Which over-temperature control should I use?

A query from a recent customer might provide insight to others….

We have an application running at 250VAC/10A which requires over-temperature control, Is the SEKI ST-22 thermal cut-out able to manage this load?

For any application, it is essential to consider the electrical load in the system to ensure the most suitable component is selected.

For temperature control and protection, the thermostat rating needs to match or exceed the application load.

The SEKI ST-22 is rated for 250VAC/7A, so in this scenario it cannot safely handle the required 250VAC/10A load.

ATC Semitec recommend a better fit would be the ASAHI US-622, a ½” disc thermostat rated for 240VAC/16A. This component provides the same function as the SEKI ST-22 (circuit cut-off at a set temperature, with automatic reset when the system cools), but it is designed for higher loads.

The main consideration here however is form-factor: the US-622 is larger than the ST-22, so may not fit within the application. If this is the case, a relay and separate control circuit may need to be used.

It is also important to account for the potential effects of self-heating and current derating in these thermostats.
Elevated electrical loads can cause internal I²R heating, leading the thermostats to trigger earlier than their specified calibration temperatures.

This highlights why defining load requirements early is critical – selecting the right component to start with prevents issues with ratings or fit later in the design. We can help to quickly identify these potential issues, make suitable product recommendations, and highlight key design considerations that need to be considered.

To view ATC Semitec’s complete range of thermal protectors/ thermostats click here

Need help ? Contact ATC Semitec.

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