Rain Frances - welcome, and thanks for following my blog!
Refrigerant (commonly referred to as "freon") never gets old or wears out. The only times it has to be replaced, is either when an hvac technician has to replace a defective component within the sealed system, or when some has leaked out. That's just the way it is....Well, one of my split systems required more refrigerant being added to it when warm weather arrived last year, and had a tiny leak somewhere in it that would become a problem again toward the end of summer. With that being said, i'll show you the best method I know for locating a leak in one, and hope that it may help someone down the road...
Note - before this method can be used, all remaining refrigerant must be removed from the system with methods and special equipment that follow guidelines set forth by the EPA. I have this equipment on hand, and realize that most homeowners do not. Anyway, a person shouldn't vent refrigerant to the atmosphere, because stiff penalties/fines are the result from doing so....EG does things the correct way, and you should too. :-)
The first thing to do, is pressurize the entire system (indoor coil, outdoor, and connecting copper tubing between each) with nitrogen at 200 psi. Use soapy water (I use water with dishwashing liquid or children's bubble solution with wand inside the bottle) to spray every bit of copper tubing on the system. A leak will appear as bubbles forming from the leak.....Anyway, in my case this still didn't indicate where the leak was, so more drastic measures were called for.
Photo below - here is the outdoor coil (condenser) removed from it's original outdoor housing. The ends of the connective piping were sealed off, and a shrader valve installed for adding nitrogen to it. It was then pressurized with nitrogen at 350 psi, and isolated to see if the pressure would drop. After allowing it to sit for a couple of hours in this state, no drop in pressure indicated that this part wasn't leaking.
Photo below - Size 128 bottle of dry nitrogen with pressure regulator attached. With around 2,200 psi in the bottle when originally filled, the regulator allows a person to adjust the outlet from the hose to meet their pressure needs, and keeps stuff from exploding, too! Never try this without a working regulator....
Photo below - due to a small rise in ambient temperature for the day, the system pressure actually increased by 5 psi to 355. With the condenser coil under pressure, you can spray more soapy solution on the entire coil, or even dunk the entire thing in a vat of water if needed. Either way, a leak will reveal itself at this pressure. (Sometimes you can even hear it hissing).
Photo below - the connecting copper lines that run through the walls, attic and ceiling of your home are referred to as the "line set". If the leak is in this part, you've got serious problems - requiring walls to be broken into for access or even the hated task of crawling around in the attic or sometimes the crawlspace under your home. Either way, it's a real pain - especially for a big person such as myself (6'4" 250 lbs). Anyway, I just isolate the line set on both ends by pinching the ends - then soldering them up, so that it can also be pressurized to 350 psi. Follow the same procedure as done with the condenser coil, and if a leak is present, the pressure should decrease a little after a few hours.
Lastly, the evaporator (or indoor coil as it's sometimes called) is isolated the same way, then pressurized to the same amount as done before on the previous 2 parts. Making sure that all service manifold gauge hose connections are tight and not leaking, allow the 350 psi to remain in the isolated evaporator coil for a couple of hours. As before in the other parts previously pressurized, a drop in pressure indicates this component is the source of the leak.
Anyway, in my situation, the brass nut that connects the high pressure liquid refrigerant line to the orifice assembly would prove to be the source of the leak. Just as a precaution though, all valve cores in service valves on the condensing unit were tightened, then the entire system was connected back as it was originally. For the record, finding a tiny leak in an air conditioning system is perhaps the most dreaded problem that a service technician is faced with.However, if they would drag out a bottle of nitrogen instead of one of those stupid little electronic leak detectors, life would be much more simple for them. Ha! EG doesn't play when it comes to fixing his AC......
I'll try to do a post on charging the unit back up with refrigerant in a month or two, and might even shoot a video of it.
Take care, and stay cool!