[PSUBS-MAILIST] K350 motors and housings - available

Tue Apr 2 14:33:09 EDT 2019

The problem with refrigerants in confined spaces, and this is true both of HFC-134a and the environmentally friendly(er) alternatives, such as HFO-1234yf, is that they release extremely toxic decomposition products in the event of fire. Of course, any fire is going to compromise your atmosphere, so this may be a moot point, but it's something to consider. HFC-134a has low acute toxicity, but is not strictly a simple inert asphyxiant. A 1 hour EEGL exposure limit recommendation that I managed to find for HFC-134a is 4,000 ppm.

In a 72 cu. ft. volume, assuming a starting FO2 of 20.9%, you could add a full 7 cu. ft. of simple asphyxiant gas before the cabin FO2 dropped to 19%. Death likely wouldn't occur due to hypoxia above 16% FO2, but you won't be accomplishing much with oxygen that low. 19.0% to 19.5% are typical occupational limits for oxygen deficient atmospheres.

That said, hypoxia is not the only risk as I pointed out. I would consider the health effects from inhalation exposure and keep to recommended exposure limits. For maximum safety, I might be inclined to separate refrigerants from occupied spaces by means of a water / propylene glycol heat exchanger circuit, but of course this will affect your energy budgets.

Sean

-------- Original Message --------
On Apr 2, 2019, 11:49, Cliff Redus via Personal_Submersibles wrote:

> Keith, I like the idea of a DIY AC system for my boat but hate the idea of dying because of a refrigerant leak.  I looked up the MSDS sheet for HFC-134a (common refrigant used in auto AC systems)     [ImageViewer](https://3eonline.com/ImageServer/ImageViewer.aspx?id=3Q%2FfAR8ne%2FvPh6syVnSymkS%2BBDo8OjmbVocxRCMEgeG%2Fk%2B6G7BpCwxJIcm%2FtzFJTddB5zxzJXIW7nbmF5mKrdg%3D%3D)  Seems like it is classified as a Simple Asphyxian which according to Wikipidia "An asphyxiant gas is a nontoxic or minimally toxic [gas](https://en.wikipedia.org/wiki/Gas) which reduces or displaces the normal [oxygen](https://en.wikipedia.org/wiki/Oxygen) concentration in breathing [air](https://en.wikipedia.org/wiki/Gas_composition). "
>
> https://3eonline.com/ImageServer/ImageViewer.aspx?id=3Q%2FfAR8ne%2FvPh6syVnSymkS%2BBDo8OjmbVocxRCMEgeG%2Fk%2B6G7BpCwxJIcm%2FtzFJTddB5zxzJXIW7nbmF5mKrdg%3D%3D
>
> ImageViewer
>
> What this mean to me is that we would to do a calc to see what the oxygen concentration in a 1-atm boat would go to if all the HFC-134a in the unit was released at one time to see if the concentration would result in hypoxia for the operator.  In my boat I measure O2 concentration as I have a PID controller tasked with keeping the O2 concentration at 21%  So I would get a low O2 alarm rather quickly.
>
> Sean, you are a technical diver, do you think there would be an issue with hypoxia if all the HFC-134a in a small AC unit were dumped into a one atm cabin say 72 cuft?
>
> Cliff
>
> On Tuesday, April 2, 2019, 11:46:05 AM CDT, k6fee via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
> The DC compressor & water cooled condenser are the most expensive items.
>
> If your a DIY'er, go to your nearest "Pick & Pull" get a car AC compressor add a DC drive motor, condenser & evap coil and roll your own.  It will take 2 HP to full drive the compressor, however you can vary the speed and control the cooling, while minimizing current drain. You'll need a refrigerant detector as a leak will kill you in the confines of a PSUB. Or go thermo electric.
>
> Keith T.
>
> -------- Original message --------
> From: Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org>
> Date: 4/2/19 8:40 AM (GMT-08:00)
> To: k6fee via Personal_Submersibles <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] K350 motors and housings - available
>
> Thanks for the links,  The MES24S - 24V unit looks like it would work great but at  $3,895 , I am not going to be ordering in the near future. In the spirit of Psub and DIY, I wonder how hard it would be to design and build on of these units.  Seems to be made up of readily available parts like a compressor, blower, coil ....
>
> Cliff
>
> On Tuesday, April 2, 2019, 9:46:03 AM CDT, k6fee via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
> Allen,
>
> Check these out.
>
> http://www.cruisencomfortusa.com/marineseries/?gclid=EAIaIQobChMIirDF5s6x4QIVcyCtBh3K8w2JEAMYASADEgIDqvD_BwE
>
> http://www.comar-marine.com/product.php?id_product=20
>
> Keith T.
>
> -------- Original message --------
> From: Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org>
> Date: 4/2/19 7:06 AM (GMT-08:00)
> To: Brian Hughes via Personal_Submersibles <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] K350 motors and housings - available
>
> To me AC on personal subs is an interesting topic.  As the Psub community frequently dives off Islamorada Florida, it is a relative thread.
> Below is a graph taken from flight recorder on the R300 during a Psub dive off the coast of Islamorada in August of 2017.
>
> [Inline image]
>
> It got very hot and humid during the 4.5 hour dive.  Note that the cabin temperature reached 96 F, the relative humidly reached 85% and the heat index reached 146 F.  To say that I could have used small AC unit in the boat is an understatement!  One of the implications of this cabin environment was that I could not keep the viewport clear.  I soaked the towels I had on board very quickly trying to clear the viewport.  As a consequence, is was hard to see.
>
> There are challenges in designing a AC system for small subs.  Ideally, it would be self contained and easily removed for service.  The unit is going to have a reservoir for capturing quite a bit of condensed water extracted over say a 6 hour design mission time.  For my boat the unit would need to be small and compact.  Would be nice if we could find a OTS small compact AC unit that was DC powered.
>
> If any one knows of a small compact AC unit, send me the link.  I would like to test in my boat.
>
> Cliff
>
> On Monday, April 1, 2019, 3:26:25 PM CDT, Brian Hughes via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
> And it occurred to me, while we discussed air conditioning systems on our personal subs, we were likely the only three people on the planet having that conversation. 'Tis a small collection of fellow adventurers.
>
> Brian
> Owner of Harold, the wonder K350 and
> Maude, the Porta Bote extraordinaire
>
> Yes, Harold and Maude ....
>
> Get [Outlook for Android](https://aka.ms/ghei36)
>
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