Two VR3 or not Two VR3 that is the question

[Mark Chase]

OK I am getting the fourth cell link for my new baby so I will be upgrading my existing VR3 to Trimix CCR fourth cell and link. I am considering a second VR3 as back up and running this one on a PP02 set point.

Will this work and would you consider it a viable option?

ATB

Mark Chase

[Drmike]

I used to know one YBOD diver from OZ who dived that way but he had a spare vr3 anyway.

Bit pricey though, why not just use the 4th cell integrated vr3 and have a bottom timer and tables as back up, heck of a lot cheaper. If your worried about the sensor drift screwing your deco just turn the sensor off and run the vr3 fixed setpoint and then only turn the sensor on durng the dive if you need to use the redundant cell (electronics failure)

[nigelH]

Originally Posted by Mark Chase

OK I am getting the fourth cell link for my new baby so I will be upgrading my existing VR3 to Trimix CCR fourth cell and link. I am considering a second VR3 as back up and running this one on a PP02 set point.

Why? You're on a rebrether. You can use tables and deco forever and get out of the water all smug. Actually UK Wreck diving our profiles are pretty square so a set of 100/100 tables would normally get me out faster than my computer so I can pad them to get some margin. All you need to do is use roughly the same mix (or 20/30 and call it air).

Use the money on something much more fun.

nigelH

[Brass Monkey]

Is it nobler in the mind to suffer the slings and arrows of outrageous computer failures, or to take arms against a sea of troubled computers?

My instructor used two, it’s expensive but seemed to work quite well for him. Will I ever take this route, don’t know it’s bad enough forking out for one but it would be nice to have a back up. Then again as Nigel said there's lots of other toys out there to spend your money on.



Dave.

[Rob Evans]

Bloody hell Chasey - why not buy a twin Cis and have done with it?

The amount of people I know (the names would surprise you) who do gas dives on a Nexus & D-timer you would not BELIEVE!

Stick with what you've got and the MKI grey matter and you'll be fine.

[NotDeadYet]

There was talk on one of the French lists that the VR3 set-point thingie was doing something weird with the calcs if you weren't using it with the 4th cell.

It went along the lines of if you were using a dil at a certain depth that if you breathed it OC would give (for example) 1.4bar. Obviously, if you put that into the loop then you would have a moment at 1.4bar and it would slowly decay to the 1.2 bar setpoint. Some divers had a feeling that although the VR3 was displaying 1.2bar it would continue still calculating deco based on the dil at 1.4

How true/untrue that is I don't know. One of the French divers tried contacting DeltaP and allegedly got quite a sharp response and not a lot of answers. Apparently they had a few bends that were hard to explain otherwise and there was a period of a lot of VR3s up for sale.

Me, I've stuck with tables long enough, they don't bleep at you, the battery never runs out and they cost bugger all

Until recently I used a D timer and an Aladin set to 49% for all my as dives, two VR3's, I want your job!

[Padowan]

Originally Posted by NotDeadYet

There was talk on one of the French lists that the VR3 set-point thingie was doing something weird with the calcs if you weren't using it with the 4th cell.

It went along the lines of if you were using a dil at a certain depth that if you breathed it OC would give (for example) 1.4bar. Obviously, if you put that into the loop then you would have a moment at 1.4bar and it would slowly decay to the 1.2 bar setpoint. Some divers had a feeling that although the VR3 was displaying 1.2bar it would continue still calculating deco based on the dil at 1.4

How true/untrue that is I don't know. One of the French divers tried contacting DeltaP and allegedly got quite a sharp response and not a lot of answers.

Interesting, as I seem to remember that on doing a 55m dive in the Red Sea on the unit with an air diluent and a 1.3SP that at the bottom of the screen where it displays the PO2 Setpoint that it showed about 1.37 (air at 55m) NOT the 1.3 that it was set to. However being at 55m on air, it is quite likely that I may have mis-read things, but it does seem familiar, and do recall noting it at the time...

[NotDeadYet]

Now you mention it, it has jogged my memory. You are right, it was displaying the ppO2 of the dil, not the setpoint. That's what they thought the VR3 was calculating the deco based on, the ppO2 of the dil at that depth rather than what would actually be in the loop.

[NotDeadYet]

I found the message and here is the (original French) text:

"Apres plusieurs coup de telephone aux differents revendeur (Uk, Belgium, Nederland) TOUS me confirme que le VR3 calcul la decompression en fonction de la ppo2 du melange utilisé a la profondeur donné si elle dépasse le set point pré-programmé !!! le vr3 SURESTIME donc le melange que vous respirez, le risque d'ADD est beaucoup plus important sur des plongees engagées et/ou plongees yoyo ... c'est abberant de la part de Delta P mais c'est comme ca !!"

As I translate it:

After many calls to VR3 agents (Belgium, UK, Holland) all confirmed to me that the VR3 calculates deco as a function of the ppO2 of the gas at that depth if it exceeds the preprogrammed set-point! The VR3 therefore overestimates the mix you are breathing and the risk of DCI becomes greater especially on yo-yo profiles... [I read the last sentence as a general slagging of DeltaP]

If anyone on the forum speaks French better than me please tell me if I've misread it. If it is true then it makes interesting reading.