David40
01-07-2010, 04:34 PM
I do mostly A/C work and I'm not that familiar with complex refrigeration system. I've come across an old system I have been asked to repair but I'm not sure about the theory of operation for this system.
I would appreciate it if anyone could describe to me how this system is supposed to operate correctly in theory so I can figure out what is wrong.
The system: A reach-in cooler running on R-22 consisting of two 2-Ton condensing units supplying four evaporators (2 each) with a TXV in each unit. Operating temp is controlled by a low pressure switch on each condenser. Defrost is accomplished by condenser off time (no heaters) controlled by a defrost timer on each condenser, which are set at 40 minutes every 3 hours. Also, each condenser has a solenoid valve on the high side that appears to energize during defrost and is also controlled by an adjustable thermostat who's sensing bulb runs through the wall into the cooler.
The uncertainty I have is the proper reason/function of the solenoid valve and the thermostat that is tied into that. :confused:
Thanks for any help.
PS. I should mention that it looks like the system was modified at some point because there are disconnected temperature switches on the wall near each of the thermostats for the solenoid valves, that looks like the box temp used to be controlled by two thermostatic switches rather than the currently used pressure switches.
I would appreciate it if anyone could describe to me how this system is supposed to operate correctly in theory so I can figure out what is wrong.
The system: A reach-in cooler running on R-22 consisting of two 2-Ton condensing units supplying four evaporators (2 each) with a TXV in each unit. Operating temp is controlled by a low pressure switch on each condenser. Defrost is accomplished by condenser off time (no heaters) controlled by a defrost timer on each condenser, which are set at 40 minutes every 3 hours. Also, each condenser has a solenoid valve on the high side that appears to energize during defrost and is also controlled by an adjustable thermostat who's sensing bulb runs through the wall into the cooler.
The uncertainty I have is the proper reason/function of the solenoid valve and the thermostat that is tied into that. :confused:
Thanks for any help.
PS. I should mention that it looks like the system was modified at some point because there are disconnected temperature switches on the wall near each of the thermostats for the solenoid valves, that looks like the box temp used to be controlled by two thermostatic switches rather than the currently used pressure switches.