Marc, I forgot to mention that the suction pressure is increased by the flooding of the entire evaporator. With regards to the flash gas being moved to the LPR and being released to the dry suction, this is a reconised problem high-lighted when single stage screw compressors are used with liquid injection, higher than normal discharge temperatures are encountered compaired with similar DX system. I think the normal way around this is to use Glycol/water mix oil coolers rejecting their heat to outside the system. Another way around the flash gas problem is the two stage LPR, which is basically an open flash economiser clamped onto the side of the conventional LPR. This removes some of the flash gas to the inter-stage usefully flashing off to subcool the liquid in the economiser. This should reduce the flash gas component in the main LPR. Two stage LPR's are unfortuately a thing of the past, I have only one site in N.I that has these, both are fitted to R22 blast freezers with RC4-2-11 compressors. The flash gas component is introduced at the low stage discharge where it enters the high-stage suction along with the injected liquid which de-superheats the low stage gas. Control of the liquid levels and indeed the high level cut out in the economiser is all by thermistors which are wired back to simple voltage sensor relays fitted with two 14ohm resistors accross them, liquid height is variable (a little) by adjusting the voltage sensing relays. Oh and on of these system also employs singer valves, an eairly bio-metal electronic enpansion valve.
As for NH3 LPR's the liquid is econimised in a shell and plate DX econimiser fitted with an AKVA to remove some of the flash gas conponent.
I hope what I,m saying makes sense, please feel free to comment as I am learning as I go and any imformation will assist.
Regards. Andy.