Hello. I am relativley new to the trade, and have a somewhat of an understanding of the basics. There is just some things about refrigeration/ A/C that I'm having trouble understanding. First off, take a service call where the system is low on charge (any refrigerant). If im low on charge you'd think id have low suction pressure, but it is in fact it is a little high (?). Im I correct in thinking thats because the box temp is high due to the abscense of liquid in the evap and thus not allowing the box temp to drop keeping the boiling temp/suction prssure high? While i know the superheat is high because the suction line temp at the compressor (even though i know it should really be checked at the evap outlet and it feels warm there) is warm. The evap is clean as is the condenser and both have good airflow. Head pressure is "okay" cant remember exactly what but i remember it was about 120 condensing temp.
I was also wondering about pressure controls used for a tstat. Ive heard and accepted the fact that this application only works with a TXV and not a cap tube/ fixed orifice. Is this because the cap tube equilizes right away during the off cycle thus keeping the contacts closed and not allowing off cycle?
While i have your attention i was wondering about sight glasses. Ive heard it said that there only applied to TXV's yet ive seen them on fixed orifice A/C systems?! Thanks for reading!!!!