Aha, so that's why you're running such a large accumulator. It's also a flash tank, or a "slobber box". It took me a while to decipher your plumbing, the reversing valve is the same color as the compressor shell! That and your full-wave bridge rectifier check valve setup threw me off for a minute. I'm somewhat confused with your TXV description, however. The condensor is not fed liquid.
The metering device in flooded systems is usually a float in the flash tank. When the refrigerant in the flash tank drops below a certain level, the valve opens to maintain that level. When the flash tank fills past this level, the valve closes. Kind of like a toilet. The flash tank sits above the evaporator, and gravity keeps fluid in the evaporator. This is obviously not what you have.
I found info about the westinghouse valves here:
http://sporlanonline.com/literature/10/210-60.pdf
http://www.refrigeration-engineer.co...bcooling-valve
A subcooling valve is the opposite of a TXV. Instead of measuring superheat against suction pressure, it measures subcooling against head pressure. Instead of regulating the amount of liquid in the evaporator, it regulates the amount of liquid in the condensor. Since you have a flooded evaporator, this makes perfect sense.
Your system is plumbed closely like what I am planning. The main differences being:
I will have only one SLHX, the big can in yours.
TXV bulb will be on the suction line just prior to entering the big can.
Two metering devices, two check valves.