2 and take a couple of breaths before ascending to cycle the gas through the loop. I do it without effort, while running reels, etc. I run the set point at 0.7 as a parachute. Granted everyone my not be as awesome as me.... :thumbsup: