Question SCR Semi Closed Rebreather

[Cio]

I made a chest mount GEM and it's awesome.
Is it a CCR? no. Is it safer than a CCR, yes. (at least I think so)

For wreck diving, the limitations aren't all that bad, and gas consumption is low, did a 100 minute (TT) 120' deco dive on a wreck with 20CF of 32% and like 5-7 CF of 60%%. I could have done a second and still been had more than enough bailout. (BM 50s manifold closed w/32% and, LP45 w / 60%)

I just got trimix certified on it and for the 3-5 trimix dives I'll do this year, it won't make it as cheap as a CCR but will be affordable.

I have added a 4 PIN nerd 2 so low PPO is easier to monitor when trying to get in the water and when shallow or on a tag line.

Whole rig fits in a carry on and by RB costs, was a deal. I can undo one bolt snap and put it in front of me to get through restrictions. With double manifolded 40s or 50s on my back, I can get through pretty small restrictions.

I will go to CCR at some point but I will continue to travel and dive with this as it is safe, simple to use and doesn't require 100%O2. Its just fun.

I can't imagine I'll look back and regret this as a stepping stone.

 

[Angelo Farina]

@Dann-Oh

You should get that “N” now. There’s really not much reason to be diving air…ever. Only time to dive air is in a pool or if you just can’t get nitrox. That’s my 02psi , ymmv

Air makes sense for us old-style recreational divers who are certified down to 50m and with deco on back gas.
For depth ranges between 40 and 50 meters (which is the best range here in the Mediterranean) and with deco times of no more than 20 minutes, a single 15-liters tank at 232 bars filled with air, with double valves, two independent regs, and perhaps a good old reserve, is all that you need.
For shallower depths and within NDL Nitrox makes more sense.
Air comes handy again for hookah diving at less than 10 meters.

 

[Dann-Oh]

I made a chest mount GEM and it's awesome.
Is it a CCR? no. Is it safer than a CCR, yes. (at least I think so)

For wreck diving, the limitations aren't all that bad, and gas consumption is low, did a 100 minute (TT) 120' deco dive on a wreck with 20CF of 32% and like 5-7 CF of 60%%. I could have done a second and still been had more than enough bailout. (BM 50s manifold closed w/32% and, LP45 w / 60%)

I just got trimix certified on it and for the 3-5 trimix dives I'll do this year, it won't make it as cheap as a CCR but will be affordable.

I have added a 4 PIN nerd 2 so low PPO is easier to monitor when trying to get in the water and when shallow or on a tag line.

Whole rig fits in a carry on and by RB costs, was a deal. I can undo one bolt snap and put it in front of me to get through restrictions. With double manifolded 40s or 50s on my back, I can get through pretty small restrictions.

I will go to CCR at some point but I will continue to travel and dive with this as it is safe, simple to use and doesn't require 100%O2. Its just fun.

I can't imagine I'll look back and regret this as a stepping stone.

View attachment 762495

Id like to see more photo of your setup.

 

[rx7diver]

The DiveRite Choptima is a chest-mounted eCCR (electronic CCR). The Triton is a chest-mounted mCCR (manual CCR).

rx7diver

@Dann-Oh, here is a neat short YouTube video (featuring the Triton mCCR) I happened upon a couple of months ago:

.

rx7diver

 

[Dann-Oh]

@Dann-Oh what is SAC in cfm? You don't say what tank your 23psi/min is on so it doesn't mean much. It sounded like that's on a HP100 though so that would be roughly .67cfm which is on the high side of normal but fairly reasonable.
You certainly need nitrox cert to dive an SCR, that's non negotiable but if you're NDL limited on air at depth then nitrox will help alleviate some of that.
120ft with that SAC rate and LP72's should let you stay down there for 30-35mins which will still exceed NDL on EAN32 for the first dive, certainly for repetitive diving, I wouldn't worry about a CCR anytime soon based on that.

Butt dump in sidemount sucks, very difficult to get to, don't prioritize that. The SMS75 dumps quite easily. CCR's are essentially neutral and the SMS75 has more than enough lift to deal with that.

O2ptima CM is the only commercially available and supported chest mount unit in the US. It is far from the only chestmount unit in the world as most of the worlds militaries use them as O2 rebreathers and there are a handful of units in the EU/UK that are available but the O2ptima is the only one really supported in the USA.

I believe the 23psi/min would be on a LP72. I don't really dive the HP100 unless I doing a deep dive (below 90ft), and then I'll sling my LP50 for out of air emergencies. During 2022 I think I use the HP100 maybe on 2 dives, most of my 2022 diving was working as a DM with OW students I did a few deep dives with an AOW class.

Im thinking ill just stick with sidemount (forget SCR and CCR for now) and look to get Nitrox this year and take advantage of the Nitrox. Im in no rush to get into more complex setups I just want to maximize the time underwater when I am able to get away from my family and dive for fun.

 

[Wibble]

Was on a dive boat a couple of years ago in the back of beyond in a far-off land (the very north west of Scotland). We were diving shallow walls and slopes, kelp, fish, nooks and crannies, etc. Max depth 25m/80ft, mostly less.

On that boat was the skipper's wife diving on a Hollis Stormtrooper SCR.

These took a fair amount of derision and they are very rarely seen.

Got chatting to her and she said she is a keen photographer. This unit works perfectly for her diving as they have no access to high-pressure oxygen which all CCRs require; all their diving's relatively shallow so she can use normal nitrox and, as an SCR range extender, use very little of it. The unit is lightweight as well.

 

[Marie13]

I believe the 23psi/min would be on a LP72. I don't really dive the HP100 unless I doing a deep dive (below 90ft), and then I'll sling my LP50 for out of air emergencies. During 2022 I think I use the HP100 maybe on 2 dives, most of my 2022 diving was working as a DM with OW students I did a few deep dives with an AOW class.

Im thinking ill just stick with sidemount (forget SCR and CCR for now) and look to get Nitrox this year and take advantage of the Nitrox. Im in no rush to get into more complex setups I just want to maximize the time underwater when I am able to get away from my family and dive for fun.

Nitrox is a perfect winter class. Book work and a few hours in the dive shop hands on learning how to analyze. No dives needed.

 

[tbone1004]

I believe the 23psi/min would be on a LP72. I don't really dive the HP100 unless I doing a deep dive (below 90ft), and then I'll sling my LP50 for out of air emergencies. During 2022 I think I use the HP100 maybe on 2 dives, most of my 2022 diving was working as a DM with OW students I did a few deep dives with an AOW class.

Im thinking ill just stick with sidemount (forget SCR and CCR for now) and look to get Nitrox this year and take advantage of the Nitrox. Im in no rush to get into more complex setups I just want to maximize the time underwater when I am able to get away from my family and dive for fun.

HP100's and LP72's are about the same volume so the ratio is about the same.
I'll refrain about commenting about the LP50 as a pony bottle, not worth opening that can of worms.

If you want to maximize time underwater, get a second HP100 and start sidemounting a pair of HP100's with nitrox in them. Then go get AN/DP so you can start doing relatively short deco. You have a long way to go on OC before you can justify a rebreather just to extend time underwater.

 

[Dann-Oh]

Nitrox is a perfect winter class. Book work and a few hours in the dive shop hands on learning how to analyze. No dives needed.

Im a drysuit diver in Southern California. Winter temps don't affect me, well Southern California winter temps (my coldest dive is lower 50°F).

 

[Dann-Oh]

HP100's and LP72's are about the same volume so the ratio is about the same.
I'll refrain about commenting about the LP50 as a pony bottle, not worth opening that can of worms.

We can chat about it in a DM. I'm interested to hear your opinion.

You have a long way to go on OC before you can justify a rebreather just to extend time underwater.

I am realizing this now. This thread has been very informative for me.