For modulating liquid level control in refrigeration, freezing and air conditioning plant, a system comprising a liquid level regulating valve type PMFL or PMFH, controlled by a pilot float valve type SV, is used.PMFL and SV systems are used on the evaporator side. PMFH and SV systems are used on the condenser side.The system is suitable for use with ammonia or fluorinated refrigerants. The PMFL and PMFH can be used in liquid lines to or from• evaporators• separators• intermediate coolers• condensers• receiversModulating liquid level regulation provides liquid injection that is proportional to the actual capacity. This gives a constant amount of flash gas, thus ensuring stable regulation and economic operation because variations in pressure and temperature are held to a minimum.