300 lbs is about 150º condensing
150º condensing is too high. Hell; at just 200 lbs. I would be looking for issues. That huge head pressure is why the compressor is drawing high amps.
First clean both coils, especially the condenser. Really Clean! See-thru clean.
Next; remove all the refrigerant and evacuate the system. Replace the LLD - make it a decent size for the system.
Charge in the R-12 substitute of your choice - I would use R-414 if it were me. Get the subcooling to about 5-6º while making sure that the pressures are not doing anything alarming. If they are - check to find out why.
As the box temp falls the SSH will fall into line. If not; add some refrigerant and check it again. About 8-10 SC with the box near within 10º of design is what you are looking for.
Forget the exotic maybes - get the basics right and you will almost always be pleased to find that all the crazy stuff has somehow gone away on it's own.
Originally Posted by GREGHVACGUY
The conventional view serves to protect us from the painful job of thinking.