3Selection Chart Page Supply Series Load Capacity Description and Special Notes Number Voltage Curtis liquid level controls Economical liquid level control sensitivity range 1/4 HP, 10 amp non-inductive ELS 3 120, 240VAC 120VAC, 1/3 HP, 240 VAC to 100,000 ohms 1/4 HP, 10 amp non-inductive Low-cost liquid level control with sensitivity up to ELC 4 120, 240VAC 120VAC, 1/3 HP, 240 VAC 50,000 ohms Liquid level control with built-in time delay 1/4 HP, 10 amp non-inductive LCT 5 24, 120, 240VAC feature for standard applications up to 100,000 120VAC, 1/3 HP, 240 VAC ohms 1/4 HP, 10 amp non-inductive Liquid level control with adjustable sensitivity LCS 6 24, 120, 240VAC 120VAC, 1/3 HP, 240 VAC ranges for detection up to 100,000 ohms 1/6 HP, 10 amp non-inductive Liquid level control with adjustable sensitivity LHS 6 24, 120, 240VAC 120VAC, 1/3 HP, 240 VAC ranges for detection up to 3,00,000 ohms Liquid level control with forward and reverse 1/4 HP, 10 amp non-inductive LC 7 24, 120, 240VAC operating modes, adjustable sensitivity to 120VAC, 1/3 HP, 240 VAC 100,000 ohms Dual liquid level control with heater/pump 1/6 HP, 10 amp non-inductive DLC 8 24, 120, 240VAC lockout feature, sensitivity range to 100,000 120VAC, 1/3 HP, 240 VAC ohms Rugged, compact contractors and enclosures Accessories 9 meeting NEMA 1, 3, 4, and 12 specifications Liquid level A variety of pressure, temperature and fitting probe options available assemblies 9 Low-cost amplifier module for liquid level RSA 10 24, 120, 240VAC applications Curtis industrial controls ELS 11 24, 120, 240VAC 1/6 HP, 10 amp non-inductive For precision photoelectric or temperature 120VAC, 1/3 HP, 230 VAC applications Curtis liquid level control principle of operation current, typically 500 microamperes, is introduced to a solid-state Operating on the principle of conductivity (the ability of a liquid to conduct electricity), Curtis Liquid Level controls sense and control the resistance-sending amplifier which provides sufficient gate signal to trigger a silicon-controlled rectifier (SCR). The firing threshold is level of almost any fluid or moist solid. These units are available with fixed or adjustable setpoints to control levels in fluids having an accurate to within 2% of operating differential and is adjustable by means of a potentiometer. The output of the SCR is used to operate external circuit resistance up to 3,000,000 ohms. Typical solution the plug-in control relay. When anticipated loads exceed that of the resistivity is shown below. standard relay, an auxiliary contactor is utilized. Typical Liquid Resistivity Control Models ELS, LCS/LHS, LCF and RSA are designed for forward mode operation. They interpret a decrease of external circuit Nominal Resistivity resistance from setpoint as an ON signal. Model LCR is designed for reverse mode operation. It energizes when external circuit resistance Liquid Range (ohms/CC) increases above setpoint. Model DLC is intended primarily for pump and heater level/lockout applications. See the appropriate catalog acids, bases and salts ................................................ 0-20 sections for specific application information. dilute acids .............................................................. 20-200 milk, beer ........................................................... 200-2,000 When selecting a liquid level control, several factors must be taken non-distilled water ......................................... 2,000-20,000 into consideration. Questions arise as to what mode of operation is distilled water ............................................ 20,000-200,000 required, what is the resistivity range of the fluid to be controlled, is a fixed or variable setpoint called for, are special functions required In operation, two or more submerged liquid level probes pass a such as a pump or heater lockout, etc. Use the connection diagrams minute electrical current through the liquid to be controlled. This to select the ideal control for your specific application. 4