vacume pump too big?

[barbar]

Oh BARBAR.... please read all my posts... I stated all the exceptions and minus 10 degrees (F) at 500 microns is the boiling point of h2o (ie WATER)... And TRANEDOG has been MISTAKEN but NEVER WRONG....lol but seriously please re-read all my posts on this subject... please post your apology... Thank you ;-) p.s. DRY ICE is not water.... so there is no relevance to comparing dry ice to water...

I apologize whole heatedly for any hurt i may have done to your sensibility!
Technically well that is different.
Read what you have just written.
at -10F water does not boil at 500microns, it does however vaporize, during the sublimation process. Which is a solid converting to a vapour(gas) with out going through the liquid stage.
We see this most commonly with dry ice (solid CO2), H20 (steam/water/ice) does the same thing.
Study freeze driers, you will find it interesting!

[beenthere]

Paysonhvac had posted a video showing water freezing while under a vacuum. Can't find it right now. But there are a few other ones on utube showing water freezing under a vacuum.

Its possible, and may happen more often then we think. Such as on those systems that pull down to 400 microns, and then rise to 800 or 900. Then after you pull the vacuum down again another time or 2 it holds. Sublimation will show as a slow rise in vacuum. Often we just take it for granite that it was just moisture(water droplets) trapped somewhere in the system. When it was small ice crystal/crystals sublimating.

There have been several discussions about this in the Pro tech forum.

[tranedog]

Please reference the following website-
29.92 inch Hg Vac. = 0 microns boiling point of water will be 80 F
29.90 = 500 microns -10 F
28.92 = 25401.07 microns
1” Hg Vac. = 25401.07 microns

http://www.hvacfun.com/f-vacuum-pumps.htm

More detail regarding vacuum pump for dehydration of a closed system....

http://www.robinair.com/acsolutions/...cuum.php#high2

[woody19]

[QUOTE=beenthere;12403541]Paysonhvac had posted a video showing water freezing while under a vacuum. Can't find it right now. But there are a few other ones on utube showing water freezing under a vacuum.

When I do vacuum pump clinics I take a clear glass beaker with about 4 drops of water in the bottom and then hook it up to the vacuum pump and micron gauge and you can watch the water freeze and then eventually go through sublimation if you wait long enough. It is interesting but not necessarily what will happen in a system. I use this example, more than anything, to emphasize the importance of a good evacuation and the use of a good micron gauge. I know there are many other factors to consider but it has sure made an impression on service techs here and also increased my sales of micron gauges.

[Nuclrchiller]

Please reference the following website-
29.92 inch Hg Vac. = 0 microns boiling point of water will be 80 F
29.90 = 500 microns -10 F
28.92 = 25401.07 microns
1” Hg Vac. = 25401.07 microns

http://www.hvacfun.com/f-vacuum-pumps.htm

More detail regarding vacuum pump for dehydration of a closed system....

http://www.robinair.com/acsolutions/...cuum.php#high2

Thanks for the link to that Robinair page. Halfway down the page is a table for the boiling points of water. It is a very useful table and one that all techs should have. That other link is badly misinformed and should be ignored. Not one piece of information you quoted from it is correct. Compare them to the Robinair chart.

[beenthere]

[QUOTE=woody19;12405781]

Paysonhvac had posted a video showing water freezing while under a vacuum. Can't find it right now. But there are a few other ones on utube showing water freezing under a vacuum.

When I do vacuum pump clinics I take a clear glass beaker with about 4 drops of water in the bottom and then hook it up to the vacuum pump and micron gauge and you can watch the water freeze and then eventually go through sublimation if you wait long enough. It is interesting but not necessarily what will happen in a system. I use this example, more than anything, to emphasize the importance of a good evacuation and the use of a good micron gauge. I know there are many other factors to consider but it has sure made an impression on service techs here and also increased my sales of micron gauges.

LOL... It is an eye opener when you first see it.

[AcDOCnTRAINING]

My logic is that if you pull the vapor moisture out of the system the LLFD and the SLFD should be able to trap any ice in the system and not allow it to dissipate and become moisture. Also the use of nitrogent whuch is resilient to acids and bases as well as oxidants and most reductants eliminate this problem.

[Doctorinky]

Always triple evacuate, its cheap easy insurance