General Coil Information

Clark-Cooper utilizes a variety of solenoids or “coils” to meet the performance requirements of our valves in all applications. Criteria for the solenoid includes AC or DC power supply, voltage, differential pressure across the valve (required pull force), NEMA rating, duty cycle, special connections, fluid and surrounding temperature, and even the length of the wire leads.

Duty Cycle:
Our valves are designed with coils that can be energized indefinitely without over heating. However, alternating current (AC) powered solenoids have limitations to the frequency of energizing them due to the high in-rush currents. Opening and closing a valve with an AC solenoid too frequently can over heat the coil, especially if the fluid/gas temperature is high. Certain versions of our solenoids have circuits that take AC power and rectify it to DC. These can be cycled frequently without risking burn out. Be sure to discuss the open/close frequency on your valve when purchasing.

Inherent to construction, our solenoids exhibit excellent resistance to moisture and ingress of particulates. Certifications apply.

Polarity and Wiring:
The solenoids supplied by Clark Cooper do not require wiring with respect to a certain polarity. Line voltage may be applied to either lead. If there are 3 wires, the green wire is ground.

A switch should always be installed in the hot leg of 120 volt circuits. When both legs are hot, such as 240 or 480 volt circuits, a double pole switch is preferable. If a single pole switch is used, then the wiring should have top quality insulation since even minute leakage currents may give rise to sticking problems. On motor hookup with step control starter, full voltage should be supplied to coil immediately.

Coils can be easily removed from valves. The coil can be rotated on top of any valve to position the lead wires as needed.

Power Consumption:
“Real Power”, measured in watts, is the actual work and heat being lost. When multiplied by time, it is the amount of energy that you are billed for by your utility company. For DC circuits, real power = VDC * I DC. For AC circuits, it is: Average Power Equation
A typical multimeter cannot measure watts unless voltage and amperage are both DC. A multimeter measures RMS voltage and RMS current. When you plug into the wall to get 120V AC, this is RMS.

“Apparent power” is measured in volt*amps. It is used to size wires, circuit breakers, fuses, etc. for a circuit. For DC circuits, the calculation is again simple: V*A = VDC * I DC. For AC circuits:


“Power Factor” = Watts/(V*A). It goes from zero to 1.0. The wattage drawn by a device is always less than or equal to the volt-amperes. This is due to capacitance or inductance of the device making the circuit “reactive”. It is possible for a device to draw significant volt*amps and product no work or heat. A power factor close to a value of 1.0 indicates an efficient setup.

“Hum” or chatter:
Chatter is often an indication that a plunger (armature) is not in full contact with a pole piece in a magnetic field created by an AC voltage solenoid. Something as simple as a piece of Teflon tape stuck inside the valve can cause a vibration with a frequency equal to the supplied AC power (60 hertz). A solenoid in this case will pull higher amperage than allowed for steady state usage and eventually burn up. Other physical damage to parts can also occur due to buzzing, hum, or chatter. If you hear the valve buzzing, de-energize and call Clark-Cooper for technical assistance. The solution may be as simple as cleaning the valve out.