How cold is cold?

[robertarak]

I have been reading and reading. Getting as much of an education as one can above the water line. There is alot of discussion of cold water diving, using a sealed 1st for cold water, etc. I have not found a number. At what temp. is cold umm..cold. Or at what temp (at depth) should you be sure you are diving with a sealed 1st? The other question is....is there any reason NOT to dive with a sealed 1st? Seems that sealed works well in all enviorments, or am I missing something?

 

[Web Monkey]

I have been reading and reading. Getting as much of an education as one can above the water line. There is alot of discussion of cold water diving, using a sealed 1st for cold water, etc. I have not found a number. At what temp. is cold umm..cold. Or at what temp (at depth) should you be sure you are diving with a sealed 1st? The other question is....is there any reason NOT to dive with a sealed 1st? Seems that sealed works well in all enviorments, or am I missing something?

"Cold" depends on the diver and the reg design.

First stage freezing is caused by water in the first stage being cooled by the expanding gas from the tank.

When the cooling rate exceeds the warming rate from the surrounding water and the internal temp remains beflow freezing, you get ice.

The cooling rate is effected by how much air is being used as well as the pressure differential between the inside of the tank and ambient.

That's why nobody can give you a hard number. A reg you can quietly breathe from in 40 degree water may freeflow if you start breathing hard.

As for the second part of your question, I have no idea why all regs aren't sealed. Both of mine are and I'd never go back.

The entire concept of worrying about how hard you're breathing seems both bizzare and counter-productive (worrying makes you anxious and causes breathing to increase).

Terry

 

[Quarrior]

In the discussion of sealed versus non-sealed regs, there is one thing usually missed because everyone is concerned about water temps and so on.

Open regs are also exposed to any debris that might be floating around in the water, whereas the sealed reg is just that, sealed.

 

[do it easy]

Diaphragm regs are essentially sealed except for the main spring. I think the biggest advantage for sealing a diaphragm reg is to prevent icing when going in and out of the water when the air temp is below freezing. Less applicable would be if you dive in contaminated waters.

For the sport diver, I don't see the need to have environmentally sealed diaphragm regs. Pistons might be another story, but I'm not familiar with.

 

[laserdoc]

cold is when shrinkage occurs. What happened to George on a Seinfeld show.

 

[spectrum]

The number 42F seems to surface frequently as the approximate dividing line. Between ice avoidance and contaminant control the only downside of a sealed system are purchase and service costs, neither of which are likely to be determining amounts of $$. There's nothing absolute about 42F though.

If you do any fresh water diving in any but the most temperate locations you are likely to tease the limit a thermocline or 2 down even with a surface temp of 80F. Sometimes that perspective makes the decision easy.

The most demanding & critical time of course is when 2 divers are breathing heavy in deep cold water, like an OOA or equipment failure situation. At that point the regulator needs to process lots of gas and adiabatic cooling will be severe. Long draws to fill bags can also be risky.

Pete

 

[DA Aquamaster]

How cold is cold is relative, but 60-65 degrees is a good place to start in terms of diver comfort in a wet suit. As far as regulator performance goes, it varies by manufacturer. Scubapro considers anything below about 50 degrees as being "extreme conditions" - which in recent history has been their cop out with Mk 25 freeze issues. But at least they designed the MK 17 to perform extremly well under those "extreme" conditions.

In my experience, many normal warm water regulators will do fairly well down to about the upper to mid 40's as long as you use good cold water technique (taking care not to inflate the BC, test the reg, or do anything else to operate and chill the reg before it is submerged, and to not over breathe the reg or simultaneously breathe and inflate BC or drysuit or do anything else to create a spike in the adibatic cooling load that may exceed the ability of the reg to transfer heat from the surrounding water.) Below that you need a dedicated cold water first stage.

In the past all second stages were metal cases and metal cased second stages never froze up as the heat transfer was excellent. However with the current plastic cased second stages, it is a concern on many models and some do much better than others.

 

[Al Mialkovsky]

The MK 17 is sealed so of course it handles the cold water. I use all scubapro gear except for the reg which is an apex 200. The MK 25 was a shop favorite until the water cooled and I've seen them freeze in 55 degree water.

It breathes good, unless it's free flowing, then it breathes really well for a very short period of time

 

[Hoosier]

Anything below 40 degree is cold because most regs can't handle lower 40 degree perfectly.

Just my 2 bar

 

[do it easy]

Geez, all this talk about cold water makes me want to go ice diving...