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Short story, how much current the float switch can carry. Amperage is what determines the size of the wire going to and from a float switch.
A “Pump Duty” float switch is designed to directly switch the power to a pump on or off. They are made to handle the running current of a pump – but there are always limits. A typical pump duty float switch can generally switch in the range of 10 amps. Of course, if we are switching a pump, we also want to minimize the number of times that pump is going to turn on and off, so people consider we want a “wider angle” float switch, but we will cover multiple float control systems later in this article, that will demonstrate why that is not always necessary. The idea is that if we have a single 120V pump, its not going to have a control panel, and it shouldn’t need one, so the float switch can work alone. Why use 120 as an example? Well, we’ll tell you. 230, 380, and 460V pumps have multiple hot legs going to the pump. Good safety practice (and.. eh em.. the National Electrical Code) require that no leg to the pump is left energized when the pump is in the off state. So for those cases, we have the “Control Duty”.
A “Control Duty” float switch is used with a control panel or alarm system rather than directly powering a pump. These are usually rated for less than 1-2 amps maximum. Why only 1-2 amps? Because normally, all these float switches are doing is activating a relay or a contactor. After using hundreds of relays and contactors over the years and checking the spec sheets that say how much current the relay or contactor is going to pull, it’s always less than about 250mA (or 0.25 Amps). So, the 2-3 amps is probably overkill.
Sump Alarms float switches are good for both Pump Duty and control duty. They operate as low as 3.3VDC with 20-30mA, and up to 10-12 Amps at voltages up to 230V. Like the NO/NC, we just don’t feel like there is a need for all the complexity for the pages in the float switch catalog. Again, our customers don’t need to wonder “is that a pump duty, or control duty switch?”. One switch can do either application, and that cuts down on overnight shipments, and customers not having what they need when they need it.