The life of the reed switch is typically 106 - 109 operations, dependent upon load conditions. The special reed blade material is selected to ensure a mechanical life of at least 3 x 109 operations. Contact Protection: The specified value of switching current and/or voltage must never be exceeded, even for very short periods. It is strongly recommended that contact protection be used whenever there are capacitive or inductive loads (long leads and relay loads). High inrush loads caused by filament lamp switching or capacitances may be compensated for by using current limiting resistors. These should limit the current to that acceptable to the reed switch.

When trying to switch loads (capacitive or inductive) that exceed the maximum steady-state current rating of the reed switch (see UL Current & Voltage Rating Chart below), Madison recommends the use of general-purpose/isolation relays or controllers to protect the switch from current overload. This will prevent the contact of the reed switch from fusing together, thereby increasing the lifespan and reliability of the switch. Madison offers the R1 general-purpose DPDT relay for switching simple loads, as well as the R2 controller to perform pump-up or pump-down control when used with at least two levels. Keep in mind that any relay or controller that you use should be rated to handle your supply voltage and have a current rating greater than your maximum supply current.

Above ratings are for resistive loads only.
Maximum voltage ratings: SPST Switches – 240 VAC; SPDT Switches – 120 VAC

We recommend that switches stay below these ratings for non-resistive loads.

Current and Voltage ratings are for resistive loads only. For inductive loads, maximum life will be achieved if appropriate arc suppression is used.

Maximum voltage ratings: SPST Switches — 240 VAC; SPDT Switches — 120 VAC

Each switch has a power rating in watts. These power ratings are for resistive loads that are at a steady state and are calculated as Power (Watts) = Voltage (AC/DC) * Current (Amps-resistive load). Most devices have other things to consider, such as current or voltage spikes caused when powering up or shutting down. Common devices such as pumps, coils and light bulbs can create these types of spikes. For these more complex cases, one must remember to stay within the maximum current and voltage ratings of the switch regardless of the power rating.

For example, our 30-watt standard switches have a maximum switching current of 1 Amp and a carrying current of 2.5 Amps. If the switch is connected to a 12 V circuit that spikes to 2 Amps and runs at a steady state of 1 Amp, the power spike exceeds the switch rating although the steady state running power is 12 Watts. Due to the heat and type of power dissipated during the spike, the contact may be damaged or even welded together, causing switch failure.

Custom designs have other elements to consider and even alternative ground paths that may affect the power delivered to a switch. It is important to consult your engineering department before assuming the system's power requirements. Contact the factory for additional assistance.