Set point change over

Pierre Farrugia · 22nd June 2005, 10:10

Hello all,

When I did course I was tough to change set point at around 15 to 20m. Last weekend I did a dive with OC buddies to 40m, descending with a shot line and can say there was some current! I still changed setpoint at 20m and reached bottom with a PPo2 of 1.5. I have some questions to ask, at what depth do you change your set point ? If you change it at the bottom, does this varies with depth, eg. if deeper than 40M you switch before?

Regards

Pierre Farrugia

Juz · 22nd June 2005, 10:13

I tend to switch between 15-20m otherwise I'll forget!

Juz

***Beanie*** · 22nd June 2005, 10:18

I was taught the 2, 5, 10
2 bubble check, equipment check etc
5 equipment check etc
10 set point switch (on the fly)

Did this on Sunday on the way to 50m my PO2 Spiked to 1.4-1.5 and settled quickly on the bottom, so works pretty well.

Padowan · 22nd June 2005, 10:27

Quote: (Originally Posted by Beanie)

I was taught the 2, 5, 10
2 bubble check, equipment check etc
5 equipment check etc
10 set point switch (on the fly)

Did this on Sunday on the way to 50m my PO2 Spiked to 1.4-1.5 and settled quickly on the bottom, so works pretty well.

Yep, the speed of descent, and your choice of dil will have a big effect on whether you get a spike. On shallow stuff (>40m) I'm using air diluent, which has a max PPO2 of 1.05 at target depth so this has a "watering down" effect (relative to 1.3bar SP) all the way down whilst it's being added so I tend to do the switch at about 20m on the fly. For deeper stuff in the UK, I'm on 10/52 usually, which again has a big "watering down" effect so the same applies. However, in the Red Sea earlier this year, I was plummetting to 60m with air inboard (1.47bar PPO2 at target depth) did my switch at 20m on autopilot and promptly had a 1.7bar PPO2 alarming at me as I got to target depth

. Memo to self: don't do a setpoint switch until target depth if I'm using a dil with a high PPO2 at depth, or alternatively don't be a tw*t and use Mix on deep dives...

**nigelh** · 22nd June 2005, 12:13

Quote: (Originally Posted by Pierre Farrugia)

When I did course I was tough to change set point at around 15 to 20m.

Personally:
Descend like a brick.
Change set point when I hit the wreck.
It's often virtually 1.3 by then anyway.
If you change early it will spike if you hesitate for any reason.

I will mess about with lots of things but not oxygen.
It takes no prisoners.

***schford*** · 22nd June 2005, 12:30

I always change set point at the bottom otherwise you run the risk of a spike you don't want - changing it manually you can make sure you hiht the bottom on what ever PPO2 you want....Scamahorn slide or not its up to you!

Stuart

PS Obviously some times you need to use you're manual O2 inject!

***caveseeker7*** · 22nd June 2005, 14:54

18 fsw, the unit switches automatically.

***schford*** · 22nd June 2005, 16:02

Quote: (Originally Posted by caveseeker7)

18 fsw, the unit switches automatically.

*grins* better not descend too fast then!

***caveseeker7*** · 22nd June 2005, 16:07

Quote: (Originally Posted by schford)

*grins* better not descend too fast then!

Either that or quicker than the unit injects.

cedricverdier · 22nd June 2005, 16:29

Hi,

I personaly prefer to change the setpoint when I reach the bottom (even with the automatic switch of the Vision electronics, I still prefer to change it manually).

I descent on a low setpoint and I take a few seconds on the bottom for the following reasons:
- no risk of O2 spike
- short break to avoid exhaustion and keep a good breathing pattern
- it helps for navigation, buddy communication, buoyancy
- handset check when I reach the bottom: check all cells and settings, change setpoint, etc
- relax, decrease stress due to descent, enjoy the dive

Cheers

22nd June 2005, 10:10	#1 (permalink)
Pierre Farrugia Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Feb 2005 Location: Malta Posts: 636	Set point change over Hello all, When I did course I was tough to change set point at around 15 to 20m. Last weekend I did a dive with OC buddies to 40m, descending with a shot line and can say there was some current! I still changed setpoint at 20m and reached bottom with a PPo2 of 1.5. I have some questions to ask, at what depth do you change your set point ? If you change it at the bottom, does this varies with depth, eg. if deeper than 40M you switch before? Regards Pierre Farrugia __________________ Pierre Farrugia My wife told me " If you don't quit diving I'm going to leave you" My reply " God, I'll miss you" www.atlam.org www.divemed.com
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22nd June 2005, 10:13	#2 (permalink)
Juz Team Kinky Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Feb 2005 Location: London UK Posts: 147	I tend to switch between 15-20m otherwise I'll forget! Juz __________________ ~KINKY DIVERS~ Because going down is fun We are all prompted by the same motives, all deceived by the same fallacies, all animated by hope, obstructed by danger, entangled by desire and seduced by pleasure. Welcome to Kinky Divers!
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22nd June 2005, 10:18	#3 (permalink)
*Beanie* give a man an inch....... Current Rebreather/s: Inspiration Classic Other Rebreather/s: Inspiration Vision Join Date: Jan 2005 Location: In da house! yeah baby! Posts: 3,173	I was taught the 2, 5, 10 2 bubble check, equipment check etc 5 equipment check etc 10 set point switch (on the fly) Did this on Sunday on the way to 50m my PO2 Spiked to 1.4-1.5 and settled quickly on the bottom, so works pretty well. __________________ Beanie Gallery Admin & Library Assistant. www.outlawdivers.org.uk www.beandiving.co.uk www.beanengineering.co.uk
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22nd June 2005, 10:27	#4 (permalink)
Padowan Proper Boffin Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Feb 2005 Location: Kent, UK. Posts: 518	Quote: (Originally Posted by Beanie) I was taught the 2, 5, 10 2 bubble check, equipment check etc 5 equipment check etc 10 set point switch (on the fly) Did this on Sunday on the way to 50m my PO2 Spiked to 1.4-1.5 and settled quickly on the bottom, so works pretty well. Yep, the speed of descent, and your choice of dil will have a big effect on whether you get a spike. On shallow stuff (>40m) I'm using air diluent, which has a max PPO2 of 1.05 at target depth so this has a "watering down" effect (relative to 1.3bar SP) all the way down whilst it's being added so I tend to do the switch at about 20m on the fly. For deeper stuff in the UK, I'm on 10/52 usually, which again has a big "watering down" effect so the same applies. However, in the Red Sea earlier this year, I was plummetting to 60m with air inboard (1.47bar PPO2 at target depth) did my switch at 20m on autopilot and promptly had a 1.7bar PPO2 alarming at me as I got to target depth . Memo to self: don't do a setpoint switch until target depth if I'm using a dil with a high PPO2 at depth, or alternatively don't be a twt and use Mix on deep dives...* __________________ Padowan The future's bright, the future's Yellow .....for now padowan.net - Latest Video: Scapa Flow Rebreather Diving
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22nd June 2005, 12:13	#5 (permalink)
nigelh New Member Current Rebreather/s: Inspiration Vision Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Mar 2005 Location: Brighton, Sussex, UK Posts: 837	Quote: (Originally Posted by Pierre Farrugia) When I did course I was tough to change set point at around 15 to 20m. Personally: Descend like a brick. Change set point when I hit the wreck. It's often virtually 1.3 by then anyway. If you change early it will spike if you hesitate for any reason. I will mess about with lots of things but not oxygen. It takes no prisoners. __________________ nigelh
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22nd June 2005, 12:30	#6 (permalink)
*schford* Despotic Overlord Current Rebreather/s: Megalodon Sport Kiss Other Rebreather/s: Join Date: Jan 2005 Location: London, UK Posts: 3,559	I always change set point at the bottom otherwise you run the risk of a spike you don't want - changing it manually you can make sure you hiht the bottom on what ever PPO2 you want....Scamahorn slide or not its up to you! Stuart PS Obviously some times you need to use you're manual O2 inject!
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22nd June 2005, 14:54	#7 (permalink)
*caveseeker7* Who loves ya, baby Current Rebreather/s: Sport Kiss Other Rebreather/s: Prism Topaz Join Date: Jan 2005 Location: Too far from Neverland Posts: 5,451	18 fsw, the unit switches automatically. __________________ Cheers Stefan "Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"
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22nd June 2005, 16:02	#8 (permalink)
*schford* Despotic Overlord Current Rebreather/s: Megalodon Sport Kiss Other Rebreather/s: Join Date: Jan 2005 Location: London, UK Posts: 3,559	Quote: (Originally Posted by caveseeker7) 18 fsw, the unit switches automatically. grins better not descend too fast then!
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22nd June 2005, 16:07	#9 (permalink)
*caveseeker7* Who loves ya, baby Current Rebreather/s: Sport Kiss Other Rebreather/s: Prism Topaz Join Date: Jan 2005 Location: Too far from Neverland Posts: 5,451	Quote: (Originally Posted by schford) grins better not descend too fast then! Either that or quicker than the unit injects. __________________ Cheers Stefan "Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"
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22nd June 2005, 16:29	#10 (permalink)
cedricverdier S21 M.I.B. Current Rebreather/s: Evolution Megalodon Other Rebreather/s: Not Bought Yet Inspiration Classic Inspiration Vision Sport Kiss Classic Kiss Join Date: Apr 2005 Location: Worldwide! Posts: 497	Hi, I personaly prefer to change the setpoint when I reach the bottom (even with the automatic switch of the Vision electronics, I still prefer to change it manually). I descent on a low setpoint and I take a few seconds on the bottom for the following reasons: - no risk of O2 spike - short break to avoid exhaustion and keep a good breathing pattern - it helps for navigation, buddy communication, buoyancy - handset check when I reach the bottom: check all cells and settings, change setpoint, etc - relax, decrease stress due to descent, enjoy the dive Cheers __________________ Cedric Verdier PADI Course Director, ANDI-IANTD-PSAI-TDI-DSAT-DAN-NAUI-CMAS Instructor Trainer Trimix (CCR and OC) and Cave Diving Instructor Trainer www.CedricVerdier.com DIRrebreather member
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