New VACUUM PUMP Needed... HELP

[gio_ayr]

Hi guys,
I'm looking to buy a new vacuum pump as the one I've got just now is approx 40 years old (3 generations old). I'm not really too sure what to look for. I take it the higher the CFM the better and obviously the higher HP of the motor is best but what about microns? Can anyone recommend a pump or at least what I should be looking for?

I've seen a few on eBay and some of them are from Hong Kong and much cheaper. They have Javec, VPUMP and the Hong Kong ones don't have a brand.

The pump I've got and always used was connected through my gauges to the 1/4 flare but most of the ones I've seen haven't got that connection so what do I connect them with?

Thanks for your help guys.

[nike123]

Check this first:
http://download849.mediafire.com/7hw...+Engineers.pdf

[monkey spanners]

What sort and size of equipment do you work on?

[gio_ayr]

Mostly small commercial units like double door Fosters, bottle coolers, cold rooms and ice machines. I do very very little air conditioning so don't really need a massive pump just something reliable and able to do the job comfortably. I don't want to have to leave it on for hours and have to come back and waste time.

I still can't make up my mind about the ones on eBay. They are cheap but I can't help but think I'll get screwed over if something goes wrong with it.

[gio_ayr]

Wow Nike123 That was one hell of a document lol. I don't even know what half the stuff means

[monkey spanners]

Found this on the Yellow jacket site

http://www.yellowjacket.com/techques...erevacfaqs.asp

If you work on stuff under 10 tons the something like this will be nice and light to carry etc and will work well, won't take too much oil either!

http://www.robinair.com/products/detail.php?id=1045

With the money you save on not bying a bigger pump you could get a vacuum gauge!

Jon

[gio_ayr]

Thanks Jon, just went on the Yellow Jacket website there and found out that the lower the number of microns the better performance of the pump. I'll be keeping that in mind when I come to part with my hard earned cash. Might even save enough to buy another bottle of gas!!!! Just paid £210 for a 13KG bottle of R134a!!!!

[chemi-cool]

Just paid £210 for a 13KG bottle of R134a!!!!

You must be joking come and buy them here, £55 is the latest price......

[nike123]

You must be joking come and buy them here, £55 is the latest price......

Here is 10£/kg.

[nike123]

Wow Nike123 That was one hell of a document lol. I don't even know what half the stuff means

In short: You don't need bigger pump with extreme end vacuum, you need valve core remover and hoses with bigger bore to vacuum system 4 or more time faster.

I recommend that you buy and use whole kit:
http://www.appioninc.com/media/video...tezspeedsystem
http://www.appioninc.com/products/mgakitfeatures.html
http://www.appioninc.com/products/tez8features.html

[r.bartlett]

In short: You don't need bigger pump with extreme end vacuum, you need valve core remover and hoses with bigger bore to vacuum system 4 or more time faster.

I recommend that you use whole kit:
http://www.appioninc.com/products/mgakitfeatures.html
http://www.appioninc.com/products/tez8features.html

Vacuuming too fast can cause problems with moisture freezing. Slow and steady is the way to go

[nike123]

Vacuuming too fast can cause problems with moisture freezing. Slow and steady is the way to go

Quote from article I linked before:

CHAPTER VI
High vacuum pump procedure for dehydrating, degassing and leak testing a refrigeration system in the field
It is a very simple procedure to properly dry out, by a high vacuum pump, a field installation of a refrigerant system. It is not
only a time saving method but, by using the proper type of gages, you can know whether the system is adequately dry and
vacuum tight before charging it with refrigerant. By no other means can you so economically establish these facts which are
so important to meet the high standards required today.
The procedure is simple and straight forward, provided you apply the basic knowledge you already have about (1) the
boiling point of water versus temperature and pressure, (2) latent heat of vaporization. ~SIC Pg. 65
I have seen it discussed many times on forums like this one by techs who are concerned about pulling a vacuum too fast and
freezing the water in the line set, thereby making the evacuation procedure take much longer than necessary. I have seen this
argued for the use of SMALLER HOSES, as we will see it is a fallacy to think this way.
In the above text two things must be considered when degassing and dehydrating a system:
1) Boiling pint of water versus temperature and pressure
2) Latent heat of vaporization.
To convert water to vapor, some heat energy must be supplied. This is called the BTU's of latent heat of vaporization. So, to
remove the water from the line set we must either heat the refrigeration system enough to boil the water off, or reduce the
pressure to boil the water off; for obvious reasons we choose to reduce pressure to boil the water off.
By reducing the pressure we need less BTU's of latent heat of vaporization to vaporize the water! In fact, the ambient air
temperature (and resultant temperature of the walls of the line set) will be enough to boil the water! However, this process
can become a vicious cycle because by removing heat from the water (vaporization) we need to achieve a higher vacuum
level to vaporize the remaining water. So, it could be possible to freeze the water in the line set, but not very probable. The
materials we use conduct heat very well. However, if there is an element that easily suspends the water, like a filter drier, this
area may freeze rapidly.
In discussing the boiling point of water it is simply enough to know that the higher the vacuum the lower the boiling point,
or, the lower the vapor pressure, same thing.
@ 50°F the vapor pressure of water is 9000 Microns, or @ 9000 Microns water boils at 50°F.
@ 500 Microns water boils @ about -13°F!
Considering that we will likely be working most of the time between these two extremes (9000-500 Microns) and the
ambient temperature is somewhere in the neighborhood of 70oF (many times it is much higher, but for the sake of argument),
we will be anywhere from 20°F to 63°F ABOVE THE BOILING POINT OF WATER! There will likely be enough ambient
heat to keep the water above the boiling point; that's not to say there will never be the chance that it may freeze in the line set,
but that chance is not good enough to justify using smaller hoses.
We will discuss removal of ice (sublimation and heating) later; it may never happen, but if it does it will be good to know
how to handle it in the quickest manner possible.
But, why is it important to keep it dry in the first place? We all know the answer to that, but here is an illustration.
One pound of water vapor @ sea level occupies about 27 Feet3, however, lower that pressure and temperature and that same
pound of water @ 9000 Microns and 50°F occupies 1,700 Feet3! Of course there isn't going to be a pound of water in your
line set, but even a teaspoon of water @ 450 Microns would be 30 Feet3! Given the inherently low conductance speeds of the
system, you can see why it is paramount to remove as much water (or keep as much out) as possible before ever beginning
the vacuum procedure.
Summary:
1) The likelihood of water freezing in the line set is minimal if you follow proper procedures. Water (liquid) in the line set is
more likely to freeze than vapor is to condense and then freeze. Remove all liquid from the line set is the best bet for quicker
evacuation times.
2) Specific Volume is directly related to temperature and pressure as well as vapor pressure, they are proportionally inverse.
3) Bigger hoses are only part of the equation, keeping the line set dry in the first place will go farther in reducing evacuation
times than anything!

[r.bartlett]

Quote from article I linked before:

He like to have it both ways.


He suggests that water freezing inside the system due to the vacuum process won't happen but if it does then you should know what to look out for..

I'll pass on his advice as interesting as it is.
Just buy a robinair 4cfm pump and change the oil regularly. It's really not worth getting all uptight over something as mundane as this..

http://advancedengineering.co.uk/uk-...duct.asp?pid=3

[lawrence1]

gio ayr,
If your old vac pump lasted 40 years,,,,wow,,,,,what brand is it?????buy the same brand,you won't go wrong.

[nike123]

I'll pass on his advice as interesting as it is.
Just buy a robinair 4cfm pump and change the oil regularly. It's really not worth getting all uptight over something as mundane as this..

http://advancedengineering.co.uk/uk-...duct.asp?pid=3

Agree, but he asked:

I don't want to have to leave it on for hours and have to come back and waste time.

That is why I recommended this "speed kit". No waste of time with this.

[r.bartlett]

Agree, but he asked:


That is why I recommended this "speed kit". No waste of time with this.

That's a valid point ...

[Toosh]

gio ayr,
If your old vac pump lasted 40 years,,,,wow,,,,,what brand is it?????buy the same brand,you won't go wrong.

If it lasted 40 years they probably out of business due to lack of sales LOL

[gio_ayr]

haha i know they've prob shot themselves in the foot by making such a good product. I don't even know who made it as my dad sprayed it green. It's still going strong but my Dad needs it for himself so that's why i'm looking for another one.

[Toosh]

Are you from Ayr

[Start the Bench]

I like the Refco eco-5. 5 cfm, nice handle, and relatively light.

[DC5-T]

Yellow Jacket all the way and get a micron gauge.... good thing to have