Float Switches
Electrical Specifications
Float assemblies with SPDT switches
Each float switch wire group, will be separated and marked for easy identification.
Assemblies with SPST and SPDT in the same sensor will typically follow standard color code unless customer specifies differently.
Use an ohmmeter ONLY to check switch operations. Switch open resistance will be infinite, closed will be typically less than 2 ohms.
Temperature Switches
Preset snap and creep action switches, type J and K thermocouples and solid state devices can be combined with liquid level assemblies.
Bimetallic element temperature switches consist of thermally sensitive metals which expand at different rates. The predictable movement is used to open or close a set of contacts. Temperature switches are surrounded with a thermally conductive material to promote faster heat transfer and accurate switching points.
Standard set point accuracy is ± 5oC with a repeatability of ±1oC. Temperature switches are either SPDT, SPST-NO or SPST-NC. Normally open switches will close on rising temperature at the specified set point. Normally closed switches will open on rising temperature at the specified set point.
Switches are available in 4 and 6 amperes at 115 VAC. High current through the temperature switch will cause set point offset due to self-heating. To eliminate this use a slave power relay for high current loads. Normally closed switches will open at a lower fluid temperature than specified. Normally open switches will reopen at a lower temperature than specified.
Temperature switches will have a delay in detecting fast changes in fluid temperatures. The fluid must heat the sensor housing, the thermally conductive material, then the switch. The delay is very application dependent. Location of the sensor will reduce or increase this time delay. Consider the function and location of the temperature switch before mounting the sensor. i.e. Two switches, in the same tank, one located near a hot fluid return line and the other in a baffled area will react differently from the average tank temperature.”
Wrong mounting locations will appear like the temperature switch is malfunctioning
