vacuum in a recovery cylinder?

[flyboy3b]

i hope this question isnt as dumb as it sounds, but hear goes,,,

i have a brand new recovery cylinder, and i pulled a deep vacuum in it. now im working on a sandwhich cooler and i find a leak in the service valve. i tried replacing the core and it still leaks so i set up to evacuate the system for repair.
the nameplate states that it holds 11 oz of mp39. when i go to recover the refrigerant, i end up with 1.5 oz in my recovery cylinder.
which brings me to my question...
it is my understanding that if you have a cylinder with "only" refrigerant in it, it will pressurize to the correct pressure for that refrigerant at that ambient temp. why is it that when i hook my gauges, it still reads a vacuum?
thanks a bunch,
mike

[Lowrider]

How big is the recycle cilinder?

11 oz is 311 gram, so on a cylinder that can hold say 28 kg that is not enough to brake the vacuum!

[monkey spanners]

You need enough refrigerant to have liquid refrigerant in the cylinder to get an acurate reading.

[flyboy3b]

its a standard sized 30lb cylinder. how much refrigerant would you guess it would take to bring it up to the right pressure at 70 deg f?
thanks
mike

[Lowrider]

Much more then you have in the sandwich cooler!

[Brian_UK]

How much air is in the cylinder that was in your manifold tubes?

[Lowrider]

The formula to calculate the amount is:

p*V=n*R*T

p= pressure in Pa (N/m2)
V= volume in m3
n= amount of gas in mol
R= gasconstant (8,314472 Jk-1mol-1)
T= absolute Temperature in K


Let me know what you came up with!