Operation of the Liquid Flow Control and the Active Charge Control

The Liquid Flow Control (LFC) and the Active Charge Control (ACC) are the refrigerant controls designed, built, and utilized by ECR that give the EarthLinked system its high efficiency and make it simple to charge and operate. They were created expressly for DX geothermal systems. However, though conventional controls failed to operate correctly for DX systems, the LFC and the ACC operate superbly with conventional air to air systems as well as closed loop geothermal enhancing their outputs and allowing more flexibility in coil design.

The LFC is, in essence, a liquid/vapor separator that allows only liquid to exit. It is the expansion device for both the cool mode and heat mode located between the condenser and the evaporator. It contains a small float that rises and falls in response to the loading of the condenser based on how much refrigerant vapor exits the condenser and enters the LFC. The float's actions cause the refrigerant to be modulated through an internal orifice and into the evaporator. The LFC does not react to conditions in the evaporator but rather only to conditions in the condenser. For example, if pure liquid enters the LFC from the condenser, the internal float will rise fully exposing the orifice to full flow. If excessive vapor is exiting the condenser, the float will fall. This will partially close the orifice reducing flow causing the head pressure to rise slightly and produce more liquid. In steady state conditions, the float will ride atop the liquid in the LFC controlling the opening in the orifice at a level proportionate to the mass flow rate required for optimum condenser output. Since the LFC is "unaware" of conditions in the evaporator, it could possibly allow too much liquid through causing compressor slugging, or it could possibly not allow enough liquid through and cause excessive superheat.

The ACC is, in essence, a liquid/vapor separator that allows only vapor to exit. Its location in the system is in that of an accumulator between the evaporator and the compressor. It doubles as a receiver by continually holding liquid refrigerant in reserve for variations in the loading of both heat exchangers in both the heating and cooling modes. The liquid refrigerant in reserve is constantly circulating within the tank during operation via the incoming vapor and a venturi device located at the bottom of the liquid. The liquid and vapor in the tank, subjected to the compressor inlet, remain at saturated temperature at all times. If an excessive amount of liquid exits the evaporator, the ACC will catch the liquid and place it in reserve within the tank. If superheated vapor inters the ACC, it will contact the liquid in the tank. The energy in the superheated vapor will evaporate a small amount of the liquid sending it into circulation. This addition of refrigerant to the system will cause the head pressure to rise slightly causing more liquid to be produced in the condenser. The additional liquid will enter the LFC causing the float to rise slightly opening the orifice, in turn allowing more refrigerant to enter the evaporator, in turn lowering the superheat to zero.
The internal design of the ACC is such that the circulating of the stored refrigerant within the tank causes any compressor oil contained in or entering the tank to be entrained in the exiting vapor. The ACC will not store or "bind" oil.

This communication between the LFC and the ACC occurs continuously during operation and guarantees that the condenser and evaporator remain operating at 100% of their capabilities regardless of loading conditions on either. The condenser utilizes 100% of its coil surface for condensing producing no sub cooling. The evaporator utilizes 100% of its coil surface for evaporating producing no superheat. These actions cause the suction pressure to be higher and the head pressure to be lower yielding a higher mass flow rate. This increases overall capacity and efficiency.