THE MAESTRO vs THE GUARDIAN
The most basic thermal control decision any Design Engineer makes regards functionality. What do you need it to do?
Do you need a Maestro that keeps your heated product functioning at maximum efficiency, or do you need a Guardian that makes sure temperature never breaks through a barrier it shouldn’t.
Temperature control devices can be said to act as the Maestro of a world-class orchestra. Their primary function is to maintain a defined, steady operating temperature, determined by the design engineer to provide for optimum performance of the product. These type of thermal controls will open and close at a preset temperature to regulate the operating temperature of some type of heater.
Temperature control applications are the most difficult for thermal controls since they must carry the full electrical load of the application. Since these controls must both open on temperature rise and close the circuit on temperature fall, they are also called on to cycle more often than other types of thermal controls. Reliability of the thermal control is critical to operating efficiency.
Over temperature protectors acting as Guardians are the heroes of the thermal control world. As their name implies they provide high limit temperature protection in applications where the normal operating temperatures have increased due to overwork or another type of fault condition. Depending on the type of fault condition, over temperature protectors will function by either “seeing” an increase in temperature or “sensing” an increase in the electrical load. They can also function on a combination of these two conditions. However they perform their task, over temperature protectors are there to prevent catastrophe. Their reliability is often critical to protecting lives and product reputations.
There are three basic types of over temperature protectors:
1. Manual Reset - These type of devices provide an extra layer of safety to design engineers. They operate in much the same manner as a circuit breaker. Once they are activated by temperature exceeding high-end limits, they must be manually reset for the application to function again.
2. Non-Reset - Operating very much like manual reset devices, non-reset thermal protectors will only reset when the power source is disconnected. This functionality is due to a special form in the middle of the bimetallic element that will not allow it to reset until exposed to temperatures of 5°C or less. This enables them to function like a thermal fuse while allowing them to be tested prior to installation in the application.
3. Self-Hold - These devices also operate in a similar fashion to both manual reset and non-reset devices, however they contain an extra heat source designed to keep the circuit open until removed from the power source. Once the power source is disconnected by turning off the power switch or removing the plug, self-hold protectors will automatically reset.
There are many different thermal controls, but only one Portage Electric Products, Inc. (PEPI®). We encourage you to start your search for reliable thermal controls at the one place where you can get any type of control you need with the engineering support you need to make the best choice.