HVAC AC refrigerant recharge maintenance guidance needed

[Suprman]

Have an AC unit. New to refrigeration, have not really done any before but time to learn. Refrigerant is removed. There are 2 schrader valve style connections. Is the top or bottom one usually the low pressure? I need to suction out the system. From the low side I believe. And then get some refrigerant in there. I have some r22 that's what the system calls for. I believe there is a newer type "drop in" replacement since the r22 is no longer used. So I have the gauges, vac pump, thermometer and scale. What's the best way to proceed? I would like to pressure test the system with inert gas before loading it with r22 and finding out I have a leak also. Thanks
Will

 

[NDT]

Fill the low side (big line) with nitrogen at 300 psi and go over everything with Mr. Bubble and a paintbrush. How we did it at the factory. Even the smallest bubble will cause the system to go low in a couple months.

 

[NDT]

Next, draw a 29" vacuum from the low side for an hour. Then, charge the 22 into the vacuum with the compressor off. When equalized, turn on the compressor and keep charging until the low side reads 60 psi with the charging valve shut. This is for a 75 degree day.

 

[Suprman]

Is the top or bottom connection the low side. They are both the same size and not marked. The tm does not specify which is the low. Can I buy a bottle of nitrogen? How do I pressurize it into the system?

 

[NDT]

The low side is always the suction which is a bigger diameter line than the high side. Borrow a Nitrogen cylinder from an A/C guy, figured you had one in your store, all my A/C service tools come from pawn shops.

 

[rustystud]

See below.

 

[rustystud]

As a Federal certified HVAC tech I can honestly say read up any and all literature on your system and A/C in general before you attempt this. You can blow up your compressor if you mess up here. NDT gave some good generic advice but every system is different and the amount of and type of refrigerant used is critical here. Our buses used over 10 gallons of refrigerant but we still needed to weigh it as it went in to make sure we did not overfill it. Also the size of the system determines the length of time you keep it on vacuum. Again our buses needed 24 hours of vacuum, but I'm sure you will not need near that much time. Also was you system ever "exposed" to atmosphere ? and for how long ? You might need to replace the desiccant in the "receiver dryer" .

 

[Suprman]

I believe the unit was working fine before the military purged it for disposal. I think they just suck out the r22 since it's not environmentally friendly. If I had a local HVAC guy that was reasonably priced I would have him come out.

 

[NDT]

To ID the suction (low side) access port, find the compressor. The compressor has a large line and a small line. The large line is the suction. Trace that line back until you find the access port, that is the low side.

Oh and "reasonably priced" and "A/C guy" can't be used in the same sentence.

 

[rustystud]

Oh and "reasonably priced" and "A/C guy" can't be used in the same sentence.[/QUOTE]

OK, that would be funny if it wasn't so true !

 

[Suprman]

One connection looks like it goes to the top of the ac compressor and one the bottom line. Both lines look around the same size. Which is low and high?

 

[NDT]

Bottom is typically suction on recips and scrolls.

 

[robertsears1]

What unit do you have? Did you look for the manual on Liberated manuals.com?

I recently bought two out of six FDECU-5 units from Ft Bragg that came up for sale. All were never used and still had the end of the power cords wrapped in factory wrapping. They also removed the refrigerant (in this case R-134a, ~$180 for a 30 bottle which should fill two units).

Robert

 

[Suprman]

Its an applied unit. Is suction the low side?

 

[Suprman]

Here is the pic. Which is low which is high port. On right of unit.

 

[NDT]

That is a scroll compressor, discharge is on top and suction (low side) is further down on the shell. Trace the small lines that come from the #11 access ports.

 

[Suprman]

I looked up the comp and figured it out. Hooked up the vac pump for 45min. Let it sit for another 45min and gages have held vacuum.

 

[Another Ahab]

I looked up the comp and figured it out. Hooked up the vac pump for 45min. Let it sit for another 45min and gages have held vacuum.
View attachment 674839

Always wondered what that gauge device was.

 

[wdbtchr]

Accepting that I've been retired for 10 years from the HVAC business, I haven't heard of a direct drop in refrigerant for R22. What exactly are you planning to use? R410 is being used in new systems but at much higher pressures.

As far as checking for leaks with vacuum, small leaks can suck debris and hide a leak, that's why smart technicians will pressure check with N2.

 

[Bmxenbrett]

Sounds like you know just enough to be dangerous, original poster. Take your time and look up how to do things.