How to maintain a vacuum

[hungry]

Hello everyone. I am an hvac student. I have a question I hope someone can answer.
Say you pull a vacuum on a residential ac system. You have achieved the vacuum level you want and it held. Now, you want to charge the system. ( this is how I understand the procedure from this point on ) You close the hand valves on the manifold and remove the vacuum hose. Two, you connect the charging hose on the refrigerant cylinder and then you connect it to the manifold. now here is my question. How do you get rid of the air that is in the charging hose and the air that went into the manifold middle port?

[bmf]

crack the hose and purge it

[R12rules]

Assuming your using the standard three hose service manifold gages ... you would ignore the tiny amount of air that got into the gage manifold itself.
The hose which is connected to the freon cylinder is used to purge the air out of the charging hose.

It only takes an instant and the air is gone.

Remember ... we are not trying to get away with venting any of those harmful ozone depleting gases ..... we are only trying to do our job.


If you picked up a four valve manifold, then you'd have a hose for just about everything.
And you wouldnt have to purge the charging hose.

But that'll come later on down the road as you progress in the field.


Welcome Hungry!

Glad you could make it.


Beware of the "goat herder"!

[hungry]

Thank you guys. Much appreciated beleive me.
BTW. I found out that yellow jacket makes a vacuum/charging manifold for those who own the three hose manifolds, so the guy said on the phone. he gave me the item # if it will help anyone. 93860-about $75.

[Reeferman]

Make sure you get a ball valve to put on the center hose and you won't have to worry about it.

[hungry]

Thank you reeferman.
Experience, can't go to school for that ! ha?