Installing an A/C unit. Can anyone help?

Question

This is pretty sad because I went to school for this but I forgot. After you braze in the refrigerant lines, and you charge it with nitrogen to test for leaks, do you have to pump the refrigerant out and if so how does that process work?

Answer 1

Well, After the nitrogen test you have to vacuum it down with a vacuum pump. Once you get a good vacuum on the system... right at 29 inches, close the gages and let it sit for about 5 to 10 minutes.

Check the pressure, if you still have a good vacuum that's great... no leaks. Now run the vacuum pump for another couple of minutes to make sure that any water vapor that may have built up is removes.

Close the gages

Shut off the vacuum pump

Now charge the unit

By charge the unit I mean fill it with refrigerant. If it is a new system and everything is sized correctly you should just have to open the valves. If you have to add refrigerant then the instructions will differ between refrigerant types.

Answer 2

Vacuum the system. To do this properly you will also need a micron guage or mercury U tube Vacuum to below 500 microns and let it set for half an hour. If your vacuum holds, you can weigh in the charge if this is an empty system. Proper evacuation is one of the most important steps in this process, and even more important now with R410A.