lermontov
Contributor
I was wondering what are the pros and cons of different CL capacities - the Erevo has 3 sizes 5.5 to 7. litre - what impact do the differant sizes have
CL capacity
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fsardone
Solo Diver
It is an issue of lung capacity.
If you CL are less than your lung your breathing will feel constrained and you will be uncomfortable or plainly endangered because you cannot breathe what you need. Also if you have an ADV it will fire more often than needed then during exhale the excess gas will be vented offboard with unusual DIL usage.
On the other end large CL will present another issue: it is harder to maintain minimum loop volume. This is an issue for buoyancy but also in OC ascents. A too large volume will cause the rebreather to add more oxygen to maintain PPO2 (even if you have switched to low setpoint) and therefore it will be more difficult to handle the ascent in term of buoyancy (you will have to manage the BCD the expanding counterlungs with the solenoid fighting you and most probably the dry suit) while obvioulsy handlyng stage rotation and gas switching (which since you left OC diving you do not practice every dive
).
So too small counterlungs are dangerous in normal conditions too large in emergency. Between the two I would accept to be (a bit) too large than too small. Get help from an experienced CCR diver or (much) better a good experienced CCR instructor.
I downsized my CL by 2 lt after a couple of years diving.
Cheers
If you CL are less than your lung your breathing will feel constrained and you will be uncomfortable or plainly endangered because you cannot breathe what you need. Also if you have an ADV it will fire more often than needed then during exhale the excess gas will be vented offboard with unusual DIL usage.
On the other end large CL will present another issue: it is harder to maintain minimum loop volume. This is an issue for buoyancy but also in OC ascents. A too large volume will cause the rebreather to add more oxygen to maintain PPO2 (even if you have switched to low setpoint) and therefore it will be more difficult to handle the ascent in term of buoyancy (you will have to manage the BCD the expanding counterlungs with the solenoid fighting you and most probably the dry suit) while obvioulsy handlyng stage rotation and gas switching (which since you left OC diving you do not practice every dive
).So too small counterlungs are dangerous in normal conditions too large in emergency. Between the two I would accept to be (a bit) too large than too small. Get help from an experienced CCR diver or (much) better a good experienced CCR instructor.
I downsized my CL by 2 lt after a couple of years diving.
Cheers
Bigger CLs "test better" on the CE test because the bubble can move around and at least part of it stays close to the lung centroid so the WOB ends up measuring lower. If anyone actually dove in (eg) a vertical orientation that might actually matter. Except for going vertical in some caves its a quirk of the CE test that has little real world relevance.
Ideally you want a CL which has just enough capacity for your normal working tidal lung volume without triggering the ADV. Any bigger is just wasted space. Depending on the unit it can be hard to tell that you're carrying around an extra liter of gas for nothing (which makes buoyancy and maintaining setpoint that much harder). If its too small you wont be able to breathe deep, shallow breathing is very bad news CO2 wise.
The only way to really know what is best for you is to try them. Although you can usually make a good guess based on your size - its not an exact science anyway. Just realize that each unit is different and a "6L" revo CL is not the same as "6Ls" on a Kiss in part because the Kiss CLs wrap around your torso and never fully inflate. They are nominal measurements. In reality its just easier to think of them as SM, MD, LG
I have also shrunk CLs compared to the OTSCLs I started with on my Meg. And my Kiss CL is smaller still.
Ideally you want a CL which has just enough capacity for your normal working tidal lung volume without triggering the ADV. Any bigger is just wasted space. Depending on the unit it can be hard to tell that you're carrying around an extra liter of gas for nothing (which makes buoyancy and maintaining setpoint that much harder). If its too small you wont be able to breathe deep, shallow breathing is very bad news CO2 wise.
The only way to really know what is best for you is to try them. Although you can usually make a good guess based on your size - its not an exact science anyway. Just realize that each unit is different and a "6L" revo CL is not the same as "6Ls" on a Kiss in part because the Kiss CLs wrap around your torso and never fully inflate. They are nominal measurements. In reality its just easier to think of them as SM, MD, LG
I have also shrunk CLs compared to the OTSCLs I started with on my Meg. And my Kiss CL is smaller still.
Brad_Horn
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Look at images of the orientation of commercial helmeted divers working. They in the real world 'tend' to be vertical. However CE testing also requires WOB and hydrostatics to be tested horizontally.
That said another factor you haven't mentioned is EN14143 for CE also has a requirement that mandates a minimal breathable tidal volume in all orientations of >4.5L. So CLs any less than 4.5L measured as simple water displacement will automatically fail testing. And as mentioned above you can have the circumstance where even units with 8L CLs fail simply because in particular orientations due to the design, not all of the volume is actually breathable. Or in the case of certain BMCL units with soft lungs they fail because on the surface with the BCD wing fully inflated the diver can't get a complete breath off the loop
Example of this testing and a more complete background that might be of interest http://www.deeplife.co.uk/or_files/DV_OR_Tidalvolume_090911.pdf
njdiverjoe
Contributor
No my old meg apecs 2.0 got destroyed by the airline after my last trip to Mexico. I sent the details in to ISC and they said it would be cheaper to buy a new one that try to repair my old one, so the airline covered $2500 and my household insurance covered the rest. My Pathfinder has APECS 4 electronics and frankly I like the Tiburon electronics better (so far)
I believe they are 4l each. They sit slightly higher than the standard version and are shorter. Tehy have a shape to them that gives more room around the neck. WOB seems to be no different than the standard lungs but I only have two dives on them so far without any of the usual gyrations and challenges they will experience after a cave trip.
I'm guessing this is slightly larger than the TOS CLs?
For me, the TOS lungs were a massive comfort improvement over the standard lungs. They are a bit of a neck pillow though. I wish there was a way to demo the minnow lungs. My T pieces are so old they actually predate the left/right threading which has been on ISC T pieces for a decade+ now. So my loop wont fit on anyone else's lungs.
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