I justhad a 14 seer American standard unit installed. It is evidently a great peace of equipment but it loses four or five degrees on 95 to 100 degree days. I was told that if I sit the unit on 72 it would hold that all day. This unit has a expansion valve and the subheat is preset. So I understand you are to use the subcooling method to obtain the proper charge. Anhyone know a simple way to find the amount of subcool right befoe the liquid enters the expansion valve. My unit is in the attic and i cannot crawl up there. I just want to check the charge for myself and be sure that it is right.
The correct subcooling for a TXV system should be on the plate on your condensor unit.
However you'll need some tools you probably do not have to properly check the subcooling.
But, for a crude check: Put your ear right on the liquid line (small tube)(perferably right before the TXV). If you hear a gurgling sound, then I would call someone to check the unit. If you hear what sound like a steady stream of flow, then I'd be less inclined to think you have a low refrigerant level problem.
What? It actually is a fair, quick test that a homeowner can do. I do it everytime I'm up in MY attic and my unit is running. Why make things complicated?
I'm not suggesting he set his subcooling by it; that would be impossible. But it's an easy way for a homeowner to see if they have gas in their liquid line. IF you hear gurgling, then you most definetly do not have a full liquid line. Then he can call someone to service the unit and figure out root cause. No different than if he saw frost on his suction line and called someone to figure out root cause.
Digress...
Back before I was in the business, I had an upstairs unit that was not cooling real well. Only had 8 deg temp drop at the supply. I called someone and told them I was probably low on refrigerant. They came out and said (or told wife) everything is fine. I called them back and got the owner out with the tech. I took them up in the attic and said "now put your ear on that 'thar liquid line. Here that 'thar gurggling? My evaporator is being starved man!"
He said, "Oh, you got one of those TXV thingys". Maybe YOU ARE low on refrigerant. He then proceded to dump gas in the system up the the high side was "a lot higher". No thermometer on the liquid line, no subcooling calulation, no leak detection..."
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